problem with fixture plate

It depends how your routines are set up. |It sounds like you have everything coming from STARTUP which is the CMM co-ordinate system (home position), and you are doing a manual alignment for each part. Once executed, do you then unmark the manual alignment and follow it with a DCC alignment? Doing things this way, you are purely relying on the fixture plate not moving and the ability of your parts to locate repeatably on the fixture plate.

Essentially, if this is the method you are following, executing the manual alignment once and then unmarking it for subsequent runs is doing the same job as recalling an external fixture alignment, it just falls over if the fixture plate moves because you have to re-execute all of your manual alignments again. With a little careful editing, it should be possible to do away with the manual alignments and just recall your external fixture alignment, maybe followed by a few additional translations / rotations to make everything match what your previous, manual alignments were doing.

If you saved programs (already run with measurements) with an external alignment on a computer that doesn't have the external alignment on it, it's extremely hard to work on the program.

I had programs saved with measurement results that had an external alignment on the production floor comp but not my offline seat, and it was terrible to work with since the hits didn't match the CAD any more.

The plate should have it's own external alignment program..if plate ever moves just re-run that program and all of your other measurement routines will work just fine

We have 2 external alignment programs for our part fixtures. The first one is measured manually. Then the second one is an iterative DCC alignment that references the manual alignment. I make the prehits and retracts larger to account for slight variations in the position of the fixtures. Then, the actual part programs reference the DCC alignment. As long as the fixtures have only moved a little, the second alignment can “find” them and we’re good to go. I remove and reinstall our fixtures all the time and I never have to rerun the manual alignment.

I highly recommend the external alignment method neil.challinor outlined. It has the additional advantage that if you ever get a second CMM, you can put a second identical fixture plate on it, define the same external alignment, and put the same tips and angles on it all your routines done this way will automagically run on both machines without any additional effort. It blew my mind the first time I got it to work on our setup.

One thing I do differently from what he said is that I still start with a manual alignment after I recall my fixture alignment. Programming that offline finds the necessary offset from the fixture alignment. And if the fixturing ever changes somehow, you can just mark and run the manual alignment and you'll be good to go. You should be able to use this to convert your existing programs - put the recall command above your existing manual alignment, then run it through including the manual alignment. The CAD may end up in a goofy spot, but your program will be properly using the fixture alignment.

Regarding offline programming, I just copied one of the .aln files to my offline workstation. I haven't had any issues with that.