Turning down a servo motor shaft. Anything to look out for?

More
26 Sep 2019 22:12 #146304 by SPH
I’ve got new Chinese ac servos on the way as discussed in another post. The large 180mm frame y axis motor has a 35mm shaft and I’ll need to reduce it to 24mm to fit the pinion gear for the reduction gearbox, as per the original yaskawa.
Being an AC motor I’m assuming I can simply remove the rotor shaft assembly, chuck it up between centres and turn it down.
When removing the encoder can I just mark it’s location on the shaft and reinstall the same way? Will that be sufficient?

Basically what I’m asking is, what’s going to bite me on this?

Please Log in or Create an account to join the conversation.

More
27 Sep 2019 01:15 #146310 by tommylight
I would strongly advise not to take the motor apart, you might end up with a paper weight.
It is an AC, but most probably a PM (permanent magnet) motor, so removing it from it's casing will badly mess up the magnetic field.
Clamp it to a lathe, wire it and let it run, use as a lathe spindle motor. No fuss, except clamping it down properly .

Please Log in or Create an account to join the conversation.

More
27 Sep 2019 01:28 #146311 by SPH
That’ll be fun ;)
Will be interesting indicating it true with such a short shaft.

Please Log in or Create an account to join the conversation.

More
27 Sep 2019 06:59 #146339 by pl7i92
there are tupper returnings for shaft size reduction

is it a relal need or can you get the servo to a side and make some Timingbelt in between

taking the servo apart is always a risk of cracking the bearings

Please Log in or Create an account to join the conversation.

More
27 Sep 2019 09:34 #146354 by tommylight

SPH wrote: That’ll be fun ;)
Will be interesting indicating it true with such a short shaft.

Motor body ? Or is that tapered ?

Please Log in or Create an account to join the conversation.

More
01 Oct 2019 21:49 #146831 by SPH
The body is square but I don’t think I’d trust it to be perfectly true to the shaft. It’ll be fine, slowly slowly during setup and lots of checking with dial indicators will get it done.

I’m just glad you guys gave me the heads up on permanent magnet motors. That would have made for a bad day.

Please Log in or Create an account to join the conversation.

More
01 Oct 2019 23:58 - 02 Oct 2019 00:00 #146840 by dm17ry
unless the motor is *very* old, i bet it has a rare earth magnet rotor which survives just fine being pulled out of the stator. the tricky part is not to scratch the rotor coating. i have replaced bearings on a few servos, although smaller ones - 1HP and lower. i also turned a straight shaft to a taper on a 400W mitsubishi servo.

i'd also think about the possibility of fixing the motor somehow to the lathe bed and turning the shaft under it own power. the one i modified was free-machining steel, very easy to turn. haven't tried that, but should work, imho :)
Last edit: 02 Oct 2019 00:00 by dm17ry.

Please Log in or Create an account to join the conversation.

More
03 Oct 2019 01:20 #146935 by andypugh
Does the motor have a rear shaft extension (possibly by taking the rear cover off)? If it does then you can consider mounting the motor between centres on your lathe.
I have a drive-centre which would then make the job pretty easy. If you don't have one then consider mounting the motor on centres but running the motor itself to rotate the shaft.

Or, what would probably work, would be to short the motor windings together and drive the motor housing, there will be full motor rated torque available for machining (I think) though the speed won't match.

Please Log in or Create an account to join the conversation.

More
03 Oct 2019 11:07 #146973 by SPH
Yeah, I'd considdered removing the encoder and having a look, there must be something there for the encoder to key onto and I'd like to bet that there's a centre drilled in whatever's back there. That might be a quick and simple answer. Shaft between centres, hold the body still (just so it's not flogging around) and use a drive dog.
Motors haven't turned up yet, I had a quick look at the original Yaskawa (which I suspect the new chinese motors are a copy of) but I'm reluctant to mess with them.

Please Log in or Create an account to join the conversation.

Moderators: cncbasher
Time to create page: 0.097 seconds
Powered by Kunena Forum