Relearn nominals option?

[MrComment]

I have a program I've spent the past few days working on, and I'm using CAD and decided to run the program thru offline to see if my Theo values all seemed to still match up tight with my CAD (As I programmed off the same CAD model also). Just a general "correctness" check because I started to question a couple of the nominal results that started coming back from some of my constructed features that I had added recently. Well after running through the program offline I found that the features were not showing up were they should on the CAD model (maybe within 1mm or so). Im not sure what went wacky, I suspect it might have been some time after I added or edited one of my alignments (You know how PCDMIS likes to help you out sometimes )

Anyway I seem to remember an option that let you relearn the nominal value for your hits based of the CAD, something similar to "Find Nominals", but how do you get PCDMIS to do this for features that are already created? Find Nominals in the PCDMIS setup options seems to only work during initial creation of the feature.

Thanks

[Matthew D. Hoedeman]

FIND NOMS ON EXECUTE under the F5 option, does not work very well, use at your own risk.

In the future, put your alignment in a seperate program, no issues with nominals chaning due to alignment changes.

[MrComment]

My fixture alignment is external to my part program, but for some dumb reason I built my final alignment within the part program on this one, I should know better by now I guess.

I'll make a backup copy of the program and try the "FIND NOMS" option once to see how or if it helps this time.

Thanks again

[TonyC]

I am a novice at PCDMIS and have experienced the situation you've described. What is the best way to go about building alignments external to a part program? Thanks for any help.

[Matthew D. Hoedeman]

I am a novice at PCDMIS and have experienced the situation you've described. What is the best way to go about building alignments external to a part program? Thanks for any help.

Create the program as you normally would. Do the manual, then DCC alignment. When done, when using a dedicated fixture, check your nets and locators. Maximum tolerance for these fixtures is usually 0.05mm (0.002"). If all locators check within YOUR fixture tolerance, your alignment is good. Then, INSERT ~ ALIGNMENT ~ SAVE and it will save the alignment as an external file. Then, start a new program, the check program. Using the drop-down at the top of the screen, select the alignmetn file you just saved. Go to OPERATIONS ~ GRAPHICS DISPLAY WINDOW ~ click on CAD=PART. Import your CAD data. You can now program your part using the external alignment you created.

The BIGGEST advantages to this are:
1) You don't have to worry about screwing up any point if you change the alignment
2) You can use the exteranl alignment for many different programs, thus allowing you to do 'sectional' work with only a single alignment
3) When they take your fixture away and tell you to still check a part, you can make an alignment program (probably iterative) using just the part and your check program is still perfect and ready to go.

[Tested]

Matt what problems have you had with "FIND NOMS ON EXECUTE" I use it alot and have never had a problem. "I use it only if offline"

[Matthew D. Hoedeman]

I have only tried to use it a couple times, I have only needed to use it a couple times and both times, it would not find the correct surfaces for updating. Granted, these times were on some-what convoluted checking fixture re-certifications, but both times, it either grabbed the wrong surfaces or even used an incorrect (backwards) vector. CRASH! And, I also did them in 'offline' mode.

[Tested]

Wow that's just strange, I have never had a problem. But I did see that you are using "CAD=PART" I never use that. I wonder if that might be the difference.

[Matthew D. Hoedeman]

More than likely, it is due to the size and change of the part/data. You have seen those bent, metal bars that they use for exhaust hangers, right? ABout 3/8" diameter or so. OK, now imagine a production checking fixture that these bent bars sit in so the production operator can check to see if he is still makeing a good part. This is what I have had to use this on. So, I am pretty sure that where the surface got 'heavier', the probe was coming from the back side and the areas where the change was 'down', it pulled a point from the side instead of moving down as the new part did, if ya follow what I am trying to describe.