36
XYZ Machine Tools Ltd
XYZ Bed Mill Safety, Installation, Maintenance, Service & Parts List Manual
Limit switches can be turned on or off with Service Code 312, however, limit switches should normally be
kept on.
Possible Cause
Check This
Limit Switches are triggered
Reset the Limit Switches using the procedure described above.
Poor Limit Switch Cable
connection
Check for any pins that are loose, pushed in, or bent. Verify that
there is a good connection between the cables on the cable
breakout box.
Limit Switch failure, try this:
Swap over 2 limit switch cables
on the cable breakout box.
Does the limit switch problem move to the other axis? If it does
then the switch is most likely the problem. If it stays with the
original axis then it could be the cable breakout box or pendant.
3.4
Problem with the Measurements
3.4.1
X, Y and Z-Axis Measurements Do Not Repeat
With a dial indicator mounted to the bottom of the spindle, touch off a fixed surface either in the X or Y-
axis direction and then set the DRO equal to 0. Crank away several centimetres and then touch off again
at the same place. If the reading has not returned to 0 on the DRO, zero the display and repeat the
procedure. If the measurement does not repeat, you have a repeatability problem that must be resolved.
Test for accumulative error by moving the axis a number of times to see if the error gradually grows by a
small amount. If so, it may be caused by a misaligned sensor or scale. If the error abruptly changes by a
large amount, it may be caused by a bad encoder.
Expected repeatability numbers should be 0.01 mm or less.
Do the following service codes and procedures:
Code 304 Toggle X sensor/glass scale on/off
Code 305 Toggle Y sensor/glass scale on/off
Possible Cause
Check This
Machine Tool & Setup problem
Check for any looseness in the setup (Tool, Tool holder, Part, Vice,
or Fixture). Make sure there is sufficient contact between the tool
holder and the spindle. See Machine Tool & Setup Section 4.1
X, Y, and Z-axis Gibs are loose
Check the adjustment of the X, Y, and Z-axis Gibs using the X, Y,
and Z-axis Gib adjustment procedures.
Scale problem
Make sure that the Scale is installed correctly according to the
manufacturer’s instructions. Check for any loose brackets or
misalignment etc. Also, check to make sure the Scale assemblies
are functioning correctly. Use service codes 304 for X and 305 for
Y to turn off the suspect encoder. Does problem still exist after
turning it off?
X and Y-axis Drive Trains are
loose
Check Repeatability using the Repeatability and Positional Accuracy
procedure. Step by step, carefully inspect the Drive Train for any
looseness. It may be necessary to disassemble and then
reassemble the Drive Train. See Mechanical Drive Train (X, Y)
Section 4.2
Encoder Disk or Reader Head on
motor are loose
Swap the motor in question with a known good motor. For
example, swap the X-axis motor with the Y-axis motor. If the
symptom stays with the motor in question, then replace the motor.
If not, then the motor is not at fault and something else is causing
the problem.
