Air bubbles in filament?

Just got a KITTAZ and am all together and have been printing happily away for almost a week now. I’ve noticed that occasionally with the silver HIPS filament there will be a “pop” sound like an air bubble popping in the filament and I will notice some imperfections in the print that look consistent with an air bubble popping while the filament is hot. Is this an issue with the filament, my Slic3r settings, extruder calibration, or am I just being entirely too picky? Any input is appreciated as this is my first 3D printer.

Edit Could this be my extruder missing steps? Would I just need to slow down my extrusions speed to fix this? I’m using the default profile from Lulzbot.

This is moisture in the HIPS. You can either live with it or attempt to dry it out. Drying it out involves putting the spool in a warm oven for a few hours. This works as long as you don’t get the spool too hot and melt the filament.

HIPS and ABS need to be stored in a dry place or else they will absorb the moisture from the air. I put mine in a sealed container with a ton of desiccant packs in it too keeps things in good shape.


Any pictures? I’ve never seen air bubbles in a print.

My filament crackles and amokes (both a sign of absorbed moisture) sometimes when heating up… But I’ve never seen bubbles in prints. Or bursted bubble patterns in prints.

I’m guessing it could be artifacts of print speed or extrusion temp.

Good to know that this is a known factor with HIPS. Turns out my printer wasn’t near as calibrated as I thought it was and I’ve been working on that all weekend with improving results and eliminating speed and temp artifacts. I’m in northern California, so moisture is definitely, going to be an issue. Any suggestions as to what temperature to run the oven at? I would guess around 170ish?

@kcchen_00 - If the filament is really moist when it pops it creates gaps in the print, not actual bubbles.

@Sawakai - I would do a search of the forums for drying out filament, I don’t want to lead you astray. But I do recall it was around 170 - 200F for 3 - 4 hours.