automatic tool changer cnc

DYNAMIC Industries Ltd.

Report on Title By Shashank Singh Roll no. 337, GR no. 71122100033 Submitted for Technical internship programme Training Supervisor and Guide

Prof. Ravi Terkar Associate Professor, MPSTME Mr. Anup Parikh Chairman, Dynamic Industries Ltd.

MUKESH PATEL SCHOOL OF TECHNOLOGY MANAGEMENT & ENGINEERING SVKM's NARSEE MONJEE INSTITUTE OF MANAGEMENT STUDIES (Declared as Deemed-to-be University Under Section 3 of the UGC Act. 1956) Vile Parle(w), Mumbai-400 056. Date:

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SVKM’s Narsee Monjee Institute of Management Studies(NMIMS) Mukesh Patel School of Technology Management & Engineering A REPORT

on Manufacturing of an injection moulded component & reduction in the CNC machining time using automatic tool changer.

By Shashank Singh MBA(Tech)-Mechanical [337]

DYNAMIC Industries Ltd.

DYNAMIC Industries Ltd.

ACKNOWLEDGMENT It gives me immense pleasure to present this in-pant training report at DYNAMIC INDUSTRIES LTD. This training provided me a golden opportunity to expose myself to the industrial environment. I am very grateful to my training Guides, Mr. Anup Parikh & Prof. Ravi Terker for their motivation and continuous support as well as guidance to pursue and complete this research. Their wide knowledge and logical way of thinking have been of great value for me. They were always there to meet and talk about research ideas, to proof read and mark-up my papers, and to ask me good questions to help me to think through my research. Without their encouragement and constant guidance, I could not have finished this synopsis. I would like to thank to Mr. Chandrakant Vichrolia, Mr. Chetan Majithia & Mr. Amol Deshmukh for their valuable support and encouragement during the research work. Further I believe that the list of people would remain incomplete if I fail to mention my supervisors & department colleagues; they were constant source of encouragement and timely help.

Thanks

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Table of Contents: ACKNOWLEDGMENT ................................................................................................................................. 3 ABSTRACT.................................................................................................................................................. 1 1. INTRODUCTION TO THE COMPANY........................................................................................................ 2 1.1. COMPANY’S QUALITY POLICY ......................................................................................................... 3 1.2. COMPANY SERVICES ....................................................................................................................... 3 1.3. LIST OF ESTEEMED CUSTOMERS..................................................................................................... 4 1.4. COMPANY PRODUCTS .................................................................................................................... 5 2. PRODUCT DESIGN ................................................................................................................................. 13 3. PRE-MACHINING................................................................................................................................... 13 3.1. SHAPING: ...................................................................................................................................... 14 3.1.1.WORKING PRINCIPLE ............................................................................................................ 14 3.2. GRINDING: .................................................................................................................................... 15 3.3. CONVENTIONAL MILLING: ............................................................................................................ 16 3.3.1.METHODS OF MILLING: ........................................................................................................ 17 4. MOULD DESIGN .................................................................................................................................... 18 4.1. MOULD BASICS: ............................................................................................................................ 18 4.1.1.TYPES OF MOULDS: ............................................................................................................... 19 4.1.2.MOULD BASES & CAVITIES:................................................................................................... 20 4.1.3.MOLDING UNDERCUTS: ........................................................................................................ 21 4.1.4.PART EJECTION: .................................................................................................................... 22 4.1.5.MOULD METALS: .................................................................................................................. 22 4.1.6.MOULD COST AND QUALITY: ................................................................................................ 23 5. MACHINING & FINISHING..................................................................................................................... 25 5.1. CNC MACHINING: ......................................................................................................................... 25 5.1.1.CNC LATHE: ........................................................................................................................... 30 5.1.2.WORKING OF CNC LATHE: .................................................................................................... 30 5.1.3.FEATURES OF CNC LATHE: .................................................................................................... 30 5.2. ELECTRIC DISCHARGE MACHING (EDM): ...................................................................................... 31 5.2.1.PRINCIPLES OF EDM-............................................................................................................. 31

DYNAMIC Industries Ltd. 5.2.2.EDM PROCESS- ...................................................................................................................... 32 5.2.3.CHARACTERISTICS OF EDM- .................................................................................................. 33 5.2.4.DIELECTRIC-........................................................................................................................... 34 5.2.5.ELECTRODE MATERIAL-......................................................................................................... 34 5.2.6.ADVANTAGES OF EDM: ......................................................................................................... 37 5.2.7.DISADVANTAGES OF EDM .................................................................................................... 37 5.3. CLASSIFICATION OF EDM .............................................................................................................. 38 5.3.1.CONVENTIONAL EDM: .......................................................................................................... 38 5.3.2.WIRE-CUT EDM: .................................................................................................................... 39 5.3.3.CONVENTIONAL EDM- DIELECTRIC FLUIDS........................................................................... 39 5.3.4.WIRE EDM- DIELECTRIC FLUIDS ............................................................................................ 39 5.3.5.FLUSHING .............................................................................................................................. 39 6. FINAL COMPONENT .............................................................................................................................. 41 7. AUTOMATIC TOOL CHANGER ............................................................................................................... 43 7.1. AUTOMATIC MANUFACTURING SYSTEMS: .................................................................................. 43 7.2. REASONS FOR AUTOMATING: ...................................................................................................... 44 7.3. TOOLING FOR NUMERICAL CONTROL: ......................................................................................... 45 7.3.1.1. Tool Holders ...................................................................................................................... 45 7.3.2.2. Automatic tool selection................................................................................................... 45 7.3.3.3. Automatic Tool Changer ................................................................................................... 46 7.4. AUTOMATIC TOOL CHANGER ....................................................................................................... 47 7.4.1.Why Tool Changer is needed? .............................................................................................. 47 7.4.2.Types of automatic tool changer .......................................................................................... 47

