Secrets of 5-Axis Machining

KarloApro

I S B N 9 7 8 - 0 - 8 3 1 1 - 3 3 7 57

ttn ril llillffill

Secrets ot S-Axis

Machining by KarloApro

IndustrialPress,Inc. NewYork

Libraryof CongressCataloging-in-Publication Data Apro, Karlo. Secretsof s-Axis lvlachining/ Karlo Apro. p. cm. Includesindex. rsBN 978-0-8311-3375-7 1. l4achinetools--Numerical control.2. Machining.I. Title. IL Title: Secretsof 5-AxisMachining. TJ11B9.A68 20OB 671.3'5--dc22 2004027254

IndustrialPress,Inc. 989 Avenueof the Americas New York,NY 10018 FirstPrinting,August,2008 SponsoringEditor: lohn Carleo lnteriorText and CoverDesign: PaulaApro Developmental Editor: RobertE. Green ProductionI\4anagen lanet Romano

Copyright O 2009 by Industrial PressInc., New York. All rights reserved.This book, or any parts thereot may not be reproduced,stored in a retrieval system, or transmitted in any form without the permissionof the publisher. All trademarks and registeredtrademarks, including Mastercam@ and Vericuto, are property of their respectiveowners. All rights reserved. STATEMENTOF NON-LIABILITY No liabilityis assumedby the author or publisherwith respectto use of information contained herein, includingfor any loss of profit or other commercial,special, or incidental damages.While every reasonableprecaution has been taken in preparing this book,the author and pubiisherassumeno responsibility for errorsor omissions. Publicationof any data in this book does not constitute a recommendationor endorsementby the authoror publisherof any patent,proprietaryright, or product,

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Dedication Thisbookis dedicated, in lovingmemory/to my motherPiroska. Shetaughtme the meaning of hardworkandperseverance. Althoughshepassedawaybeforethe completion of this book,her spiritcontinues to livewith me.

Acknowledgements I wouldlike to thank Yavuzlvlurtezaoglu for giving me the inspirationto write this DOOK.

A specialthanksto LauraNortonfor her humblinginsights. And aboveall, I would like to thank PaulaApro, my hard-workingwife, friend,editot designer,and manager.For without her this book would neverhave come to be.

All the imagesin this book, includingthe virtual machines,were modeledusing (CNCSoftware,Inc.). The virtual machineswere broughtto life using f4astercamo (l"loduleworks) the machinesimulationcapabilitiesof 14achSim and VERICUT6 (CGTech). Formore informationon these productsor companiespleasecontactl Machsim/Moduleworks CGTech/VERICUT CNC Software/Mastercam ModuleworksGmbH 9000 ResearchDrive 671 Old Post Road Ritterstr,12 a Irvine, California 92618 Tolland,CT 06084 52072Aachen,Germany 949.753.1050 860.875.5006 +49.241.4006020 www.cgtech.com www.mastercam.com

www.moduleworks.com

Formore informationon the author,Dleasevisit www.multiaxissolutions.com

Table of Contents Introduction

... ....., . . .1

Chapte1 r : H i s t o r y o fs - A x i s M a c h i n e.s. . . . . . . 3 C o m m ol n4 i s c o n c e p .t .i o . .n, s R e a s o nt o s l J s eM u l t i a x li \s4 a c h i n e s .

.... .......4 ,,,....,B

C h a p t e r 2 !K n o w Y o u r M a c h i n e . . . . . . , , , . , . . 1 3 l4ultiaxisl\4achineConfigurations .........74 T a b l e / T a b l e M u l t i a x i sf l44ai cl lhi ni nge s . . . . . . . . . . . . . . 1 8 I \ 4 a c h i nReo t a r yZ e r oP o s i t i o(nl v l R Z P ) N e s t i nPgo s i t i o n s ,

......21 ............26

RotaryTableDynamicFixtureOffset . . . , , , , , , , . . . . . 27 H e a d / T a b l e M u l tl i4ai xl liisnl vg l a c h i n e s . . . . . . . . . . . . . . 3 1 H e a d / H eM a du l t i a x i s l v l il l4l a i ncgh i n e s . . . . . . . . . . . . . . 3 6 F i n d i ntgh e P i v o D t istance 4 - A x i ls\ 4 a c h i n e s

......37 .............3S

Genemll4aintenance & Issuesfor 14ultiaxis lYachines. . . 40 I\4illing l4achinesWith Five-or l.4ore-Axes. . . . . . . . . . . . 43

C h a p t e r 3C: u t t i n g S t r a t e g i e s . . . . . . . . . . . . . . 4 5

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Chapter4r Indexing MultiaxisToolpaths . . . , .49 I n d e x i nl vgl e t h o d s

........,,.51

H o wC A D / C A |SVyI s t e m sH a n d l eI n d e x i n gW o r k . . . . . . . .

56

MachineCoordinateSystems. . lulachine Home Position . . ActiveCoordinateSystem . . ,

60

I\4achine RotaryCenterPoint , .

60

CAD/CAMSystemOrigin . . . SynchronizinglYachineand CAD/CAMcoordinateSystems .

Chapter 5: SimultaneousMultiaxis Toolpaths. ,65 T h eO p t i m uW m o r kE n v e l o p e Feedrates. I n v e r sTei m eF e e d r a,t.e P o sPt r o c e s s o r s .

............70 .......,,72 .......,,,...74 ....,........76

Chapter6: Commonsimultaneous Multiaxis cAM ,.....79 Toofpath C o n t r o l s. C uP t atterns. T o oAl x i sC o n t r o l .

.......79 ............

86

T o oTl i pC o n t r o l .

.............90

C o l l i s iCoonn t r o l

.............93

A d d i t i o nMaLl r l t i a x i s I s s u e s a n d C o n t r o l s . . . . . . . . . . . . , 9 8 D o v e tE a fi lf e c t . C u t t i nDgi r e c t i o n I v l u l t i aRx o i su g h i n g .

....,.......98 ..........100 ........101

C h a p t e r TM r achineSimulation....,..,,..,1O3 G - c o d e S i m u l a t i o n V e r s u s C A M S i m u l a t i o n . .1. 0. ,5. . . . . C o n f i g u r i n g V i r tM La r ac lh i n eFso r S i m u l a t i o n . . . . , . . . . 1 0 5 VirtualMachineBuilding...,,......,...106 T h eS k e l e t o n C o m p o n e nv tss.l t 4 o d e. l.s.

.....106 ...,......I07

M a c h i nSei m u l a t i Ionnt e r f a c e. s

.........116

U s i nM gachin S ei m u l a t i .o, n. .

...,,....7I7

Chapter 8: Selecting The Right Machine For your Application ...........119 Head/Head Machines (with long X or y - axis linear travel, b u tl i m i t e d r o t a r ya x e st r a v e l ). . ......,.I21 Head/Tablel4achines(with long X-axis travel) . . . . . . . I23 H e a d / T a bl l4ea c h i n e .s

,......126

R o t a rT y a b l e- T i l t i n gH e a dC o m b i n a t i o n. .s. . . , . . . . 1 2 8 T a b l e / T a bl vl ei a c h i n e s . . G a n t r yT y p eH e a d / H e aldv l a c h i n e s . .

..,....I32 .,....

L34

Chapter 9! Choosing a CAD/CAM System For your A p p fi c a t i o n . ..,,.,..,,,tg7 SpeciP a lu r p o sSeo f t w a r .e. .. . C A D / C AT Io4o l b o x .

... ..,,..

.,......,,139

MultiaxiscAD/CAlvlConsiderations .,..... M u l t i a xCi sA f 4 . l 4 u l t i a xCi sA D / C ATI 4. a i n i n.g. , ,

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139

.,...I4O ....,,..I44

Behindthe Scenes:CAD/CAMSoftwareDevelopment. . 145 GeneralGuidelinesfor ResearchingCAD/CAMSoftware. . 146

Chapter 10: Putting ItAII Together, . , , . . . . .149 W h y U s e l 4 u l t i a x i s l v l a c h i n i n g T e c h. n . .i.q. .u.e. .s. ? W h a ti s a S t a n d a rsd- A x i sl \ 4 a c h i n e ?

152

......153

W h a t i s t h e S t a n d a r d A x i s C o n v e n t i o. .n. ? . ........

154

What are the ThreeMajor Multiaxisf4achineTypes?. . . 154 What are the l'.lajorBuildingBlocksof a CNCl4achine?. 1 5 6 What are the 14ostImportantPhysicalPositionsof a [4ultiaxis14achine?

157

What Toolsare Neededto FindMRZP?.. .

159

Description of Indexing/Rotary Positioning Work. . . . . . 1 5 9 Whal i5 a PostProccessor?.

159

DefiniLion of an Axis

160

Defininga Simultaneous 5-axisToolpath

160

Whatare the ThreeCommonSimultaneous lYultiaxis CAM ToolpathConLrols. 161 14ultiaxis MachineOffsels.. .

167

FindinglYachineRotaryZero Posilion.. .

162

Findingthe PivotDistance

164

I n d e x i n g / R o t a r y P o s i t i o n W o r k O v e r v i .e. w . . .. .. .

166

Pickinga CAD/CAMSystem for Multiaxis Work . . . . . . . 166 14achine Simulation.

167

Conclusion

767

Introduction Are you utilizing5-axismachining?Couldyour shop benefitfrom the efficiency and powerthat 5-axismachiningoffers?The majorityof peoplenot embracingthis technologylacka true understanding of 5-axispractices.Thereare many common misconceptions on the subject,and the intent of this book is to demvstifv5-axis machiningand bring it within the reachof anyoneinterestedin usingthe technology to its full potential.The informationpresentedin this book was gatheredduring 30 yearsof hands-onexperiencein the metal-workingmanufacturingindustrybridgingcountries,continents,and multiplelanguages(both human and G-code.) The authorworkedin Hungart Germany,Canada,and the USA,specializing in multiaxissolutions,He spent many yearssettingup, programming,and reparnng CNCequiprnent,and has used a number of different CAD/CA|Ysystems. He has workedas a self-employed multiaxisconsultant,as well as djrecuyfor CGTech(the makersof VERICUT@) and CNCSoftwareInc. (the makersof ttastercamo.) The authorhas instructedcountlessmultiaxistrainingclassesover the past decade, Theseclassescoveredtopicssuchas operatingCNCequipment,programming CNCequipment,both manuallyand with CAD/CAMsystems,and bujldingvirtual machineswith differentverificationsystems.Throughthe years,the author has met many professionals aroundthe world and has come to a realizationthat they atl havethe same questions,misconceptions, and concerns,when it comesto 5-axis machining.The needfor unbiasedinformationon the subjectbecameapparent. Up to this point,the best way to get informationon 5-axismachiningwas to talk to peersin the industry in the hopethat they would sharewhat thev had learned, Visitingindustrialtrade showsand talkingto machinetool and CAD/CAI4 vendors are other options- exceptthat these peopleall give their individualpointsof view and will promotetheir own machineor solution.Everybodvclaimsto havethe best mouse-trap,and it is left to the individualto choosethe right one. This book is not a trainingmanualfor any particularmachineor CAD/CAMsystem. Rather,it is an overviewof multiaxismachinetyDesand the commoncontrol methodsthat CAD/CAMsystemsuse to drivethe machines.The book will guideyou throughthis realm,from basicto complexconcepts,and will provideinformation to helpyou choosethe right tools, includingthe machine,work-holdingmethod, CAD/CAMsystem,and machinesimulationpackagethat will best suit your specific application. The bookcontainsnumerousillustrations to help you to precisely implementthesetools.

