Newbie: is there difference between stepper and servo motor?

[g888h]

I've got a stepper motor but someone told me to do the job I want to do I should use a servo motor because my stepper motor gets around 80C.
I have a Vexta H266-02-A17 with Ocencontrols(OC) serial decoder module + OC driver module.

All I am trying to do at this stage is to turn a long screw vice ( 300 mmm) a certain number of turns and be able to repeat this operation accurately.
I am not sure I've chosen the right motor?

As an electronic techo, I use to repair pinball machine and the sign of any coils with no, or one_or_two preloaded fields getting at 80C temperature is a sign of aging and increase internal resistance. (in other bad news)

Is this the same with steppers?

Guy

[klick0]

I've used 2 types of steppers before, a cheap japan stepper that was like $20 and a vexta something that was around $150. They both got very hot when working or doing nothing (nothing meaning holding a phase or 2). I always ran only activating 1 poll/phase (don't really know what they are called) at a time to reduce heat. The cheap steppers definatly got much hotter then the vexta though.

I always did wonder if it was the controlanything.com stepper drives that did it, or if it was just how steppers were. I've since then switched to servo's with gecko servo drivers, they've never increased in temperature at all, they are pretty oversized for my table, and draw 10 watts total when cutting at most.

To answer your first question, steppers and servos are entirely different, not similiar at all. Steppers are generally cheaper, theres no feedback to tell where its at. Servo's are usually brushed dc motors, don't know anything aobut ac or if anyone uses brushless motors. They have an optical encoder, generally from us digital, that basically tells the shaft where it's at. The servo driver uses that to either simulate steps, like my gecko driver, or .. well there's a million ways it could work, but it uses the optical encoder to tell where its at and how to hold/move the motor.

About the heat of the stepper, i'd like to hear other peoples comments on this.

A stepper can most definatly do what you want to do, and do it accurately.

Ross

[Kipper]

I can leave mine idling for hours on end and they dont get warm even :shrug: when working they dont seem to get "hot" either as far as accuracy I like to start in one place and send the carriage all over the place then tell it to "go home" I then notice that it's all accurate enough for me I do have a slight hiss however which doesnt bother me as i'm about deaf :lol:

[Torchhead]

Overheating motors usually indicate that they are being run on the high end of their ratings. Some feel it is best to run the motors at whatever voltage the driver will handle. Any power the motor can't use as work will go up as heat. A lot of drivers have current reduction after sitting idle for a few seconds so they don't waste extra power at zero RPM.

I am not familiar with the motor driver and controls but if it is self-powered it is probably designed for a specific motor or series of motors. The general rule of thumb is to use from 10 to 20 times the rated motor voltage as the Motor DC but the problems with general rules is that theay are....well, general and are not optimal for any specific motor.

I use the two second rule. If I can hold my hand on it for two seconds without screaming in discomfort then it's okay (:-)

[NC Cams]

Steppers versus servos:

http://www.cnczone.com/forums/showthread.php?t=17419

Enjoy the read....