[cncuser1]

I apologize in advance if this doesn't belong here but I have to start somewhere.....
I see servos are used to move axiis and also to run spindles on mills.

What is the difference between the two?
Is the difference a subtle difference is specs or is it a substantial difference in a technology or construction etc?

I am looking at spindle motors now and want to avoid a basic mistake.

[rcheli]

There is no difference. Moving an axis is usually done with a stepper or servo motor. A spindle can be driven with almost any motor that has enough horsepower and the RPMs required by the spindle it is driving. On a given mill a servo driving the spindle will likely be larger that the servos moving an axis but it really depends on your requirements.

I chose to switch the standard DC motor on my mill spindle to servo motor that had more HP, better speed control, and an encoder which allows me to do ridged tapping.

[cncuser1]

So an AC servo motor and driver that runs an axis is essentially the same as one that runs a spindle, except for the relevant specs of RPM, HP, torque etc.

OK, simple enough, thanks

[rcheli]

I just put the DMM DYN4 1.8kw servo on my spindle. I geared it 1:1.8 so I get 5400 rpm at the spindle. The motor max is 3000 if running on 240v.

[skrubol]

A large axis servo can run the spindle, but not always the other way around. Some spindle servos are induction motors and not suitable as an axis motor (can't accelerate/respond quickly enough.)
If you get an AC servo, make sure you get it's matched driver. Most AC servo drives will only work with a few different servo motors of the same brand.

[cncuser1]

skubol, that is an important nugget of info: induction AC servo is suitable for a spindle. Are there types of AC servos ( other than induction) that are NOT suitable for a spindle? I have seen reference to brushed, brushless, shunt etc and it is too mush to figure out.

I know it is a basic question, sorry again.

[mactec54]

So an AC servo motor and driver that runs an axis is essentially the same as one that runs a spindle, except for the relevant specs of RPM, HP, torque etc.

OK, simple enough, thanks

Only if you are using a real servo for the spindle motor and Servo Drive, post a photo of what you have as you may have a Ac motor and a VFD Drive which is very normal also but are very different from a servo motor and drive

[skrubol]

skubol, that is an important nugget of info: induction AC servo is suitable for a spindle. Are there types of AC servos ( other than induction) that are NOT suitable for a spindle? I have seen reference to brushed, brushless, shunt etc and it is too mush to figure out.

I know it is a basic question, sorry again.

Brushed and shunt (or series) wound motors are not AC motors, they're DC. Just about any kind of motor can be used for a spindle (except for a linear motor..) though some are not well suited. Steppers for example are good for positioning, but lousy as a spindle, as they are very inefficient. Induction motors are heavy, but are workhorses, and often have a wide max power band. PM (permanent magnet) AC servos are usually much lighter than induction, but are usually much more expensive and generally have a narrower power band. BLDC (Brushless DC) motors work fine for spindles, they aren't usually configured as servos, but otherwise are similar to PM AC. Brushed motors are fine (whether permanent magnet, series wound or shunt wound,) but are less efficient, noisier, dirtier and have brushes that wear out. They can be quite inexpensive though.

What kind of spindle do you have? Type of motor is less important than size, speed, torque, how it's connected to the spindle, etc.

[cncuser1]

I have a Sieg X2, the stock brushed DC 110V motor is OK but the controller needs replacing and eventual connection to a G540.

So wading into the options got me lost. The simplest option was to get a used KB controller, which is probably an SCR type KBLC-19M. Better yet KB has better PWM controllers. So up until there I am OK.

If I wanted to look at other motor/controller pairs then the deluge of options was confusing. But now I know an induction AC motor( servo or not) is OK. BLDC seem to be an option. Brushed are OK, but less preferred than the others.

Are there other controller options other than KB, would you know?