History of S-Axis Machines LongbeforeCNCcontrollersappeared,4-5-6-12-and more-axismachines,referred to as multiaxismachines,were beingused.Ihe individualaxeswere controlled mechanically through leversridingon cam plates.Some machineshad more than 12 cam plates,controllingnot onJytool/tableand rotary motions,but also clamprngand unclampingof work-holdingfixtures.Thesemachineswere cumbersomeano atme consumingto set up, but they were perfecUysuitedfor mass production. The first NC (numericalcontrolwithout internalmemory) machineswere cumbersometo set up and operate,but they also were great for massproduction.At first, only the most affluentand establishedshopscouldaffordthem. programm,ng was a lengthy,error-proneprocess.Soon,machinebuildersaddedintern;l memory to their controllers,then they addedthe abilityto executesimplebranchinglooping logic,and to calJsubroutinesfrom other subroutines.It was possibleto us; these macrolanguagesdirectlyon the machineand to quicklychangeset_Lrps, especially for familytype parts. Differentmachinebuildersdevelopedvarioussoluiions,which createda numberof CNC(computernumericalcontrolwith internalmemory) programmrng tanguages.Companieswith familiarnameslike Fanuc,Acramatjc, Heidenhein, Siemens,I\4azatrol, etc., all developedtheir own languages,but thesequicklybecamean issue.Some shopsran ten machineswiih eigfrtOifferent languages.If a repeatjob came in, and the originallyprogrammedmichine was bus, a new programwould haveto be re-writtin from sc-ratch becauseof the languagedifferences. N.ext,-the first.rudimentary CAD(ComputerAidedDesign)/CAM (ComputerAided lYanLrfacturing) systemswere devejoped.At first, these softwaresoluiionswere introducedby the same companiesthat developedthe controllers.Soonafter, enterprisingindividLrals wrote their own CAD/CAI4 software.Thisjump in tecnnorogy was huge becauseit allowedengineersto draw their parts in a CADprogram, generatea toolpathin the CAMsystemt genericlanguage,and then translateit into multipleG-Codelanguagesquickt, usingthe appropljatepost processor. This progressmeantthat CNCmachineswere no longerthe exception,and tney startedto becomethe norm. They were no longerusedonly for mass_production and they becameversatile,accurate,and affordable. Ivlultiaxis machineswent througha similarprocess,but becausethev were more complicaled,this processlook longer.First,Ihe machineswere expensiveto

purchaseand maintain, and harder to program,Only large aerospacecompanies had the need, the money,and the personnelto handle multiaxisapplications.Some companieskept their own processescloselyguardedin order to gain an advantage, Many softwarepackageswere born out of necessity- in order to solve specific applicationchallenges.Software,in general,is alwayson the very leadingedge of technology- pushingthe limits of softwarepossibilitiesand hardwarerestrictions. Today,there are many machinebuildersofferinga variety of multiaxisequipment in a wide range of configurations,quality,and price. Computershave becomevery affordable,and CAD/CAMsystems now offer excellentmultiaxiscutting strategies with great tool control and large post-processorlibraries.As a result, even smaller shopscan, and do, implementmultiaxismachining. Mostmachinebuildersare expandingproductionand embracingnew technology, Many believethat it is imperativeto competein the global market, especially againstcountrieswith abundantcheap labor.This attitude has resultedin increased multiaxismachinesalesand some machinebuildersnow havewaitinglistsof customersfor multiaxismachines,Multiaxismachiningis a constantlyexpanding field,with almostendlesspossibilities.

Common Misconceptions Most peopleassociatethe word "s-axis" with complicatedmotions such as those for the inductionpump illustratedin Figures1-1 and 1-2, and the programming techniquesneeded,This view is reinforcedby visits to any industrialtrade show to see both machinebuildersand CAD/CAMvendorsshowinooff their most complicatedcreations.

Figures 7-7 Exampleof inductionpump set-up Secretsof s-Axis Machining

Figure I-2 Exampleof induction pump design. In reality,the majorityof s-axisusersdon,tevermakean impeller,or finish portsfor a.racing-engine cyrinderhead.Mostof them machineparisusingsimpre 3-axisdrilling,contouring, and pocketmillingroutines,whileroiatingthe-part' occasionally in a rotaryindexingmechanism, as illustratedin Figurei1-3 and 1-4. very elaboratepartscanarsobe machinedby apprying3D surfa-cing toorpathsand engagingthe partfrom differentanglesby indexinga rotarytable.-

Figures t-g and l-4

Examptesof positioning work.

Usinga multiaxismachinewill greatly simplify the motions required,the programmingeffort, and the amount of fixturing neededfor machiningcomplex workpieces.other benefitsincludethe eliminati-onof multiple set-upsf increased accuracy,and better surfacefinish.

Historyof s-AxisMachines

common MisconceptionrI don't ilo enough S-axis work to warrant a S-axis machine.

Manyshopsare currentlymakingparts by movingthem manuallyto different fixtures on 3-axis machines.Comparedwith this procedure,productioncan be increasedgreatlywithoutmuch effort by usinga 4- or a 5-axismachine.If simplya single-or dual-rotaryindexingtablewas added,only slighteditswould be needed files.ExamDles to the CNC-code are shownin Fiqures1-5 and 1-6.

Figures 7-5 and 7-6 Third-party rotary mechanisms. Movingto multiaxismachiningrequiresthinkingin spaceinsteadof in a flat plane. Dedicatedmultiaxismachineshave beendevelopedfor the kind of indexingwork Figures1-7 and 1-8, usingtombstonetype fixtures. shownin the accompanying

Figure 7-7 Example of tombstone fixture. Secretsof s-Axis Machinino

Figure 7-8 Example of 4-axis positioning. Onceyou enterthe multiaxisrealm,new doorswill be openedfor your shop.your companywill quicklybecomemore adeptand ableto tacklemore comDlexwork. Beforetoo long,your shopwill start takingon more and morejobs, and will need to be exoanded. Common Misconception: S-axis CAD/CAM is too expensive and is hard to use, The abovestatementswere true in the past, but not any more. If you currenfly own a CAD/CAMsystem, there is a good chanceyou already have s-axis positioning capabilities. MostcAD/cAMsystemsincludethesecaDabilities in their basepackage.Manytimes, it is just a matter of trainingthat is neededto get up a n d r u nni n g . When you are shoppingfor a CAD/CAMsystem, make sure to chooseone from a reputablecompanywith a commitmentto trainingand localsupport.Remember that a CAD/CAMsystem is just another tool in your tool belt. you can buy fancy tools that are very capable,but they are worthlessif Vou don,t know how to use them. Great localsupport may very well be the most important feature of vour new tool.

Historvof s-AxisMachines

If you do a lot of simultaneousmultiaxiswork, the price of the CAD/CAMwill be only a smallfactor.Moretrainingwill be needed,but you will be ableto charge almostdoublefor your hourlymachinetime. The'hardto use'paft alwayscomes down to training - was it easy to learn how to operateyour first CNCmachine? job. If Don'tenterthe multiaxisworld by startingwith a complex,simultaneous you alreadyown a 3-axismachine,start with a single-or dual-rotarytableand apply indexingtechniques.You will make parts faster and more accurately,and you will be ableto investin more equipment.Whenyou decideto buy new equipment, see if you can bundlea CAD/CAMpurchasewith the machine'spurchaseorder. This is also a good time to make sure your CAD/CAMsystem speaksyour specific machine'slanguage- in other words, that it has the correct post processor. Somecompaniesbuy equipmentwith a turn-keysolution,whichensuresthat their specificjob will run on the machineupon deliveryfrom the manufacturer.Many engineers,who in machinetool buildersemploycapableteamsof applications turn, work closelywith CAD/CAMdevelopers,Together,the teams determinethe most efficientway to machineany specificpart, basedon many factors such as; and toolingavailability. material,quantity,tolerancerequirements,

Reasonsto Use Multiaxis Machines Reduced Set Up work One important reasonto use multiaxismachinesis to reduceset-up time for parts such as those shown in Figures1-9 and 1-10. Extra custom fixturing for secondary operationsis very costly and time-consuming.Most parts can be manufacturedin one or two set-ups, eliminatingthe need for extra fixturing and time.

Figure 7-9 Example part requiring positioning multiaxis machining. Secretsof s-Axis Machining

Figure 7-7O Part requires two separate set-ups for machining. Accuracy Everytime you move a workpiecefrom one fixture to another,there is a risk of misalignment- either during the set-up itself or during operation.It is easy to build up (stacked)errors betweenmachinedsurfaceswhen they are milled in multipleset-ups.The use of indexingrotary tables, or dedicatedmultiaxis machines,as shownin Figures1-11 and 1-12, allowsprecisemovementof short, rigid, high speedcutters for the best cutting engagement.More aggressivecuts can then be taken, with higher RPMand feed rates, while the highestlevelsof accuracy are maintained.

Figurc 7-17 Dedicated dual-rotary machine set-up. Historyof s-AxisMachines

Figure 7-72 Dedicated dual-rotary machine set-up. Better Surface Finishes Usingshortertoolswill causelesstool deflection,whichwill minimizevibrationand producesmooth, precise,cuts. When using ball-nosecutters it ls recommended that the contact point be moved away from the tip of the cutter that isn't spinning. By tiltingthe tool, as shownin Figures1-13 and 1-14,the workpiececan be engagedby a desiredcutter area, which will not only improvethe surfacefinish and repeatability,but will also greatly improvetool life.

Figures 7-73 and 7-74 Machiningparts such as fhese requires simultaneous cuttino motions.

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Secretsof s-AxisMachining

Open New Possibilities some partsare impossibre to cut on a 3-axismachine.other partswourdtake too many set-upson a 3-axismachineto be profitable.Onceyour shopgets comfortable with indexingwork, you will be able to start machiningpart; suchas thosein Figures1-15, 1-16, and 1-17, usingsimurtaneous murtiaxismotions,and openyour buslnessto many new possibilities.

Figures 7-75, 7-76, and l-t7

More examples of parts that require simultaneous cutting motions.

A word of caution: Simultaneousmultiaxiswork is inevitablyJess accuratethan indexingwork becausethe machinemust be run in a loose mode with the rotary drives unlocked.It is recommended that all possibleroughingoperationsbe done by indexinqthe rotariesto optimum angles,becausethe machinein lockld mode is much more rigid.This type of work is also called2+3 machining.The two rotary axes are first positionedand locked into the optimumattack position,then a standard3-axisprogramis executed.

Historyof s-Axisl\ilachines

11

Know Your Machine Whatdo you picturewhen you see the words"standards-axismachine?,, lvany industrybuzzwordsare usedwhen describings-axismachines.Someof them include:staggeredgulde-ways,constantdynamiccontrol,digitalAC servomotors with pre-tensioned permanentpositioningmonitoringsystem,maximum ball-screws, utilizationlayout,long-termaccuracy, and so on. To simplifythings,we will say that thereare three major buildingblocksto thesetypesof machines.

The physical properties of the machine The physicalpropertiesof the machinedescribethe wav tne axes are stacked,the rigidityand flexibilityof the iron,the horsepower, torque, and maximumRPMof the spindlemotor,the qualityand workmanshipof the guides/slides, and the rotary bearings. The CNCdrive system The drivesystemis the musclesor the components that makethe machineslidesand spindlesmove.The systemincludesthe servo motors,drivesystem,ball screws,the way positioningis controlledand monitored,and the rapid-traverse and feed capabilities. CNCcontroller capabilities The controlleris the brainof the machine.Data handling,availableonboardmemorysize,and dynamicrotarysynchronization controls,are someof the thingscontrolledhere. The perfectcombination of the abovecharacteristics will builda fast, accurate,easyto-programand operate,s-axisCNCmillingmachine.lvanymanufacturers have spentmany yearstryingto come up with the perfectcombination, and as a result there are manVvariationsand solutions. The lllustrations in Figure2-1 showsomeof the varietythat existsin the machines that make up the CNCmanufacturing industry.

13

Figure 2-7 Typical arrangements of multiaxis CNCmachines.

Multiaxis Machine Configurations The arrangementsshown in Figure2-1 are all very popularconfigurations,but none of them is "standard."There is no such thing as a standardS-axis machine. First, let's establishthe definitionof an axis. Any motion controlledby the NC controller,either linear or rotationalis consideredan axis. For instance,in the iflustration in Figure2-2, both the spindleheadand the quill are capableof moving in the same direction,but are controlledby two separatecommands,Movementsof the head are controlledby Z and those of the quill by W.

TU

Figure 2-2 The spindle head and the spindle quill move along parallel axes. 14

Secretsof s-AxisMachinino

The terms multiaxisand s-axisare often usedinterchangeably and theseterms can be confusing.The widelyrecognized term in the industryis 5-axis,but it is misleadingbecauseg-axisstandardpossibilities exist - withoutaddingadditional sub-systems. In addition,a 4-axismachineis alsoconsidered to be a multiaxis machine.Despitethe title of this book,the more accurateterm multiaxiswill often oe useo. The followinglist providesthe industrystandardnomenclature for the basicg-axis designationsand directions.

