Is anyone here familiar enough with legacy profile to explain the difference between form only and form and location? I think that form and location locks to the origin, but i am not sure how the form only works. I have a customer who wants to use legacy dimensioning and i am not familiar with it.
When selecting the "Form only" radio button tells Pc-dmis to only determine if a particular profile matches the same form as its nominal.
Form only ignores whether the "location of the profile" is outside of acceptable tolerance.
Form only I describe it as an overlay for a comparator that you can move around the overlay to "fit the form" so all surfaces can fit in between the tolerance band. If you can fit it in then it passes if you can not it fails.
Form and location ---same overlay but you must first locate on the datum then the profile must fall in between the tolerance bands
Your customer that wants you to use legacy dimensioning, you will need to have the alignment to match the feature control frame and the active alignment when you report that profile. Exact measure handles the alignment and fitting based on FCF for you.
Form only does a secondary fitting of the data, to determine whether the data conforms to the shape of the surface. It is regardless of location, meaning that the alignment/datum structure is ignored for that particular dimension.
This would be used when you see a profile callout with
no datums in the FCF.
thanks everyone for the help! i was just unsure of exactly how it works. I use Xactmeasure and build off of my FCF so i usually dont have to deal with legacy stuff.
my final question then is if i have my alignment to A B and C datums, would form only work if my profile is called back to my B and C? my A datum is my Z level and B and C are x rotation and x,y location. I want share a print, but i cant due to security reasons. i could probably post the program though. I dimensioned the profile the way it was called with B and C on the print with exactmeasure and then tried dimensioning the same thing using form only, but non of the best fit options seemed to match my exactmeasure readings.
Profile to B and C means that you now treat B as your primary and C as your secondary, and evaluate the profile to this new DRF. Form only is for NO datum called out in the FCF.
so it isnt even correct to use form only if there are datum callouts? I am writing a new program for a legacy part that has been programmed using form and location for the past 10 years. I was just under the assumption that they either needed to use B and C on exactmeasure or form only if they wanted to use legacy dimensions
That helps a lot. they have been checking this entire part with legacy dimensions for the past 10 years. Not it makes sense why we never seem to correlate. Thanks for your help!
