1. NOTICE : This presentation was given at the October 2007 “Lunch N Learn” at Ellison Technologies in Charlotte. The presentation is meant to be viewed with the narration and detailed explanation of the presenter. Last Updated: 8/27/2014Understanding True Position1

2. Part 1 : Grasping the “Basics” Last Updated: 8/27/2014Understanding True Position2

3. 2.00±0.01 1.00±0.01 The Part Last Updated: 8/27/2014Understanding True Position3

4. 2.00±0.01 1.00±0.01 The Tolerances 1.992.01 0.99 1.01 Last Updated: 8/27/2014Understanding True Position4

5. 1.99 2.01 0.99 1.01 The Tolerance Zone Part 1 Center Part 2 Center Last Updated: 8/27/2014Understanding True Position5

6. 1.99 2.01 0.99 1.01 The Question… Which Part is Better? Part 1 Center Part 2 Center Last Updated: 8/27/2014Understanding True Position6

7. 0.99 1.01 Part 1 is within the tolerance zone, but… Part 1 Center 1.99 2.01 Last Updated: 8/27/2014Understanding True Position7

8. 0.99 1.01 Part 2 is closer to the Nominal Center and will assemble easier than Part 1 Part 2 Center 1.99 2.01 Last Updated: 8/27/2014Understanding True Position8

9. How can we set up a tolerance band that fairly and functionally judges the position of features? Last Updated: 8/27/2014Understanding True Position9

10. 1.992.01 0.99 1.01 Part 1 Center Part 2 Center Use a Circle instead of a Square! Last Updated: 8/27/2014Understanding True Position10

11. Definition Time!!! The result of a True Position Characteristic is the diameter of a circle, centered on the basic dimensions from the specified datums, that contains the actual center point. Last Updated: 8/27/2014Understanding True Position11

12. Mathematically Speaking…. True Position = ΔX 2 + ΔY 2 * 2 ΔX = Difference from Basic X value from Actual X value ΔY = Difference from Basic Y value from Actual Y value Last Updated: 8/27/2014Understanding True Position12

13. 2.00 1.00 New Part Print w/True Position No Tolerances Ø 0.01 A B C A B C True Position Diametral Zone Primary, Secondary, Tertiary Datums Tolerance Last Updated: 8/27/2014Understanding True Position13

14. 2.00 1.00 Here’s an Example Calculation Ø 0.01 A B C A B C Last Updated: 8/27/2014Understanding True Position14

15. 2.00 1.00 CAN WE SHIP IT? Ø 0.01 A B C A B C Actual Measurements: X=2.003 Y=1.004 Last Updated: 8/27/2014Understanding True Position15

16. Actual X = 2.003Actual Y=1.004 Basic X=2.000Basic Y=1.000 Δ X = 0.003 Δ Y = 0.004 TP = 0.003 2 +0.004 2 * 2or TP = 0.009+0.016 * 2or TP = 0.025 * 2or TP =.005 * 2 so….. Last Updated: 8/27/2014Understanding True Position16

17. True Position = 0.010 Hole Center 0.005 from Nominal 0.005 True Position Result = 0.010 0.003 0.004 Nominal Center at X=2, Y=1 from Basic Dimensions Last Updated: 8/27/2014Understanding True Position17

18. 2.00 1.00 Ø 0.01 A B C A B C Our True Position is within the Specification…. Barely! YES, WE CAN! Last Updated: 8/27/2014Understanding True Position18

19. Let’s do this very example in Calypso and see if the math works out! Last Updated: 8/27/2014Understanding True Position19

20. Last Updated: 8/27/2014Understanding True Position20

21. This is a Theoretical feature with X Y coordinates placed exactly at 2.003 and 1.004. Last Updated: 8/27/2014Understanding True Position21

22. Last Updated: 8/27/2014Understanding True Position22

23. 2.00 1.00 Same Print, this time a “ Real ” Part Ø 0.01 A B C A B C Last Updated: 8/27/2014Understanding True Position23

24. On a “Real” Part: X= 1.9619 Y= 1.0081 Last Updated: 8/27/2014Understanding True Position24

25. Actual X = 1.9619Actual Y = 1.0081 Basic X = 2.000Basic Y = 1.000 Δ X = -0.0381 Δ Y = 0.0081 TP = -0.0381 2 +0.0081 2 * 2or TP = 0.0015+0.0001 * 2or TP = 0.0016 * 2or TP =.0390 * 2 so….. Last Updated: 8/27/2014Understanding True Position25

26. True Position = 0.0779 Hole Center 0.0390 from Nominal 0.0390 True Position Result = 0.0779 0.0381 0.0081 Nominal Center at X=2, Y=1 from Basic Dimensions Last Updated: 8/27/2014Understanding True Position26

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28. Explanation Time!!! The GD&T standard specifies that the FUNCTIONAL center be used for calculations. This means for a hole, that the Maximum Inscribed fit be used. Calypso does this automatically! Last Updated: 8/27/2014Understanding True Position28

29. Let’s see how this changes things. Last Updated: 8/27/2014Understanding True Position29

30. Last Updated: 8/27/2014Understanding True Position30

31. Watch out for Outliers! Last Updated: 8/27/2014Understanding True Position31

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33. Now that we have that sorted out, ONE MORE TIME! X= 1.9504 Y= 1.0104 Last Updated: 8/27/2014Understanding True Position33

34. Actual X = 1.9504Actual Y = 1.0104 Basic X = 2.000Basic Y = 1.000 Δ X = -0.0496 Δ Y = 0.0104 TP = -0.0496 2 +0.0104 2 * 2or TP = 0.0025+0.0001 * 2or TP = 0.0026 * 2or TP =.0507 * 2 so….. Last Updated: 8/27/2014Understanding True Position34

35. True Position = 0.1014 Hole Center 0.0507 from Nominal 0.0507 True Position Result = 0.1014 0.0496 0.0104 Nominal Center at X=2, Y=1 from Basic Dimensions Last Updated: 8/27/2014Understanding True Position35

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37. “So if True Position only gives me distance from center, how do I know how to make my offsets?” ONE MORE THING….. You might say : Last Updated: 8/27/2014Understanding True Position37

38. Turn on Additional Position Result in the Characteristic Settings Editor. Last Updated: 8/27/2014Understanding True Position38

39. Understanding True Position You’ve got Questions, We have answers. Part 1 : Grasping the “Basics” Last Updated: 8/27/2014Understanding True Position39