[TTalma]

I want to add a high speed 4th axis on my machine to use like a lathe. To get clean cuts I need to spin the workpiece up to 3000 rpm (I think). It will also need to have a decent amount of power as I'd like to spin some alrger pieces, up to 20 lbs. I don't know anything about servo motors. My questions are:

Can a servo motor spin this fast?
How big a motor do I need?
Can the motor speeds go as low as 1 rpm up to 3k?
will the motor maintain positional accuracy at all it's speeds?
Where can I learn about servos and configuring them?

I went down this road because I got a SEM MTS30M4-48 servo motor for free. I do not have anything else other than the motor. Would this motor work?

[ardenum]

small servos 60-110mm spin 3000-2500 and the bigger you go the slower they get, you'd have to compute how much torque you need to spin 20 lbs at 3000 rpm plus machining load and then you can go and search for a servo, at this high speed though the torque gets really small. Also the pieces diameter matters too because you wanna know how much N is at the circumference, servos specs are in Nm so you have to convert it.

are you sure you need 3000? the range on mill turns is usually around 300-800RPM and they do just fine.

Since you already have a motor I'd make a good stiff housing for the components and then just see how far you can go with what you have. You can make it future proof as well so that you only have to upgrade the servo when needed.

[Al_The_Man]

Are you talking about a Live Axis?
Usually the X axis on a lathe.
Although it sounds as though you want to spin the part like a lathe chuck, not so clear what you are doing? You also mention positioning?
The three axis that rotate around the X,Y,Z are noted as A,B,C axis.
What is the nature of the present machine?
AC servo motors can easily achieve 3krpm.

[Al_The_Man]

That motor looks as though it is DC brushed so limited to around 2krpm-2.5k5rpm tops.

[Jim Dawson]

I want to add a high speed 4th axis on my machine to use like a lathe. To get clean cuts I need to spin the workpiece up to 3000 rpm (I think). It will also need to have a decent amount of power as I'd like to spin some alrger pieces, up to 20 lbs. I don't know anything about servo motors. My questions are:

Can a servo motor spin this fast?

Yes

How big a motor do I need?

Good question, it depends on the required torque for the operation

Can the motor speeds go as low as 1 rpm up to 3k?

Yes. That type of motor should produce near full torque from 0 to near max RPM.

will the motor maintain positional accuracy at all it's speeds?

With the right controller it will be pretty close. However for a spindle drive, positional accuracy is not normally a factor until you are doing indexing, or rotary axis profiling, which is normally done at reasonably low speeds.

........Would this motor work?

Maybe, depends on how much torque you need. The torque requirement depends on how much material you are trying to remove at one time, and the diameter of the workpiece.

Based on the scant information available for your motor it looks like it is about 1HP and has a maximum RPM of about 2900. As near as I can tell, the -48 means 48 volts/1000 RPM. It's a brushed DC servo motor.

[TTalma]

Thanks for all the feedback. It sounds like what I have may not be ideal. I injured my shoulder and will be out of the shop for a few weeks. This should give me some time to do more research and figure out what I need.

[allencncrouter]

4 th axis , do you have find rotary ? such as chuck size ,diameter ,length ?