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Adding additional power supply

Probably a basic question but want to verify before letting all the magic smoke out of either my mini Gerbil or the power supply of my K40.  Can one simply replace all power leads from the existing power supply and feed the mini with a new supply?  Do I need to do some additional protected ground sharing for this?  I'm having missed step issues with my y-axis if I try to run at any reasonable speed (and when powered and locked, the y-axis can easily be moved unlike the x-axis).  I've increased current to so I get .34v with a milti-meter which has helped (it came at .29v) but I really think the y-axis motor is overly weak and would like to replace both with some heavier Nema 17's I have left over from a printer upgrade.


-- Joel


I just saw your post.

Yes, another power supply can be added, as long as the common (ground) terminals are joined.

However, dropped pulses are rarely PSU related, and not too often motor related either. Good to see that you have trimmed the motor currents, that can catch people out.

Bigger motors are likely to cause more problems than they solve - mounting them being the most obvious.

Look to these issues first:

  1. Slipping belts is the number one cause of what looks like dropped steps in 3d printing/laser cutting. There are endless forum posts with people swearing that all the grub screws were tight on their pulleys, and then coming back several days later to say that tightening up the screws solved the problem.
  2. Step pulse duration too short. Some stepper drivers require step pulses > 1uS. The defaults $0 = 10 (uS) should be fine.
  3. Speed (step frequency) too high $110, $111. Try backing these off. The default $110 @ 12000 (200mm/sec) could be a little high for some printers, particularly if air assist has been added. $111 @ 5000 (83 mm/sec) should be OK. Try halving them, and then increase until the issue recurs, back off 20%.
  4. Acceleration too high (corners, or start from stopped) $113, $114. As above for solution.

I hope this helps.

-- Richard



Thank you for the reply.  I have a highly modified Prusia i3 clone 3d printer (does not look like an i3 any more...)  with customized Marlin  firmware for the hardware attached so stepper motors, speed, and current are well understood.  Unfortunately, the issue I have is directly related to stepper hold power.  The motor in my machine just simply cannot accommodate the fast movement of the entire x-axis weight without over stepping (creep).

As to the common ground, are we talking adjusted (24v), straight (110v) or are they all the same?  And if adjusted, should I add diodes for security due to the potential for high-frequency pulses or back-splash?  From a common-sense perspective, common grounding makes sense, but there is always that "what-if" regarding backflow...

Again, sorry if these are basic questions.  I have not had to tie multiple power supplies for this type of system before.

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