VFD for lathe, sensorless vector

[hacklordsniper]

As im upgrading my lathe with VFD and larger motor, i have 2 options in sensorless vector control. It is speed control or torque control, which one is better for lathe and why?

 

[Wizard69]

As im upgrading my lathe with VFD and larger motor, i have 2 options in sensorless vector control. It is speed control or torque control, which one is better for lathe and why?

I would have to say speed control. The only drive technology I have any experience with torque control is for large extruders in the plastics industry. I would think that running at a fixed speed is more important than a fixed torque.

However this thought did come to mind, would torque control compensate for diameter variance in facing operations? I don't really believe it could be reliable that way. Some drives can switch dynamically between the two methods and some after a reconfiguration. If the drive is capable of this then you certainly could do some testing, in the end I think speed control would be easier to work with.

 

[adrianjs]

You definitely need speed control. If you try torque control then you will end up breaking things and also getting an aweful surface finish.