I‘m new here but not so new to 3D printing. But now I’m stumbling across a problem that I can’t solve. I‘m using a P1S with 0.4mm nozzle and want to print a upright hole in a 2,5mm wall. The hole isn‘t the Problem but the Layer at the end of the hole. It produces a Kind of offset to the Layer before
Initially I printed with a calibrated Polyterra muted PLA but it also occurs with other filaments. Speed and flow seems to be uniform and identical to the other layers. Tried a little Bit with speed and the inner/outer option but no success.
Any clues on why that happens? Thinking of more or less time to cool down than the previous layers, but I don‘t have a clue how to adress this.
I do not have an answer or a solution but an observation based on my model prints doing the same thing.
I do not have a printed model in hand but have seen my prints that have an opening, such as the hole in your model, and it will do that same thing downstream of the hole. When the nozzle gets to a place where there is a bridge with no filament flow, when the flow restarts after the bridge you get that offset.
If you had say 4 holes/bridges at different levels you will see that offset downstream of each bridge.
If you have a hole/bridge on 4 sides of a box you will see 4 of those offset looking surface defects.
It would help to see a screengrab of the model as it sat on the build plate in the preview mode. More importantly, I’d like to understand what that layer looked like as a cross section of the slice.
Either way, I think you are on the correct path of suspecting temperature to be a culprit. I might suggest first trying to change the wall order from the default of inner/outer to outer/inner. This will force the wall to set up first.
The other option might be to also enable Arachne as opposed to the default of “classic”. This will force the head movement to get into the nooks and crannies. That doesn’t look like the issue here but it’s worth a try.
Also, don’t forget to check the diagnostics when it comes to fan speed and temperature to see if there is a correlation between that and where you are seeing artifacts.
I tried that without any improvement unfortunately.
In the preview everything (flow, speed, temperature, fan speed, …) looks homogeneous. The only thing that stands out is Layer Time. But based on the preview, I would expect to see more lines like this than just at the end of the hole.
It’s a well understood phenomena that when filament density changes in a geometry, that’s where we see changes in both flow and shrinkage that the slicer does not readily reveal.
Here’s an example using a simple arch where flow rate option is selected in the preview.
Now in this example, manual filament tuning fixed the problem but calibration alone is only one tool.
Unfortunately, this is where the science starts to fade and the art of 3D printing takes over. What do I mean by that? Trial and error.
Depending on how badly you want to get this perfect, here’s checklist of things you can try as experiments. First thing I might suggest is to use the cut tool to cut this specific model down to a smaller piece that reproduces this problem. This will allow you to run quicker iterations and experiment on each variations.
Increase the wall width. If it was at 2 change it to 6 and see if it has an affect.
Manual filament calibration
Varying the placement of the tree supports using the support paint tool or changing the threshold angel may also work. You want to expand the placement of supports such that it covers more area and spread out the thermal gradient. The hope is that this may change the transition temp and spread it over a greater area but at the expense of having more support to cut off, it’s trade off.
Experiment with turning the fan on 100% or 0% at that layer and see which one has a better affect. You’ll have to manually do this with GCode using the M106 command, I am not a GCode expert but you should be able to find this elsewhere in this forum. Conversely, you can do this in the filament setting for the chamber fan.
Try varying the layers at that height using the variable layer height tool. Note that this will change the smoothness too so it may be undesirable.
Change the layer height for the entire model and lower it to a finer threshold down to 0.08mm. I realize this will increase print time but if you’re looking for perfect results, for an overnight print, you may want to try this and see the results in the morning.
Try using silent mode once print starts and reduce all nozzle movements to 50% at the expense of doubling print time. This is my least optimistic suggestion but again, if you’re printing cut sections of the model, you can experiment with speed and the silent mode is a one-click solution. Alternatively, you could go into the speed menu and just change outer or inner wall speeds.