XYZ are linearaxeswhereZ is alignedwith the spindleof the machine. ABC are rotary axes rotating aroundXyZ respectively. UVW are parallellinear axes along XyZ respectively.

KnowYourMachine

15

Unfortunately,different machinebuildersabide by this standardin differentways. Some buildersallow the end user to changethe machine'srotationaldirections or behavioron the fly. Third-party rotary devices,as shown in Figure2-3 and elsewhere,can be purchasedand mounted on a machinein a variety of ways, The end result of this flexibilitycan causetwo machines,of the same make and model, to have completelydifferent S-axisbehavior. Everymachineis a compromiseof some sort. Rotationaldirections,start positions, and limits, will be differentfrom one machineto another.The effectivework envelopeis greatly modifiedby changingthose variables,Some rotary axes can rotate in both directions.Some axes will choosethe rotary directionbasedon the existingposition- shortestdistanceversus clockwise(CW) or counter-clockwise (CCW).Some machinesthat are equippedwith dynamic rotary fixture offset mode will move the linear axis while rotating the rotary one basedon a rotary command. To understandthese machinescompletely,it is necessaryto look at every machine as a uniqueentity, to look under the skin and understandhow the skeletonis constructed,You need to know where all the joints are, where the rotary axes are, where the rotary zero positionsare, what makesthem move, and how the whole unit functionsin unison. Differentmanufacturersand CAD/CAMsystemshave many different namesfor the same things. Let's establishsome commonterms that will be used in this book in order to avoid assumptionsand confusion. Machine Home Position (MHP) - Most machinistsrecognizethe home position as the placeto whichall the axes movewhen you initiallyturn the machineon and selectZero return.

Figure 2-3 Machineat Home PositionX0. Y0. 20. A0. 80. 16

Secretsof s-AxisMachining

MachineRotary Zero Position (MRZP)- On multiaxismachines, machinerotary zeroshownin Figure2-4, is at the intersection of the rotary/pivoting axes.This pointmaybe unreachable by the machine.

Figure 2-4 Close-upshowing MachineRotary Zero position. lrogram Zero Position (PZP) CAMsystem.

- programZeropositionis the part datumin the

Figure 2-5 Another view showing the relationship between Machine Rotary Zero Position and program Zero position.

KnowYourMachine

17

Whensettingup/ operating/and programmingmultiaxismachinesit is essentialto maintainthe properrelationship betweenthe machinezero position(MRZp) and the programzero position(PZP). If the machinedoesnot havespecialfeaturesthen the PZP must coincidewith the MRZP. lYultiaxis millingmachinescan be organizedfurtherinto 3 major machinetypes:

Table/Table multiaxis machines execute the rotary motions by the dual rotary table, The primary rotary table carries the secondary rotary table, which in turn carries the fixture and the part. Head/Table multiaxis machines execute the rotary motions by the table, which carries the work piece, The spindle head articulates the tool with tilting motions. Head/Head multiaxis machines execute all rotary/pivotang motions by articulating the spindle head of the machine, The work piece is stationary.

Keepin mind that the focusof this book is milling,althoughthe line betweenthe mill and the latheis blurringmore and more everyyear.Thereis a new breedof multi-taskingmachinesavailablethat can do millingand turning,and thoseare calledMill/Turnmachines. Forthe sakeof simplicity,we will focusonly on multiaxismillingmachines.

Table/Table Multiaxis Milling Machines Table/Table multiaxismillingmachinescan be vefticalor horizontal.All the rotarymotionsexceptthe spindleare done by the tablesof these machines.The main rotarytable carriesa secondrotarytable,as shownin Figure2-6, to whichis fastenedthe fixtureand the Dartto be machined. Toollengthoffsetswork the sameway hereas with anv conventional 3-axis machine.The tool lengthcan be changedwithoutthe needto re-postthe NCdata. On thesemachines,the part is physicallyrotatedaroundthe tool. The machine's rotarydevicesneedto be capableof handlingthe weightof the part and the fixture,and this capabiiityis an impodantfactorwhen rapidmovementsare considered. Anothervariationis seenin Figure2-7. The examplesshownrepresentonly a smallfractionof the availableTable/Table variations.Mostof thesemachineshaveminimumand maximumrotarv limitson 18

Secretsof s-AxisMachining

oneof the rotaryaxes.somewill haveunlimitedrotary motionon the otheraxis. Someevenhavethe capabilityto spinthe work,as a lithe woutd. Table/Table machinesare the mostcommontypesof murtiaxismachines.Most peoplewill enterthe s-axisworldby purchasing-a single-or dual-rotarydeviceand boltit to their3-axismillingmachine

Figure 2-6 Simulation of a dual rotary mechanism fastened to the tabte of a standard 3-axis CNC milting machine.

Figure 2-7 A third-partyrotary mechanismfastenedto the tabteof a standard 3-axis CNCmilling machine.

KnowYourMachine

19

Figure 2-8 Third-pafty single rotary mechanism and tailstock, fastened to the table of a standard 3-axis CNC milling machine. After machiningone side of the work piece it is possibleto index the rotary unit to machinethe secondside, and so on. This type of work is called indexingor positioningwork. Some manufacturersuse specializeddual rotary mechanisms. such as the one shown in Figure2-9, which is designedfor machininginternal combustionenginecomponents.

Figure 2-9 Specializeddual rotary mechanismusedin enginemanufacture. 20

Secretsof s-Axis Machining

Dedicated Table/Table machinesare very capableof doingindexing/position ing work and are equarrycapabreof simurtaneous work. The inherentdiflerences betweenthe two are worth mentioning. The rndexing method hordsthe workpiecemuch more rigidrythan it is herdfor simultaneous machiningwork becausethe rotaryaxesare-rocked when machining. when rotatingan axis,the rotaryaxis must firsl be unrockedwith a designateJ M-code.The axis is then rotated,and it is rockedwith anotherM-Codeb-efore machiningis resumed.This sequenceallowsmachiningto be done in the machine,s most rigidstate. when usingsimurtaneous mi||ingtechniques, aI the brakesmust be disengaged, whichwill put the machinein its roosemode.Forthis reasonit is arwaysu g-ooi ideato use (when possible)indexing/position ing millingtechniques foi roujhing cuts.

Machine Rotary Zero position (MRZp) Commonly,MRZP representsthe intersectionpoint of the rwo rorary axes, althoughsometimesthe two rotaries may be offset by a specificdisfance.This distancemust coincideor be relativeto the part datum pZp (program Zero Point) of the CAMsystem. To accuratelyset up, operate,and programthesemachines,it is necessary to find the intersection of the rotarycentersof the machineaxes.some. but not ali, manufacturershave the varuesstampedon their rotary devices.However,those numbersare not to be trusted,and must be recalibrated regularly.

Finding the precise center of rotation is the foundation of accurate work.

Evensmalldiscrepancies will magnifyerrors.furtherawayfrom this machinerotary zero point.

KnowYourl\.4achine

21

Here are the steps to be taken: 1. Level the table by "zeroing" the indicator on either side of the table, as shown in Figures 2-1O and 2-11

Figures 2-7O and 2-77 Method of checking the level by dial-indicating both sides of the workholding table

Figure 2-72 Setting the dial indicator to zero before checking the level of the table.

Secretsof s-AxisMachining

2. Find the XY zero, using the dial indicator, Zero xy and A at this point, as shown in Figure 2-13,

Figure 2-73 ZeroingXY and A positionson the work-holdingtable. 3. RotateA+9O degrees and touch the OD of the table as shown in Flgure 2-t4,

Figure 2-74 After rotating the A axis through 90 degrees, touch the outside diameter of the table with the dial indicator.

KnowYourMachine

4. Rotate A-axis through 18Odegreesfrom the previous position and make sure the indicator reads zero on the other side.

Figure 2-75 After rotating the A axis through-90 degrees,touch the outside diameter of the table with the dial indicator' 5. Move the Z-axis in minus direction the radius of the rotary table and set up a gage tower. The gage tower is used to set all the tool length offsets

to z=o.

Figure 2-76 A gage tower is built to represent the MRZPto allow tool length offsetsto be set. 24

Secretsof s-AxisMachining

This location is the machine's rotary zero position (MRzp), as illustrated in Figure 2-17,

Figure 2-77 The rotary zero position of the machine, as establishedby the outlined procedure. Note that the intersectionof the dual rotary center lines is abovethe table in the examplegiven.This locationwill be differentfor every machine,even from the same manufacturer.It is imperativethat this positionbe checkedregularry, especially aftera heavyworkloador a crash,Smallmisalignments can causeiarqe errors becausethe tool positionis measuredfrom this intersectionpoint. All the Active coordinate systems also referredto as Nesting positions or Locaf Coordinate Systems, for example G54 - Sg, are relativeto the Machine Rotary zero Point (MRZP) position.It is good practiceto set one of the nesting positionshere, so that it will be capturedin the Registry allowingit to be recalle-d quickly,usingMDI (Manual Data Input). F o re x a m p l ec: 9 0 c 5 4 x 0 . y 0 . A 0 . c 0 .

The PZP(Program Zero point) of the CAMsystemsmustbe set exac v to the MachineRotary Zero point, as seenin Fiqure2-19.

Know Your Machine

Figure 2-78 Relationshipbetween the MRZPand the PZP. Some CAMsystemscall this positionthe World Zero, Master Zero, or the Origin. The main thing to remember is to draw the part in the same specificposition relativeto this World Zero as it sits on the machine,relativeto Machine Rotary Zero Point.

Nesting Positions Nestingpositionsare widely used for positioningwork. These positions,shown in Figure2-19, are temporaryActive Coordinate Systems and are typically set in relationto different faces of the part or fixture face, tooling ball, or dowel pin.

Figure 2-19 Sketchshowingsomeofthe many localcoordinatesystemsusedin CNCprogramming. Secretsof s-AxisMachining

The advantageof using these Locar.coordinate systems is that you can easiry followthe programon the controller,s displaysc.eenbecausethe absojute valuesshown there will reflectthe valuesrelativeto each locally-nestedposition. Z+1.000,for examplewill be 1.000(inch)abovethe part face. Despitethe fact that cAM systemsa use different naming conventionsfor their coordinatesystems/they alr handrethe rocarcoordinatesystemin a simirarway. Some.ofthe names used by_CAD/CAMsystems include:p'art Datum, Active Coordinate System, Local Coordinate System, System View, and Tool plane with an Origin. The disadvantageof using a number of different rocarcoordinatesystems is the potentiarfor misarignment when pickingup thesepositionsmanuairywith a dial indicator.Many programmersus_eonly _onecoordinatesystem for S_axiswortA

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Figure 7-4 Verticat s-axis machine with a dual, rotary, nutating table' The machinein Figure7-4 is a dedicateds-axis Table/Table vertical machining ."nt"r- f,lot" the rigid machinebase. Such a machinecan handle heavy work with Drecisionand confidence'

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Secretsof s-AxisMachining

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Figure 7-S Vertical s-axis machine with a trunnion-type dual rotary table. Trunnion-typedual rotary configurations,as shown in Figure7-5, are very popular in the industry.This may be becausethey are competitivelypricedand easy to set up and ooerate,

MachineSimulation'l'l'l

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Figure 7-6 Vertical s-axis machine with a dedicateddual rotary table. Figure7-6 showsanotherexampleof a sturdy,dual-rotary,s-axisvertical machining center. Thismachine alsohasthe abilityto spinthe C-axisas a spindle, allowing for turningworkto be done.

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Secretsof s-AxisMachinino

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Figure 7-7 Horizontal/vertical s-axis Head/Table machining center. The machinein Figure7-7 is calledVH - Verticaland Horizontal.It is a s-axis Head/Table machine,and its design allowsfor exceptionalflexibility in additionto formidablerigidity.

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Figure 7-8 Vertical s-axis Head/Table machining center. The vertical S-axis,Head/Table machinein Figure7-8 providesan amazing combinationof speedand precision.

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Figurc 7-9 Vertical s-axis profiler, with a dual rotary head. Many manufacturersoffer variationson the type of Head/Head configuration shown in Figurc7-9, commonlyknown as a profiler.Typicallythese machineshave limited rotary range combinedwith long bed travel.

Machine Simulation 115

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Figure 7-7O Vertical s-axis laser machine, with a dual rotary head. The verticals-axis machineshownin Figure7-10 is usedfor laser-machining, but this kind of Head/Head configurationis also very popularfor milling and water-jet machining.

