Build plate moving during long prints
This has happened to me a few times now, where the build plate itself shifts a few cm away from the notch causing a layer shift. I double-checked nothing is hitting anything. Anyone run into this?
RE: Build plate moving during long prints
Check your magnets are all in place.
Once the flexible sheet is in place it's very difficult to move it in any direction. Usually belts are skipping before the sheet can move. The only case where I can see it happen is, if you lost some magnets.
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RE: Build plate moving during long prints
If the plate is sliding around on the bed, you have some admirable adhesion going on. And are certainly not using stock motors and drivers.
Post a photo of your setup.
RE: Build plate moving during long prints
^^ It can happen. Not during normal printing moves but I had a fast travel move on a PETG print once hit a curl on the part and do exactly this. Keep in mind the magnets are very strong at pulling the surface onto the heat bed, but less so in keeping it from sliding around; there are no "counter" magnets in the sheet to resist that and the magnets are perfectly happy attracting any part of the sheet. Same reason you can separate magnets by sliding them but not by pulling straight apart.
RE: Build plate moving during long prints
^^ It can happen. Not during normal printing moves but I had a fast travel move on a PETG print once hit a curl on the part and do exactly this. Keep in mind the magnets are very strong at pulling the surface onto the heat bed, but less so in keeping it from sliding around; there are no "counter" magnets in the sheet to resist that and the magnets are perfectly happy attracting any part of the sheet. Same reason you can separate magnets by sliding them but not by pulling straight apart.
Just admit it was a self written gcode without z-hop and warping material hitting flat big object in lower z-regions, high speed in negative Y-direction 😋
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RE: Build plate moving during long prints
Okay - so it MIGHT happen, if the situation is perfect and loaded the sheet/bed interface with petroleum jelly or Crisco (or have never cleaned the surfaces and let dust and debris accumulate as a lubricant), have custom firmware with maximum drive currents and no crash or stall detection, and then plan a forced move across the bed to maximize sled inertia ... a qualified maybe.
Actually, I seriously doubt my extruder could move my PEI sheet horizontally. And I have had some serious nozzle knockers stall the extruder and never had it happen. Heck, it is hard for me to shift the sheet when I want to adjust the edges to align when placing it after a wash. And there is no way I can slide the sheet and not move the bed when the motors are idling -- I have to press hard enough I move the entire printer if I don't hold it down.
If I weren't printing, I'd get out my scale and see just how many pounds it takes to slide my PEI sheet ... so it's on my to-do list. I suspect I'll peg my 8 lb scale.
RE: Build plate moving during long prints
Well, like I said it's happened several times now on long, complicated prints. I didn't check if a crash was triggered though.
Magnets are all in place, and I should amend it by saying its a few mm not a few cm 😉
I'll take a picture next time. It's bizarre.
RE: Build plate moving during long prints
Okay - so it MIGHT happen, if the situation is perfect and loaded the sheet/bed interface with petroleum jelly or Crisco (or have never cleaned the surfaces and let dust and debris accumulate as a lubricant), have custom firmware with maximum drive currents and no crash or stall detection, and then plan a forced move across the bed to maximize sled inertia ... a qualified maybe.
Actually, I seriously doubt my extruder could move my PEI sheet horizontally. And I have had some serious nozzle knockers stall the extruder and never had it happen. Heck, it is hard for me to shift the sheet when I want to adjust the edges to align when placing it after a wash. And there is no way I can slide the sheet and not move the bed when the motors are idling -- I have to press hard enough I move the entire printer if I don't hold it down.
If I weren't printing, I'd get out my scale and see just how many pounds it takes to slide my PEI sheet ... so it's on my to-do list. I suspect I'll peg my 8 lb scale.
I just tried it with my spring force gauge. The PC sheet slips at 72oz (2Kg) of horizontal pull. And I just cleaned the heatbed of grease/oils after a Y axis service.
RE: Build plate moving during long prints
How have you attached the gauge to the sheet? I just tried to pull hard holding the edges with my fingers and it takes a lot of force until it slips.
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RE: Build plate moving during long prints
Hours and hours remaining on my print ... 10 am tomorrow will be my first opportunity.
RE: Build plate moving during long prints
I have had similar issues when printing stuff (in PETG) that almost entirely filled my buildplate. It looked like a layer shift at first but turned out to be a buildplate that slightly moved.
In my case the part tried to warp but had such good adhesion to the bed that it simply lifted it up. With the increased distance from the buildplate to the magnets their pull decreased which allowed the builplate to be moved when the nozzle crashed into the warping part. In my second attempt of that part I simply clamped the build surface down with binder clips at the corners. The part finished without major problems but the picture still shows a gap between the PCB heated bed and the steel sheet.
RE: Build plate moving during long prints
How have you attached the gauge to the sheet? I just tried to pull hard holding the edges with my fingers and it takes a lot of force until it slips.
The PC sheet has holes in the front and my gauge has a hook end.I did have to slide it forward a smidge so I could insert the hook without lifting the sheet but it should still have been "covering" all the magnets.
Yes - I've had the build plate warp with some PETG prints too. That definitely doesn't help the magnetic holding and will contribute to the issue.
RE: Build plate moving during long prints
The PC sheet has holes in the front and my gauge has a hook end.I did have to slide it forward a smidge so I could insert the hook without lifting the sheet but it should still have been "covering" all the magnets.
Interesting. My smooth PEI sheet doesn't have holes but my textured ones does.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Build plate moving during long prints
The PC sheet has holes in the front and my gauge has a hook end.I did have to slide it forward a smidge so I could insert the hook without lifting the sheet but it should still have been "covering" all the magnets.
Interesting. My smooth PEI sheet doesn't have holes but my textured ones does.
It does as the base steel sheet is the same; they're just covered over by the PEI sticker and so not readily visible. If one was adventurous they could be cut out with a sharp blade, I suppose.
RE: Build plate moving during long prints
Will not try to find those, I'm ok 😊.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Build plate moving during long prints
Print finished, using my trigger pull scale, applied torque to left hand corner, and here's what I get:
-- at 6 pounds, the printer starts moving across the table, no movement of the sheet on the bed whatsoever. Once moving the torque reduced to 4 pounds.
RE: Build plate moving during long prints
Textured sheet has a bit less contact area for friction, so that more or less agrees with my results of 72oz to get it moving. Of course the printer can't move across the table by pushing against itself, but something's gonna give...
RE: Build plate moving during long prints
Timo-m's experience sounds most likely: a warping part deformed the bed to the pint the magnets failed to hold. I've seen things that hinted my sheet was bending under the part - no delam/lifting, but head was knocking into the part. But it's never cause me to lose a part - yet.
ps: weird, timo-m, same name, same second initial. Feels almost like vintage-tim's experiences. Play Twilight zone theme.
RE: Build plate moving during long prints
The Tims are coming! The Tims are coming!
RE: Build plate moving during long prints
Textured sheet has a bit less contact area for friction, so that more or less agrees with my results of 72oz to get it moving. Of course the printer can't move across the table by pushing against itself, but something's gonna give...
In my case, the spring steel sheet was going nowhere, I could have easily pegged the gauge trying, but using two hands while standing up requires coordination skills I've never mastered -- Use one hand to hold the printer the other to pull the gauge - say whaaaat?
I'm not going to go down the rabbit hole that a 40 N-cm motor can't create the torques we are talking about, so we'd be guessing at kinetics to get the forces required. Still unlikely on a bed touching properly, but if the sheet were being lifted by part warp, I can see that reducing the field strengths to where the plate could move a lot more easily. Paper clips to hold the sheet is a great idea.