Heatbed not centered  

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aurru
(@aurru)
Active Member

Hello everyone,

I received the printer last week, assembled and started printing without many issues, but one of the things that surprised me is that the heatbed does not seem to be centered (the center in prusaslicer does not correspond with the center in the printer) as seen below.

I don't have any need for now, but if I ever decide to print something relatively large, I could see it becoming an issue.

Has anyone encountered this ? Any suggestions?

Posted : 17/05/2020 2:50 am
JoanTabb
(@joantabb)
Moderator

the easiest thing to do, is re scale the model in Prusa slicer so that it is Full size, 250mm x 210 mm, and try re printing it. if the oval shows two straight sections  then it would suggest that the print area is restricted. somehow. 
If the print succeeds and remains out of line with the markings on the build sheet, then please accept that there are manufacturing tollerances involved and that the markings are only a guide...

My latest build plate has no markings on it.  at all, and I have a selection of build plates with different graphics on them, for instance the textured sheet simply has the perimeter and text plus 4 tiny crosses on the print area 

if there is a restriction of print area, then  please be aware that , the X and Y axis do not have endstop switches,  they work by sensing the rise in motor current when the X or Y axis collide with the end of travel. 

It is possible that the printer is erroneously sensing the increase in current earlier than expected...  

lots of things could contrive to cause an issue like this, including, belt tension,  Y axis ubolt tightness, x axis backplate tightness and friction within the bearings, Cable bundle flexing resistance, cables catching o n something, ...   and the build plate could, in fact be off centre

I would start by lubricating the smooth rods, if the linear bearings were not lubricated during the build process (Yes I do know what the assembly manual says! )  you are seeing an issue that displeases you, so consider this as your first maintenance period.

https://help.prusa3d.com/en/article/i3-printers-regular-maintenance_2072#rods-and-bearings  

the link above discusses application of lubrication after the build (I lubed mine during the build... and have not had problems like this ) 

the next easiest things to change are the Ubolt tension and the X axis back panel tension, try loosening both a tiny bit... 

best wishes, and good luck,

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 17/05/2020 11:58 am
bobc
 bobc
(@bobc)
Reputable Member
Posted by: @aurru

I don't have any need for now, but if I ever decide to print something relatively large, I could see it becoming an issue.

Has anyone encountered this ? Any suggestions?

The markings on the steel sheet are not accurate and should not be relied upon. It's a trivial test to do, try printing something with nominal max dimensions of 180x 180 like the attached STL. The printer axes can move a bit more than 180mm, so you should have no problem printing the max size.

Probably the bigger issue is achieving uniform adhesion across the bed, it might require careful adjustment of the Z offset.

Posted : 17/05/2020 1:35 pm
aurru
(@aurru)
Active Member

So I finally had time to post the solution I came up with for this.

In general the off center of the heatbed was not affecting the maximum size of the things I could print, I successfully printed all the area (180x180), although it was using some of the margins of the building plate. I lubricated all the bearings just in case, but it made no difference, I think mine were properly lubricated from factory (still not a bad thing to do).

Eventually I solved it just by entering in the Prusaslicer and changing the origin values in the Bed Shape settings (Printer settings tab). After a couple of quick prints for calibration it is now centered and working like a charm. It also opens the possibility to fully utilize the margins of the build plate in the future 🙂

Note: If you change the default values from the bed shape you lose the Specific Prusa mini 3d model in the plater of Prusaslicer. However you can reload them in the Texture and Model sections in the same window where you change the Bed Shape. They are located in the installation folder.

Posted : 01/06/2020 1:17 am
3Dprintedgr
(@3dprintedgr)
Estimable Member

My bed is the same but it also suffers from a xz error which means that except from the off center the x line is not parrallel to the grid line.

Original Prusa Mini + Smooth PEI
Prusa Slicer 2.2.0...
Posted : 03/06/2020 5:54 am
Festello
(@festello)
New Member

@aurru

I changed the origin values and had no difference in alignment, still off centered. Not sure what I'm doing wrong. 

 

Posted : 04/10/2020 7:20 pm
AB
 AB
(@ab-3)
New Member

@aurru

Hello everyone -

Same issue on my mini as several here.  I can also utilize the full area, just not rely on the markings on the sheet.  The more troubling, to me anyway, is the inaccurate representation in the slicer. For some things, I pack them pretty tight and have used the lines for guidance.  As mentioned though, it's not a hard work around. I also have found that setting the origin values did not affect anything, at least in 2.3.0.

 

Thanks.

Posted : 15/02/2021 5:11 pm
AB
 AB
(@ab-3)
New Member

Follow-up to earlier post in case someone else searches on this topic.

Setting the origin did indeed work.  For my mini (Jan2021) under printer settings/General/Bed Shape - Origin X value: +2.9, Origin Y value: +1.9.

In response  to @aurru, to have an effect on the print, you must remember to re-center the object after you set these values accordingly. That did the trick for me.

Posted : 16/02/2021 6:30 pm
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