Machine Simulation Interfaces A GUI (GraphicalUser Interface), or form of text file, can be used to build virtual machines.With such a program, models,or whole componentbranches,can be manipulatedindividually. For example,the virtualmachinecan be usedto translate,rotate, or set dependencies,translucencies,or reflectivity. Oncethe virtualmachineis built,all its axescan be movedindividually with MDI (ManualData Input) commands,or slider bars, to check if the correct modelsare assignedto the correct axes. Thesecommandscan also be used to check if the positiveand negativemotions are correct. Rememberthat all simulationsoftware is uselessif it is not emulatingthe movementsof the real machine.The models representingthe real machinemust be accuratein relationto the businessend of the machine.This area is nearthe work envelopeand includesthe spindle, fixturing, and rotary devices. Oncethe physicalmodel of the machineis built, the virtual controllermust be configured.In a CAMsystem this work is done with the post processor.In Vericut, configurationis achievedwith a reversepost processor.This configurationprocess is criticalin emulatinothe behaviorof the real machines. 116

Secretsof s-AxisMachining

Using MachineSimulation Thesedays, very few peopleprogram exclusivelyby hand. Most peopleuse a CAD/ CAlvlsystem to generatecode.The palt is typicallyeither designedor imported, and then toolpathsare generatedusingtoolsfrom an internalor an external library.Machinesimulationcan be run at any time duringor at the end of this process,providedthe groundworkhas beenlaid down and the machineshavebeen b uilt. The processof settingup machinesimulationis very similarto settingup a real machine.The part must be placedon the machinein the correctorientationand then the Local Coordinate System needsto be set relativeto the Machine Rotary Zero Position. The tools then need to be loadedinto the magazineand the Tool Length Offsets must be set correctly.This work can be time-consuming if there is no direct interfacebetweenthe CAD/CAMand the simulationprograms. If there is a well-configuredinterface,or if the simulationis an intricate part of the CAD/CAM, then settingup will take only a few secondsof processing time. NativeCAD/CAMsimulationloadstools from its libraries.Vericutuses its own tool managerfor it will builda tool libraryautomatically if it is integratedwith a CAM system.Oncethe part, tools,and toolpathsare loaded,the simulationis ready to be run, eitheras singleblocks,or continuously. The simulationcan be slowed down or sped,and the modelcan be dynamicallyrotated.Somesystemsallow movementsforward or backwardat any time, but others don't offer this option. Somesystemswill show materialremovalwith simulation,and somewill permit analysisand measurementof the virtualpart. Mostsystemswill signalif there is a near-missor collisionbetweenany configuredcomponents. They will also display an alarm if the limit switchesare hit by over-travelling on any of the motionaxes. Operatorsare ableto see throughmodelsby makingthem invisible,whichallows examinationof the cuttingprocessin waysthat are not possibleon a real machine. Thereare many benefitsto machinesimulation,whichallowsdifferentideasto be tested out without pressure.Estimatedprogram cycletimes can be accessed,to helpdeterminethe bestone. Crashinga machineon the computerscreenis not a big concern,whereascrashinga real one is a catastrophe. But not usinga multiaxis machineto its full Dotentialis a shame.Simulationallowsthe best ideasfrom different cutting strategies,and the most efficientmotion for any specificmachine to be combined.

The processof setting up machinesimulationis very similar to setting up a real machine.The part must be placedon the machinein the correct orientationand then the Local Coordinate System needsto be set relative to the Machine Rotary Zero Position.

l\ilachine Simulation

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SelectingThe Right Machine For Your Application Makinga multiaxisequipmentchoicedecisionis similarto choosinga car make and model.The decisionneedsto be basedon the intendeduse, budget,and personality, alongwith many other considerations. The multiaxis\\garage"includes the equivalents of racecars,all-terrainvehicles,buses,and luxuryvehicles.There are general-purpose machinesand there are machinesmadefor specificapplications. This chapter may help narrow the searchbasedon the specificparts being manufactured. Mostsmallshopsenterthe multiaxisarenaby addinga single-or dual-rotaryunit to their existing3-axisverticalmachiningcenter.The additionof the single-or dualrotary unit allows pafts to be manufacturedmore quickly and makes it possibleto machinemore complexpartsthat were previouslyout of reach.Thisadvancemay causea chain reaction.When shops get better at producingcomplexparts, they start to chargemore for those parts. They then seek out even more challengingwork to make more money.In turn, these ventureswill stretch the limits of capabilityof the equipment,promptingconsideration of purchasing more new equipment. The availablebudgetis alwaysthe big consideration. The priceof any machinewill reflect its quality, but as with cars, the price may also be affectedby the name brand. However,budgetaryconsiderationsare outsidethe scopeof this book. Machinemanufacturers spenda great deal of time developingmachines.They also spendtime on their salesand marketingefforts. Reputablemanufacturershave applications teamswho installnew equipment,train new customers,and provide ongoingtechnicalsuppoft.They alsoemploydedicatedapplications specialists who can preparebenchmarks,or turnkey solutions,for prospectsand customers. Regardlessof the specificmachinetype under consideration,it is smart to research the reputationearned by the support servicesprovidedby different manufacturers. MostCNCequipmentis sold by a dealernetwork.Not all dealerswill maintain the same quality of service.It is wise to visit local shopsthat have different CNCequipmentand talk to them abouttheir experiences. Ask them how their equipmentis performing,what the serviceis like when there is a problem,and if the manufacturerprovidedgoodtraining.It may also be wiseto ask if the suppliers deliveredon all their Dromises.

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tr criteria,and then take a Selecta machinemanufacturerthat suitsthe applications good look at the variety of pafts currently being manufacturedin your plant. Also considerthe partsyou intendto manufacturein the future.Considerthe following scenarios. How many parts are typically run after each set-up? If your shop produces500,000of the same parts per year,it would be wiseto look for a dedicatedmachineor machinesto producethat part. Investigatethe possibility of a turnkeysolutionfrom the machinebuilder.Sucha solutionmay includea completemachiningcell,possiblywith multitaskingmachinesand roboticloaders. Does your shop/company thrive on challenging jobs and have a reputation for producing complex work? Some shoos like to take on work that others considerto be too difficult.These companieslearn from every challengeand becomebetter and better with every job. Takingon difficultjobs may be risky, but it can pay great dividends.Before contracting for suchdemandingjobs, ensurethat your multiaxisequipmentis precise, flexible, and adaptableenoughfor the challenge. Are your existing CNC machines waiting for programs, or are your CNC programmers waiting for a free machine? If existingequipmentsits idle waiting for programs,then the workflow,CAD/ CAMsystem capability,and programmers'andoperators'proficienciesneed to be If programmersare waitingfor free machines,it is againa good idea scrutinized. to checkthe CAD/CAMsystem'scapability.Couldthe cutting strategy be improved? Are the right tools beingused?Imaginerunningold style high-speedsteeltools on a modernCNCmachinecapableof 40,000 RPMand 1500 IPM - the limitationsof cheaptoolingcouldhold backa very capableand very expensivemachine.In the same way, if your CAD/CAMsystem is obsolete,you won't be able to use your CNC equipmentto its full potential. Are you happy with the performance of your CAD/CAM system, and are you using it to its full potential? Makesure that your CNCprogrammers are up-to-datewith their trainingon your CAD/CAMsystem to ensure it is being used to its full potential.It is much cheaper and easierto get organized,trained, becomeefficient,and promote teamwork, than it is to buy a brandnew machineand put it into production. Is your shop/company dedicated to a single manufacturing field, for instance automotive, aerospace, mold & die, medical or oil? field you are workingin will alsoaffectyour choiceof machine The manufacturing type. There are differenttorque, speed,and precisionrequirementsin every field.

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New Possibilities After determiningthat your shop is runningfull out and needsadditional equipment,it is time to considernew possibilities. The first obvious consideration is the physicalsizeof the machine,and that is dictatedsimply by the sizeof the partsthat will be machinedand the sizeof your shopfloor. The next consideration is the materialthat will be used,whichwiil determine the rigidityneeded.The qualityrequirements of the machinewill be affected by the expectedtolerancesyou want to hold, and budgetaryrestraintsmust also be kept in mind. Asidefrom theseproperties,keepin mind that some multiaxisequipment is better suited for certain types of work than others,

Head/Head Machines (with long X- or Y-axis linear travel, but limited rotary axis travel) The manufactureof airplanewingsand fuselagepanelsis a goodfit for Head/ Head machines.The panelsare designedfor strength,but are kept as light as possible. Thereare severaltapered-wallpocketingmachinesthat are perfectly suitedfor swarf-typetoolpaths.Typicallythesepartsare madefrom solidbilletst n two set-ups,as shownin FigureB-1.

Figure 8-7 A vertical mill set-up for machining an aerospacepanel. SelectingThe RightMachineFor YourApplication

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An airplanewing stringeris a goodexampleof a part that is long,but very slim. Partslike this are typically machinedfrom specialextrusions,which can be over parts likethesewere madeon machinessimilarto the ones 40 feet long.Typically, shownin Figures8-2 and 8-3, usingmultipleset-upsand elaboratefixturing.

Figure 8-2 Gantry-type Head/Head machine.

Figure 8-3 Bridge-type Head/Head machine. The Dartswould tend to deform betweenset-ups becausematerialwould be removedunevenly,first from one side, then from the other, in a secondsetup,The machineshownin Figure8-4 solvesthis problem.

Secretsof s-AxisMachining

Figure 8-4 Dedicated extrusion milling machine. The machinein Figure8-4 is well suitedfor machininglong extrusions.It is a s-axis machinewith X, U, Y, Z and A-axes.The U-axismoves parallelwith the X-axisand it has two sets of rotary jaws that are usedto clamp and traversethe extrusionpast the cutting tool. Cutting takes place in a narrow but rigid corridor in successivesections,The overall lengthsof the parts are limited only by the support systemsat eitherside of the machine.

Head/Table Machines (with long X-axis travel) Long parts, similar to the examplesshown in Figure8-5, requiresevererotary motions in the primary axis and limited rotary motions in the secondarvaxis.

Figure 8-5 Typicalrotary parts. SelectingThe RightMachineForYourApplication

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These Dartswould be best manufacturedon the Head/Table machine configurationshown in Figure8-6.

Figure 8-6 Head/Table type milling machine' The rotary pivotingconfigurationshown in Figure8-6 is very suitablefor manufacturinglong rotary parts. The weight of the part is supportedby a tail stock, and the part is rotated around its center of mass. Ineftia is an important for when usingmultiaxismachines'Considerthe configuration consideration in machine the differences porting and imagine in Figure 8-7, shown engine head movementswhen comparedwith Figure8-8.

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Secretsof s-AxisMachining

Figure 8-7 Head/Table engine head-port milling.

Figure 8-8 Dedicated Table/Table port milling dual rotary attachment.

SelectingThe Right MachineFor YourApplication

125

The machinepicturedin Figure8-7 is designedto rotate the head around its center unwantedcenfrifugalforces' The machinein Figure8-8 of mass without generating "nock-and-Roll" dual-rotarydevice.It is designedespecially nas sometningcitted a for machining-portson engine heads.The entire fixture holdingthe part is rocked una |.ori"athioughout thelutting processto presentthe work to the cutter.These fixtures need to be carefullybalancedto ensuresmooth motion'

Head/Table Machines

suchas thoseshownin Figures8-9, 8-10' and 8-11' are Head/Table configurations urnon6tn" most virsatile choicesfor a variety of other multiaxisapplications.This ""rr"t]f ii'l"ri"es from the fact that the steady rest can easily be removedand the spa."canbeusedformountingadditiona|fiXtures.CustomizedfiXturescana|sobe built to suit specialjobs.

Figures 8'9.and 8-7O Additionat versatility using multiple fixtures'

Figure 8-77 Machining an auger feed spira! for an injection molding machine' 126

Secretsoi s-AxisMachining

Figure 8-72 Machining a rotary windmill unit.

Figure 8-73 An impeller. Figures8-12 and 8-13 representexamplesof veftical machineswith long X-axis travels,but Head/Table machinesare built in many forms and shapes.

SelectingThe RightMachineForYourAppllcation

127

Rotary Table- Tilting Head Combinations Theexampleshownin Figure8-14 blursthe linesomewhatbetweenthe vertical and horizontaldefinitions.

