Wavy, lumpy print in ASA: possible causes?
Hi there. I made a first print in ASA on my Prusa MK4. This is Prusament ASA. It was printed with adaptive cubic infill @25%, 0.2mm layer height, input shaper SPEED profile. This was printed in an Prusa enclosure with all default Prusament settings, using Prusa slicer. It did not come out nearly as well as my PLA prints. I am curious if y'all can suggest why.
My first guess is that I should have dried the ASA. It has been sitting for about two weeks in a box at 35% RH. I know that it is supposed to be dried, but I was impatient lol. If the artifacts here seem a likely result of wet filament, then just let me know and I'll go home with my tail between my legs.
HOWEVER, I did not see any stringing or other artifacts that I have seen associated with wet ASA, so I'm wondering if there is another issue here. I thought I would come to the forums to ask if anyone has seen this before and what the likely cause is. I am wondering if maybe I'm not supposed to use the SPEED profile with ASA?
The other reason I wonder if maybe this is the problem is that the lumps seem most severe at the end of long, straight walls. It makes me wonder of the printer has had time to build up speed and then something weird happens in the corners? But I don't understand why this would only happen with ASA and not PLA . . .
Problem 1: banding on long straight extrudes.
Problem 2: strange, uneven geometry at corners.
I don't have a picture of it right now, but I also have what I would describe as "holes" on the top of some of the parts. They aren't through holes, just places where the extrusions were not even and there are gaps in the final layer.
Please let me know if there is any other info I can provide that might assist in diagnosing the problem.
RE: Wavy, lumpy print in ASA: possible causes?
I may have spoken too soon . . . I notice these sorts of issues with my PLA prints too now after switching back to Prusament PLA. I wonder if something about the Hatchbox PLA that I had been using has just been papering over the issue? Particularly, it seems like the printer is moving a lot faster with the Prusament PLA than it was with the Hatchbox PLA! Or maybe something got out of whack during my last ten hour print?
Switching to 0.2mm STRUCTURAL strongly improves the performance, but there is still a noticeable bulge at certain corners where before there was none. My best guess right now is that I'm looking at a belt tension issue. I was never able to get the app working on my android phone so I kinda just eyeballed it. Printing out the physical belt tension tester right now and will give it a go in a tad.
RE: Wavy, lumpy print in ASA: possible causes?
Retensioning the belts: the app did not initially work on Android. However, the printed PETG tension tester showed the tension to be far below the minimum allowed. I raised the tension to the higher end of the allowed range, then tried the app again. The Prusa app this time would show the tension! And in fact it wanted me to raise the tension just a touch beyond where the printed tension meter said it should be. After buttoning the printer back up again and rerunning the test, I am seeing a vastly improved print quality and the lumps at the corners are gone.
Here is a picture of before and after belt tensioning. Notice the ridges at the corner of the cube on the right. Same gcode, same filament, only difference is the tensioning of the belts. Note that this is done at the STRUCTURAL profile, which shows the issues I was noticing to a significantly lesser degree than the SPEED profile I had selected before.
In short, I'm glad this happened because even though it wasted a night of printing I really learned something. Tension those belts properly. The Prusa belt tensioner guide can be a good way to get into the right ball park if your Android phone isn't working with the online tuner! 🙂