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Table of figures: Figure 1: General CNC machines................................................................................................................... 5 Figure 2: Electrical discharge machine(EDM) ............................................................................................... 6 Figure 3: Conventional Miling Machine ........................................................................................................ 7 Figure 4: Under bonnet components - TANKS .............................................................................................. 8 Figure 5: Various Molded tanks .................................................................................................................... 9 Figure 6: Under bonnet components.......................................................................................................... 10 Figure 7: Major industrially accepted products .......................................................................................... 11 Figure 8: Mould process chart .................................................................................................................... 12 Figure 9: Shaping machine .......................................................................................................................... 14 Figure 10: Surface grinding machine .......................................................................................................... 15 Figure 11: Milling machine.......................................................................................................................... 16 Figure 12: Climb milling method ................................................................................................................. 17 Figure 13: Conventional milling method..................................................................................................... 18 Figure 14: Basic components of NC system ................................................................................................ 26 Figure 15: Typical CNC machine .................................................................................................................. 27 Figure 16: Motion control system, (a) Open loop; (b) Closed loop ............................................................ 29

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ABSTRACT The project is related to the production, design & manufacturing of an injection mold component, called Shroud in this case, and also to reduce the machining time in CNC milling by suggesting automated tool changing using automatic tool changer(ATC) instead of changing the tools manually. Presently the firm is using the method of manually changing the tool which consumes time and thus affects overall productivity, so I’ll be suggesting the automated tool changing using an automated tool changer & a tool pre-setter. In my training here, I’ll be monitoring and studying the whole mold making process starting from the product design to the final trial & correction, alongside with the work on the automatic tool changer by observing & studying the conditions and environment of and near the CNC machines so that ATC can be successfully implemented thereby helping in increasing the overall productivity of the firm.

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INTRODUCTION TO THE COMPANY

Dynamic Industries is originally a mould making and moulding company specialized in Automobile, Air-conditioners, Water Purifier System, Thermoforming, Television and House Hold Industries. This company is a partnership firm professionally managed by Mr. Deepak Gandhi & Mr. Anup Parikh and is executing enduring services to clients. They have integrated product development, mould design and manufacturing facilities along with injection moulding facilities to provide one-step service. Following industries are covered in the services for this industry. The company’s services are available to the industries like-

Automobiles

Water Treatment

Electrical and Electronics

Consumer Appliances

Bio-Medicals

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COMPANY’S QUALITY POLICY Company have a integrated product development, mould design and manufacturing facilities along with injection moulding facilities to provide onestep service. So that trial-testing can also be done at one go. Quality policy is to achieve sustained, profitable growth by providing services which consistently satisfy the needs and expectations of our customers. To achieve and maintain a level of quality which enhances the company’s reputation with customers. To provide a quality product that satisfies our customer’s requirement, deliver on time. We are committed to continuously improve our processes to provide goods and services at a better value to our customers.

COMPANY SERVICES  CAD-CAM Engineering  Reverse Engineering  In house mould design, part design consulting, assistance in project development  EDM- Electrode manufacturing  On-time delivery at competitive price  Weekly process report

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DYNAMIC Industries Ltd.

LIST OF ESTEEMED CUSTOMERS • Mutual Industries Ltd. • Ronch Polymers Ltd. • TVS Motor Company Ltd. • Sundaram Auto-Components Ltd. • Tata Auto-Components Pvt. Ltd. • Banco Products (India) Ltd. • Alkraft Thermotechnologies Pvt. Ltd. • Kabra Extrusiontechnik Pvt. Ltd. • Jyoti Plastic Works Pvt. Ltd. • Polysmart Technologies Pvt. Ltd. • Auro Plastic Injection Moulders Pvt. Ltd • Hitachi Home & Life Solution Ltd • Rajoo Engineers Ltd. • Tata Infotech Ltd. • Sui Generics • Transpo International • Polyset Plastics • Transasia Bio Medicals • Kirti Industries Ltd. • Rita International • Harita Infoserve Ltd. • Lear Corporation • Supreme Treaves Pvt. Ltd. • Vipul Plastocrafts

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COMPANY PRODUCTS

Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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Figure 8

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PRODUCT DESIGN Product design is provided by the customer to the manufacturer, in order to get the required mould.Product design is made on the 3D-CAD softwares like NX, PRO-E etc by the customer itself then it is sent to the manufacturer and finally it is checked for feasibility study.

PRE-MACHINING Pre-machining the the process of machining the raw material before putting them into CNC or EDM machining in

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SHAPING: It is a simple and yet extremely effective machine. It is used to remove material, usually metals such as steel or aluminium, to produce a flat surface. However, it can also be used to manufacture gears such as rack and pinion systems and other complex shapes. Inside its shell/casing is a crank and slider mechanism that pushes the cutting tool forward and returns it to its original position. This motion is continuous.