Figure 8-74 This Head/Table machine is available in both vertical and horizontal configurations, The rotary-tableand tilting-headconfigurationsshown in Figures8-15 through 8-18 are not suitablefor long parts, but can readily be adaptedfor a variety of multiaxisapplications.

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Secretsof s-AxisMachining

Figures 8-75 and 8-76 Head/Table aerospacetand Head/Table automotive applications.

Figures 8-77 and 8-78 Two Nutating Head/Table configurations. SelectingThe Right Machine For YourApplication

129

All rotary-table,tilting-headmachinestend to rotate the workpiecesaround their centersof mass while maintainingthe capabilityto reachall their featuresby tilting the head.Thesemachinesare built in many sizesand are widelyusedin many different industries,from manufacturingsmall medicalparts (Figure8-19) where precisionand speedare the main requirements.to manufacturinglarge earthmovingequipmentparts (Figure8-20), whererigidityand horsepower are the focus.

Figures 8-79 and 8-2O Typical medical part, and heavy equipment component manufacturing. In the mold and die industry,most of the roughingoperationsare done on 3-axis, verticalor horizontalmachiningcenters.In this manufacturing field,one of the challenges is cuttingdeep cavitiesor tall cores,The deep cavitiesare designed with steepsidewalls,usuallyat anglesof 1 or 2 degrees,and often requireuneven floors with small fillets along the intersectionof the wall and floor surfaces,as shownin Figure8-21. Cuttingthesefilletson a 3-axismachinewould requirelong, ball-nosecutters. Small steps need to be taken, causinglong cycletimes. The tool is often deflectedby the high cutting forces,causingvibration, excessivecutter weaq and poorsurfacefinish.

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Figure 8-27 Typical plastics-mold cavity. Usinga s-axis machineallowstapered ball-nosecutters to be used for this work. The taperedconfigurationmakes the ball-nosetool much more rigid for the same diameter,and the ability to tilt the tool also allows use of a shorter cuttet as shown in Figure8-22. More aggressivecuts can then be taken, shorteningthe cycletime. Deflectionof the rigid tool is less, and vibration is eliminateddue to the reduced deflection.Tool life is increased,and a precise.good-qualitysurfacefinish is achieved.

Figure 8-22 Multiaxis machining allows for the use of shorter, tapered cutters, SelectingThe RightMachineForYourApplication

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Table/Table Machines Figures8-23 and 8-24 show the most commonconfigurationsof Table/Table machines,The partsto be machinedare clampedto a dual-rotarytable and are rotated around the tool, Inertia is a consideration.The dual-rotarytable is either mounted on the machinetable or is a dedicateddual-rotarycomponentof the machine.These machinesare not suited for manufacturinglong parts' The work envelopeis fairly limited, especiallywhen some tool changerlimitationsare considered,Despitethe limitations,this configurationis very popular.

Figure 8-23 A populartrunniontype setup.

Figure 8-24 A dual rotary "rock and roll" fixture. 132

Secretsof s-AxisMachining

Table-mountedunits are not completelyrigid, but dedicateddual rotariescan be both agile and rigid. They are equally well suited for 3+2 indexingwork, and for simultaneousmultiaxiswork. Some applicationsare shown in Figures8-25 through 8-28.

Figures 8-25 and 8-25 Machiningan aerospace bracket, and a fixture component.

Figures 8-27 and 8-28 Machining rotor blades, and machining a medical comDonent.

SelectingThe Right MachineFor YourApplication

I,5J

Gantry Type Head/Head Machines cantry type Head/Head machines,as shown in Figure8-29, arc used for large parts, mostly in the aerospace,oil, and wood industries,This configurationpermits long lineartravels.Some machinesare designedto allowchangesof heads in additionto tools. Rigidityand precisionmay not be the strong suit of these machines,but long reach capabilityis.

Figure 8-29

Water-jet/milling combination machine.

Some more machinevariationsare shown in Figures8-30 through 8-33. However' it is impossibleto describeall the different machineconfigurationsthat are available,especiallybecausethis is a constantlyevolvingfield.

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Figure 8-3O A s-axis laser cuttinq machine.

Figure 8-37 This machine presentsa good compromise between lonq reach and rioiditv.

SelectingThe Right MachineFor YourApptication

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Figures 8-32 and 8-33 A 6-axisindustrialrobot, and a 7-axisindustrialrobot. Thischapterhasonly coveredthe mostpopulardesigns,and somesuggested spend It is recommended that engineers applications basedon experience. sometime on initialresearchwhenchoosinga machine,researchnot only of the machine, but alsothe intended use.

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Choosinga CAD/CAMSystem For Your Application Choosingthe appropriateCAD/CAMsystem is as important, if not more important, than choosingthe most suitablemultiaxismachine.Thereare many specialized machinesthat are dedicatedto specifictypes of work, howeverone CAD/CAMsystem will driveall the CNCequipmentin the shoD. It is importantto make sure that the selectedsystem can handlenot only all the differenttypes of work the shop does now, but will also be capableof taking on futurechallenges. CAD (ComputerAided Design)/CAM(ComputerAided Manufacturing)is always referredto as one combinedsystem becausemost CAD/CAMsystemsoffer both designand manufacturingcapabilities.Be aware, however,that very few excel in both CADand CAM. Systemswith heavy CAD emphasishave their roots in CAD and are better at solid modelingso that they can handle large assemblieswith ease.Thesesystems have associativitybetweenall the componentsso that when a changeis made to one feature on one part in an assembly,it will propagatethroughoutthe entire assembly. Thesesystemsare very good at managingCAD data, but their CAMcapabilitymay have been added later and it often does not have the same deDth. Systemswith heavy CAMemphasisare good at everythingrelatedto toolpath creation,from simple2D drilling,contouring,and pocketingto multi-surface and multiaxismachining.Toolpathscan be generatedfor all kindsof CNCequipment includingwire- and other- EDM,water-jets, lasers,lathes, mills, and multitasking machines.These systemshave intelligenttool librarieswith associatedfeeds and speedsfor different materialsand cutter types. Instead of heavy CADcapability, these systemsare very good at importing CADdata from any system, with the main goal of generatinga toolpath from that data.

Special Purpose Software Many specializedCAD/CAMsystems have been designedfor specificpurposes.For example,some shops in the mold and die industry use CAMsvstemsthat have virtually no CADcapability,but they can import large, complex,multisurfacefiles quickly.The user only needsto choosethe tools and selectfrom a short list of

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A toolpathis soongenerated,posted,and readyautomatedcuttingstrategies. changes to-go.The trade-offfor this speedand easeis realizedwhen engineering are necessary,Those changesneed to be made on a separateCAD system and imported back into the CAMsoftware.Also, these specializedCAIYsystemswill not suppoftany other kind of CNCmachines(lathe,EDM,plasma,waterjet,etc,) and many won't even supportsimplecontour,drill, or pocketroutines.Thistype of specialpurposeCAMsoftwareonly makessensefor shopsthat are machining to purchasea separate largemold cavitiesday in and day out. It may be necessary programmingseat of CAD,and maybeeven anotherseat of generalpurposeCAl4. Softwarethat can dynamicallychangethe feedratethroughoutthe cutting process is anothergood exampleof a specialized CAMfeature.Thisfeaturemimicsan operatorstandingat the machineand overridingthe programmedfeedratesby manuallymanipulating the feedrateoverridedial. In mold and die manufacturing, largeamountsof materialneedto be removed.The topographyof multisurface moldsis often so complexthat it is impossible to maintaina constantstep-over,or even a constantdepth of cut. Cuttingforceson the tool vary greatlythroughoutthe processof machininglargemoldsand dies,and the work can take hours,days,and to standby the machineand anticipateevery evenweeks.It would be impossible motion of the axes, and overridethe correspondingfeedrates,but with feedrate This optimizationtakes optimization, the softwarewill vary the rate automatically. place before any cutting is done, basedon constantsfor volume removal rate, chipload, surfacespeed, and other factors. Feedrateoptimizationproducesconstant cutting forcesthat are designedto lengthentool life, increaseaccuracy,and shoftencycletime. dramatically Softwarethat is specificallydesignedto generatetoolpathsfor lathes is one more CAD/CAM. ThissoftwareofferslimitedCADcapabilityand exampleof specialized only turning-specifictoolpaths.The softwareis often built in to the controllers on certainmachines,and only generatestoolpathsspecificto that machine's conversationallanguage.With this type of softwarethere is no need for a post processor.The approachis very direct, and that can be an advantage.Howevet it can also be a disadvantage becausethesetoolpathscannotbe transferredto any other machines.Grinders,lasers,water-jets,plasmacutters,and other specialized machinescan all operatein this samefashion. In additionto CAD/CAMsystems,othertoolsare availablethat can closethe loop Simulationsoftwarepackagescan help check betweendesignand manufacturing. generated the results by CAMsoftware,and are a very importantlink and optimize betweenthe virtualand physicalworlds.Ensuringthat toolpathsare bulletproof in the virtualworld will savethe shoptime and moneyin the long run. Thesetools shouldnot be overlookedwhen the shoo is beinooutfittedfor multiaxiswork.

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CAD/CAM Toolbox Buyinga CAD/CAN4 system is like buying a fully stockedtoolbox, but care must be takento ensurethat it containsthe right toolsfor the job. All tradesmenhave their own ideaof the perfectset of tools.A perfectset of sharp,high-qualitychisels wouldbe uselessto an electrician. At the sametime, it would be cumbersometo usea SwissArmy knifeas a screwdriverall day long. Very few CAD/CAMsystems can do everythingwell. They all have their strengths and weaknesses. On the other hand,very few companiesneedall the power affordedto them by a modern CAD/CAMsoftwaresystem.The trick is findinq the right balance. Some CAD/CAMcompaniesprovidefor the capabilitiesof their softwareto be increased as the companygrowsand demandsmore functionaiitv. Mostfirst time CAD/CAI4userswill start off with softwarethat can perform only simple 2D drilling, contouring,and pocketingtoolpaths.Oncethe users becomeproficient,they can take on more complex,3D, multi-surface machining,or multiaxis3+2 indexing work. Fromthat point,userscan move into complex,simultaneous, multiaxis milling,or evenoperationof multi-taskingmilling/turning machines.

Multiaxis CAD/CAMConsiderations Multiaxismanufacturingrequiressoftwarethat is very strong in CAlv.CAD capabllityis needed,but mostlyto import CADfilesfrom all the major CAD systems,in all the popularCADdata formats.On top of that requirement, additionalCADcapabilityis neededto createsuppoftinggeometryfor tool axis control,fixturedesign,or virtualmachinebuilding. High-endCAD/CAMsystemsare fully associative. If a designchangeis made,the changewill propagatethroughthe entiredatabaseand will modifythe necessary movementsin the toolpath.This featureis helpfulif one softwarepackageis used for the entiredesign-to-manufacturingprocess.If a single,all-encom passing packageis not used, then extra cost is being incurredfor associativitythat cannot be used. Unfortunately,most geometry associativityonly works with native geometry. Most multiaxisshops import files from a variety of customers.Thesefiles could havebeendesignedin any numberof CADsystems,so it is crucialto be able to readand write in multipleCAD/CAMlanguages. Oncethe modelis imported,it is criticalto havegoodanalysistoolsto analyzeit and then separateits major featuresinto organizedlayersor levels. After the modelhas beenanalyzedand organized,someadditionalgeometry creationmay be needed.This geometrycouldincludeadditionalwireframe,edge curves,lines,arcs,points,non-trimmingsurfaces,or evensomesolidmodel creation.This work will requirelight-dutyCADcapability.

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Multiaxis CAM The categoryof 3+2 indexingwork requiresthe ability to quicklyand easilychange the work planes,which are alwaysperpendicularto the spindle/toolaxis. The creationand manipulationof these work planes,also known as Active Coordinate Systems, should be intuitive and easy-to-use'Some systemswork interactively by allowingthe user to simply pick a solid face, an arc, two lines,three points, and such. to definethe orientationof a new Active Coordinate System. This selection is a light-duty capabilityfor most CAMsoftware. Heavy-dutyCAMcapabilityis neededfor tacklingsimultaneousmultiaxis applications.This capabilityhas to be a delicatebalancebetweencontrol,flexibility, and ease of use, A shotgun approachdoesn't work well here - the precisionof a rifle is needed. consider mold and die work as an example.This work is one of the most demandingand accuratefields in manufacturing.Moldscannot be mass-produced but are made one or two at a time, and they have predictablefeatures,either a core, or a cavity,or a little of both. A good 3-axis roughingstrategy will always work well here. Some CAMsystemscan quickly and automaticallyanalyzethe featuresand then automaticallygeneratea toolpath to machinethem' In this shotgun approach,a wide field of targets can be coveredwith one shot. Precisecontrol is neededwhen it comes to driving simultaneousmultiaxis machines.The followingis a list of must-havetools from a well-rounded,multiaxis, CAMsoftwaretoolbox. Pleaserefer to Chapter6 for detailedexamples. Cut Pattern Control It is important to have a variety of ways to define and control the pattern that will be followed by the cutting tool. These patterns can be anythingfrom a simple wireframeto complexsurfacepatternssuch as that shown in Figure 9-1.

