Help with warping on lithophanes  

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Jon
 Jon
(@jon-5)
Active Member

Hi everybody - built my mk3s from a kit back in September and have been very happy with the quality of most prints, but I have an issue I can't seem to solve and would appreciate any suggestions.

I've been printing lithophanes for some holiday presents, and i've been getting a lot of warping at the ends touching the bed (upload won't complete for the image, hopefully this link works: https://www.amazon.com/photos/shared/HjS5MHVLTh6p_khUnvBIMQ.WxakFz7k8yxDC4MNqDblkx - you can see the material pulling at the brim circled).  Sometimes it's one corner, sometimes it's another, and sometimes it's both.  Tried printing in different orientations (along X axis, along Y axis ... heck, even tried one diagonal) and doesn't seem to match up to any specific spot on the bed either.  For the side I print PLA on, I clean the bed with 91% isopropyl alcohol and a lint free cloth.  For the PETG side I use windex and a different lint free cloth or sometimes a paper towel.

I have the powder coated sheet and was using Hatchbox white PLA for a few, and decided to try out their PETG since it sticks to the bed much more strongly it seems (and it really does).  All save one sliced in Prusaslicer (one in simplify3d), with either stock settings or also tried the "pretty lithophane for mk3" from github, both in PLA and PETG versions all with varying levels of success.  The lithophane image itself looks great, just the frame at the bottom is never straight due to the warping.

I've tried brims of various widths, same with rafts, and rafts and brims together and nothing eliminates it completely.  I've also tried increasing the number of walls and using a much lower infill (so the litho prints the same but the base is mostly 15/20% infill so it's not as dense) but that didn't help either.  I'd be happy to try any suggestions you fine folks may have as i've run out of ideas.

PS: as a side note, the one I tried in simplify3d had the least amount of warping, but it had a thicker brim (3 or 4 layers of brim I believe) - couldn't find an option in Prusaslicer to increase brim thickness, only width.  Is that an option that i'm missing somewhere?  If not, where is the proper place to suggest it for future updates?

This topic was modified 1 year ago by Jon
Posted : 09/12/2019 3:55 am
rmm200
(@rmm200)
Noble Member

For both your sheets, start with a good detergent and water scrub. Dry with clean paper towel - and never touch the print surface. No IPA for first print.

Nothing particularly hard about printing lithophanes - not enough mass to have bad warping. But I do blame adhesion. I use brims also.

Posted : 09/12/2019 7:40 pm
Jon
 Jon
(@jon-5)
Active Member

Tried a water/dish soap before the previous one, no change. Always printed with a brim but the warping pulls up at the brim. Tried increasing/decreasing bed temps as well. I agree that it's a bed adhesion issue but not sure what else to try. Dialed in live z with calipers to get it as close as I can without scarring and I've printed large flat parts before with no warping issues (raspberry pi mount, boxes, etc) but only the lithophanes seem to be warping.

Posted : 09/12/2019 7:58 pm
Steve
(@steve-3)
Estimable Member

Another post mentions adding "mouse ears" to the corners of your design.  They are simple circles that overlap the corners of the design in the slicer.  25mm diameter by 0.2mm tall should create a solid first layer in the corner.  They should be easy to break off after the print is finished.

If you add them as separate objects in PrusaSlicer, you will end up with the perimeter of the circle showing on the bottom of your print.  It will look better if you can bring the STL into a CAD program and merge everything into a single object.  I can't seem to find a setting in the slicer to treat overlapping objects as a single entity.

btw: I can't see your picture, but your description was good enough to understand the issue.

Steve

Posted : 09/12/2019 8:08 pm
rmm200
(@rmm200)
Noble Member

Let me add an actual product recommendation. I have had excellent results with 3D Solutech Real White. And it is inexpensive...

Posted : 09/12/2019 10:26 pm
Jon
 Jon
(@jon-5)
Active Member

@robert-rmm200

I've used their translucent PLA before in a few projects, i'll give them a try when I need to re-order more white PLA.  Had great luck with Hatchbox so far on everything else.  Will give some mouse ears/supports a try and go from there.

 

Thanks for the advice, everyone!

Posted : 10/12/2019 12:33 am
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