Figure 9

WORKING PRINCIPLE

The job is rigidly fixed on the machine table. The single point cutting tool held properly in the tool post is mounted on a reciprocating ram. The reciprocating motion of the ram is obtained by a quick return motion mechanism. As the ram reciprocates, the tool cuts the material during its forward stroke. During return, there is no cutting action and this stroke is called the idle stroke. The forward and return strokes constitute one operating cycle of the shaper. The main functions of shaping machines are to produce flat surfaces in different planes. The cutting motion provided by the linear forward motion of the reciprocating tool and the intermittent feed motion provided by the slow transverse motion of the job along with the bed result in producing a flat surface by gradual removal of excess material layer by layer in the form of chips. The vertical infeed is given either by descending the tool holder or raising the bed or both. Straight grooves of various curved sections are

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also made in shaping machines by using specific form tools. The single point straight or form tool is clamped in the vertical slide which is mounted at the front face of the reciprocating ram whereas the workpiece is directly or indirectly through a vice is mounted on the bed.

GRINDING: Grinding is a finishing process used to improve surface finish, abrade hard materials, and tighten the tolerance on flat and cylindrical surfaces by removing a small amount of material. Information in this section is organized according to the subcategory links in the menu bar to the left. A distinguishing feature of grinding machines is the rotating abrasive tool. Grinding machine is employed

Figure 10

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to obtain high accuracy along with very high class of surface.

In grinding, an abrasive material rubs against the metal part and removes tiny pieces of material. The abrasive material is typically on the surface of a wheel or belt and abrades material in a way similar to sanding. On a microscopic scale, the chip formation in grinding is the same as that found in other machining processes. The abrasive action of grinding generates excessive heat so that flooding of the cutting area with fluid is necessary. Reasons for grinding are:  The material is too hard to be machined economically. (The material may have been hardened in order to produce a low-wear finish, such as that in a bearing raceway)  Tolerances required preclude machining. Grinding can produce flatness tolerances of less than ±0.0025 mm (±0.0001 in) on a 127 x 127 mm (5 x 5 in) steel surface if the surface is adequately supported.

CONVENTIONAL MILLING:

Milling machines are very versatile. They are usually used to machine flat surfaces on square or rectangular parts, but can also produce many unique and irregular surfaces. They can also be used to drill, bore, produce slots, pockets and many other shapes. The type of milling machine in the UCR Mechanical Engineering Machine Shop

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DYNAMIC Industries Ltd. is a variable speed vertical spindle, knee-mill with a swiveling head (also known as a “Bridgeport”). Although there are several other types of milling machines, this document will focus only on the vertical milling machine. A milling machine removes metal by rotating a multitoothed cutter that is fed into the moving workpiece.

METHODS OF MILLING:

Climb-milling: Climb milling, is sometimes referred to as Down milling, where the direction of the cutter rotation is the same as the feed direction. This method is probably the most common option on the shop floor and will normally produce a better surface finish.

Figure 12

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DYNAMIC Industries Ltd. Conventional-milling: Conventional milling is also sometimes referred to as Up milling where the direction of the cutter opposes the feed direction.

Figure 13

MOULD DESIGN MOULD BASICS: At the most basic level, moulds consist of two main parts:  Cavity &  Core The core forms the main internal surfaces of the part. The cavity forms the major external surfaces. Typically, the core and cavity separate as the mold opens,so that the part can be removed. This mold separation occurs along the interface known as the parting line. The parting line can lie in one plane corresponding to a major geometric feature such as the part top, bottom or centerline, or it can be stepped or angled to accommodate irregular part feature. Choose the parting-line location to minimize undercuts that would hinder Or prevent easy part removal. Undercuts that cannot be avoided via reasonable adjustments in the parting line require mechanisms in the mold to disengage the undercut prior to ejection. Page 18

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TYPES OF MOULDS: The two-plate mould, the most common mold configuration, consists of two mold halves that open along one parting line (see figure 7-1). Material can enter the mold cavity directly via a sprue gate, or indirectly through a runner system that delivers the material to the desired locations along the parting line. The movable mold half usually contains a part-ejection mechanism linked to a hydraulic cylinder operated from the main press controller.

The three-plate mold configuration opens at two major locations instead of one. Figures 7-2A through 7-2C show the mold-opening sequence for a typical threeplate mold. Typically, a linkage system between the three major mold plates controls the mold-opening sequence. The mold first opens at the primary parting line breaking the pinpoint gates and separating the parts from the cavity side of the mold. Next, the mold separates at the runner plate to facilitate removal of the runner system. Finally, a plate strips the runner from the retaining pins, and parts and runner eject from the mold. Unlike conventional two-plate molds, three-plate molds can gate directly into inner surface areas away from the outer edge of parts: an advantage for centergated parts such as cups or for large parts that require multiple gates across a surface. Disadvantages include added mold complexity and large runners that can generate excessive regrind. Also, the small pinpoint gates required for clean automatic degating can generate high shear and lead to material degrada- tion, gate blemish, and packing prob- lems. Because of the high shear rates generated in the tapered runner drops

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and pinpoint gates, three-plate molds are not recommended for shear-sensitive materials such as Cadon SMA and materials with shear-sensitive colorants or flame retardants. MOULD BASES & CAVITIES: The mold base comprises the majority of the bulk of an injection mold. Standard off-the-shelf mold bases are available for most molding needs. Typical mold bases are outfitted with a locating ring and provisions for a sprue bushing in the stationary or “A” half of the mold and an ejector assembly in the moving “B” half. Both halves come with clamp slots to affix the mold in the press. The “B” half has holes to accommodate bars that connect the press ejection mecha- nism to the ejector plate in the mold.

