Air bubbles in my print

[asesapie]

I have recently started getting really bad air bubbles in my prints. I am using a Lulzbot Taz4 with matter control and curaengine to slice. It is only printing the air bubbles in certain places in the print and I can't seem to figure out why it is doing it. See the pics below. Thanks for all suggestions and help in advance.

[asesapie]

Any ideas out there? I have tried adjusting temp on the extruder and slowing the print down without a change in the print.

[3dkarma]

It looks like filament starvation. Possible causes:

Stepper driver missing steps - check for overheating and/or vref set too low.
Extruder not gripping - adjust tension on the guidler.
Blockage in the nozzle - raise temp above your normal print temperature, then lower it to a bit above your filament's glass transition temperature (about 90 for PLA works well), then retract the filament. You should see a straw on the end and it should drag out any blockage. Rinse and repeat until you're happy.

From the overall look of the piece and the top layer, it looks like you're over-extruding as well. Have you calibrated e-steps per mm?

[3DPBuser]

If lack of filament, why would it be in the same area?

I was thinking it might be too high extruder temp, causing re-melting of the previous layers in areas that are thinner.

[3dkarma]

If it were re-melting of the filament, I would expect to see gaps on the left hand side of the print in that second photo, but it's easy enough to check. What temperature are you printing at? Anything over about 195 for PLA is too high.

It might be re-melting though. How many perimeters are you printing, what's your temp and what's your perimeter speed? You could try lowering temp and/or increasing perimeter speed. If you're only printing one perimeter you could try increasing the number. A thicker wall could solve some problems if the head is dragging lower layers back around with it, rather than laying new plastic on top.