[Izahny]

Hello guys,
I'm newbie seeking for opinion.

We are running double spindle lathe machine with fanuc-21i controller to cut an aluminium.

We observed 1 spindle is significantly performing better than another (output dimensional accuracy) with 100% measurement.
Spindle A: drifting dimensional (range of 8µM)
Spindle B : Stable (range of 2µm)
Had carried out few checking to understand the reason but yet we did not found any abnormality.

- fanuc card - no faulty
- back lash - 2µm( compensated 2µm) - normal
- repeatability test (using dial indicator) - <1µm range.

Is there any other thing that I overlook.
I attached my machine performance

[ssuebsak]

Did you check the spindle baring runout and other when it have load and no load at the spindle.

[underthetire]

Looks like thermal growth to me.

[ssuebsak]

If thermal growth. Mean the machine will have 2 turret 2 ballscrew in each turret.

Does it ?