Figure 9-7 Spiraling cut pattern on a turbine blade. 140

Secretsof s-AxisMachining

Tool Axis Control Toolaxis control providesthe ability to set and manipulatethe center axis alignmentof the tool duringthe cuttingprocess,as illustratedin Figure9-2. Thesecontrolscan be dynamic or static, but it is essentialthat they work in a predictable,stable way.

Figure 9-2 Positions of tool axis controlled by lines. Tool Tip Control The tool tip control targets the precisearea of the tool tip's engagementwith the part, as shownin Figure9-3.

Figure 9-3 Tool tip compensated to follow the outer surfaces of the work. Choosinga CAD/CAMSystem For YourApplication

141

Collision Avoidance Measures Care must be taken to avoid potentialcollisionsbetweenmoving components/ and betweenmoving and stationarymachinepads when multiaxistoolpaths are being generated,As illustratedin Figure9-4, this particularcontrol focuses on meansto avoid collisions,particularlybetweenthe cutter,arbor, holder,and the workDiecefixture assembly.

Figure 9-4 Dynamic shank collision avoidance. Stock Recognition Roughing Strategies duringroughingwill savetime. Illustratedin Figure9-5, Stockrecognition stock recognitiontrims the toolpath to the stock size.This stock can be the initial CAD data or the in-processmaterialcreated by previousmilling operations.Multiaxisroughingcan be a time-consumingaffair and this feature is a must-havein creatingefficientroughingtoolpaths.

Figure 9-5 Plungeroughing,usingstock recognition.

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Machine Simulation Machinesimulationeliminatesthe guessworkand the needto prove-outnew machiningprocesseson real machines,Usinga real machineto prove-outa toolpath wastesvaluableproductiontime and risks potentialcollisions.Userfriendly and powerfulvirtual machinesimulations,as shown in Figure9-6, can improve productivitytremendously,but care must be taken to configurethem properlyfor each machine.Pleaserefer to Chapter7 for detailedexamples.

Figure 9-6 Properly configured virtual s-axis machines emulate the movements of real machines, Post Processor A good post processor is the most important part of any multiaxis CAD/CAM software. Without post processing,parts can be cut only in the virtual world and not on real machines.The role of anv CAMsoftwareis to generatecode that will drive the movementsof the axes on a CNCmachineso that a part can be machined,The native CAMlanguagemust be translatedto matchwith eachmachinet specificlanguage.Customized multiaxispostsare usuallyan extra charge,It is importantto find out if they are availablefor each specificmachineand how much they will cost. A professionalpost processoris usuallydeliveredwith supportingdocumentationthat explainsits featuresand all the availableswitchesto activatethem. CAMsoftwaretypicallycomes with a set of genericpost processors,which are user-configurable. Ask if postdevelopmenttrainingis available.

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Multiaxis CAD/CAM Training that Becauseof the complexityof multiaxismachining,it is not recommended multiaxisprogrammersbe self-taught.Trainingis a very important part of getting the most out of the softwarepurchase,and the best training is hands-on throughoutthe entire process.Trainingshould includeimportinggeometry,creating and simulatingthesetoolpathson a virtualmachine, toolpaths,post processing, Thesesteps representhalf the job. The next step is to learn how to set up a real machine,find the machine'sRotary zero Point, set the tool locations,load the toolpath into the machine'scontrollel and then cut the real part. Nothingcan replacethe feeling of excitementassociatedwith running a new programon a real machine. It is essentialto find out if this kind of programmingtraining is offered by the CAD/CAMcompanythat respondsto your requestto quote. Many programmers take three- to five-day,cannedtraining courses,which use pre-arrangedtraining sessionsand step-by-stepinstructions.It is possibleto completethese training coursesby simplyfollowingthe carefullylaid-outsteps,but there is no requirement for the user to retain any insight into why they are followingthose steps.These user/traineeswill get back to work and not know where to start. Very specific questionsneed to be asked about the training optionsoffered. On-linetrainingcoursesare alsoan option.Someof thesecoursesare very good, offering narratedvideos, and hands-ontraining sessions.The appealof these coursesis that users can take them at home at their convenience. CAD/CAMcompaniesalso offer on-site training,This arrangementensuresthat the focus is on the operationand the parts for which the programswill be used. The Caremust be takento stay on course dangerwith on-sitetrainingis interruptions. at all times. companyshouldprovide What happensafter training?The chosenCAD/CAM applicationssupport after training is complete.It is very helpfulto have that support availableas a safety net for at least the first few jobs. How about update training?As mentionedearlier,CAD/CAMsoftwareis constantly evolving,and it is important to keep up with these changesby attending periodic updatetrainingsessions.Userforumsare alsoa very goodway of keepingup with changesand a good way to exchangeideaswith peers.

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Behind the Scenes: CAD/CAMSoftware Development The softwarethat is ultimately chosenwill have a profoundeffect on the business. Not only will the shopget the softwarefunctionality to run its machines,it will also be allying itself with a companythat can provideyears of experienceand invaluable support.Considerable thoughtshouldbe givento the companybehind the software.A well-established,reputable,companycan becomea valuableasset and partnerto the operation. Understandingthe developmentcycle of modern CAD/CAN4 systemscan be helpful when softwarecompaniesare being researched.The followingbehind-the-scenes look at the developmentcyclewill illustratewhy it is importantto selecta large, well-esta blishedcompanyas opposedto a fly-by-nightbusiness. CAD/CAMdevelopmentis a very dynamic process.A successfulCAD/CAMcompany consistsof many teamsof individuals workingtowardthe samecommongoal.The individualsall strive to make powerful,flexible,and user-friendlysoftwarefor the end-user.This task is difficult becausethe more adaptiveand powerfulthe software is, the more complex it becomes.Complexityand ease-of-useoften conflictwith each other,and writers of good softwarestrive to find a balancebetweenthe two. Imaginationis a very important and fundamentalpart of CAD/CAMdevelopment, but it can be tricky becauseit must be tempered with todayt (and tomorrow,s) hardwarelimitations.Theoreticalpossibilitiesare always restrictedbV current hardwarelimitations.CAD/CAMdesignis a long-term,ongoingproject,and hardwareadvancesmust be correctlyanticipatedand implementedinto the software. Softwaredevelopmentplanningis done by mixedgroupsof individuals who includesoftwareengineers,mechanical engineers,applications engineers,sales, and marketingpeople.Thesegroupsare also heavilyinfluencedby feedbackfrom existing users. Existingusers help these groups make up the "wish list,,of new tools, as well as the recommendedimprovementsslotted for the next software release.The softwaredeveloperstake a close look at the.'wish list.,and determine what can be done,when,and how. Oncethe softwaredevelopmentteam has producedthe first usableproduct, they will make it availableto the rest of their teams,includingqualitycontrol, applications, and post development. All thesegroupswill conducttheir own usabilitytests and providefeedback.The developerswill use this feedbackto fix bugs,improvethe interaction, and make performance enhancements. This cvcleis repeatedcontinuously, until a stable,predictable, user-friendly Betaversionofthe softwareis created. The Betaversionis distributedto a specialgroupof end-userswho will conduct their own tests. At the same time, the softwaremanufacturer,sapDlications departmentwill conduct more tests by cutting real parts on real machines.

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Throughoutthis developmentprocess,everythingis carefullydocumented. groupwritesHelpfiles,and trainingmanualsare The technicaldocumentation developedand tested for each product. process, At the very end of this planning,development, testing,and documentation a new versionof the softwareis launchedand monitoredat every step. At that point,a dedicatedtechnicalsupportteam is readyto assistcustomerswith any issuesthat may a rise. But this point is not the end of the developmentprocess.The planninggroupkeeps on dreamingand makingnew plans.The softwaredevelopment team staysbusy workingon those plans,and so on. A goodsoftwarecompanyhas largeteams in orderto be ableto continuallydevelopnew and improved of professionals softwaretools.The work is neverdone becauseit is literallyon the leadingedge of technology.

General Guidelines for Researching CAD/CAM Software Start CAD/CAMresearchonline.This approachcan be a greatway to comparethe featuresand benefitsof severaldifferentsoftwarepackages.Many sites include demo video files, which can providea good feel for the software'sinterfaceand will often illustratethe software'snewestfeatures.The web site will also indicate detailsof any localresellerin your area. Conversations with peersor with companieswith whom the shopwill work are usefulto learn what kind of softwarethey are using and why. Ask peopleif they are happywith the localsupport,and was the softwareeasyor hardto learn?Can filesfrom outsidesourcesbe importedand exportedeasily?Werethere any hidden costs?Is the local resellerreDutable?Wouldthev recommendthe softwarethev are using? Visitsto tradeshowsare stronglyrecommended. Tradeshow demonstrations are short and are gearedto show off the latest hot featuresof the software.Visiting softwarecompaniesat tradeshowsalso providesthe opportunityto talk directlyto their corporatestaff, and the staff can includepeoplefrom all the different groups responsible for the softwaredevelopment. Chancesare that the localresellermight also be on handto explainspecificfeaturesand services.Suchvisitsare a prime opportunityto learnwhetheryou would like workingwith the firm's employees,and to see if they are genuinelytrying to helpyou or just trying to make a sale. lvlostof today's modern CAD/CAMpackageshave very similar features,making it extremelydifficultto comparethem with each other.Another problem is that the packagesare alwayssubject to development,and thereforeare constantly changing.Bewareof anyonewho makescomparisons betweencompetingCAD/ CAIYsystems,and bewareeven more of peoplewho are trying to make a sale by puttingothersdown.A tradeshowis a great opportunityto meet the peoplewho developand supportthe software.In additionto lookingat the latesthot features 146

Secretsof s-AxisMachining

tr of the software,take the time to assessthe peopleyou wouldbe workingwith if you decidedto purchasethe software.Are they enthusiastic abouttheir product?Are they behavinglike a team, or are they shifty.disinterested and unhelpful? The following are among important questions that should be asked when visiting software companies: .

Can you start smalland then increasefunctionality as your business grows?Many softwarecompaniesoffer different levelsof the software, Findout if you can buy only the functionality you needtoday,and add to it lateras the businessdeveloos.

.

Findout whereyour localreselleris located,and try to meet someone from the company.Ask questionsregardingtraining,support,post processors/and other aspectsof purchase.Makesure you are comfortable with the resellerbecausethe supportyou receivecan make or breakyour softwareexDerience. How establishedis the softwaremanufacturer?It is a good idea to find a reputablecompanywith a largeuser-baseand supportnetwork.Findout how many programmingseatsare usedworldwide.Is use of the particular softwareat which you are lookingtaught at trade schoolsor colleges?You may want to considerhow easy or difficult it may be to find employees that already know how to operateyour softwareof choice

The next importantstep is to set up a demonstration at your plant.The localsales representative shouldvisit your shop,Iookat your operation,and basedon what kind of work you do, evaluatewhetherthe softwareis the right fit for you. If it is, he/ she can also recommendthe propersoftwarefunctionality you need.Bewareof sales representatives who start with "Do I havea solutionfor you!" even beforethey see the type of work you do.

Choosinga CAD/CAMSystemForYourApplication

Putting It AII Together By now, readersshouldhavea good graspof the multiaxismachiningprocess,with a clearunderstanding of the differenttypes of machines,multiaxistoolpathtypesand machiningtechniques,multiaxisCAD/CA|Y controls,simula on options,and how they all fit together.To test your new knowledge,try to answerthe followingquestions. Answeringthe questionssuccessfully meansthat you are readyto bre;k lnto the fast growingmultiaxismachiningworld. AIIquestionswill be answeredon subsequentpages.and rneseanswerscan serveas a quickreferenceguidefor the most importantlessonslearnedin this book.

