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NOTICE :

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. Part 1 : Grasping the “ Basics ”. 1.00±0.01. 2.00±0.01. The Part. 1.99.

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  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. Understanding True Position

  2. Part 1 : Grasping the “Basics” Understanding True Position

  3. 1.00±0.01 2.00±0.01 The Part Understanding True Position

  4. 1.99 2.01 1.01 0.99 1.00±0.01 2.00±0.01 The Tolerances Understanding True Position

  5. 1.01 Part 1 Center Part 2 Center 0.99 1.99 2.01 The Tolerance Zone Understanding True Position

  6. 1.01 Part 1 Center Part 2 Center 0.99 1.99 2.01 The Question… Which Part is Better? Understanding True Position

  7. 1.01 Part 1 Center 0.99 1.99 2.01 Part 1 is within the tolerance zone, but… Understanding True Position

  8. 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 Understanding True Position

  9. How can we set up a tolerance band that fairly and functionally judges the position of features? Understanding True Position

  10. 1.99 2.01 1.01 Part 1 Center Part 2 Center 0.99 Use a Circle instead of a Square! Understanding True Position

  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. Understanding True Position

  12. Mathematically Speaking…. True Position = ΔX2 + ΔY2 * 2 ΔX = Difference from Basic X value from Actual X value ΔY = Difference from Basic Y value from Actual Y value Understanding True Position

  13. Diametral Zone Tolerance True Position Ø 0.01 A B C No Tolerances A Primary, Secondary, Tertiary Datums 1.00 2.00 B C New Part Print w/True Position Understanding True Position

  14. Ø 0.01 A B C A 1.00 2.00 B C Here’s an Example Calculation Understanding True Position

  15. Ø 0.01 A B C A Actual Measurements: X=2.003 Y=1.004 1.00 2.00 B C CAN WE SHIP IT? Understanding True Position

  16. Actual X = 2.003 Actual Y=1.004 Basic X=2.000 Basic Y=1.000 Δ X = 0.003 Δ Y = 0.004 TP = 0.0032+0.0042 * 2 or TP = 0.009+0.016 * 2 or TP = 0.025 * 2 or TP = .005 * 2 so….. Understanding True Position

  17. True Position = 0.010 Hole Center 0.005 from Nominal 0.005 True Position Result = 0.010 0.004 0.003 Nominal Center at X=2, Y=1 from Basic Dimensions Understanding True Position

  18. YES, WE CAN! Ø 0.01 A B C A Our True Position is within the Specification…. Barely! 1.00 2.00 B C Understanding True Position

  19. Let’s do this very example in Calypso and see if the math works out! Understanding True Position

  20. Understanding True Position

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

  22. It Works! Understanding True Position

  23. Ø 0.01 A B C A 1.00 2.00 B C Same Print, this time a “Real” Part Understanding True Position

  24. On a “Real” Part: X= 1.9619 Y= 1.0081 Understanding True Position

  25. Actual X = 1.9619 Actual Y = 1.0081 Basic X = 2.000 Basic Y = 1.000 Δ X = -0.0381 Δ Y = 0.0081 TP = -0.03812+0.00812 * 2 or TP = 0.0015+0.0001 * 2 or TP = 0.0016 * 2 or TP = .0390 * 2 so….. Understanding True Position

  26. True Position = 0.0779 Hole Center 0.0390 from Nominal 0.0390 0.0081 0.0381 True Position Result = 0.0779 Nominal Center at X=2, Y=1 from Basic Dimensions Understanding True Position

  27. What??? Understanding True Position

  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! Understanding True Position

  29. Let’s see how this changes things. Understanding True Position

  30. Understanding True Position

  31. Watch out for Outliers! Understanding True Position

  32. Understanding True Position

  33. Now that we have that sorted out, ONE MORE TIME! X= 1.9504 Y= 1.0104 Understanding True Position

  34. Actual X = 1.9504 Actual Y = 1.0104 Basic X = 2.000 Basic Y = 1.000 Δ X = -0.0496 Δ Y = 0.0104 TP = -0.04962+0.01042 * 2 or TP = 0.0025+0.0001 * 2 or TP = 0.0026 * 2 or TP = .0507 * 2 so….. Understanding True Position

  35. True Position = 0.1014 Hole Center 0.0507 from Nominal 0.0507 0.0104 0.0496 True Position Result = 0.1014 Nominal Center at X=2, Y=1 from Basic Dimensions Understanding True Position

  36. YES!!! Understanding True Position

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

  38. Turn on Additional Position Result in the Characteristic Settings Editor. Understanding True Position

  39. You’ve got Questions, We have answers. Understanding True Position Part 1 : Grasping the “Basics” Understanding True Position

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