Leader pins projecting from corners of the “A” half align the mold halves. Return pins connected to the ejector plate corners project from the mold face when the ejection mechanism is in the forward (eject) position. As the mold closes, the return pins retract the ejector plate (if not retracted already) in preparation for the next cycle. Mold cavities, here meaning core and cavity sets, can be incorporated in the mold three ways: they can be cut directly into the mold plates, inserted pieces into the mold base, or inserted as complete cavity units. Cutting cavities directly into the mold base can be the most economical approach for large parts and/or parts with simple geometries. When doing so, select the mold base steel carefully. The physical properties of standard mold base steels may be inadequate for heavywear areas or critical steel-to-steel contact points. Use inserts made of appropriate materials in these areas. Assembling the cavity in the mold base lets you select different metals for the various cavity components, optimizing the mold’s durability and performance. It Page 20

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also simplifies and speeds repairs for worn or damaged cavity components, especially if you maintain spare mold pieces for vulnerable components. Additionally, assembling the cavities from pieces can simplify component fabrication. Some of the drawbacks of mold-base cavity assemblies include high initial mold cost, less-efficient mold cooling, and potential tolerance accumulation problems with the cavity components. MOLDING UNDERCUTS: Undercuts, part features that prevent straight ejection at the parting line, tend to increase mold complexity and lead to higher mold construction and maintenance costs. Whenever feasible, redesign the part to avoid undercuts. Minor part design changes can often eliminate problematic undercuts in the mold. For example, adding through- holes can give access to the underside of features that would otherwise be undercuts. Likewise, simple modifications enable the mold to form a hole in the sidewall with bypass steel rather than with a side action mechanism Undercut features that cannot be avoided through redesign require mechanisms in the mold to facilitate ejection. These types of mechanisms include side-action slides, lifter rails, jiggler pins, collapsible cores and unscrewing mechanisms. Side-action slides use cam pins or hydraulic (or pneumatic) cylinders to retract portions of the mold prior to ejection. Cam-pin-driven slides retract as the mold opens. As the mold closes, the cam pins return the slides to their original position for the next injection cycle. Slides driven by hydraulic or pneumatic cylinders can activate at any time during the molding cycle, an advantage in applications requiring the slides to actuate prior to mold opening or closing. Shallow undercuts can often be formed by spring-loaded lifters (see figure 7-6) or lifter rails attached to the ejector system. These lifters move with the part on an angle during mold opening or ejection until the lifter clears the under- cut in the part. A variation on this idea

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PART EJECTION: Typically, molds have ejector systems built into the moving “B” half. The ejection unit of the molding press activates these systems. Rods linking the press-ejector mechanism to an ejector plate in the mold enable the press controller to control the timing, speed, and length of the ejection stroke. Reverse- injection molds eject parts from the stationary side of the mold via independent ejection mechanisms operated by springs or hydraulic cylinders. This con- figuration facilitates direct injection onto the inside or back surface of cosmetic parts. The added complexity of reverse- injection molds adds to the mold cost.

Specialized ejection components, such as knockout (KO) pins, KO sleeves, or stripper plates, project from the mold ejector plate to the part surface where they push the part out of the mold (see figures 7-9 through 7-11). These topics are discussed in this section. MOULD METALS: Mold designers consider a variety of factors when selecting the mold metal including, machining ease, weldability, abrasion resistance, hardness, corrosion resistance, and durability. Metals can range from the soft, low-melt-temperature alloys used in inexpensive, cast-metal, prototype molds to the porous metal used in vent inserts. Metals are chosen based not only on the cost, manufacturing, and performance requirements of the mold or component, but also on the experience and comfort level of the mold design and construction shop. Aluminum, long a popular choice for prototype molds, is gaining acceptance in moderate-run production molds. Improved aluminum alloys, such as QC-7, exhibit greater strength and hardness than standard aircraft-grade aluminum, and sufficient durability for some production molds. Hard coatings can raise the surface hardness of alu- minum molds to more than 50 Rockwell C (HRC) Page 22

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for improved wear resistance. Steel inserts and mechanical components are usually used in high wear areas within the aluminum mold to extend mold life. Aluminum offers easier machining and faster cycle times than conventional mold steels at the expense of wear resistance and mold durability. Most high production injection molds designed for engineering plastics are fabricated from high-quality tool steel. Mold bases are usually made of P-20 prehardened to 30 – 35 HRC and are often plated to resist corrosion. Specifications for high-quality molds, especially for medical parts, often specify 420 stainless steel to eliminate corrosion concerns.

Cavity and cores steels vary based on the production requirements, machining complexity, mold size, mechanical needs, and the abrasive or corrosive nature of the molding resin. . P-20 steel (30-36 HRC) provides a good mix of properties for most molds running non-abrasive materials such as unfilled PC or ABS. Prehardened 420 stainless (30-35 HRC) can also be used when corrosion resistance is needed. For longer mold life and increased durability, many medical molders select 420 stain less hardened to 50-52 HRC for their molds running unfilled resin grades. This highly polishable stainless steel resists corrosion and staining but provides less efficient cooling than most other mold steels. MOULD COST AND QUALITY: The true cost of a mold includes not only the costs of design and construc- tion, but also mold-maintenance costs and the mold-related costs associated with scrap, cycle time, part quality problems, and press down time. In the long run, the least-expensive mold option seldom produces the most economical, high-quality parts. Extra engineering and expense up front can improve molding efficiency and increase the number of good parts the mold can produce. When developing the mold specifications, consider the following: Page 23

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• Hardened steel molds last longer and require less maintenance and rework than soft steel molds. • Money spent on enhanced mold cooling can pay back many times over in reduced cycle time and improved part qual0ity. • Hardened mold interlocks and alignment features ensure proper mold alignment and prevent wear or damage due to misalignment. • Spare parts for items prone to wear or breakage are usually cheaper to manufacture during mold construction than after the mold is in production. Spare parts reduce costly down time.

