ASA: nozzle hitting top layer
Hello, I am trying print some larger prints with ASA. It's much steeper learning curve than with PLA or PETG. I had issue with first layer adhesion to satin sheet but I think I mostly solved it by turning off fan and printing at 50 % speed for first layers (10 or so).
My model has 3 solid layers at the bottom that are perfect and on top of that 15 % gyroid infill. When printing top layers it starts rather well bridging infill without any issues. Second layer was also good but third one started to create these little waves and last layer was so bumpy it was being scratched by nozzle printing next layer.
Is it known issue with ASA? I suspect it has something to do with possible warping but I am not sure what's being warped. Bottom layers were still attached to the plate.
Printed inside Enclosure (~33 ° ambient), 260°/110°, 50 % speed, MK4 IS 0.2 mm structural, Prusament ASA
RE: ASA: nozzle hitting top layer
I guess I have a similar problem. I printed a lot of flex filament on the MK4 and the top layer most of the time gets messed up due to a filament jam in the nextruder.
I assume the slicer puts funny things into the code. Maybe the Z is not properly set for the last layer resulting in what we see in your and my result...
RE: ASA: nozzle hitting top layer
Those ripples on the red ASA print look like warping to me. ASA and large prints are a perfect combination for that. Not much warping is needed to start messing the print, just a few cents of mm. are enough. Every further layer increases the ripples and finally the nozzle ends up scratching the model. Are you sure that all the bottom layer, specially the periphery, remains perfectly attached to the bed until the print is done ?. Very small gaps aren’t easy to see while the part is being printed. Inspect carefully the model (successfully finished or not ). See if the bottom isn’t slightly warped, checking against a perfectly flat surface ( a glass sheet for instance)
To fix the issue I suggest : 1) higher temperature inside the enclosure (if possible). 2) Adding a wide brim to the model. 3) Although the satin plate is fine in general, for troublesome models the smooth plate has better adhesion. 4) Adhesive helps a lot as well and it’s almost compulsory with ASA and the smooth plate. Don’t use hat messy white glue stick. 3Dlac, hairspray or similar give a much better finish to the bottom of the print.
RE:
I agree, the result is slightly warped (~0.4 mm) after completion but I didn't notice any warping during the print. Could it warp during cooling the sheet at the end? I printed it with a skirt and it was attached without any visible warping.
However, the explanation is sound. The issue started to appear at the periphery. While infill was being printed, there was a lot of room where filament could go. When I got to solid top layer, it started to do funny stuff. I was able to salvage (second) print by reducing flow factor to 90 %. After scary two layers, it was able to stabilize a bit and complete the print on 95 % flow. I still got ugly top layer but it's only a cosmetic issue.
Somewhat interesting is that it was able to print borders for next couple of hours without any further issues.
As to your advice, do you think it's better to focus on adhesion to the sheet or to reduce warping tendencies? I am not sure what's the cause and I cannot immediately test your suggestions.
I agree, warping.
Also check the print-sheet is not being lifted away from the magnets - warping forces can be huge...
Cheerio,