Dual shaft steppers on X and Y (non-Primo)?

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The printers are spitting out some Primo parts here! Kinda excited to tinker with another machine again. We’ve got a standing order starting up for a regular supply of ice cups to a local hotel so I’m going to shrink down the current MPCNC and purpose build it for the ice cups using hard endstops and no homing so I can run it off a Mini. Is there any reason I can’t use dual shaft steppers and run the backside of the stepper across to a bearing mount on the other sides of the X and Y?

The steppers that are closest to 0,0 are the ones most exposed to the snow that blows out of the cuts and during our last order the X and Y endstop switches iced up and froze on me preventing homing until we figured out the issue and thawed them. If I run the dual shaft steppers on the far sides of the X and Y they will stay clear of the blowing snow and with no homing switches - no switches to freeze up. I’ll also be fashioning some sort of cover to keep the steppers from too much exposure to the snow. Electronics will be enclosed in a heated (light bulb) something or other. And I’m contemplating running heat tape through the tubes so they don’t ice up which will only work if they transfer their heat through the tubes to the bearings.

I’m actually going to measure up the machine size requirements and see if I can’t find a chest freezer to drop the machine into. Cut a plexiglass window into the lid above the machine so I can monitor what’s going on and run the electronics outside of the freezer.

Any thoughts/concerns I’m not seeing clearly here?

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Here are my thoughts:

  1. You’ll have half the steppers, so even if you have perfect mechanics, you’ll have half the torque. May not be an issue in ice, IDK.
  2. You’ll be constraining them in a new way. The two can’t move independently when there is no power. So you’ll want a way to adjust them separately to get the two ends in “phase” and then keep them that way. Maybe a coupler on a shaft is enough to give you that flexibility.
  3. How are you going to connect the two pulleys? With each component comes some backlash, so you’ll want to pay attention so you’re not losing all your precision unwinding a bunch of gears.
  4. Watch out for flex on the shaft. Whatever method you use to transfer that motion across the workspace needs to avoid twisting. The bit may not be providing much load, but if it crashes, you don’t want a too small rod twisting.
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Well I can certainly confirm that if we don’t blow the snow out of the cuts it packs in so hard that a subsequent deeper pass will cause the current two stepper setup to skip steps so that’s important to note. With half the torque I could reduce the DOC (currently 25mm on a 3" long, 3/8" dia. bit) but the tradeoff then is job runtimes. Currently each set of four cups takes 12 minutes. If I shield the steppers from the blowing snow properly I guess the need for using single steppers maybe is moot. I should perhaps focus my energy on that and the air assist for this particular build.

Printing the last Primo foot now…two hours to go and then I keep working my way up the machine!

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Cost-wise, a second stepper and some wires are almost always going to be cheaper than a complicated rod setup. There is a reason the absolute cheapest i3 style printers still have 2 Z motors.

If you were in a very low torque situation, like drawing with a pen, but with a small footprint, you might be able to get away with one motor and nothing on the other side. Just remove the motor and the belts and see how that works.