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Manual vs DCC alignment

acooke
I have taken the basic 1 week PCDMIS course from Hexagon.

Currently I have only modified part programs written by the programmer at our parent company location to run on our cmms.

I work with version 3.7 on cmm 2 and 2014 on cmm 3.

Cmm 1 has Measuremax which I am not sure how to program. This question is regarding cmm 2.

I think I may be a little confused about the purpose of running the dcc alignment after the manual alignment has run. I was under the impression that the manual alignment was to locate the part on the cmm, and the dcc alignment was the "fine tuning" and would adjust for very slight placement changes.

We have a fixture that is bolted to the fixture plate. The part is then mounted on the fixture and screwed into place using 1 screw. The part is secure, but due to different cavities with different die conditions may sit slightly different in the fixture each time. We are measuring the true position of a bore on the x minus side of the part with respect to the plane and bore at the x/y/z 0 position that is used to set the part alignment.

What we have noticed is that when we run the first part with the manual alignment the true position is within tolerance (.04mm). When we run a second part, if I mark all but choose not to mark the manual alignment portion, we see true position values between 0.1mm and 0.2mm.

If I then run the program on that same part again using the manual alignment without moving the part the true position values are again within tolerance. From what I read online yesterday after lots of digging it looks like the dcc alignment serves only to ensure the alignment features are properly probed and defined.

Is there any way around running the manual alignment each time? I don't mind if it's necessary for different cavities or runs, but for a 300pc cpk it's quite time consuming. Thanks in advance for any answers and/or suggestions. Oh, and I'm well aware of the noob hazing here. I have thick skin Slight smile.

Amber
  • Sorry Josh but I think btad's got this one!

    When I used to teach people I'd get them to do an alignment check-list for every alignment.

    LEVEL [ ]
    -----------------
    ROTATE [ ]
    -----------------
    ORIGIN X [ ]
    ORIGIN Y [ ]
    ORIGIN Z [ ]
  • The other option, instead of adding a 2nd DCC alignment would be to do a DCC iterative alignment, set to measure all always, which will also eliminate any possibility of the level/origin/rotate/origin/origin potential issue.
  • in your final allignment A4 you level your X axis and then translate, you hten rotate your Y axis, but you then translate your X axis again to a different feature and then you translate your Y axis.

    you have translated your X axis twice and forgotten about the Z axis so not locking all 6 dof.

    This true
  • Also, there is one additional change that must be made: after each Level portion of the alignment and before circles are measures, the WORKPLANE really needs to be set to XPLUS for those circles to get good data. This is probably contributing to some of that positional error.


    Not when using Auto circles surely?
  • Not when using Auto circles surely?

    In my 20+ years of Pcdmis, auto-feature circles do NOT require a workplane since the feature itself HAS a 'workplane' built in, with the vectors. Workplane is required for a learned circle, not for an autofeature circle. The autofeature circle does require the correct vector, which will come from the CAD or correctly typed in by the operator. If the autofeature circle does NOT have the correct vector, then workplane will not help it at all. Now, in doing 'auto dimensions', the workplane may have an effect of what is reported (as in, which axis it selects) but not in correct XYZ values themselves.
  • A big thanks to all who have responded. I did fix my alignment issue where I had forgotten to translate Z. By the way, my workplane was set to XPlus after leveling and before the circles were measured. I checked Slight smile. That did not eliminate my need to run a manual alignment on the 2nd part, however. My values were still off and out of tolerance. I then added the 2nd dcc alignment (I made sure to include all of the steps this time Blush) and voila! The program now runs parts back to back without the need to run the manual alignment each time. I knew there had to be an answer out there somewhere. I really appreciate the in depth explanations! I'm sure you will be seeing me again. It seems the more answers I find the more questions I ask. Darn my inquisitive mind!
  • A big thanks to all who have responded. I did fix my alignment issue where I had forgotten to translate Z. By the way, my workplane was set to XPlus after leveling and before the circles were measured. I checked Slight smile. That did not eliminate my need to run a manual alignment on the 2nd part, however. My values were still off and out of tolerance. I then added the 2nd dcc alignment (I made sure to include all of the steps this time Blush) and voila! The program now runs parts back to back without the need to run the manual alignment each time. I knew there had to be an answer out there somewhere. I really appreciate the in depth explanations! I'm sure you will be seeing me again.

    Excellent work - and you're welcome.

    It seems the more answers I find the more questions I ask. Bless my inquisitive mind!
    Fixed that for ya. Never stop learning.
  • I am a fan of the Read Point, a rough DCC Alignment, then fine DCC Alignment. Sooo easy especially since the machinest\toolmakers check their own parts most of the time.
    Just my 1/2cent!
  • I am a fan of the Read Point, a rough DCC Alignment, then fine DCC Alignment. Sooo easy especially since the machinest\toolmakers check their own parts most of the time.
    Just my 1/2cent!


    We run higher volume automotive parts in many of the machines and if you're lucky and have rayco, or threaded gridplates, you can do what I call drop an go programs.

    "Find" the part using your check distance set to 4" or 100mm, then do a rough DCC alignment (fixture to part), then a refined alignment 2nd DCC on part, and go from there.

    Operators just have to set up fixtures per instructions (and pictures) in program and press execute - NO moving of the probe head manually AT all!

    Works awesome to keep the cave monkey's from wrecking TP20's. Went from 22K last year in TP20's to 2K this year to date. Plus it speeds up the number of parts you can check a shift when you're not needing to take all the time to manually align parts.

    Also, when you do the 2 DCC alignments you'll find that on especially tight positional tolerance parts (say .030mm) you'll usually gain a few microns when doing this and those extra microns make the difference between scrapping good parts!

    My .02 cents

    4/1/96
  • Unfortunately we didn't cover any of these topics in class. I'm not familiar with read points, although I've seen them mentioned several times in this forum. We do have threaded gridplates. Currently cmm 2 is mainly used for checking the part with the fixture that my original question involved. Occasionally we check service parts there which do not have fixtures, so I usually set them up the best I can with the fixturing tool set we have from Te-co and run a manual alignment. Cmm 3 is currently being used primarily to measure a new part we are running, and that fixture rarely moves. We are in the process of having a threaded gridplate built for that machine (which I'm thoroughly excited about Smiley). I have noticed better position outputs on machine 2 after adding the second dcc alignment. I used to talk about being able to hear the positional difference from part to part when an ID was measured, but apparently I was the only one who noticed. I no longer hear such a huge difference. I'm also unfamiliar with iterative alignments, although I've seen them mentioned here as well. This has brought to mind one more small question while I'm here. On cmm 3 (PCDMIS 2014.1) it seems like I remember the probe retracting automatically when a manual point was taken. It no longer does this. Now you have to manually back the probe away from the part. We've done a lot of digging into the settings, although I really didn't change any, and I wonder if this may be due to a box accidentally being unchecked. Any ideas?

    And thanks for the fix Josh. It's a blessing and a curse. Which one just depends on which day I'm asked Wink.
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