Struggling to print a perfectly flat (no warping) cube in PETG
 
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nirurin
(@nirurin)
Active Member
Struggling to print a perfectly flat (no warping) cube in PETG

Imgur link shows the model. It's pretty big (20cm x 20cm), and the idea is to have it printed twice, and then glued bottom-to-bottom to make a cube. However every time I print it (I've been changing settings, and adding more of those 'tags' to it to increase brim area) the corners are always warped up slightly, meaning two of them don't meet flush.

I've printed a similar sized thing that was a circle/hemisphere, and that worked fine. I know 'corners' are more prone to warping, but I thought this would have been enough to prevent it. Any tips?

https://imgur.com/a/bSikXAe

Posted : 06/11/2020 6:42 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: Struggling to print a perfectly flat (no warping) cube in PETG

One suggestion I've had elsewhere is to try using a raft instead. Is this a likely solution?

Posted : 06/11/2020 7:35 pm
Neophyl
(@neophyl)
Famed Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

Not in my experience no. What surface are you printing on btw ? Smooth pei or textured pei. Large boxes in petg are a pain in the rear. 

Posted : 06/11/2020 7:46 pm
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(@)
Illustrious Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

The key is to keep the plastic layers all at the same temperature so there is no difference in thermal expansion. Enclosures help, but only so much. The rest is understanding the cooling properties of the plastic, and controlling the print speed and airflow around the part to ensure it anneals as you print. That said, every part is different, and there is no sure-fire formula that works every time. If there were such a thing, Prusa would include it as a standard profile.

Posted : 06/11/2020 8:46 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: Struggling to print a perfectly flat (no warping) cube in PETG
Posted by: @neophyl

Not in my experience no. What surface are you printing on btw ? Smooth pei or textured pei. Large boxes in petg are a pain in the rear. 

Smooth PEI magnetic from the Mk3s. 

Posted : 06/11/2020 9:33 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: Struggling to print a perfectly flat (no warping) cube in PETG
Posted by: @tim-m30

The key is to keep the plastic layers all at the same temperature so there is no difference in thermal expansion. Enclosures help, but only so much. The rest is understanding the cooling properties of the plastic, and controlling the print speed and airflow around the part to ensure it anneals as you print. That said, every part is different, and there is no sure-fire formula that works every time. If there were such a thing, Prusa would include it as a standard profile.

I use a slow/medium print speed (around 35mm/s) and I have no cooling fan running and no fans in the room. Would an enclosure be likely to help? (I don't own one)

Posted : 06/11/2020 9:34 pm
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

Have you tried flipping it over and printing it the other way ?

 

The Filament Whisperer...
Posted : 06/11/2020 11:38 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: Struggling to print a perfectly flat (no warping) cube in PETG

@dan-p12

No. The top edges are bevelled, so without cooling they'll be rough printed that way. They'll also warp, and the top needs to be flat as well. So if it won't print one way, it won't (I would think) print the other way. 

Posted : 07/11/2020 12:45 am
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

I would try it, I don't have the model but it looks to me (from your images) like you could do it, also its ok to use some cooling on PETG, depending on the model features I use between 30 & 50% and you have the option in Prusa slicer to only apply it on the layers needed,. your trying to print something that's known to be difficult to print, so IMHO its time to step it up a bit and try something new, if you haven't used cooling with PETG before It works and is a valid option. also you can adjust the layer heights on the chamfered areas to help with over hang and roughness.

It's Just a suggestion

The Filament Whisperer...
Posted : 07/11/2020 1:13 am
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: Struggling to print a perfectly flat (no warping) cube in PETG

@dan-p12

If my current attempts fails, I may well give that a try next

Posted : 07/11/2020 1:41 am
Peter M
(@peter-m)
Noble Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

Use big brim attach to model, like 6 or 8 lines.

Use glue stick for extra sticking, if needed.

Clean bed with dish soap, for every print.

Let bed heat up for a longer time, before you print.

First layer needs to be 100% hitting the bed, if it is to high it will release sooner.

First layer print hotter,

first layer slower speed,

it is also possible to print a extra wall around the model to keep it warm and no wind can hit the model, see slicer settings.

Normally you need to spray windows cleaner so it does not stick to much, do only a little .

Posted : 07/11/2020 9:31 am
Neophyl
(@neophyl)
Famed Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

@peter-m26

That in general is good advice but it doesn’t always work.

I printed a large box in petg for a friend who was building   some control electronics for his home heating. The box was in 2 parts similar to the original posters, although I printed mine flat surface to the bed for maximum adhesion, it didn’t have the rounded edges as it was designed for 3D printing from the start. 
My mk3 is in an enclosure and I was printing on the smooth sheet. I had approximately 10mm warping up at the corners. Bed adhesion was perfect, it was stuck to the steel sheet in the corners, the petg had actually lifted the bed away from the magnets.  Now maybe the petg I was using was more prone to warping but the temp In the enclosure was a steady 32 degrees c, no drafts etc. First temp was with the bed at 85, second was at 90.  Both warped badly. I ended up just reprinting it in pla and it came out perfect first time. 

Posted : 07/11/2020 9:43 am
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(@)
Illustrious Member
RE: Struggling to print a perfectly flat (no warping) cube in PETG

Sorry for the pause- but yes, an enclosure helps higher print temps as it allows you to keep the bulk of the part much warmer. It is the goto solution and why the Lack Enclosure is so popular.  Keep in mind though, you'll need to tweak the printer to run warmer, like add a cooling fan to the extruder motor, move the power supply outside the box, etc.

 

One experiment to try is to print a full height skirt.  If that provides a better result, the enclosure may be justified.

This post was modified 1 year ago 2 times by --
Posted : 08/11/2020 9:43 am
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