Z axis moves while printing (not layer changes)?
I am printing a large square object on my C1+ that takes up a lot of the print area. I just noticed that when the print head moves from the back side of the bed to the front side (along the Y axis) the Z level raises and lowers a mm or two as it moves front to back. Specifically, it lowers about a MM or two when it moves to the front (door side) of the bed, and then raises back up the same amount as it heads back to the rear. About 1/4 turn of the Z axis screws. I never noticed this before I guess because I don't typically print very large Y axis objects. I am printing the same object on my Bambu X2D and that bed isn't moving other then at layer changes.
Any idea why my C1 would do this?
The bed-levelling at the start of the print maps the required Z offset and the early layers adjust height and extrusion to compensate until the upper layers can be extruded completely level. It means your print sheet isn't perfectly flat (none are) and the printer is taking care of it.
Cheerio,
RE: Z axis moves while printing (not layer changes)?
Interesting. I would have thought auto-homing would set the bed at the limit of its travel, essentially leveling it. But I guess not. I wonder if I made that 1/4 turn of the left and right forward Z screws manually while the printer is off, would that "level" it?
The bed-levelling at the start of the print maps the required Z offset and the early layers adjust height and extrusion to compensate until the upper layers can be extruded completely level. It means your print sheet isn't perfectly flat (none are) and the printer is taking care of it.
Cheerio,
RE: Z axis moves while printing (not layer changes)?
Is this z-hop?
RE: Z axis moves while printing (not layer changes)?
I think z-hop is only applicable when travelling, not while extruding. This happens while its extruding along the Y axis.
Is this z-hop?
RE: Z axis moves while printing (not layer changes)?
Interesting. I would have thought auto-homing would set the bed at the limit of its travel, essentially leveling it. But I guess not. I wonder if I made that 1/4 turn of the left and right forward Z screws manually while the printer is off, would that "level" it?
Connect a USB-C cable between your printer and PC/laptop, download this: Prusa Slicer Filament-Edition then go to the Calibration menu and run Bed Mesh -> Probe Bed.
I wonder if I made that 1/4 turn of the left and right forward Z screws manually while the printer is off, would that "level" it?
It might - but it still wouldn't be flat.
Cheerio,
RE: Z axis moves while printing (not layer changes)?
Well this is disturbing... I ran it initially and it came back all zeros (excellent rating), which I was momentarily thrilled with. Then I noticed the recommended 85deg setting for PETG, instead of the default 60 for PLA. Since I use mostly PETG, I ran it again at 85 deg and got this: (marginal)
After a minor outburst of profanities, I ran it again at 60deg to see if it reverted to "excellent", but no joy, still marginal. So I don't know what was up with the initial "excellent' results, but apparently I have a marginal bed.
Any way to correct this? Or action to take?
Interesting. I would have thought auto-homing would set the bed at the limit of its travel, essentially leveling it. But I guess not. I wonder if I made that 1/4 turn of the left and right forward Z screws manually while the printer is off, would that "level" it?
Connect a USB-C cable between your printer and PC/laptop, download this: Prusa Slicer Filament-Edition then go to the Calibration menu and run Bed Mesh -> Probe Bed.
RE: Z axis moves while printing (not layer changes)?
Well this is disturbing... I ran it initially and it came back all zeros (excellent rating), which I was momentarily thrilled with. Then I noticed the recommended 85deg setting for PETG, instead of the default 60 for PLA. Since I use mostly PETG, I ran it again at 85 deg and got this: (marginal)
After a minor outburst of profanities, I ran it again at 60deg to see if it reverted to "excellent", but no joy, still marginal. So I don't know what was up with the initial "excellent' results, but apparently I have a marginal bed.
Any way to correct this? Or action to take?
I'm surprised initially it came back all zeros because that's close to impossible. When you heat the bed, it expands in all 3 dimensions. Running the probes at 85° is sensible. One thing I would try first is remove the sheet and tighten all the screws on the bed. Don't over do it though. Run the measurement again. You can "tram" the bed somewhat by loosening slightly screws in the corners that aren't red. But I would advise not to get locked into chasing error. Close enough is good enough.
RE: Z axis moves while printing (not layer changes)?
Yeah maybe I did something wrong. Who knows. I'll start with the loosen/tighten procedure. You wouldn't happen to have a torque spec, would you? I have a little torque bit driver I used to use for rifle scope mounts when I shot competitively. It comes in handy from time to time...
Well this is disturbing... I ran it initially and it came back all zeros (excellent rating), which I was momentarily thrilled with. Then I noticed the recommended 85deg setting for PETG, instead of the default 60 for PLA. Since I use mostly PETG, I ran it again at 85 deg and got this: (marginal)
After a minor outburst of profanities, I ran it again at 60deg to see if it reverted to "excellent", but no joy, still marginal. So I don't know what was up with the initial "excellent' results, but apparently I have a marginal bed.
Any way to correct this? Or action to take?
I'm surprised initially it came back all zeros because that's close to impossible. When you heat the bed, it expands in all 3 dimensions. Running the probes at 85° is sensible. One thing I would try first is remove the sheet and tighten all the screws on the bed. Don't over do it though. Run the measurement again. You can "tram" the bed somewhat by loosening slightly screws in the corners that aren't red. But I would advise not to get locked into chasing error. Close enough is good enough.
