Should z-axis steppers be ‘locked’ between levels?
My son and I have a Shenzen-style Prusa i3 as linked below, and are trying various things to improve print quality.
Our biggest problem right now is the 2 z-axis steppers are not staying in sync, with one gradually lagging more and more and messing with prints.
I switched their wiring from parallel to series and it made absolutely no difference.
What I have noticed is that I can EASILY rotate the threaded rods with my fingers during printing.
Aren’t the steppers supposed to be ‘locked’ into position? (via the right coils remaining energised).
And would this be a firmware compile-time option? (Firmware came ready-installed and no source code)
Might the manufacturer have ‘turned this off’ to save power draw/component heat? (The original supplied power supply popped after just a few weeks of use…)
At the moment I DO NOT have access to the firmware source, but I am working on that… (Configuring up firmware myself is a last resort I suppose…)
The controller board is a Melzi Ardentissimo (1.0/2.0 eBay Hybrid).
I have a stainless steel Zonestar, which looks almost identical to that, its pretty close, uses a melzi 2.0, I have all the files(firmware, build instructions, setup etc) they gave me in a zip folder. If you wanted to sort them out , and give them a try. here’s a link https://docs.google.com/uc?export=download&confirm=Iz7m&id=0B-iqGBAct8_ubWN6M1BHUllYNjA
I can’t tell from the photo and I don’t have a printer of this sort. Are there couplers from the motor shaft to the z-rods? You didn’t say in your post that you checked for tightness of those screws. A loose setscrew would provide the characteristics you describe. That would be too easy, wouldn’t it?
@Fred_U Ha! Yes, too easy. No coupling on the Z-rods. In fact, it seems the steppers and rod in this product are a special build. The rods appear to be permanently part of the stepper assembly, somehow… There is no visible sign of how they are fixed. Weird, I know. I found an old (dead) link to a replacement (stepper and rod in 1 piece) on Alibaba, that the thread indicated were hideously expensive. If my z-steppers ever give up it will time to re-build the z-axis…
But my question still stands - As a fairly new user/tinkerer, my question is simply: SHOULD I EXPECT the z-steppers to be locked pretty firm between levels???
And IS IT a (typical?) firmware option to play with?
@Peter_Nann Depending on your firmware the motors may not be engaged when not in use. For example in Marlin it’s via the #define DISABLE_Z parameter (on or about line 372)
As you have figured, if the motor is engaged you should not be able to turn it though depending on the quality of the motor or the the motor current settings on the board it’s possible you could turn it if either of those weren’t up to spec.
There is more about your board at Melzi - RepRap with some links to firmware that may work with your system.
Thanks @dstevens_lv ! I think you have nailed the info I needed with that github link. Champion.
So it seems it may be normal(ish) to disable Z between levels. But I am pretty sure that is causing our problems - The heavy side with the mounted X-stepper is the one that lags. I am guessing that after some steps it ‘glides’ back a little - Not surprising as it takes almost no effort with my fingers to turn it ‘down’ during a print, but a bit more to turn it ‘up’.
Looks like building and configuring my own firmware is in my future…
Thanks again.
Lookout for our next chapter in a couple of weeks. ;-p