• In the long run, it is usually more economical to adjust the mold steel to produce parts in the middle of the tolerance range at optimum processing conditions than to adjust dimensions by processing within a narrow processing window at less- than-optimum conditions. When obtaining quotations for new mold construction, make sure that every mold maker works from the specific set of mold specifications. Also consult processing, mold-maintenance, and inspection personnel at the molding facility for mold design input based on experience with similar molds

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MACHINING & FINISHING Machining stage includes mainly two processes, one is the CNC machining & secondly is the Electrical discharge machining (EDM).

CNC MACHINING: It is a process used in the manufacturing sector that involves the use of computers to control machine tools. Tools that can be controlled in this manner include lathes, mills, routers and grinders. The CNC in CNC Machining stands for Computer Numerical Control. On the surface, it may look like a normal PC controls the machines, but the computer's unique software and control console are what really sets the system apart for use in CNC machining. Under CNC Machining, machine tools function through numerical control. A computer program is customized for an object and the machines are programmed with CNC machining language (called G-code) that essentially controls all features like feed rate, coordination, location and speeds. With CNC machining, the computer can control exact positioning and velocity. CNC machining is used in manufacturing both metal and plastic parts. Page 25

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Figure 14

First a CAD drawing is created (either 2D or 3D), and then a code is created that the CNC machine will understand. The program is loaded and finally an operator runs a test of the program to ensure there are no problems. This trial run is referred to as "cutting air" and it is an important step because any mistake with speed and tool position could result in a scraped part or a damaged machine.

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Figure 15

Computer numerical control is the process of manufacturing m/c parts using computerized controller to command motors which drive each machine axis. In order to achieve high precision machining, many efforts have been made to develop more accurate computerized numerical control (CNC) systems. CNC systems are commonly used in industrial and commercial applications for its compact size, high power-to-weight ratio, reliability, and low maintenance.

CNC System includes a PC, motion board, servo motor drive and motors, spindle drive and motor, automatic tool-changer and general I/O card. A tool magazine is an indexable storage used on a machining center to store tools not in use. These machines are designed to perform a number of operations in a single setting of the job. A number of tools may be required for making a complex part. Modern CNC milling machines differ little in concept from the originally Page 27

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developed NC machines. Mills typically consist of a table that moves in the X and Y axes, and a tool spindle that moves in the Z (depth). The position of the tool is driven by motors through a series of step-down gears in order to provide highly accurate movements, or in modern designs, direct-drive stepper motor or servo motors. Open-loop control works as long as the forces are kept small enough and speeds are not too great. On commercial metalworking machines closed loop controls are standard and required in order to provide the accuracy, speed, and repeatability demanded. As the controller hardware evolved, the mills themselves also evolved. One change has been to enclose the entire mechanism in a large box as a safety measure, often with additional safety interlocks to ensure the operator is far enough from the working piece for safe operation. Most new CNC systems built today are completely electronically controlled. CNC-like systems are now used for any process that can be described as a series of movements and operations. These include laser cutting, welding, friction stir welding, ultrasonic welding, flame and plasma cutting, bending, spinning, pinning, gluing, fabric cutting, sewing, tape and fiber placement, routing, picking and placing (PnP), and sawing.

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Figure 16

There are many advantages to using CNC Machining: (a). The process is more precise than manual machining, and (b). It can be repeated in exactly the same manner over and over again. (c). It can produce complex shape would be almost impossible to achieve with manual machining (d). It is used in jobs that need a high level of precision or very repetitive tasks.

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CNC LATHE: Automated version of a manual lathe is known as CNC lathe. Programmed to change tools automatically, it is used for turning and boring metals etc. WORKING OF CNC LATHE:  Controlled G and M codes.  These are number values and co-ordinates.  Each number or code is assigned to a particular operation.  Typed in manually to CAD/CAM  G and M are automatically generated by the computer software FEATURES OF CNC LATHE:  The tool or material moves  Tool can operate in 5-10 axes.  Larger machines have a machine control unit which manages operations.  Movement is controlled by motors.  Feedback is provided by sensors.  Tool magazines are used to change tool automatically.

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ELECTRIC DISCHARGE MACHING (EDM): PRINCIPLES OF EDMElectrical Discharge Machining (EDM) is a controlled metal-removal process that is used to remove metal by means of electric spark erosion. In this process an electric spark is used as the cutting tool to cut (erode) the workpiece to produce the finished part to the desired shape. The metal-removal process is performed by applying a pulsating (ON/OFF) electrical charge of high-frequency current through the electrode to the workpiece. This removes (erodes) very tiny pieces of metal from the workpiece at a controlled rate.

