Composite true positions in Legacy

Looks like I'm a little late to the party.

I don't want to upset anyone but I must point out that it is impossible to create a composite position or profile command using legacy dimensions and have it be fully compliant with ASME Y14.5. This is because of the rules governing how the lower segments work. Besides the fact that you will not be able to correctly apply datum shift where material modifiers are applied to datums, there are other problems. Only the upper segment functions "as normal" in that its datum reference frame (DRF) is allowed to constrain rotation AND translation and, if necessary can be fully constrained (locking all 6 degrees of freedom). The lower segments only allow the pattern to rotate and translate when there are no datums referenced. When datums are referenced they are only allowed to constrain rotation - so the pattern can only translate relative to the DRF. Under ASME, datums must also be fixed in orientation and location relative to each other which is not possible to achieve using traditional alignment commands - which is why you get different results using legacy than you do with the geometric tolerance command.

This post shows the ASME rules governing composite feature control frames: https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/504603-coaxial-holes?p=504628#post504628

The geometric tolerance command is designed to handle composite feature control frames of up to five segments. It performs the complex datum fitting and calculates the material boundaries whilst fixing datums in orientation and location to each other as per the ASME rules. It simulates how hard gauging would work.

Looks like I'm a little late to the party.

I don't want to upset anyone but I must point out that it is impossible to create a composite position or profile command using legacy dimensions and have it be fully compliant with ASME Y14.5. This is because of the rules governing how the lower segments work. Besides the fact that you will not be able to correctly apply datum shift where material modifiers are applied to datums, there are other problems. Only the upper segment functions "as normal" in that its datum reference frame (DRF) is allowed to constrain rotation AND translation and, if necessary can be fully constrained (locking all 6 degrees of freedom). The lower segments only allow the pattern to rotate and translate when there are no datums referenced. When datums are referenced they are only allowed to constrain rotation - so the pattern can only translate relative to the DRF. Under ASME, datums must also be fixed in orientation and location relative to each other which is not possible to achieve using traditional alignment commands - which is why you get different results using legacy than you do with the geometric tolerance command.

This post shows the ASME rules governing composite feature control frames: https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/504603-coaxial-holes?p=504628#post504628

The geometric tolerance command is designed to handle composite feature control frames of up to five segments. It performs the complex datum fitting and calculates the material boundaries whilst fixing datums in orientation and location to each other as per the ASME rules. It simulates how hard gauging would work.