Build plate moving during long prints  

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ali.s5
(@ali-s5)
New Member

I experienced this issue today in the last layers of a 13 hours print!!

Inland Transparent PETG/ extruder temp 240/ bed temp:90

Incident timelapse video:  Bed_Shift_PETG

the scene before shift:

Scene after the shift:

Next Layer:

This post was modified 1 year ago 2 times by ali.s5
Posted : 24/03/2020 3:19 am
jbienz
(@jbienz)
Active Member

@ali.s5, did you ever figure out what was causing this? Tried my first large print last night (as far as the Mini+ is concerned) and ended up with a plate shift I can't explain.

Posted : 03/03/2021 1:52 pm
cwbullet
(@cwbullet)
Illustrious Member

@jbienz

I had a similar issue.  Mine was caused by stacked prints.  I stacked two prints by mistake on the slicer.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 06/03/2021 11:54 pm
jbienz
(@jbienz)
Active Member

Thanks cwbullet. You mean you stacked to prints vertically one over the other or you had two parts taking up the same space?

I think my problem was trying to use PVB for something it wasn't intended to print. I'm still very new to 3D printing and still learning. I'm pretty sure the nozzle crashed into the part which caused the sheet to shift, but I'm still not sure how or why.

Luckily I did do a time lapse, but the pictures weren't very clear because the light level was low. Here's the last clear frame before the sheet shift:

 

Here's the first clear frame after the sheet shift:

 

At the end of the print there was curly PVB material all over the place.

 

So I don't know if somehow the head caught it or what.

This post was modified 2 months ago by jbienz
Posted : 07/03/2021 10:25 pm
cwbullet
(@cwbullet)
Illustrious Member

It was actually two copies of the same print.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 07/03/2021 10:30 pm
Antonio da Catania
(@antonio-da-catania)
Moderator
Posted by: @ali-s5

I experienced this issue today in the last layers of a 13 hours print!!

Inland Transparent PETG/ extruder temp 240/ bed temp:90

Incident timelapse video:  Bed_Shift_PETG

the scene before shift:

 

Scene after the shift:

 

Next Layer:

 

Sometimes if the overhang is too steep or too thin it may happen that the edge start curling up, until the point the head crash on the print and possibly shift. 

Parlo italiano...but I'm not an expert....
Posted : 07/03/2021 11:05 pm
jbienz
(@jbienz)
Active Member

Thanks Antonio. I think that must be what happened.

Anyone know why the PVB curled so bad in my images above? Are my temps wrong? I used the Prusa PVB settings in the slicer and pretty sure I used the recommended temperature settings on the printer. Is PVB just not meant for this kind of design? It seems most people use PVB for hollow vases or very small figurines.

Posted : 09/03/2021 12:29 am
Charlie Essers
(@charlie-essers)
New Member

Experiencing this same thing with a long (28hr) print with PLA. Failed twice now overnight. Cannot explain it. No apparent warping. Will try binder clips next time, but sure would love to know what is really going on.

Posted : 07/04/2021 4:24 pm
doot doot beep
(@doot-doot-beep)
Active Member

How much space is between the build plate and the blinds when its all the way retracted? Mine was tapping a shelf behind my printer at certain points of the print. It took hours but it would eventually move the plate. 

Posted : 07/04/2021 4:35 pm
jbienz
(@jbienz)
Active Member

Wow, that's a huge shift in the build plate. At least the one on the left. It's interesting that the shift happened at a similar height and in a similar rotation and direction both times. That does seem like the head colliding with the part rather then grabbing some curling or something like mine did. (FYI, I did reprint the car with a different material and did not experience the layer shift.)

It would be interesting if you could point a good camera at the back side of the model and let it record while you're doing the print. At least when you get close to that Z height. I say the back of the model because I think that's where the collision is happening based on the shift direction.

If this is a collision, I found an article that may help:

How to Fix 3D Printer Nozzle Hitting Prints or Bed - 3D Printerly

I also saw people saying that adding a Z hop can help, but this may be a band aid rather than fixing the real underlying problem.

Posted : 07/04/2021 5:16 pm
Charlie Essers
(@charlie-essers)
New Member

Thank you both for the replies. The blinds are not nearly as close as they look in that photo. And I was printing in my "enclosure" anyway (an upside down clear storage container). 

I do think it may be the nozzle hitting the print at some point. Prusa has an article on layer shift that recommends slowing down taller prints and I will give that a try next as well set up a camera.

Posted : 07/04/2021 7:17 pm
Charlie Essers
(@charlie-essers)
New Member

Success! As the print neared the offending layer I slowed the printer to 50%. Once it had passed that area I sped it back up to 80% and let it finish. No problems.

Posted : 14/04/2021 7:27 pm
Ahand59
(@ahand59)
Active Member

I have an unmodded Prusa Mini that I have had since December 2020 and have this same thing happening.

  • I am using the original prusa smooth plate with no modifications or adhesives. Just a good scrub once in a while and cleaning with isopropyl alcohol before each use.
  • I am printing 8ish hour prints and somewhere around the 4th hour, these are phone stands, which are the height of about half the z axis limit.
  • The material I am using is Hatchbox PLA, reliable filament I have used for years on my Prusa I3 MK3S.
  • The magnets are all present and accounted for. 

I am certain the nozzle moves past something it just prints, and catches on it, causing the entire plate to shift. Regarding bed adhesion, these are parts that have a lot of plate surface area, so bed adhesion  with them is pretty high. I have had this happen 4 times in 4 months of near constant usage. This invariably causes "Spaghetti" which if not caught, typically causes the Y axis belt to pull out due to spaghetti rolling around the belt rollers. Twice it happened with a silicone "Sock" on it, which was apparently pushed off during the incidents. The 2 other times, there was no sock on at all. 

Slippage of the build plate does occur... It's not someone making something up. I've been printing lately with octoprint using timelapse, but it hasn't occurred with the timelapse on yet... 

 

Posted : 16/04/2021 7:43 pm
Ahand59
(@ahand59)
Active Member

I forgot to add this picture. This is what happens when the bed shifts...

Posted : 16/04/2021 8:07 pm
Charlie Essers
(@charlie-essers)
New Member

@ahand59

See my above just above yours. I think we had the same problem. I slowed the print down to 50% before the offending layer and it was successful. Hopefully that helps you.

c

Posted : 19/04/2021 5:02 pm
jbienz
(@jbienz)
Active Member

Hey @Ahand59, just wanted to say that I took at look at the photo you posted and from what I can see I'm not sure your first layer is too healthy. Check out a minute or two from this video at 12:35.

I wonder if your Live-Z (first layer Z adjust) is too low. I believe this would make your nozzle lower than expected for the whole print. Slowing down as Charlie said may help. Adding more of a "Z Hop" may help. But I do recommend verifying that your initial layer height isn't too low.

Posted : 05/05/2021 4:31 am
Tim
 Tim
(@tim-2)
Illustrious Member

Curl ... you're printing along and the layer goes down over infill but the ends of the path have nothing to attach to. Thermal effects cool the top differently that the bottom of the layer, and the plastic bends upward. Next pass the nozzle connects with the curl and bang: either a stall or the part breaks loose.

It is always wise to get more than one opinion...
Posted : 05/05/2021 8:17 am
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