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CMM Won't Position

BL Metrology
When I set the head to any angle other than A0B0, the CMM will not return to what I set as the X,Y,Z origin during alignment.

For Example:
At an angle of A7.5B-90, if I touch a point on the granite surface, set an alignment as X,Y,Z origin, and then program it to go back to 0,0,0, it will actually go to 0.0145, 0.0094, -0.4356. All of the programming is done in DCC Mode. This problem also occurs when I go through a full alignment on any part.

We do not have this problem when at A0B0, if I do the same thing at A0B0 it will return to 0,0,0 within tenths of a micron. The deviation with the angle is seen with all angles we have tried so far and the deviation does seem to increase with the A angle. All angles used are successfully calibrated prior to use.

The machine was calibrated on 3/17/09 and the technician spent an extra two days trying to troubleshoot the unit (Hexagon). We have also had our local reps in and they have not been able to troubleshoot the problem. The machine seems to be mechanically fine and it seems to be an issue with PC-DMIS.

Has anyone else experienced this and know of a workaround? We are waiting for Hexagon/Wilcox to resolve this, but I am assuming it could take some time.
Parents
  • Thanks to everyone for the prompt replies, I will try to answer each one here starting with the newest first. Please keep the thoughts flowing, even if it is basic, your help is appreciated. I will also try to copy up the code this afternoon.


    JVau425033 Do you have the right probe angle in your probe set-up.
    Yes, probe angle is correct in set-up.


    cmmguy Inch or Metric? machine Model?
    Metric, Browne & Sharp Global 5.7.5,
    running PC-DMIS 4.2 MR1


    Goodluck How are you doing this? Movepoint? Measuring a point at 0,0,0?
    Your recommended method is how we have been programming the unit.


    Otto Square How could it ever possibly return to 0,0,0? That is the surface of the table. PC-DMIS goes from the center of the probe. The probe would have to be imbedded into the granite.

    Using the method described by Goodluck, measure a point on a surface. Do an alignment making that point my X,Y,Z origin, doing a move point, measure a point with theoreticals of (0,0,0) and a vector of (0,0,1), the measure the position of that point.


    Ironhoe is A7.5B-90 a calibrated probe ang?

    Yes, it is calibrated with the results file indicating a std. dev as a couple tenths of a micron.


    Matthew D. Hoedeman

    Not mean at all, good to start with the basics. Yes, there is a command line for the angle. Yes, cursor is below the command (that has burned me in the past and is always the first thing to check).
Reply
  • Thanks to everyone for the prompt replies, I will try to answer each one here starting with the newest first. Please keep the thoughts flowing, even if it is basic, your help is appreciated. I will also try to copy up the code this afternoon.


    JVau425033 Do you have the right probe angle in your probe set-up.
    Yes, probe angle is correct in set-up.


    cmmguy Inch or Metric? machine Model?
    Metric, Browne & Sharp Global 5.7.5,
    running PC-DMIS 4.2 MR1


    Goodluck How are you doing this? Movepoint? Measuring a point at 0,0,0?
    Your recommended method is how we have been programming the unit.


    Otto Square How could it ever possibly return to 0,0,0? That is the surface of the table. PC-DMIS goes from the center of the probe. The probe would have to be imbedded into the granite.

    Using the method described by Goodluck, measure a point on a surface. Do an alignment making that point my X,Y,Z origin, doing a move point, measure a point with theoreticals of (0,0,0) and a vector of (0,0,1), the measure the position of that point.


    Ironhoe is A7.5B-90 a calibrated probe ang?

    Yes, it is calibrated with the results file indicating a std. dev as a couple tenths of a micron.


    Matthew D. Hoedeman

    Not mean at all, good to start with the basics. Yes, there is a command line for the angle. Yes, cursor is below the command (that has burned me in the past and is always the first thing to check).
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