The 3D printing process is cool, but it’s also really annoying at times. Specifically, when you want to get a part printed, and no matter how you orientate things, what adhesion aids you use or what slicer settings you tweak, it just won’t print right. [David Malawey] has been thinking a little about the problem of the edges of wide prints tending to curl upwards, and we believe they may be on to something.
Obviously, we’re talking about the lowest common denominator of 3D printing, FDM, here. Other 3D printing technologies have their gotchas. Anyway, when printing a wide object, edge curling or warping is a known annoyance. Many people will just try it and hope for the best. When a print’s extreme ends start peeling away from the heat bed, causing the print to collide with the head, they often get ripped off the bed and unceremoniously ejected onto the carpet. Our first thought will be, “Oh, bed adhesion again”, followed by checking the usual suspects: bed temperature, cleanliness and surface preparation. Next, we might add a brim or some sacrificial ‘bunny ears’ to keep those pesky edges nailed down. Sometimes this works, but sometimes not. It can be frustrating. [David] explains in the YouTube short how the contraction of each layer of materials is compounded by its length, and these stresses accumulate as the print layers build. A simple demonstration shows how a stack of stressed sections will want to curl at the ends and roll up inwards.
This mechanism would certainly go some way to explain the way these long prints behave and why our mitigation attempts are sometimes in vain. The long and short of it is to fix the issue at the design stage, to minimize those contraction forces, and reduce the likelihood of edge curling.
Does this sound familiar? We thought we remembered this, too, from years ago. Anyway, the demonstration was good and highlighted the issue well.
Thanks to [Keith] for the tip!
So whats the conclusion? What can we do to prevent this?
according to the video, part design.
But specifically how? “Design it differently” is by itself not very helpful. Are there any concrete suggestions in the video or does it just come up with a good hypothesis for why the prints warp, with anything else left as an exercise for the viewer?
Solution: Don’t do the thing that causes warping.
Honestly why did none of us think of that before?
In essence it comes to this: “use less material”. Prevent long continuous areas/stretches of 3d printed material.
If you use a plastic that (for instance) has a shrinkage of 1%, it will shrink 1mm over 100mm, but only 0.01 over a distance of 1mm, although both is the same 1%, the effect of a part wanting to be 0.01mm smaller has less impact then something that needs to shrink 1mm. And this works in all directions, but mostly only causes real problems in the X-Y because there all the plastic will cool down at the same rate but in the Z direction the difference in temperature and therefore effective shrinkage can almost be neglected as the layer benath is already cooled down when the next layer is added, therefore the layer below has already shrunk and therefore the shrinkages do not accumulate over the total distance (unless you have a very small but tall part that is not allowed to cool down before the next layer is added).
But this doesn’t mean you can’t do large prints, just allow for the shrinkage to happen (allow for the diversion of the shrinkage forces) or prevent the buildup of these forces by breaking up large areas into smaller areas by adding holes. Using honeycomb fill patterns instead of a solid fill certainly helps and it decreases you print times. I hope this answers your question.
PEI+PVP gang here.
I bought an empty marker with a 50mm wide felt “brush” attached to it from China, ordered a bunch of PVP glue sticks from China. I made thin slices of the glue, put it in a sauce pan with water until it was all liquid, then added it to a mason jar. I fill up the marker with that glue water when empty, and wipe my entire bed with it before printing. Made thousands of prints without warping, never bothered to clean the bed in between, just put a new layer on before printing. Haven’t had a warped print since I started with it.