I am trying to print a model of the inner ear. The model has numerous overhangs and they have generally printed well with the exception on a small area that also shows a small area that touches the build plate.
No exotic material. A blue/grey Bambu Lab PLA Basic.
This picture is with support painting turned on. There is that small point to the right of the base.
I have done the print without and with support and there is no fundamental improvement. I first took a crack a printing the models probably 6 months ago and they came out pretty decent with the exception of the region where the spot is when support painting is turned on.
I cancelled the print today rather than waste time on running to completion. The 6 month old prints have the same problem though.
This 3rd picture is with supports enabled but in auto. That is way worse than the ones I printed with supports off.
The problem is consistent in that one area. While my experience with supports is minimal, it seems almost if it is unable/unwilling to get the support built under the model so it is some conglomeration of bridging, coupled with poorly printed supports because the model is too close to the plate.
Would making a raft raise the model enough t0 allow good support structure?
Overhangs, especially flat ones are pain in FDM…
I use two main cheats to get a better result.
- Variable layer height.
The new layer needs something to bond to and the larger the layer height the less material there is to place the new layer on.
If you check the slicing preview for your model in 0.2mm and compare it to 0.08mm you will see how the free hanging part of the overhang is much smaller.
- More wall loops (if possible).
As before, more loops can provide not just more area to bond to but they also increase the layer time a bit - in return the filament has more time to cool down and get stiff.
Combined with a slower print speed this usually provide a significant improvement.
Cheating big time…
If all fails and I only have a few overhang areas that struggle I cut the model into pieces within the CAD program.
E.g.: I would cut off the bottom to include a bit that is again printing fine.
I export both parts as STL and import them as one model with multiple parts.
Like this they are placed where they should be placed and I can use a very thing layer height and other tweaks on the problem area while the rest of the model is printed as usual.
If you do models like these a lot it might be worth to check on dissolvable filament and to then use solid interference layers with no gaps to the model.
