hexagon logo

CMM Won't Position

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
  • +1

    The feature that you are measuring has NO X or Y components. Only Z!
    The error you see is the inablilty of the CMM to maintain the position of the probe in an exact position. Completely within any reasonable expectation of the machine to hold. The Z direction has the surface of the granite to control when the probe is activated. There is no surface to control the X or Y


    Good point. I missed or didn't think about that. The X and Y values are what the machine is capable of driving itself to. The Z value is what the machine is capable of measuring. A 3D feature (sphere) or 1 feature in each axis would be a better test.
Reply
  • +1

    The feature that you are measuring has NO X or Y components. Only Z!
    The error you see is the inablilty of the CMM to maintain the position of the probe in an exact position. Completely within any reasonable expectation of the machine to hold. The Z direction has the surface of the granite to control when the probe is activated. There is no surface to control the X or Y


    Good point. I missed or didn't think about that. The X and Y values are what the machine is capable of driving itself to. The Z value is what the machine is capable of measuring. A 3D feature (sphere) or 1 feature in each axis would be a better test.
Children
No Data