First layer help (raised bumps)
anyone know what setting to change in order to smooth those raised bumps? I didn't think it was overextrusion because the lines actually look fine where they meet the perimeter. The bumps happen closer to the middle of each line (on both sides).
I'm currently printing lipstick red prusament at the recommended temperatures (215 nozzle; 50 bed) using the default .4mm HF nozzle and the .2mm STRUCTURAL input shaper profile. I've turned the extrusion multiplier down to 95% for this print just to double rule out overextrusion.
Best Answer by Marcel:
So I went and looked a little bit more into this and it seems what is also greatly factoring into Problems like this is "Small Area/Distance Overextrusion". The following Video will explain everything with examples:
In Short: To much filament on turning points and small distances, leading to to much filament, which then sticks up. To solve this one needs a post processing script, which alternates the G-Codes Flow rate according to a table. The latter can be altered to fit your needs.
There seems to be a feature request on Prusa GitHub, but I could not see it implemented, would be great though. Go to GitHub and push to speedup the process 🙂
RE:
Hey,
It always helps if the filament is tried befor use, even the freshly bought ones.
Having said this, as you can see it is always on the area where there is more heat deposition / printer makes a turn. You could try to increase the fan speed for the first layer or reduce printer speed and see if that helps.
Print 5x5 cm layers with 0.2 mm thickness to test.
RE: First layer help (raised bumps)
So I went and looked a little bit more into this and it seems what is also greatly factoring into Problems like this is "Small Area/Distance Overextrusion". The following Video will explain everything with examples:
In Short: To much filament on turning points and small distances, leading to to much filament, which then sticks up. To solve this one needs a post processing script, which alternates the G-Codes Flow rate according to a table. The latter can be altered to fit your needs.
There seems to be a feature request on Prusa GitHub, but I could not see it implemented, would be great though. Go to GitHub and push to speedup the process 🙂
RE: First layer help (raised bumps)
Hey Marcel,
My apologies for the late reply. With the holidays incoming, it took me a while to free up the time to test your recommendations. I really wanted to thank you for going above and beyond with your advice and the linked video. Truthfully, it was the only method that actually eliminated the raised bumps on the first layer, although I came to discover that the bumps would be smoothed out in subsequent layers even without the postprocessing code if I fixed the following issues:
1. I initially calibrated the printer on the floor where I built it and then lifted it onto a card table to make it more accessible. This card table was somewhat wobbly, though, and I think the wobbling of the printer during acceleration/deceleration contributed significantly to the inconsistent extrusion during short paths. After moving the printer to the top of a very sturdy fire safe and recalibrating, the bumpiness was significantly reduced.
2. My first layer adhesion was poor and I think that was also a major contributor to the print failures that I blamed on the bumps. Postprocessing and using a stable table resolved the bumpiness of the first layer, but I only stopped having print failures after lowering the print speed (as you also mentioned) of the first layer from 45mm/s to 15mm/s. Because it's only one layer, making it slow doesn't add much print time, relatively speaking. I also discovered the Prusaslicer setting to adjust the Z offset and set that to -0.02 to get a little better squish.
3. Finally, I double checked my belt tensions and discovered that, since my initial tensioning that I performed immediately after building the printer, both belts had relaxed slightly and required 1/8 of a turn of the tensioning bolts to bring them back to ~94Hz. Not sure if this changed the print quality at all considering that I didn't do a before/after print for comparison, but I thought that I'd mention it.
I am getting very good prints now (picture incoming in the next day or two if I remember). If anyone experiences the same issue as me in the future, I can recommend the method described by Marcel for getting smoother layers, but would also caution users that first layer bumps may not actually be the true culprit behind print failures, and that checking the stability of their printing surface, their first layer speed, the Z offset, and the belt tension may also be necessary.