Help! Fanum 10M Axis Position Drift Problem Kitamura MyCenter 1
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  1. #1
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    Default Help! Fanum 10M Axis Position Drift Problem Kitamura MyCenter 1

    I have a late 80s Kitamura MyCenter 1 with a Fanuc 10M control and Fanuc red servos.
    I have had it for over a year, but have only made a few one-off parts mostly in aluminum that were fairly quick.

    This last week I have been machining some timing sprockets in 4140HT steel. The parts take a couple of hours to machine both sides. I started noticing some mismatch when the parts were flipped. This mismatch varied each time but was up to .010".
    Going back to the fixture origin I found that the position had shifted by .0012" in X, .008 in Y, and .0006" in Z after 2 hours of run time.

    Today I checked the backlash, and it is within .0001" on all axis. I tried rapid moves back and forth, and then coming back to the indicator, and it returned to within .0001". (This was just for a few minutes though.)

    I had a similar problem on the X axis of a Bridgeport R2E3 that turned out to have been caused by plugged lube metering units.

    This machine has all new lube metering units.

    I find it hard to imagine it can be a bad encoder or coupling because it seems to effect all 3 axis.

    Has anyone else experienced any problem like this?

  2. #2
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    Sounds like thermal growth. Y shifts the most in the spindle head due to heat from the spindle and drive. Your .008 is a lot though. Does the head feel warm at the end of the 2 hour run? Is the tool taper hot? Does the machine have an oil cooled spindle? If it does, is the cooler/chiller working properly?

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    Tram the table and report back what you find.

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    The machine does have an oil cooled spindle, but I have not confirmed if the chiller is working. I assume it only comes on when the spindle is warm?
    The taper is not warm after a run that I noticed. I have pulled out tool holders, and they were cool.

    I did tram the table a year ago, and found it very perpendicular across the X direction, but out a few thousands over 12" in Y. The head is tilted slightly in Y, but it moves perpendicular to the table in both X and Y. I checked Z travel with a Granite reference angle. In other words, the column is straight, but the head has sagged slightly.

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    Well I think I found the problem! The parts are held in machined steel soft jaws in a double vise. I did not record the vise's absolute position when I started, but I did indicate it in parallel to within a tenth. I went back to check it today, and it is several thousands out of parallel. The vise has moved! The heavy vibration from cutting the 4140HT has been moving the vise around.
    I sure hope this is the only problem. This would not explane the Z shift, but .0006 could be from thermal expansion.

    Hopefully I will get a chance to re-align the vise, secure it better, and try again next week.

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    Quote Originally Posted by mclausen View Post
    I have a late 80s Kitamura MyCenter 1 with a Fanuc 10M control and Fanuc red servos.
    I have had it for over a year, but have only made a few one-off parts mostly in aluminum that were fairly quick.

    This last week I have been machining some timing sprockets in 4140HT steel. The parts take a couple of hours to machine both sides. I started noticing some mismatch when the parts were flipped. This mismatch varied each time but was up to .010".
    Going back to the fixture origin I found that the position had shifted by .0012" in X, .008 in Y, and .0006" in Z after 2 hours of run time.

    Today I checked the backlash, and it is within .0001" on all axis. I tried rapid moves back and forth, and then coming back to the indicator, and it returned to within .0001". (This was just for a few minutes though.)

    I had a similar problem on the X axis of a Bridgeport R2E3 that turned out to have been caused by plugged lube metering units.

    This machine has all new lube metering units.

    I find it hard to imagine it can be a bad encoder or coupling because it seems to effect all 3 axis.

    Has anyone else experienced any problem like this?
    The couplings on the motor to ball screw are slipping.


    John


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