When I try to print with ABS, it seems to stop extruding mid print, then resume. It leaves holes and gaps in the layers where the plastic extrusion slows down and strings out, then starts coming out again. I have tried both ReplicatorG and Makerbot Desktop, slower print speeds, faster feed rates, and more. PLA prints perfectly and doesn’t exhibit these issues. Does anyone have any ideas as to what could be happening?
I am new to 3D printing, so I am probably missing something simple, but I haven’t been able to find anyone else with this issue.
I just printed a test cube and you can see where it stopped extruding when it was building the raft a couple of times. First on the bottom, then again as it was about to start printing the cube. The cube itself printed well aside from some slump from poor support where the raft hadn’t been fully printed.
That can happen for many reasons but usually it’s because of very low or high temp, or extruder is clogged, or filament is not being fed freely to the nozzle, maybe the spool is too heavy (that feeder usually chews the filament before entering the nozzle).
I guess probably because of wrong temp/filament diameter/Z offset the ABS is not going through the nozzle easily and the last two are happening to your prints, when the head is moving in one direction (like X) getting far from spool holder, it actually pulls the filament (if your feeder is on the head) and causes the spool to rotate and then when it goes back in opposite direction, the feeder easily feeds filament to the extruder for a while because there is more pressure on the filament. After a few line surface fill it under extrudes (chews the filament again and cannot pull) and then the same thing happens again (depends on your object position on the bed and filling direction). If it only happens in the first few layers then you are printing very close to the bed for the selected layer height. Specially when you use raft give the nozzle a little bit more Z offset (not too much) because filament is coming out with maximum speed for the first layer of raft.
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Thanks for the reply! I’m using Shaxon ABS with a print temperature of 200-265c. I have tried prints at 220, 230 and 240 with no change. The problem occurs even when there is slack in the filament and is seemingly random. The stepper motor keeps turning but the filament just stops moving. Could the extruder be clogged and still allow filament to flow intermittently, and still work fine with PLA? I will see if changing the offset helps at all.
I also see “upgraded” tensioner mechanisms for the extruder using a spring. Mine is set and cannot be adjusted. Apparently this can cause issues with soft filaments like Ninjaflex but I haven’t tried those yet. Could that be causing my issue with ABS and not PLA?
Maybe, but keep that in mind that glass temperature of ABS is around 105 but PLA is 65. That means if they are being fed to the nozzle, PLA melts twice faster so for ABS you need to print slower and let it reach completely to the nozzle temperature. Try it without fans for a few first layers, see what happens.
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