This not meant to be a discussion as to whether or not it should be done but of how it could be done. What mods would be required to use closed-loop steppers (e.g., MKS Servo42) on the X and Y axes of the LR v3?
Taking a quick look at the pictures & drawings, it looks like the motor mounts and the YZ plates into which the motors mount would have to be elongated and the plate extended.
Obviously, elongating the YZ plate would result in it interfering with the table surface; however, this can be overcome many ways. The preferred would be to elevate the Y-axes surfaces (under the rail blocks and the bearings) by at least the amount of the hole elongation. This essentially makes a U-shape bed like the Momus CNC.
Looking at the pictures on the site, it’s hard to tell what mods, if any, would be required for the X axis.
On a side note: that the Z-axis wouldn’t necessarily benefit from a CL stepper, but would the core have to be modified or is there sufficient clearance for the additional motor length?
In the pic that you’ve marked up that’s the z motor, the hole on the right is the y motor. You would just need to rearrange things above the y motor there in that hole on the right.
For z it might be easier to shift the x gantry up in elevation… but the more you extend that the more wobbly things would get.
Another thing I might add is that the closed-loop back-end could go on a shorter stepper. With open-loop steppers, there has to be a healthy safety margin between the max torque of the motor and the torque of the load, because any deficiency, even momentarily, is catastrophic.
With a closed loop stepper you can probably get away with a smaller margin because if the load exceeds the motor torque it will just deflect, somewhat like an elastic element. As long as you are not driving at max torque 100% of the time, you should be okay.
In the end it depends how much torque is lost in going to the shorter motor, and it might not be enough, but it is possible that it could work in the same amount of space.
@kimnach, how’s it going? Curious if anyone’s using closed loop steppers, any recommendations and lessons?
They seem like a smart way to push performance and overall job reliability, especially if the overall job orchestration is able to throttle speed based on number of skip events detected.
