Print either fails or has low quality only on "Gap Fill" sections
After a long period of testing and diagnosing, I've determined that my printer appears to be performing terribly when printing what Prusaslicer calls "Gap Fill" (white colored in preview). For example, when printing the following object on Thingiverse:
www.thingiverse.com/thing:3029750
The print either has terrible quality on gap fill areas or has low quality that results in print failure. Note the gap fill areas indicated in white in PS:
When these areas are printed, no matter where in the model, they have terrible finishes, usually with warts/zits sticking up or out. A clear example of these are can be found on the top rings of the model in this print:
The rest of the print is essentially flawless. But again lower on the model where there are "gap fills" the finish is terrible:
I was able to print a single instance, though I heard the nozzle scraping on the warts on the top area. However, when printing multiple instances the print always fails around the top ring -- I suspect the top inner ring based on this print (which resulted in a clogged nozzle):
This is after lowering the "gap fill" speed to 20mm/s, which had no appreciable effect on the quality of the gap fill areas. (see coils in middle, edges of cylinder on "legs", and side edges of "feet" above) I believe that the "gap fill" warts stick up and the nozzle catches on them and strips the top layers off of some of my prints as it has done in other files. Setting gap fill speed to 0 disables it, but the gap fill is actually pretty important for the actual print to look like the STL. All other aspects of the print are good. What can I do to fix this?
Settings:
- Prusa MK3S Stock
- Hatchbox PLA
- 1st Layer: 205'
- 2nd Layer: 190'
- Layer Height: .2mm
- Extrusion Width: .45mm (standard)
RE: Print either fails or has low quality only on "Gap Fill" sections
My retraction distance is 1mm and retraction speed is 45mm/s.
RE: Print either fails or has low quality only on "Gap Fill" sections
Have you calibrated your extrusion multiplier for that specific filament? If you've got filament oozing out of tight spaces or bulging at the top, that's an indicator that you want to tweak this setting. There's a Prusa howto article that gives a good summary.
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RE: Print either fails or has low quality only on "Gap Fill" sections
The warts are normal and expected wipes that happen when the printer moves from one spot to another. Parts with several discrete peaks will have these. This stringing is worse with humidity and some filaments are just poor performers. Adjusting print temps to deal with filament differences - change wipe, retract and z-lift can help change the behavior somewhat.
Printing multiple parts at once, while convenient, takes longer than printing each sequentially. I admit, I'm like you and I want to press go once and pick the parts up tomorrow. But the risk is one minor failure ruins the entire plate.
190 is pretty cold for any PLA (in my experience), cold PLA may explain the gooey strings and under extrusion. Try printing the parts at a nominal 210 setting.
Nozzle clogs come in all sorts of shapes and sizes. At the next clog, when you unload the filament, take a good clear / sharp / in-focus photo of the melt end and post it up.
RE: Print either fails or has low quality only on "Gap Fill" sections
Thanks for all the feedback. After trying adjusting the temperature, extrusion multiplier, retraction length and speed, there did not seem to be any significant difference in the quality of the gap fill warts. On the other hand -- the Prusa default profiles tended to produce superior prints to any of my attempts to tweak (with the exception of lowering the temperature to 190 which is recommended by Hatchbox for their filament). I'm a tinkerer but it seems that Prusa has done a lot of legwork to make the machine print as good as possible out of the box.