My co-worker and I were discussing this today as we are headed from 2017 to 2022 or 2023. We pulled up a 2017 program in 2023, and edited a GDT callout. It was set at LSQ, perhaps a carryover from 2017, or perhaps a default settings setup.
What I'm saying is I believe if you measure your datum features using LSQ, you can keep that toggled to LSQ in Geotol and it won't use the default external fit type that they call 'constrained least squares'. I cannot stand that term, bc unless you are somewhat experienced you may think constrained least squares is a LSQ type fit when it is primarily an external fit as criteria #1 from my understanding. I"d prefer to call the new Geotol default 'External least squares' b/c that is what it is.
Are you able to verify the CMM results manually on the granite plate? That's where I'd start.
That's blasphemy! My CMM (program) is NEVER WRONG!! are words a good programmer will never utter. Most dimensions can be verified in one way or another. Some 3D geometrical features are not so easy but can be figured out with a vivid imagination and some surface plate knowledge.
That's blasphemy! My CMM (program) is NEVER WRONG!! are words a good programmer will never utter. Most dimensions can be verified in one way or another. Some 3D geometrical features are not so easy but can be figured out with a vivid imagination and some surface plate knowledge.
Poor wording on my part, do you have the resources available to verify the CMM results manually on the surface plate?
PC DMIS changes their software too much for me to have any desire to use GEOTOL or Xact Measure. I personally don't ever want to get into a situation where I now have to update 3000 programs because they decided to yank part of the software out & call it an "update".
I always create alignments that RECALL/STARTUP that have all six degrees of freedom controlled & my results always correlate with the surface plate measurements which should always be our overall goal. I've never once had someone question me about "whats my datum shift?" nor have I ever worked with anyone that wanted to understand/use the datum shift info unless it was another CMM programmer.
If you don't mind me asking (I'm relatively new), what's the end goal for having your alignments that RECALL/STARTUP? I always have a manual and DCC alignment that constrains all 6 degrees, but they build off of each other, and now I'm wondering if I'm forgetting to do something important.
visual reference of the trihedron. every time creating an alignment will show that little thing moving around so when you create a new alignment and constrain it properly it stops moving.
I hope to NEVER have to use it anymore then I absolutely have to. I hate the alignments and re-alignments and all the other BS that goes along with it. fortunately for me, I am down to a couple times a year! WOOHOO!!!
If your programs are giving you accurate data then you're not doing anything wrong my friend.
That said..
I have gotten in the habit of having alignments that constrain 6DOF recall "startup" because when you have one alignment feeding into another & into another & into another & so-on, it makes your code much harder to edit should you ever want to change those alignments. They're all chained together so one small change sends a cascade of tweaks (many unexpected ones) all through your program.
My programs are all very similar to one-another, heres my rough procedure:
-Bang out a quick pln/cir/pnt alignment or something similar to find the part. Recalling startup. (A1)
-Once part is found, find ALL of the datums in order of precedence (A1 is still recalled).
-Create all of my datum alignments one after another. Each one recalls startup. ABC..DEF..GKL..whatever they are.
If I want to edit the top of the program, the bottom of the program is safe because of this structure.
Next.....
-Recall the necessary alignment, beep that part of the item
-Recall ABC & beep that area...recall DEF & beep that area...recall GKL & beep that area...and so on and so forth.
-At the end of the program, recall necessary alignments & workplanes and output the data you need
Using this strategy not only makes your alignments easier to edit in the future due to them not being chained together...it also has the benefit of making your program more "immune" (as immune as PC DMIS can be :cool to software crashes. I have seen programs with a lot of alignments chained together & once you edit one it s*it whips the entire program & next thing you know its corrupted and doing all kinds of funky unexplainable stuff.
this process you describe is exactly why I hate legacy, I don't have to do any off that with GEO TOL, but to each his own. 100 ways to skin a cat as they say...
:cool
to software crashes. I have seen programs with a lot of alignments chained together & once you edit one it s*it whips the entire program & next thing you know its corrupted and doing all kinds of funky unexplainable stuff.
