[urvesh123]

Hello friends,

I am using Puma 250 turnmill center with Fanuc 16T control and Alpha-12 series motor with Incremental type Alph I 64 type pulse coder,there is one permanent problem in machine.
When machine is in running condition,there is not a single size variation issue.but after power off and on,X-axis home position deviates from -0.5mm to +0.3mm means sometimes (-0.5mm,0.2mm,0.1mm etc..)
I have tried out following,
1.I have cleared coupling doubt by straight mark on machine body, ballscrew,ballcrew coupling and motor shaft - but mark shifts from machine body to ballscrew side only.hence conclusion is no slippage in coupling.
2.I have swapped encoders for X and Z axis but problem still on x-axis.means encoder has no problem.
3.I have tried decreasing ref speed but result is same.
4.I have tried by decreasing servo gain from 3000 to 1500.but no improvement.

Expecting some help on this issue...

[Superman]

Have you checked to see if there is any swarf (or other contaminant) around the limit switches, or a loose mounting ?

[hitachibos]

i agree with superman. try looking for chips packd under the way covers. if it continues to change on powerups try moving the trip dog or switch a very little bit. .5mm