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I've got a Prusa i3 MK3. I have printed with PLA, PETG and tried HIPS. Haven't had any clogs with PLA and PETG, but with HIPS I've got a weird problem.

My first three test prints in HIPS went fine, but then I got a very bad clog (required total disassembly of the extruder) twice. And every time, it was at the same moment during a print. The object I was printing was a hollow cylinder. The walls were about 5 mm thick, getting thinner near the top edge. At the moment the walls started getting thinner, the problems started.

I've read that HIPS can clog if the filament moves too slow through the hotend. At the moment the clog occurred, the printer was printing a very narrow part, and the extruder had to move around a lot. Is it possible that, at that moment, the filament moves too slow and the problems starts? I have also printed two copies of the object in a single run, and then the problem didn't occur.

I hope my explanation makes sense, but here's what it comes down to: Does HIPS clog easily when the filament moves too slow, and if it does, what can I do to solve this?

1 Answer 1

This has been sitting for a long time without an answer, so let me answer with an experience I've had with PETG rather than HIPS.

PETG seems to be a relatively soft plastic. It isn't soft like TPU, but it is softer than PLA or ABS. The HIPS filament (which I have but haven't used) appears to also be softer, so it is possible that my PETG problem could relate to your HIPS problem.

I was printing and re-printing an object with PETG that had worked fine with PLA. Three times in a row, I got a filament jam in about the same place.

The problem was that the filament was retracting, returning, retracting, and returning many times within a very small amount of extruded plastic. My extruder was set for high pressure between the drive roller and the idler. When the filament went back and forth through the extruder, it flattened enough that it would jam from being too wide to fit through the next stage (in my case, a Bowden tube).

When I reduced the compression of the filament in the extruder, the problem stopped. I also reduced the retraction distance, and increased the minimum travel before the slicer would do a retract. Both were intended to reduce the number of times any single bit of filament would pass through the rollers.