Fig. A rough diagram showing the EDM process

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EDM PROCESSIn EDM, a potential difference is applied between the tool and workpiece. Both the tool and the work material are to be conductors of electricity. The tool and the work material are immersed in a dielectric medium. Generally kerosene or deionised water is used as the dielectric medium. A gap is maintained between the tool and the workpiece. Depending upon the applied potential difference and the gap between the tool and workpiece, an electric field would be established. Generally the tool is connected to the negative terminal of the generator and the workpiece is connected to positive terminal. As the electric field is established between the tool and the job, the free electrons on the tool are subjected to electrostatic forces. The high speed electrons then impinge on the job and ions on the tool. The kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermal energy or heat flux. uch intense localised heat flux leads to extreme instantaneous confined rise in temperature which would be in excess of 10,000oC. Such localised extreme rise in temperature leads to material removal. Material removal occurs due to instant vapourisation of the material as well as due to melting. The molten metal is not removed completely but only partially. Generally the workpiece is made positive and the tool negative. Hence, the electrons strike the job leading to crater formation due to high temperature and melting and material removal. Similarly, the positive ions impinge on the tool leading to tool wear. In EDM, the generator is used to apply voltage pulses between the tool and the job. A constant voltage is not applied. Only sparking is desired in EDM rather than arcing. Arcing leads to localised material removal at a particular point whereas sparks get distributed all over the tool surface leading to uniformly distributed material removal under the tool.

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CHARACTERISTICS OF EDM• The process can be used to machine any work material if it is electrically conductive • Material removal depends on mainly thermal properties of the work material rather than its strength, hardness etc • In EDM there is a physical tool and geometry of the tool is the positive impression of the hole or geometric feature machined • The tool has to be electrically conductive as well. The tool wear once again depends on the thermal properties of the tool material • Though the local temperature rise is rather high, still due to very small pulse on time, there is not enough time for the heat to diffuse and thus almost no increase in bulk temperature takes place. However rapid heating and cooling and local high temperature leads to surface hardening which may be desirable in some applications • Though there is a possibility of taper cut and overcut in EDM, they can be controlled and compensated. EDM is a thermal process; material is removed by heat. Heat is introduced by the flow of electricity between the electrode and workpiece in the form of a spark. Material at the closest points between the electrode and workpiece, where the spark originates and terminates, are heated to the point where the material vaporizes. While the electrode and workpiece should never feel more than warm to the touch during EDM, the area where each spark occurs is very hot. The area heated by each spark is very small so the dielectric fluid quickly cools the vaporized material and the electrode and workpiece surfaces. However, it is possible for metallurgical changes to occur from the spark heating the workpiece surface. A dielectric material is required to maintain the sparking gap between the electrode and workpiece. This dielectric material is normally a fluid. Die-sinker type EDM machines usually use hydrocarbon oil, while wire-cut EDM machines normally use deionized water.

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DIELECTRICIn EDM, as has been discussed earlier, material removal mainly occurs due to thermal evaporation and melting. As thermal processing is required to be carried out in absence of oxygen so that the process can be controlled and oxidation avoided. Oxidation often leads to poor surface conductivity (electrical) of the workpiece hindering further machining. Hence, dielectric fluid should provide an oxygen free machining environment. Further it should have enough strong dielectric resistance so that it does not breakdown electrically too easily but at the same time ionise when electrons collide with its molecule. Moreover, during sparking it should be thermally resistant as well. Generally kerosene and deionised water is used as dielectric fluid in EDM. Tap water cannot be used as it ionises too early and thus breakdown due to presence of salts as impurities occur. Dielectric medium is generally flushed around the spark zone. It is also applied through the tool to achieve efficient removal of molten material.

ELECTRODE MATERIALElectrode material should be such that it would not undergo much tool wear when it is impinged by positive ions. Thus the localised temperature rise has to be less by tailoring or properly choosing its properties or even when temperature increases, there would be less melting. Further, the tool should be easily workable as intricate shaped geometric features are machined in EDM. Thus the basic characteristics of electrode materials are: • High electrical conductivity - electrons are cold emitted more easily and there is less bulk electrical heating • High thermal conductivity - for the same heat load, the local temperature rise would be less due to faster heat conducted to the bulk of the tool and thus less tool wear • Higher density - for the same heat load and same tool wear by weight there would be less volume removal or tool wear and thus less dimensional loss or inaccuracy • High melting point - high melting point leads to less tool wear due to less tool material melting for the same heat load • Easy manufacturability - should be easy to manufacture

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The followings are the different electrode materials which are used commonly in the industry: • Graphite • Electrolytic oxygen free copper • Tellurium copper – 99% Cu + 0.5% tellurium • Brass

Fig. Sparking occurs at closest points between the electrode and workpiece. In EDM, the spark occurs between the two nearest point on the tool and

workpiece. Thus machining may occur on the side surface as well leading to overcut and tapercut as depicted in Fig. Taper cut can be prevented by suitable insulation of the tool. Overcut cannot be prevented as it is inherent to the EDM process. But the tool design can be done in such a way so that same gets compensated.

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Fig. Tapercut & Overcut

Fig. Tapercut prevention

The EDM process can be used in two different ways: 1. A pre-shaped or formed electrode (tool), usually made from graphite or copper, is shaped to the form of the cavity it is to reproduce. The formed electrode is fed vertically down and the reverse shape of the electrode is eroded (burned) into the solid workpiece. 2. A continuous-travelling vertical-wire electrode, the diameter of a small needle or less, is controlled by the computer to follow a programmed path to erode or cut a narrow slot through the workpiece to produce the required shape.

