Servo Motors in Vacuum

Not really a PLC question but I know forum members have a very wide range of experience.

I have a project running at the moment that requires some small servo motors (up to 6NM)to run inside a vacuum chamber. I wondered whether anyone has experience of this and can offer any advice / recommendations.

One name that has come up so far is Aerotech.

Thanks in advance,

Nick

mechanical is no problem.
watch for the grease not to evaporate from the bearings, and keep in mind that vacuum has a strange effect on sparks. remember an old amplifier was a pin in a vacuumlamp, with some strange mesh around it, and heated with 6.3 volts.
so be aware of higher voltages. ( i would just try it the simple way.

The two major concerns are contamination of the vacuum chamber from out-gassing from the servo motor and the second concern is overheating of the motor.

You don't specify how much of a vacuum we are talking about most of what I've been involved in was in the milli-torr range. Of course the lower the pressure the more outgassing is a concern. In addition to lubricants, you'd be surprised how much outgassing comes off PVC wires in a vacuum--Teflon is your friend.

You got nice small motors but just remember you won't have any convective cooling at all. You'll have to rely on conductive cooling.

Thanks for the answers.

This isn't a particularly low vacuum application.

Aerotech sell motors prepared for use in vacuum (correct grease etc). I wondered whether anyone had experience of an alternative supplier.

I was also interested to learn more about the potential phenomenon of ionisation at motor terminals. Anyone experience this?

Nick

My experience has been with small stepper motors from Micromo. I know of others who have used Aerotech and been happy with the products.

I've never experienced ionization as typically the voltages used are too low.

You need to be very careful here work closely with the motor manufacturer.

Motors running in a vacuum are prone do build up a corona discharge around the windings, esp at higher voltages. Unless your motor is designed for use in a vacuum this WILL result in high currents and it WILL damage your motor unless the motor is designed for operation in a vacuum.

Don't panic though, there are lots of motors designed for vacuum (think semiconductor industry and even the ISS's robotic arms).

You might want to take a look at this article for other concerns:
http://machinedesign.com/archive/working-vacuum