QUrZ 1.) Name three benefits to using multiaxis machining techniques, 1.

2.) Describe a standard s-axis machine?

149

3,) which of the following is the standard axis convention?

B

A 4.) what are the three major multiaxis machine types? 1. ') 3.

5.) what are the three major building blocks of a cNc machine? (Circlethree.) . Machinetable servo drive system

. CNCcontrollercapabilities

. SpindleRPMand horsepower

. CNCdrive system

. Physicalpropeftiesof the machine

. Lineartable limit switches

. Chipconveyorunit

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i 6,) What are the most important physical positions of a multiaxis machine? .

Centerof gravity, Home Base ProgramHome Base,IncrementalZero Position,Spindletype

.

MachineHome Position,MachineZero Position,ProgramZero Position

7.) What tools are needed to find the Machine Rotary Zero Position (MRZP)? (Circle two.) .

level

.

edgefinder

.

dial indicator

.

maintenance manual

.

hammer

8.) Describe indexing/rotary positioning work,

9.) What is a post processor?

Puttinglt All Together

't5t

ANSWERS 1,) Why use multiaxis machining techniques?

't52

.

partsmoreefficiently Multiaxismachiningtechniques are usedto manufacture and accurately by eliminatingextraset-upsand fixturing.

.

Standardshortertoolingcan be used,whichresultsin the abilityto rough moreaggressively, whileincreasing tool life.

.

A moreprecisesurfacefinishcan be achievedby avoidingcontactwith the non-spinning deadcenterof the tool.

Secretsof +Axis Machining

Figure 7O-7 Multiaxis machining manufacturesparts more efficiently, increases tool life, and producesa more precise surface finish, 2.) What is a standard S-axis machine? This is a trick question!Thereis no suchthing as a standards-axismachine. Multiaxismachinesare availablein many shapesand forms. Figure10-2 shows examplesof the varioustypes of s-axis machines.

Figure 7O-2 Examplesof the varioustypes of 5-axis machines.

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3.) What is the standard axis convention?

Figure lO-3

The standard axis convention,

The X, Y Z linear axes shown in Figure10-3, representingthe Cartesiancoordinate system,move in straightlines,in plusand minusdirections. The A, B, and C rotary axes rotate about the X, Y and Z axes respectively.The U, V and W axes move in straight lines, parallelwith the X, Y and Z axes respectively. 4,) What are the three major multiaxis machine types?

TABLE/TABLE HEAD/TABLE HEAD/HEAD

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Secretsof s-Axis Machining

Table/Table Multiaxis Machines

Figure 7O-4 Table/Tablemachines can be configured vertically or horizontally. Table/Table multiaxis machinescan be configuredverticallyor horizontally,as shown in Figure 10-4. The rotary motions are executedby the dual rotary table of the machine.The rotary table carriesanother rotary table, which in turn carriesthe fixture and the part. With these machinetypes, the part is physicallyrotated around the tool. The weight of the part and fixture need to be handledby the machine's rotary devices,so inertia will be a factor when consideringfast movements. Head/Table Multiaxis Machines

Figure 7O-5 Head/Table machines are very capable and versatile.

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Head/Table machinesare arguablythe most capableof the three groups.They can machinelarge, heavy parts. On some Head/Table machines,the work piece is held by a rotarytable and is supportedby a tailstock,as shownin Figure10-5. The work piece rotates around its own axis. The pivoting head only carriesthe weight of the tool and it handlesthe cutting pressuresgeneratedas it articulates aroundthe work Diece. The rotary axis on these machinesusuallyhas unlimitedrotary motion, Some can even spin the rotary as a lathe would. The secondarypivotingaxis has an upper and lower rotary/pivotinglimit, Head/Head Multiaxis Machines

Figure 70-6 Head/Head machines can be both vertical and horizontal. On Head/Head machines,an exampleof whichus shownin Figure10-6, all rotary/pivotingmotions are executedby the head of the machine.Head/Head machinescan be both vertical and horizontal,where one axis has limited motion. Somecan changeheadsin additionto tools.Headscan be straight,90 degree, nutating,or continuously articulating.In additionto milling,these machinescan also be outfitted to manipulatea water-jet or a laser. 5.) What are the three major building blocks of a CNC machine? 1. The physical properties of the machine The physicalpropertiesof the machineare representedby the machine'sskeleton. Everymachineis built on a uniquebase.The qualityof the iron givesthe machine its rigidity.The linear and rotary axes are stackedfirst onto the base,then onto eachother.The qualityof the linearslidesand rotarybearingsgive the machine

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its flexibilityand potentialaccuracy.The spindlemotor'storque and horsepower further definethe characterof the physicalmachine. 2. The CNC drive system The CNCdrive system representsthe muscles of the machine.The CNCdrive system consistsof componentsdesignedto move the machine'slinear and rotary axes. These componentsincludethe servo motors. drive system, and ball screws, which are responsiblefor moving the machine'slinear and rotary componentsin a smooth, preciserand rapid manner, 3. CNC controller capabilities The CNCcontrolleris the brain of the machine.Data handling,availableon-board memory size, and dynamic rotary synchronizationcontrols,are some of the things controlledhere. 6.) What are the most important physical positions of a multiaxis machine? Machine Home Position - Most machinistsrecognizethis positionas the placeto which all the axes move when the machineis initiallyturned on and Zero return is selected,as shown in Figure 10-7.

Figure 7O-7 Machine at Home Position.

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Machine Rotary Zero Position - MachineZero Positionis the intersectionof the rotary/pivotingaxes shown in Figure 10-8. This point may be unreachableby the machine.

Figure 7O-8 Machine Rotary Zero Position. Program Zero Position - This position,shown in Figure10-9, is also the part datum locationin the CAMsvstem.

Figure 7O-9 ProgramZero Position.

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7.) What tools are needed to find the Machine Rotary Zero position (MRzP)? The tools neededto find MRZPare a level and a dial indicator. 8,) Description of indexing/rotary

positioning work

Most CAD/CAMsystems let the user define multipleActive Coordinate Systems in space,and then create toolpathsusing the orientationof each individual coordinatesystem.As shown in Figure10-10, the Z-axesof these coordinate systemswill align with the spindle,signalingthe post processorto output rotary indexingcommandsinto the NCcode.

Figure 7O-7O Multiple Active Coordinate Sysfe/.ns. 9,) What is a Post Processor? CAD/CAMsystemsgenerates-axis vector lines along 3D paths.The 3D paths representthe tool motion as it followsthe cut pattern. The vectorsrepresentthe tool axis direction(IJK vectors) as the tool followsthe 3D (XyZ) pattern. Every vector representsa line of code,This informationis written in a genericlanguage. The genericCAD/CAMcode must be translatedinto a machine-readable language. This processis called post processing.A post processorwill calculatemotions neededon a specificmachineto reproducethe CAMvector model, which will govern the machine'smotions in order to cut the part. A different post processoris neededfor every type of multiaxismachine. Puttinglt All Together

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1O.) Definition of an axis Any motion controlledby the NC controller,either Iinearand/or rotational consideredan axis.

Figure to-t7 In this examplethe spindleheadand the quill move in the same direction,but are controlledby two separatecommands,z and W respectively. 11,) Defining a simultaneous S-axistoolpath multiaxistoolpathsmust moveall 5 False.Mostpeoplebelievethat simultaneous whilecutting,whenin fact a singlerotary axesof the machinetool continuously multiaxis cuttingmotion. to be simultaneous is considered andlinearcombination Figures 10-12 and 10-13. in areillustrated multiaxis toolpaths Typical simultaneous

Figures 70-72 and 7O-73 Examplesof simultaneous multiaxis toolpath motions' Secretsof s-AxisMachining

12,) What are the three common simultaneous multiaxis CAM toolpath controls? 1. Cut Pattern - Guidesthe tool along cutting directions. 2. Tool Axis Control - Controlsthe orientationof the tool's center axis as it followsthe Cut Pattern. 3. Tool Tip Control - Controlsthe geometryto which the tool tip is compensateo. In additionto the abovethree major controls,quality CAD/CAMsystemsalso offer additionalcollisioncontrol. Even near-misscollisionavoidanceof the cutter, shank, and holder can be checkedagainst any part of the workpiece,fixture, or machine comDonents, Pleaserefer to Chapter6 for more detail.

More in Review: Multiaxis Machine Offsets

PIVOT

= TANCE

COMPOFFSET LENGTH'

Figure 70-74 In addition to Tool Length compensation,multiaxis machinesuse other offsetsincludingGageLengthand RotaryPivotDistance.TheRotaryTool ControlPointDistanceis the sum of Pivot Distanceplus GageLengthOffset. PuttingltAll Together

161

Quick Reference:How to Find Machine Rotary Zero Position For Table/Table Machines:

Figure 7O-75 Step 1: Level the A-axis.

Figure 70-77

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Secretsof s-AxisMachining

Figure 1O-16 Step2: Findx,Y center.

Step 3: RotateA+90 and set dial indicator to Zero.

Figure 70-78

Step 4: RotateA-90. Dial indicator should read Zero

Figure 70-79 Step5: log Z minus the radiusofthe rotary table diameter,and adjust gage tower height to match.

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Finding the Pivot Distance For Head/Table and Head/Head Machines: First,makesurethat the machineheadis in a perfectverticalorientationand that the spindleis runningtrue.

Figure 7O-2O Step 1: Use a dial indicatorto checkfor verticalalignment.

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Secretsof s-AxisMachining

Figure 7O-27 Step2: Checkif spindleis runningtrue.

Figure 70-22 Step 3: Record Z max.

Figure 70-23

Step 4: Record Z min.

Z max Z min GL - Gage Length R - Dowel pin radius = .5OOO Formula to calculate Pivot Distance: PD=Zmax-Zmin-GL+R

ltAllTogether 165 Putting

Indexing/Rotary Positioning Work Overview Also known as 3+2 machining,indexing/rotarypositioningwork, illustratedin Figure 10-24, is the most basicmultiaxisconcept.The rotary/pivotingaxes are used only for positioning,and the cutting takes placewith only the three linear axes moving.Indexingwork is rigidand precise,It is recommended that all possibleroughingoperationsbe performedin this rigid state.

Figure 70-24

Indexing/rotary positioning work is the most basic multiaxis concepL

Picking a CAD/CAMSystem For Multiaxis Work When selectinga CAD/CAMsystem for multiaxiswork, make sure it is CAM oriented,and has a powerfulCADtranslator.The CADtranslatoris very important becauseit's likely that files will be receivedfrom many different sources.Makesure the CAMsystemhas all the multiaxiscontrols,pluscollisionchecking.Havingan onboard,easy-to-use.machinesimulationis a big plus, especiallywhen project planning.Machinework envelopeand machinecomponentcollisioncheckingare reouired. In additionto the abovefeatures, it is also very important to researchthe CAD/ CAMsystem developerand the local dealer.Do they providequality training and support, and do they have post processorsfor your machine? Pleaserefer to ChaDter9 for more detail.

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Machine Simulation Do not assumethat machinesimulationis usedonly for prove-outswith the sole aim of findingerrorsin the code.Instead,machinesimulationshouldbe regarded as an additionaltool to help make clean,efficient,and accurateprogramsevery time. Machinesimulationpermitstesting of differentapproaches,differentcutting strategieson different machines,without leavingthe desk. There is also no need to tie down a machinefor VourDrove-outs. Machinesimulationiets you builda replicavirtualmachineon the computer screen,where cutting processescan safely be simulatedto make sure that the most effectivecut has been created,that the part is locatedin the machine's "sweetspot,"and that no fixtures,toolsor any machinecomponents are meeting unexpectedly.

