I recently burned out one of my z-axis steppers, so I installed a new pair. They seem to be working fine, but I've recently noticed that prints are being slightly compressed on the z-axis, by about 10%. I haven't changed my config at all, other than to increase the z-axis motor current in case the new motors needed more juice, but it hasn't helped. Everything else is the same, so I cannot understand the problem. Does anyone have any ideas?
You don't "increase current in case the steppers need more juice". That's going to cause exactly the kinds of problems you are having.
What you do is you look up exactly how much current the stepper motors need, and set exactly that value, and then things will work.
Then once that is confirmed to work, if and only if your steppers are too loud, you can try setting current *lower*, and if that does not introduce new problems, it will make them quieter.
But you don't go over the rated current.
Thanks for the advice. They're not set over the rated current. When I first built the printer I set them to the rated current and then dialed that back,as you suggest. I'd left the config at the same current as the old motors when I first replaced them, and only ramped it up by 30% when I noticed the z-scale problem. They're still set a little less than the rated current but seem to have bags of torque. I'll try setting them to the full rated current and see if that helps. I'll let you know.
you were absolutely right! I set the current to the rated one on the stepper and it now prints perfectly. Previously I had used about 50% of the rated value and it worked a treat. Obviously steppers vary in their tolerance to current below the rated value.
As per my experience you must have to increase current for stepper motors because they need more current for their operation. I think this the only problem in your case.
You must look up exactly how much current the stepper motors need and set exactly that value, and then things will work.
After also you need to supply the countinous current what they required.
Thanks - that was definitely the problem. It was strange though, because the previous brand of steppers (ebay - cheapest available) would work quite happily at about 30-40% of the rated current. The new brand (ebay - cheapest available) require pretty much the full rated current. It's a learning experience.