RE: Z axis moves while printing (not layer changes)?
Well this is disturbing... I ran it initially and it came back all zeros (excellent rating), which I was momentarily thrilled with. Then I noticed the recommended 85deg setting for PETG, instead of the default 60 for PLA. Since I use mostly PETG, I ran it again at 85 deg and got this: (marginal)
To me, your "marginal" scan mainly looks like the print head (specifically the fan shroud on its rear) bumped into the heater cable cover when probing the rear left bed area. That can cause the pronounced depression you see in your profile. Overlay this with a linear front-to-back tilt, which is easily compensated by adding shims to adjust the bottom end stops, and you get exactly the result you show.
Maybe the difference between the good and the marginal scan was not the temperature, but that you switched to a thinner print sheet which caused the collision to happen?
It's a known design issue with the Core One heatbed connector. You can unscrew the connector's top cover, make sure the thick cables beneath it are pointing straight back and not upwards, and switch the screws to a type with a flatter head. That should be sufficient to avoid a collision even with thinner print sheets.
RE:
I think that 0.0, 100% perfect results were an error. So I'm not taking that into consideration. All scans were with the same Biqu Glacier plate, of course I didn't change plates between scans. Give me a little credit, huh? 🙂
Not sure I'm following your interference theory. The high spots are the rear right corner (looking in at bed through the door), while the bed cable connector is on the left side. So no way there was any contact on the high side. Maybe i'm not understanding you?
Anyway, I loosened all the heat bed screws and retightened following the build instructions. Center, edges then corners. No help there. Then I tried again with the Biqu, no help there. Lastly, I tried with a Prusa satin sheet, and again, no substantial change.
Seems like i'm stuck with a crooked bed... As long as the software does its thing, it probably only matters to my OCD...
Well this is disturbing... I ran it initially and it came back all zeros (excellent rating), which I was momentarily thrilled with. Then I noticed the recommended 85deg setting for PETG, instead of the default 60 for PLA. Since I use mostly PETG, I ran it again at 85 deg and got this: (marginal)
To me, your "marginal" scan mainly looks like the print head (specifically the fan shroud on its rear) bumped into the heater cable cover when probing the rear left bed area. That can cause the pronounced depression you see in your profile. Overlay this with a linear front-to-back tilt, which is easily compensated by adding shims to adjust the bottom end stops, and you get exactly the result you show.
Maybe the difference between the good and the marginal scan was not the temperature, but that you switched to a thinner print sheet which caused the collision to happen?
It's a known design issue with the Core One heatbed connector. You can unscrew the connector's top cover, make sure the thick cables beneath it are pointing straight back and not upwards, and switch the screws to a type with a flatter head. That should be sufficient to avoid a collision even with thinner print sheets.
RE: Z axis moves while printing (not layer changes)?
Not sure I'm following your interference theory. The high spots are the rear right corner (looking in at bed through the door), while the bed cable connector is on the left side. So no way there was any contact on the high side.
My theory is that there is a pronounced low spot in the rear left corner, for the reasons described, namely a collision with the heatbed cable cover. Plus a general tilt to lower positions towards the front, due to the end stops of the Z axis (i.e. the base plate of the printer) not being parallel with the CoreXY movement plane.
RE: Z axis moves while printing (not layer changes)?
I'm going to use an old mechanics trick and smear some grease on the bed connector. When I run the probe, if contact is made, the grease will transfer to the fan shroud. Well. maybe not grease, but something of similar consistency. Grape jam maybe?
Not sure I'm following your interference theory. The high spots are the rear right corner (looking in at bed through the door), while the bed cable connector is on the left side. So no way there was any contact on the high side.
My theory is that there is a pronounced low spot in the rear left corner, for the reasons described, namely a collision with the heatbed cable cover. Plus a general tilt to lower positions towards the front, due to the end stops of the Z axis (i.e. the base plate of the printer) not being parallel with the CoreXY movement plane.
RE: Z axis moves while printing (not layer changes)?
You can also just remove the top cable cover temporarily for a test, to take another height profile scan. It's easily unscrewed and replaced.
RE: Z axis moves while printing (not layer changes)?
Oh thats probably a better idea then using food products
You can also just remove the top cable cover temporarily for a test, to take another height profile scan. It's easily unscrewed and replaced.
RE: Z axis moves while printing (not layer changes)?
Well I'm annoyed as hell as I just wrote an long response and when I hit reply this crap site threw an error. So I'm done for now and will pick this back up later.
RE: Z axis moves while printing (not layer changes)?
Took the weekend off from messing with this. I removed the heat bed cable cover and probed, no real change, though it changes slightly every try - go figure that one out... I loosened and retightened the heat bed screws in the proper order again, no change. I'd love to know if there is a torque spec. However it prints fine so I'm going to write it off as a bad copy of the heatbed and just live with it for now. Not going to bother with trying support as I'm not using any official means of measurement and even though it shows as marginal, it prints ok as I said. Oh well. We'll see what the next printer I buy does for me...