In Conclusion Congratulations on the commitmentto becomemore informedaboutmultiaxis machining!Multiaxismachiningis a dynamic,constantly-evolving field,full of possibilities. lYultiaxis machinetoolswill becomemore complexand capable,and CAD/CAM systemswill developadditionalcapabilities to controlthem. Userswill continuallylook for more capability, combinedwith easeof use,and this demand will pressurethe machinebuildersand CAD/CAlvl developers to combinetheir effoftsin buildingmachine/controller combinations with built-inintelligence. As pasttrendsshow,thesedevelopments will open yet more possibilities, addingmore complexity. Creativitydoesnot fit into a box, but knowingthe basicconceptswill allow engineersto think outsidethe box. Hopefullythis book has demystified this field and inspiredyou to take the next step in training yourselfto becomemore proficientand competitivewith all the toolsavailable. The best measureof competencyin any field is mastery of the availabletools. Mere possession of more powerful tools doesn't make one more capable, but knowledge does. The manufacturing industryin general,and multiaxismachiningln padicular,is bestsuitedfor thosewho can think outsidethe box.Thereare alwaysmultiple ways to solve any problemand that solutionalwaysstarts with oneself.The biggest secretof s-axismachiningis the realization that all the expensiveCNCmachinery, CAD/CAM, and simulationsoftwareare meretools.Withoutthe knowledgeto use them properly,nothingcan be accomplished. With the availabletoolsand the right knowledge,all you haveto do is imagine- by applyingyourself,your imagination will becomea realitv.

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Index Cuttnrg

A ABC lineara{es.l5 system.5? Absolutecoordinate Activecoordnrabsystems,25 2'7, 57,59-61, 140 Acturl part zeropoint, 27 Aligneduniversc,62 Avoidingcollisions.45 Automaticlool changing,16.423

dircciion,l00 strategies, 45.70. 103,117,138.167 variablepitchthread,67

D 9, 10 Dedicated multiaxismachnrcs. anddirections of multiaxismachine Designations

B

Desiredcutterarea.engaging,l0 Dovetail effecl. 98 Dynanic contol of tool axis,90,98 robry fixtureoffset.16.27-8,36

Bal]-nose cutters,10,96,130 Bettersurfacelinishes.l0

E

dcfined,l4 substitution,32

(3,7. 27, CAD/CAMsystems, capabilities.l39 I 39 multiaxiscoDsiderations, origin,60 selecting,137 145 softwaredevelopmcnt, rcsearching,146 tmining,l4,l pivotdisiance(PD),33,37-8,169 Calculating CAM, multiaxis,139 multiaxismachines,3 Can-operated 53 spindleheads, Changeable repeatibjlity.'12 Checkingpositioning Circular 73 interpolation, Cleancore,92 CNC 3, 76 controllers. capabilities,l3,157 l3 drivesystems, (seeAvoidingcollisioDs) Collisionavoidance 4, 6. 7 misconccptions, Common of rvork, 120 Complexity Computernunericalcontrol,3, 92 Crashirg,I I 7 94, 140,161 Cutpattem,79,86

Effectivcwork envelope.16 Engagingdesiredcutterarea,l0 Extrusionmillingmachine.123

F Fanucprogritn,34 Fcedrate,T2 138 dynanicchanges. inversetime,74 6 optimizaiion,l3S standardlime. 74 Findingthe ccnterofrotation.21.27'8 pivotdistance, 33,36-9.l6l. l6,l XYzero,23 5'axis nachineierms,13 vectorInres,76,159 nachines,39 positioning,T

G Gage length(GL),36-9. 161 tower,24,163 122,134 machines, Ganrrytypehead/head G codes,29.30.56, 104'106 169

sinulntion.105 G 90code.29.30 G-91code.29.30 ll6 Gaphicaluscrnrtel1ace,

H nrultiaxismachines. 18.367. ll5 6. Head/head l2l 2. 13,t.156,i64 bridgeiype. 122 ganlry1ype,122.13,1 lasercuttingmichnre,116.135 warcrjer miling machnre.ll6. 134 18,31.36.113,1 Headltablenrultiaxisnrachnrcs, 123,1.155 129,133 aerospace, automotive applications, millingenginchcadports,125 nilling longrotarypafts.124 mdd anddic applications, 130 nuiatingheadconbinations,129 rotafylxble,rilthg head.12830 1249 variousconligurations, with longX'axis tavel. 123 work,56 Ho\vCNCmachines Historyof 5 axismachining.3

I I n d e x n r g , 2 l , 4 4 , 5 11 , 5353. lixtures,5l methods.5l toolpaths.49 wirh rotar)devices.52 wo*.:19.55 Indusrrial robots.135 Interpolation circular,T3 linear,73 Inversetnncleedrate, 72-4.76

L Leadandlag jn milling.100 Lnnihlions,,16 Linear .txis,14 6,34.,19.74, 106.121,166 73 interpolation. Localcoordinate systems.25 7.56 8.61 2,117

170

Secrets of s-Axlsl\,4achining

M Machine 7.57 61.140,15' aclivccoordirrte system.25 4, 167 1136,116-7,139.1,13 bxildingvirtual,64, cnd,6,l,107.125 busnrcss 159 7,56-7.61'2.1,10. coordinate systems,25 157 homeposidon, 16,57.60.78. slstcns,25,26. 6l localcoordinate

hone positior(MRHP),l7 zeropoint,21,25-7,36.60 2,1 1 2, 1M (MRZP).I 6 '7,21,25.21.36, zeroposition 1 1 7 , 1 5 8 ,r96.2 1036. 143.1657 simulrtion,27,63-4,98. graphicaluserinlefaccs.I l6 using.tl7 Machirlnlg centcrconJigul"tion. 108 I l0 complexworRpicccs,5 cngnrccomponents.20 profiling. ll5 progrrn,29 104.138 routines.5. spnd bevelgears.68 Machsimsoftwxlc,106 Maintenance issues.40 Manualclrt.tinpur(MDl),25.1l6 Master system,60 coordinalc zero,26 M-code.2l,43,60 Milling nachineswith nvc or moreaxes.4:l \ 4 o , r e l i n2-r. ., ' 1 . u l . l l ' . I n - P l l 6 l 1 - - r ) 159 6. 8, 17-9,40,7,1. 124.153 Multiaxis machines.3 140 camtype.3. dedicated,6. 9 10.21.39,52-3,110,l2l) anddirections.l5 designilions physicalpropeties,13.156 rorghing. 21.101.130,1402, 166 58. 61 Multiplenestnrg,

N 25.26,56 8, 61 NeslingpositioDs. Newpossibilities, 11.121 parts, Nunbersof 120

Nunerical conlrol. 3

o Old schoolsimulatifl. 104 One zero meihod,60 Optimum rvork envelope.70 Odgin,26,60

P Palletchargers, 40, 54, 107-8 datum,17,21.27,58,158 zeropoirt (PZP),27 8 Plungeroughing,101-2,142 Probesandprobing,94-5,103',1 I'hysicalproperties of5-axismachines, 13 Pivot distance.33 point,379 Pivonngspindleheads,18,32-6,38. 124.156.lbo Pockct nrilling.5.86, l2l, ll7 9 $ork. 5, 7, 8. 13,20-l, 26. 42,49,52, Positioning

R pxltcrns,l0,l Rcpcating Rotary andpivotingaxcs,32.74 axis,16,21,33.,12.60.71.7.1, 107.i21, 156 d c v i c c1 s ,6 , 1 8 . 2 1 . 521, l l 6 . 1 5 5 xrdexingnechanisns,5, 54 mcchanisns. 6, 19,20.39.403. 52 3. 7l tool cortrolpoint(RTCP).33'4.36.l6l Rotarytables,5. 8.9. 18,21,278.31 2. 130-2.

r 5 56 .r 6 3 brakes,21,.10, 52.l0,l d e v i c e1s 6. ,1 89 , 2 1 , 5 12 . 7 7 .1 0 9 1. 1 6 ,1 2 61. 5 5 dynxnicfixlurcoft.\cl(RTDFO).16,27 8.36 sinsleanddual. 6, 8. 18.39.ll9 Roughnrg. 11,21,101'2,130,140'2,152,166 Routnrcs,5.40,42, 1045 S Secondrotart table,18 Selecfirgnachnlcs,I l9 Selecting software.137 Stullrlaftrn, 19,27,47.63 4.98.10317.I38,1667

r 5 9r,6 6 processing,3.4.8.34,40,76 8. 103-6,138, 1 4 37 , 1 5 9 r, 6 6 processor,3,4, 8,39,40,769. 10zl6, I16,138. 1 4 3 1, 4 7 , 1 5 9 Probingroutines.1045 Program nnnurleditnrg. 104 subloutines. 9, ,13-4. 10.1 (PZP).l6 8,25.32.117.158-9.162 zcroposition P r o g r d m n r i l gq...118 . 2 4/ 5 . 6 .5 4 . 6 ) . l . l 0 : . 105.138,144.147 .onsiderations, 46 languages,3 limitrtions.46

a

46. I 44. I 41. 119 Qucstbnsandanswers, physicalpositions,151,157 standard axisconvention. 150.154

cutlingmotions,10,71 millingte.hniques.2l muhiaxistoolpathconirols,79,101,152.161 toolpaths. 5.48.65.78. 103,105,107.l2l Special-puryose softlvare,137 heads. Spindle changeable. 31.53 Spil"l splines,99 Standard multiaxisnomenclature. 15 Slock(natcrial)option1.47.102 rccognition,1,12 104 Subroutines.3.43. Surlacelinishes.better,5,10 origin.60 view,27

T Txblc/lxblc multiaxis machnrcs, l8 9.24.I10.125, 1 3 2 1, 5 5 . 1 6 2 wjth port-nillingaftachment, 125

'171

111,I32 honnionandrock andro11Iixtules,71. 133 variousapplications. 5 toolpaths, 3D surfacing Tiltingspindleheads,31 Tombstone lixtures,6, 40, 58-9,108 Tool 139,l4l, 161, axiscontrol,79,86,89,91-2,98, lengrhoffsets,18, 24, I 17 lists,46,140,145 for lathes.138 simultaneous,65 planewith odgin,27 tip control,79,90-91,l4l Tradeshows,146 Training,144 2 + 3 positioning,49

U UsingmotionsXYZ andC,67 Unlockedrotary drives, 11 U\r!V linear axes,15

v Vericutsoftware,1,95, 106,116-117 Verilication system,27, 104 1, 146-7 Visitingsoftwarecompanies, Virtualmachine,103,105 building,l06 components andmodels,107 configudngfor simulation,105 kinematiccomponenttlee, 107 skeleton,106

w wire franes,79,103,139-40 Worldzero,26,60

x 7,74 XYZ linearaxes,15.32,66

z Zeroingthe indicator,22 17,21,117.158,162 Zeroposition, Z-Maximum,37 Z-Minimum,38

172

secrclsof s-Axislrachining

Virtual MachiningCD Allthe imageson this CD, includingthe virtualmachines,were modeledusinglvlastercam@ (CNCSoftware,Inc.). The virtualmachineswere broughtto life usingthe machinesimulation capabilitiesof l4achsim (lYoduleworks)and VERICUT6(CGTech). Installation The enclosedCD should run automaticallywhen inserted into a CD-ROlqdrive. if the autorun feature does not work. please use File I\4anagerto navigateto the CD. Find the file called Index.htmland dolrble-click it.

System Requirements The CD was built to run ootimallvon a PCwith: . . . . . .

WindowsXP or Vista Internet Explorer(Version7) or higher 1024x 768 resolution(or higher) installed. (Go to http://www.adobe.com/downloads/to install a Adobe@ Acrobat Reader@ free version,) to installa AppleQuickTimeplug-ininstalled.(Go to hftp://www.apple.com/quicktime free version,) If you installthis cD on your hard disk.you will need650 l4Bfree space.

Virtual Machining CD Contents: . over 25 Interactive Machine simulations - self-extractingexecutablefiles launch interactivemachinesimulationsessions.Take control of all aspectsof the simulation, includingview manipulation, simulationspeed,and individualaxis control.Lookat the machiningprocessfrom various views impossibleto see on a real machjne.This offers a uniquevisualization to helpunderstanda varietyof multiaxismachiningconcepts, .

Real Machining videos - watch a real s-axis machine pefform several different 5-axisparts, multiaxiscuttingroutineson complexsimulLaneous

.

virtual Machine Siniulation Videos - WatchVERICUT in action;F it elecutesmachine simulationand verification on over a halfdozendifferentexamplesof complexmultiaxis parts.

.

Printable PDF Files - Quick Referenceguidesfor the most important aspectsof setting up a s-axismachineand commonmultiaxisconceptsall availableas easyprint-outs,

.

Image Gallery - See full colorexamplesof many of the partsand machinesfound throughoutthe book.

Technical Questions: or to the authorat Pleaseemailyour questionsto info@industrialpress,com and go to the link for FAQS. [email protected]. Or visit www.5axissecrets.wordpress.com