Hey folks. Need a little help.
Im printing a number of different style enclosures and I have the same problem on all. I have a weird ringing/over extrusion which always happens on the base of the last solid layer. 0.4mm nozzle and it doesnt matter which PLA or PETG filament I use.
I think the pictures explain the issue better than I can.
Thanks
Are you printing these one at a time or multiple on the build plate?
This is a common problem. Search the forum for “water line” or “hull line”. The bulge corresponds to the layer with a floor in the interior of the model. No real fix. Artifact of the printing process.
Thanks @Rocketsled. At least I know what this issue is called.
I generally print singularly, is it worth printing multiple?
I wondered if the bed temperature had something to do with it. Like the base layers (usually 3-5mm thick) are holding more heat, so when the next layers go down, which aren’t whole (like the base layers) it flattens the layer more causing the bulge?
Appreciate your reply thankyou.
It has to do with changes in layer time. Each layer starts to cool as soon as it’s printed. As the plastic cools, it contracts, the perimeter gets a little smaller. If the next layer comes along quick enough, there’s just a tiny bit of offset and it’s not noticeable. But if you go from printing an infill to printing a solid top surface, the layer time changes significantly. The previously printed layers shrink to a greater extent during this time. The next layer gets printed and it appears to bulge out but really it’s that the layers beneath that got smaller.
More models on the build plate will probably make it worse. But the cooling is to some extent asymptotic. With multiple models on the build plate, all the layer times increase significantly. That might make things better. Might be worth a shot.
Also, anything you do that reduces how fast/how much each layer cools off will help. Hotter build plate, hotter chamber temp, lower extrusion temp. Look at the layer time in the slicer. If you have fast layers followed by slow layers followed by fast layers again, messing with minimum layer time to reduce the delta (slowing down the fast layers) might also help.
Try changing the wall generator to ARACHNE.
Thanks @ElektroQuark - Ive tried that and unfortunately no difference.
@RocketSled Thanks again for your advice. I’ve slowed the entire print down but maybe not enough - I think your theory on print speed difference may play a part though. - See below my current speed settings but I may drop all down to more similar speeds and see if that helps?
Yeah. The closer the layer times are to each other, the smaller the problem should be. You aren’t able to really speed up the layers that are the ones that take longer, so the only option is to slow down the layers that take less time…
You could try and crank up the minimum layer time parameter, too.
Thanks @RocketSled
Dialing all speeds down didnt change the outcome. Ill play around with minimum layer time parameter. But I can cross out speed being the issue I assume?
Speed itself isn’t the issue. It’s the change in layer time that triggers the issue, shorter to longer… so you need to minimize the time delta between the layers just below the artifact, to the layers where the artifact is being printed.
This is a difficult problem to solve. Search the forum, you’ll see plenty of discussion…
One thing that can help a little is to enable print infill first in conjunction with Inner-Outer wall print sequence.
If the wall above the solid layer is thin then an internal filet in the part design can help with making the transition more gradual and with it less noticeable on the outer visible surface.
It’s one of those issues with FDM printing that is difficult to avoid so either need to accept that or make the part design in such a way that this “water line” gets hidden by a feature and/or minimized.
Maybe in the future the slicer will incorporate detection of such transition areas and calculate wall offsets in such areas to minimize/avoid this but that certainly is not something that is easy to do.
