Need Help!- Y zero moving alot during warm-up

[drmrby]

Hey,

I'm running an older vf1(bought used a while ago) and the y axis zero moves about .03 from start up till i've run it for about and hour or 2.
I just replaced the front bearing and that didn't help at all. They way it slowly corrects itself while warming up suggest to me that it is an expansion issue of some sort.

what might be loose or worn?

thanks

[HAILINHAAS]

Use a magbase and indicator.
Attach magbase with indicator on the table.
Put the stylus up against the spindle.
Use the jog handle to jog the axis in .001
Zero the handle jog.
Jog + .010
jog - .010
back to zero.
The indicator should be +/- .0001 maybe .0002

If not you have backlash ... more than likely a popped coupler.

[drmrby]

thanks for the reply. guess i should have stated that backlash is not an issue...it is fine.
i have just turned my machine on(after inspecting encoder and its fine) and homed it. moved the table to the center and put a dial on the y. it is actually creeping over gradually and consistantly.
tech guys i talked too seem to have no idea

[HAILINHAAS]

What year is it? Does it have linear scales on it?

[mactec54]

Hi Drmrby
Seeing that you had it apart is the motor direct drive to the ballscrew, the connection
between the motor & ball screw could be slipping alittle on the shafts mark the 2
shaft's to the couplings with a sharpy & see if there is any movement there after you run
it.

[drmrby]

its a '91 and does not have linear scales.
i have narrowed it down to something electronic because it slowly moves even with out running anything...just having the machine on. when i turn it off for 5-10 min...rezero...goes back to same position as previous cold start