ETSE Zeiss True Position Basics 9-29-2014 Update (Compatibility Mode) PDF

 

NOTICE :

This presentation was given at the October 2007 Lunch N Learn at Ellison Ellison Technologies Technologies in Charlotte. 󲀜

󲀝

The presentation is meant to be viewed with the narration and detailed explanation of the presenter.

Last Updated: 8/27/2014

Understanding True Position

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Part 1 : Grasping the Basics 󲀜

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Understanding True Position

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1.00󰂱0.01

2.00

󰂱

0.01

The Part Last Updated: 8/27/2014

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1.99

2.01

1.01 0.99

1.00󰂱0.01

2.00

󰂱

0.01

The Tolerances Last Updated: 8/27/2014

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1.01

Part 1 Center Part 2 Center 0.99 1.99

2.01

The Tolerance Zone Last Updated: 8/27/2014

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1.01

Part 1 Center Part 2 Center 0.99 1.99

2.01

The Question… Which Part is Better? Last Updated: 8/27/2014

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1.01

Part 1 Center 0.99 1.99

2.01

Part 1 is within the tolerance zone, but… Last Updated: 8/27/2014

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1.01

Part 2 Center 0.99 1.99

2.01

Part 2 is closer to the Nominal Center and will assemble easier than Part 1 Last Updated: 8/27/2014

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How can we set up a tolerance band that fairly and functionally  judges the position of features?

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1.99

2.01 1.01

Part 1 Center Part 2 Center 0.99

Use a Circle instead of a Square! Last Updated: 8/27/2014

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Definition Time!!!

The result of a True Position Characteristic is the diameter of a circle, centered on the basic dimensions from the specified datums, point. that contains the actual center

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Mathematically Speaking…. True Position =

∆X2

+

∆Y2

*2

∆X

= Difference from Basic X value from Actual Actual X value ∆Y

= Difference from Basic Y value from Actual Y value

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True Position

Diametral Zone

Tolerance

Ø 0.01 A B C A

No Tolera olerances nces

Primary, Secondary, Tertiary ertia ry Datums

1.00 2.00

B C

New Part Print w/T w/True rue Position Last Updated: 8/27/2014

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Ø 0.01 A B C A

1.00 2.00

B C

Here s an Example Calculation 󲀙

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Ø 0.01 A B C A

Actual Measurements: X=2.003

1.00

Y=1.004 2.00

B C

CAN WE SHIP IT? Last Updated: 8/27/2014

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Actual X = 2.003

Actual Y=1.004

Basic X=2.000 ∆ X

Basic Y=1.000

= 0.003

∆ Y

 

TP =

0.0032+0.0042 * 2

or

TP = TP =

0.009+0.016 0.025

or or

TP =

.005 * 2

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*2 *2

= 0.004

so…..

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True Positi Position on

=

0.010 Hole Center 0.005 from Nominal

True Position Result = 0.010

Nominal Center at X=2, Y=1 from Basic Dimensions Last Updated: 8/27/2014

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Ø 0.01 A B C A

Our True Position is within the Specification….

1.00

Barely! 2.00

B C

YES, WE CAN! Last Updated: 8/27/2014

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Let s do this very example in 󲀙

Calypso and see if the math works out!

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This is a Theoretical feature with X Y coordinates placed exactly at 2.003 and 1.004.

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Ø 0.01 A B C A

1.00

2.00

B C

Same Print, this time a Real Part 󲀜

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On a 󲀜Real󲀝 Part:

X= 1.9619 Y= 1.0081

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Actual X = 1.9619

Actual Y = 1.0081

Basic X = 2.000

Basic Y = 1.000

∆ X

= -0.0381

∆ Y

 

= 0.0081

TP =

-0.03812+0.00812

*2

or

TP =

0.0015+0.0001

*2

or

TP =

0.0016

TP =

.0390 * 2

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*2

or so…..

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True Positio Position n

=

0.0779

Hole Center 0.0390 from Nominal

True Position Result = 0.0779

Nominal Center at X=2, from BasicY=1 Dimensions Last Updated: 8/27/2014

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Explanation Time!!!

The GD&T standard FUNCTIONAL centerspecifies be used that for the calculations. This means for a hole, that the Maximum fit be used. Calypso does Inscribed this automatically!

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Let s see how this changes 󲀙

things.

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Watch out for Outliers!

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Now that we have that sorted out, ONE MORE TIME!

X= 1.9504 Y= 1.0104

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Actual X = 1.9504

Actual Y = 1.0104

Basic X = 2.000

Basic Y = 1.000

∆ X

= -0.0496

∆ Y

 

= 0.0104

TP =

-0.04962+0.01042

*2

or

TP =

0.0025+0.0001

*2

or

TP = TP =

0.0026 .0507 * 2

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*2

or so…..

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True Positio Position n

=

0.1014

Hole Center 0.0507 from Nominal

True Position Result = 0.1014

Nominal Center at X=2, Y=1 from Basic Dimensions Last Updated: 8/27/2014

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ONE MORE THING…..

You might say :

So if True True Position only gives me distance from center, center,

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how do I know how to make my offsets? Last Updated: 8/27/2014

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Turn on Additional Position Result in the Characteristic Settings Editor. Editor. Last Updated: 8/27/2014

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You ve got Questions, We have answers. 󲀙

Understanding True Position  Part 1 : Grasping the Basics 󲀜

Last Updated: 8/27/2014

Understanding True Position

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