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ADVANTAGES OF EDM: • Complex shapes that would otherwise be difficult to produce with conventional cutting tools. • Extremely hard material to very close tolerances. • Very small work pieces where conventional cutting tools may damage the part from excess cutting tool pressure. • Any material that is electrically conductive can be cut using the EDM process. • Hardened work pieces can be machined eliminating the deformation caused by heat treatment. • X, Y, and Z axes movements allow for the programming of complex profiles using simple electrodes. • Complex dies sections and molds can be produced accurately, faster, and at lower costs. • The EDM process is burr-free. • Thin fragile sections such as webs or fins can be easily machined without deforming the part. DISADVANTAGES OF EDM: • The slow rate of material removal. • Potential fire hazard associated with use of combustible oil based dielectrics. • The additional time and cost used for creating electrodes for ram/sinker EDM. • Reproducing sharp corners on the workpiece is difficult due to electrode wear. • Power consumption is high. • Excessive tool wear occurs during machining. • Electrically non-conductive materials can be machined only with specific set-up of the process

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CLASSIFICATION OF EDM CONVENTIONAL EDM:

In the EDM process an electric spark is used to cut the workpiece, which takes the shape opposite to that of the cutting tool or electrode. The electrode and the workpiece are both submerged in a dielectric fluid, which is generally light lubricating oil. A servomechanism maintains a space of about the thickness of a human hair between the electrode and the work, preventing them from contacting each other. In EDM ram or sinker machining, a relatively soft graphite or metallic electrode can be used to cut hardened steel, or even carbide. The EDM process produces a cavity slightly larger than the electrode because of the overcut.

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DYNAMIC Industries Ltd. WIRE-CUT EDM:

The wire-cut EDM is a discharge machine that uses CNC movement to produce the desired contour or shape. It does not require a special shaped electrode, instead it uses a continuous traveling vertical wire under tension as the electrode. The electrode in wire-cut EDM is about as thick as a small diameter needle whose path is controlled by the machine computer to produce the shape required.

CONVENTIONAL EDM- DIELECTRIC FLUIDS During the EDM process the workpiece and the electrode are submerged in the dielectric oil, which is an electrical insulator that helps to control the arc discharge. The dielectric oil, that provides a means of flushing, is pumped through the arc gap. This removes suspended particles of workpiece material and electrode from the work cavity. WIRE EDM- DIELECTRIC FLUIDS The dielectric fluid must be circulated under constant pressure to flush (wash) away the metal particles and assist in the machining or erosion process. If red sparks occur during the cutting operation, the water supply is inadequate. To overcome this problem, increase the flow of water until blue sparks appear.

FLUSHING

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Flushing is the most important function in any electrical discharge machining operation. Flushing is the process of introducing clean filtered dielectric fluid into the spark gap. Flushing applied incorrectly can result in erratic cutting and poor machining conditions. There are a number of flushing methods used to remove the metal particles efficiently while assisting in the machining process. Too much fluid pressure will remove the chips before they can assist in the cutting action, resulting in slower metal removal. Too little pressure will not remove the chips quickly enough and may result in short-circuiting the erosion process

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FINAL COMPONENT Fan shroud to be used by Ashok Leyland-Nissan with a joint venture in commercial vehicles.

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AUTOMATIC TOOL CHANGER A CNC tool changer fulfils the requirement of multiple tooling for a wide variety of machine tools. A CNC machine tool raises the productivity by automatically translating designs into instructions for a computer controller on a machine tool. The spindle axis of a CNC machine tool fixes the chucks which is integral to the lathe’s functioning. A CNC tool storage system is an organized, efficient, and secure method of storing tools at all stages and time. The main component of a CNC tool storage system is a CNC tool holder. A CNC tool holder is suitable for vertically storing all types of preset tools.

AUTOMATIC MANUFACTURING SYSTEMS: Automated manufacturing systems operate in the factory on the physical product. They perform operations such as processing, assembly, inspection, or material handling in some cases accomplishing more than one of these operations in the same system. They are called automated because they perform their operations with a reduced level of human participation compared with the corresponding manual process. In some highly automated systems, there is virtually no human participation. Examples of automated manufacturing systems include: 

Automated machine tools that process machine parts

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Transfer lines that perform a series of machining operations

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Automated assembly systems

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Manufacturing systems that use industrial robots to perform processing or assembly operations.

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Automatic material handling and storage systems to integrate manufacturing operations

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Automatic inspection system for quality control

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REASONS FOR AUTOMATING: 

Increase labour productivity to get better output.

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Reduce labour cost and to mitigate the effects of labour shortages

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Reduce or eliminate routine manual and clerical tasks

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Improve worker safety

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Improve product quality by confronting with quality specifications & uniformity.

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Reduce the time between customer order & product delivery thus providing competitive advantage.

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Improved accuracies with consistency of quality parameters.

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Suitable for mass production with better material handling and reduced WIP (Work-InProcess).

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Automatic data acquisition for computer aided quality control and inspection.

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Flexible with zero set-up change over time.

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TOOLING FOR NUMERICAL CONTROL: Since NC machines are in general, more expensive than general purpose man-operated machine tools, special attention is given to the design of the NC machines and production tooling in order to reduce the time spent in both work and machine set up. Tooling systems for NC are designed to eliminate operator error and maximize productive machine hours. They do this in one or more of the following ways: 1. Using quick change tool holders 2. Automatic tool selection 3. Automatic tool Changer 4. Presetting of tool 5. Facilitating tool selection and tool changing through the numerical control program While tooling for NC machines might appear to be specialized, the actual components and principles involved have much in common with what would be considered proper practice for conventional machine tools.

1. Tool Holders Quick change tool holders are designed so that cutting tools can be readily positioned with respect to the spindle axis of the machine. This requires that tolerances on length and/or diameter be held on all tools used in the machine. Arbor type cutters such as face mills and shell end mills are held in arbor type tool holders. Shank type mills are held in positive lock holder. Drills, reamers and boring tools are held in a straight shank collet type holder. Taps are held in a tension and compression collet type holders.

