ETSE Zeiss True Position Basics - Ellison Technologies Zeiss... · True Position Basics Explanation...
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True Position Basics NOTICE : This presentation was given at the October 2007 “Lunch N Learn” at J&H Machine Tools in Charlotte. The presentation is meant to be viewed with the narration and detailed explanation of the presenter.
Transcript of ETSE Zeiss True Position Basics - Ellison Technologies Zeiss... · True Position Basics Explanation...
True Position Basics
NOTICE :
This presentation was given at the October 2007 “Lunch N Learn” at J&H Machine Tools in Charlotte.
The presentation is meant to be viewed with the narration and detailed explanation of the presenter.
True Position Basics
Understanding True Position
Part 1 : Grasping the “Basics”
True Position Basics
2.00±0.01
1.00±0.01
The Part
True Position Basics
2.00±0.01
1.00±0.01
The Tolerances
1.99 2.01
0.99
1.01
True Position Basics
1.99 2.01
0.99
1.01
The Tolerance Zone
Part 1 Center Part 2
Center
True Position Basics
1.99 2.01
0.99
1.01
The Question… Which Part is Better?
Part 1 Center Part 2
Center
True Position Basics
0.99
1.01
Part 1 is within the tolerance zone, but…
Part 1 Center
1.99 2.01
True Position Basics
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
True Position Basics
How can we set up a tolerance band that fairly and functionally judges the position of features?
True Position Basics
1.99 2.01
0.99
1.01
Part 1 Center Part 2
Center
Use a Circle instead of a Square!
True Position Basics
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.
True Position Basics
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
True Position Basics
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
True Position Basics
2.00
1.00
Here’s an Example Calculation
Ø 0.01 A B C
A
B
C
True Position Basics
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
True Position Basics
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…..
True Position Basics
True Position = 0.010 Hole Center
0.005 from Nominal True Position
Result = 0.010
0.003
0.00
4 Nominal Center at X=2, Y=1 from Basic Dimensions
True Position Basics
2.00
1.00
Ø 0.01 A B C
A
B
C
Our True Position is within the Specification….
Barely!
CAN WE SHIP IT? YES, WE CAN!
True Position Basics
Let’s do this very example in Calypso and see if the math works out!
True Position Basics
True Position Basics
This is a Theoretical feature with X Y coordinates placed exactly at 2.003 and 1.004.
True Position Basics
True Position Basics
2.00
1.00
Same Print, this time a “Real” Part
Ø 0.01 A B C
A
B
C
True Position Basics
On a “Real” Part:
X= 1.9619
Y= 1.0081
True Position Basics
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…..
True Position Basics
True Position = 0.0779
Hole Center 0.0390 from Nominal 0.0390
True Position Result = 0.0779
0.0381 0.00
81
Nominal Center at X=2, Y=1 from Basic Dimensions
True Position Basics
True Position Basics
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!
True Position Basics
Let’s see how this changes things.
True Position Basics
True Position Basics
Watch out for Outliers!
True Position Basics
True Position Basics
Now that we have that sorted out,
ONE MORE TIME!
X= 1.9504
Y= 1.0104
True Position Basics
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…..
True Position Basics
True Position = 0.1014
Hole Center 0.0507 from Nominal 0.0507
True Position Result = 0.1014
0.0496 0.01
04
Nominal Center at X=2, Y=1 from Basic Dimensions
True Position Basics
True Position Basics
“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 :
True Position Basics
Turn on Additional Position Result in the Characteristic Settings Editor.
True Position Basics
Understanding True Position
You’ve got Questions, We have answers.
Part 1 : Grasping the “Basics”
