Bubbles on top layer

[waynejacobsen]

I'm printing on a TAZ 6, with PETG at temp 235: bed 77 with 20% fill and 10 top layers with fan off. There appears to be randomly placed un-poped bubbles that show as bulges in the top finished layer. Any suggestions on eliminating them.

[wirlybird]

What print speed? PETG does not like fast. Maybe over extruding a little

[waynejacobsen]

60 mm/s

[wirlybird]

Most likely too fast. I'd start at 35-40mm/s and see how it goes. PETG does not like to print fast.

[S3D-Alex]

I would agree with slowing down your print speed but I would also suggest making sure your filament is dry. PETG has a tendency to absorb a lot of moisture and it can cause serious printing defects like bubbles.

[SusiT140V]

Hi Wayne,
Without photos it's hard to guess.

It's likely to be one of two things -
Delamination due to it being extruded too cool (the surface will have a matt/silk-like finish) - try 240-245°C ,
or moisture - dry a full 1kg reel in a food dryer/dessicator at 55-60°C (or a preheated electric fan oven) for at least 6 hours.

Hope this helps,
Susi.

[waynejacobsen]

I did try to attach a photo of the part. I will try slowing print speed and drying filament, then report back, Thanks (photo attached again)

[waynejacobsen]

I made the changes suggested so far, to no avail. I hope this photo shows the problem. Keep in mind that except for top layers all other parts of the part works great

[TinaNamdev]

I did try to attach a photo of the part

[SimpleScott]

PETG sags a lot (does not bridge well). This includes bridging over sparse infill; it just sags down into the gaps.

Recommend you increase infill density, and increase number of top layers when using PETG. Specific to the print in your photo, I’d suggest doubling the infill density. Thicker layers also helps, but denser infill and more top layers are the key.