Articulations reading way off

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  • Articulations reading way off

    We recently had to take the PH10T head off of our Sheffield Endeavor for maintenance. I realigned the head using the master ball and the A90B90 / A90B-90 method and I'm confident that it is "good enough."

    I used to notice that within a program, whenever an articulation changed the angles and vectors were not always exactly what they should have been.

    (ie: From A0B0 0,0,1 and 0*° moving to something like A90B90 you wouldn't have a 1 (or -1) and 0's followed by 90°... but rather numbers like .9987, .0003, .001 and an angle of 89.99899°)

    I've noticed since we've got up and running again, a few numbers that look way, way off... the worst was in a new program I was writing. Visually the head will articulate to 90°, but in the code it will read as 79° or some odd number like that and the vector is a mess of decimals. Does PC Dmis base the angle and vector off of the leveled plane in your program?

    I've always gone in and manually changed the vectors and angles to be perfect anyway, but I was wondering if anyone else had this ever happen or if they knew why it would.

    I'm having problems now where I can set up a part in a fixture and start with a read point... let’s say the part runs through fine. I can unload it and put a different part in the same fixture, run the same program but after the read point it will get all screwed up and have an unexpected hit somewhere. If I then shut down PC-Dmis, reopen it, and load the program again (all without moving the part) it will run fine.

    Possibly a related problem?

    PC DMIS v3.7 mr2
    Sheffield Endeavor
    Brown & Sharpe One

    "The Dude Abides..."

    John R. Sacheli

  • #2
    First, I double check that the head is tight on the z-ram. Second, just for good measure, I'd re-check the squareness of the head. It is a lot easier to see btw if you use a small tip (2mm) and compare to that. The smaller radius makes it easier to center the two diameters. And for the comparison, what works well is if you have a TP20 or similar probe that uses modules. Build up another tip with a 2mm sphere and place it on the table to compare to.

    Next, the funky vectors... Is it possible your machine is drifting while you take manual hits? Try locking out the directions you don't need to move with the buttons on the jog-box.


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