2. Automatic tool selection Automatic tool selectors in NC make all the tool changes required to complete a predetermined sequence of machining operations on a part. There are two basic approaches to automatic tool selection:  When relatively small number of different tools is required, automatic tool selector is the turret type. The turret is rotated under program control to bring the proper tool into position. The tools are held in preset tool holder adapters which are mounted into turret spindles.

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

An automatic tool changer and magazine of tools is frequently used in preference to the turret approach, when the number of tools to be used is large. Each tool is inserted in a common spindle as required. The tools which are mounted in uniform holders, are automatically picked up, placed into the spindle and locked in place. When the operations using that tool are completed it is returned to the tool storage magazine. For changing tools rapidly it is better to place tool in magazine or turret in the order in which they will be used.

3. Automatic Tool Changer For three axis machines which perform a wide variety of operations tool changes a programmed into the tape for fully automatic selection and replacement. The automatic tool change system may consist of following elements:     



Rotary tool storage magazine for numerous tools. Automatic tool changer to remove tool holders from the machine spindle and replace them with tape programmed tools. Basic tool holders adaptable to a multiplicity of cutting tool types and work specifications. Tool coding rings and system for selection of proper tools in accordance with tape signals. In operation, the automatic tool change is accomplished in four steps: By tape command (and from any location the magazine) the tool magazine rotates to proper position to bring the pre-selected tool into place for particular operation. One end of the tool change your arm then grasps the tool while the opposite end grasps the tool to be replaced in the spindle. The tool changer arm moves out away from the spindle removing one tool from the magazine and other tool from the spindle

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AUTOMATIC TOOL CHANGER An Automatic Tool Changer is equipment that reduces cycle times by automatically changing tools between cuts. Automatic tool changers are differentiated by tool-to-tool time and the number of tools they can hold. CNC tool changers allow a machine to perform more than one function without requiring an operator to change the tooling. A CNC tool changer can quickly change the end effectors without the requirement of multiple robots. Tool changers can be a manual tool changers or automatic tool changers. A CNC tool changer fulfills the requirement of multiple tooling for a wide variety of machine tools.

Why Tool Changer is needed? Tool changer is equipment which is used in CNC machines to reduce the cycle time. The term applies to a wide variety of tooling, from indexable insert, single point tools to coded, preset tool holders for use in automatic tool changers. It includes power-actuated, cross-slide tooling and turret tool holders for single spindle chuckers, interchangeable-block boring tools. A number of basic types of tool holders are available that accommodate most face mills, end mills, drills, reamers, taps, boring tools, counterbores, countersinks, and spot facers. Arbor type cutters such as face mills and shell end mills are held in an arbor type tool holders. Shank type mills are held in positive lock holder. Drills, reamers and boring tools are held in a straight shank collet type holder. Taps are held in a tension and compression collet type holders.

Types of automatic tool changer There are mainly three kinds of tool changers available in market according to the tool magazine arrangements provided. 1. Tool change system with gripper arm 2. Tool change system with chain magazine 3. Tool change system with disc magazine 1. Tool Change system with gripper Arm In this system, there are mainly two elements  Disc with magazine  Gripper arm In this system, a disc is provided with magazine, in which different types of tools are loaded. It can hold maximum 32 tools. In magazines, all the tools which are required are fixed in the magazines. The tool which is programmed in controller according to the program will be indexed in front of the gripper arm and then the gripper arm grips the tool and performs the operation. After completion of the operation by each tool, the gripper arm places the tool back in to the magazine. Page 47

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Description of the gripper arm The tool changer gripper arm consists of a central aluminum structure with terminal tool grippers of hardened steel. Tool gripping and release are obtained by means of a springoperated mechanism actuated by the rotation of the arm. The latter, in turning, engages or disengages the grippers from the tools when these are in exchange position.

2. Tool Change system with chain magazine In this kind of system, a chain is provided with magazines for tool holding. This chain can hold numerous tools so it is used in heavy machineries. Starting from 32 it can hold more than 100 tools. These chain is indexed in front of the head stock directly as per the tool. In this kind of system there is no arrangement like gripper arm. The chain itself is indexed and the machining is done while keeping the tool in the chain only.

Fig: Tool Change system with chain magazine

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3. Tool change system with Disc magazine

In this system, the tools are held in a big disc. This disc is not similar to the disc provided in gripper arm mechanism. In this disc, there are tool grippers provided separately for each magazine these grippers holds the tool and performs machining operation as well. This system disc can hold 32 to maximum of 64 tools. These type of tool changers are used in medium capacity machineries.

Fig: Tool change with disc magazine

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CONCLUSION: After the successful implementation of the automatic tool changer along with tool a pre-setter, following will be some of the major advantages:  It would save 6-8 seconds of time per cycle, on an average, which is very good in terms of time-reduction.  It can perform multiple operations in a single set up.  It can re-tool quickly in order to accommodate product designs that are changing in timely response to market demands  It is able to replace quickly a worn out or broken part

REFERENCES: Page 50

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 Reintjes, J. Francis (1991), Numerical Control: Making a New Technology, Oxford University Press.  Design and Simulation of Microcontroller Based Automatic Tool Changing System in CNC Machine, La Pyae Lynn, Theingi and Win Khaing Moe.  Malloy, Robert A. (1994). Plastic Part Design for Injection Molding. Munich Vienna New York.  Hanser.Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). Manufacturing Processes Reference Guide. Industrial Press, Inc.

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