Steppers and Servos on the same machine?

[chmedly]

I've been working on a moving gantry cnc router design for quite a while. As most projects like this go, I've made a lot of changes along the way such that the design is quite different than it started out. Initially I bought some garden variety 1.8 degree steppers from Automation Technologies but then decided they were altogether inappropriate for what I was doing. After reviewing industrial motors that appear frequently used, and looking at the requirements for my machine, I decided that Oriental Alphastep 5 phase closed loop motors looked good. I got decent deals on the motors for the vertical axis and the short cartesian axis but I’m kind of stuck with the long axis. I need two motors with gearboxes and I’m not finding the exact models (and drivers) available for a price that I’m willing to pay.

So, I decided to look at the ClearPath servos that I’ve read so many wonderful things about. Wouldn’t you know it, they have a motor that looks perfect as far as torque and RPM! And without a gearbox at all! And it costs less, brand new, than the used Oriental motors would be.

I’m planning to use LinuxCNC with a Mesa 7i76e. I think that using SDSK motors with step and direction signals, they can be used in basically the same way that the Oriental motors on the other axises would be used. But, I figured I would ask here for opinions. Are there any issues, in this context, with mixing servo and stepper motors on the same machine?

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[Jim Dawson]

No issues at all. From the control perspective, the Clearpath motors are steppers. They only become a servo at the drive that is integral on the motor.

[Teknic_Servo]

I've been working on a moving gantry cnc router design for quite a while. As most projects like this go, I've made a lot of changes along the way such that the design is quite different than it started out. Initially I bought some garden variety 1.8 degree steppers from Automation Technologies but then decided they were altogether inappropriate for what I was doing. After reviewing industrial motors that appear frequently used, and looking at the requirements for my machine, I decided that Oriental Alphastep 5 phase closed loop motors looked good. I got decent deals on the motors for the vertical axis and the short cartesian axis but I’m kind of stuck with the long axis. I need two motors with gearboxes and I’m not finding the exact models (and drivers) available for a price that I’m willing to pay.

So, I decided to look at the ClearPath servos that I’ve read so many wonderful things about. Wouldn’t you know it, they have a motor that looks perfect as far as torque and RPM! And without a gearbox at all! And it costs less, brand new, than the used Oriental motors would be.

I’m planning to use LinuxCNC with a Mesa 7i76e. I think that using SDSK motors with step and direction signals, they can be used in basically the same way that the Oriental motors on the other axises would be used. But, I figured I would ask here for opinions. Are there any issues, in this context, with mixing servo and stepper motors on the same machine?

Hi chmedly,


Thanks for your interest in Teknic's products. We’ve seen other customers mix ClearPath with stepper motors before, and while it is certainly doable, there are a few points to be aware of:


In regard to the controller, the ClearPath motors require 5-24Vdc Step and Direction signals. As long as your controller can output these signals, you can send the same Step & Direction commands to both the ClearPath - SD motors and the stepper motors. Not all controllers output these signals natively though (e.g. some output a 3.3V signal), so you’ll want to make sure your controller is compatible.


When mixing motor types, on a CNC machine in particular, you’ll want to take certain steps to configure the motors properly. For starters, you’ll want to account for the potential differences in your command resolution. You can configure the ClearPath motors in a number of ways, and their input resolution may differ from that of your stepper motors. If you don’t properly account for the differences, you may find your machine cutting ovals instead of circles.


Additionally, you may need to minimize your reliance on Teknic’s Regressive Auto Spline (RAS) feature. The RAS limits the Jerk and Jerk-derivative of the motion profile resulting in smoother/quieter motion and improved cut quality (here is a link to a video that explains more if you are interested: ). While you have control over how much RAS you use, increasing the RAS too much will create a discrepancy in the motion between the ClearPath and stepper-driven axes.


Please feel free to contact us directly for more details at support@teknic.com.


Best regards,
Mark D. - Teknic Servo Systems Engineer

[adam_m]

Showing my ignorance here but can you run ClearPath servos from say a G540 since they are "Steppers"?

I'm unfamiliar with how they work...

Adam,

[skrubol]

Showing my ignorance here but can you run ClearPath servos from say a G540 since they are "Steppers"?

I'm unfamiliar with how they work...

Adam,

No, a G540 has the stepper drivers integrated. Clearpath's also have their drivers integrated, so you'd be doubling up on the drivers.
You could rig a breakout board before the G540 to take the step/dir signals to a clearpath.

[adam_m]

No, a G540 has the stepper drivers integrated. Clearpath's also have their drivers integrated, so you'd be doubling up on the drivers.
You could rig a breakout board before the G540 to take the step/dir signals to a clearpath.

So you would use something like the Ethernet Smooth Stepper to send signals to them?

https://www.amazon.com/Ethernet-Smoo.../dp/B00R8FNLW4

Adam,

[ger21]

Showing my ignorance here but can you run ClearPath servos from say a G540 since they are "Steppers"?

Clearpath servos are not steppers.

So you would use something like the Ethernet Smooth Stepper to send signals to them?

Any controller than can send step direction signals.