Curve and True Position

[[Ji...]]

Has anyone had success with using Curve on oval slots then recall feature points in a point for TP? I tried it and it looks to be centered of the slot and the math works out this time. Just want to see if this is a viable method.

[[Ro...]]

Why not recall the feature points into a slot feature? You get the length and width, and have greater control of the nominal feature.

[[Cl...]]

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Ditto!

[[Ji...]]

Will the slot give me the ability to use True Position and have an accurate center point? Never needed to use Curve then try and find TP of that feature.

[[Ji...]]

I tried it both ways and get .0014" with the point and .0043" with the slot. Which way is correct?

[[Ro...]]

Generally your not going to have 1 position result for a slot feature, because it's considered an elongated/irregular feature of size and isn't calculated using a diametrical tolerance zone. It uses a linear tolerance zone. That's why you won't see a diameter symbol for the position. Usually slots are dimensioned as symmetry in each axis, and generally the width will have a much tighter tolerance than the length.

What is the print callout? Is it dimensioned both ways? Although I can't test it right now, I don't see how recalling a curve into a point will give a proper result. A curve has no centroid. It's just a collection of points.

I would recall the unmeasured/nominal curve into a slot feature so that you get perfect nominals. If you recall after you measure the curve it will calculate the nominals based on the actuals. You don't want that. Then I would output 2 results: 1 for each axis with the tolerances from the print. You would use a linear tolerance zone and select only X or Y, or the appropriate axis relative to your alignment.

[[Ji...]]

I have attached the slot call out on the print. I took the curve alignment WCcurve to get to the point. I see what you are saying about the curve not having a true zero. I also understand what you are saying with the proper call out for a slot. The attached is what I have to try to work toward getting a good answer for.

SHPM_Copier22022515190.pdf

[[Cl...]]

I've normally see this callout as bilateral position 2x, one in X, the other in Y.

[[Ro...]]

What are datums A and B relative to the slot? Depending on how many DOF they constrain, you may be able to best fit any that are unconstrained.

The callout itself is questionable. Profile would be a better choice, if not the only choice, in my opinion.

Position uses opposing points to calculate the position. The slot not only has length and width, but it also has those radii in the corner. So if you were to check this as I previously stated, you would need to output 4 results: Length, width, and corner radii to radii X2. I really doubt that's what they after, but who knows.

[[Je...]]

Jimmy,

I agree with Robert and Clarke (Edit: I guess Robert is not on board with me on this 😃 )

Curve is a powerful tool in Calypso, but it's not the best choice here. It's probably possible to capture the points using curve and then recall them into center-point based features, but the process would be time-consuming since you would need to exclude point zones for each of the four features (2 circles and 2 lines).

I would recommend either using the slot construction feature or using symmetry constructions.
The latter strategy might look like this:

1. create two circles at the same depth in the slot.
2. create two 2D lines at the same depth as the circles.
3. create a symmetry of the two circles
4. create a symmetry of the two lines
5. create a third symmetry using the two symmetries created in steps 3 & 4.
6. Bonus (optional but recommended): create a projection of the final symmetry to the surface of the slot opening.

The final feature is a point that can be controlled using the position characteristic.


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Jeff Frodermann
Meier Tool & Engineering
Anoka, Minnesota

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[[Ro...]]

Hi Jeff,
I don't think he has a better option than curve, because of the radii in the corners. The stock slot feature won't work for that.

Depending on what the real intent is of the drawing, the easiest solution could be to just measure the slot as a regular circle, and report the position with 2 results: inner and outer tangential.

Or you could go full deep mode and measure the virtual/resultant condition of the slot and dimension it with segmented tolerance zones.

Maybe time to talk to the engineer? I suspect with that callout and tolerances that's it's not a super tightly controlled feature.

[[Ji...]]

Thanks everyone. At least you gave me a few more things to try. The slots are for bolts to go in so not real tight. Real confusing with the call out. I will let you know if I find a good way to do this. I have done the circle and max inscribe min circumscribe before. The only bad thing is the way the probe goes around the slot when done as a circle worries me that it could give bad readings, the form is out rages when ran like that.