The indentation is uniformly consistent around the entire shelf.
The rest of the print looks very good, fairly smooth sides, super smooth top. I printed this with 3 walls, 5 bottom, 5 top shell layers, 25% cross hatch infill, .2 layer height .4mm nozzle, Eryone PLA.
I printed a piece with a similar transition from a solid base to a ribbed structure and noticed the same issue.
Do you have any idea what might cause this issue and how to avoid it?
It looks like the indentation is where the side wall joins the bottom.
If you designed this, thatās where I would start.
It is also possible that if you use more walls or increase the infill, it might work.
Look at this post, it offers some options for fixing that. I think a fillet on the inside corners of the wall might also work if it is large enough, but I havenāt tried it yet.
You also have warping on the bottom, so you can try glue or a Brim (with 0 gap if needed).
I encountered similar issues with PETG. You can also tackle the problem from the material and process side by looking at cooling. Three main points:
Build space temperature: I never managed to encounter nozzle clogs with regular PLA. So I close it up and keep the build space nice and cozy for a more uniform cooling.
Cooling parameters: In PETG, I did have some success by replacing part cooling with aux cooling. However, I never had the feeling that I understood what was truly happening. But my geometry was much more complex.
Slower input of thermal energy: This is unpopular but actually quite effective. Reducing the amount of thermal energy put on your model gives a more uniform cooling. Since it is a volumetric effect, halving for example the layer height will reduce the energy input by a factor of 8. So you may want to print the lowest part with a lower layer height.
When the filament is extruded, itās hot. As it cools, it shrinks. If the time between passes of the outside wall is short enough, the shrinkage is unnoticeable. But if the layer time changes significantly, the already-printed plastic will contract more before the next layer gets printed. So when the next layer gets printed, the outside wall will have a āstepā because the printhead is aligned with where the wall should be and the print has shrunk, the actual wall position is no longer aligned with where it is supposed to be.
You can try reduced extrusion temp, increased build plate temp, and if youāre printing with an enclosed printer, waiting until the chamber temp gets up to 45ĀŗC or so before you start the print. The idea is to minimize how much the plastic will cool and shrink between the shorter and longer layer times associated with that region of the model. Lowering how hot the plastic is when itās extruded, while maximizing how hot the āambientā environment is, are your only āknobsā if youāre not able to modify the model or its orientation to reduce the delta in layer times.
I have created and printed dozens of models with similar variations in layer time, including many containers for the IKEA Skadis pegboard, like these:
None of my previous prints exhibited this issue, so I am trying to identify the decisive factor in this case. I suspect it may be related to the bottom layerās thickness. The container has a solid bottom layer approximately 1.6 to 2 mm thick, while the problematic shelf has a 5 mm thick, non-solid bottom layer. The subtle curling occurs regardless of the presence of support ribs, indicating that the difference in layer time is not the cause.
I experimented with cooling settings without success, but my options are limited (P1P), and I prefer not to rely solely on printer settings for a solution. When I tested a shelf with a 2 mm thick, solid bottomāsimilar to the containerāthere were no issues. This leads me to believe the problem arises because the heat from the heatbed can transfer effectively through a fully solid and not-too-thick bottom layer, preventing significant shrinkage.
In summary, the most promising solution seems to be a redesign to either cover or prevent curling, such as a slimmer bottom, recessed support ribs, or another print orientation (though this is not an option for this model).
Will making the bottom thinner reduces the strength of the shelf though? Is there any harm to just leave the indentation be and think of it as a design pattern even if not by design?
This shelf is designed for heavy loads, as indicated by the support ribs. A thin top surface does not fit in this case.
While I can tolerate the indentation, my passion lies in continuously learning and enhancing my 3D modeling and printing abilities. Thatās why Iām eager to refine the outcome.
No question about keep improving the design. I am just wondering if improving cosmetics comes at the cost of reducing functionality, in this case a slimmer bottom that may affect the weight the shelf can hold, then is it the right direction to go.
Or maybe I confused about the ābottomā and the ātopā? In that case, never mind.
Itās not a real solution, but more of a workaround: the issue becomes less noticeableāor even disappearsāwith a thinner bottom layer. Iāve adapted the design to minimize the problem.
