Adventures with PETG

General LulzBot TAZ
1

I am running a Taz5. I recently decided to try out some PETG. I’ve gotten very good results with ABS, HIPS and PLA. So far with PETG my results have been very poor.

The surface is horribly rough.
Print 240
Bed 85
Fan Low
I’ve used suggested profile settings from others in this forum.

This example is from - http://www.thingiverse.com/thing:555872
It’s approximately 6" across and 17 layers high.

Close Up of the circular border -

The top layer looks like a blob at each end with a thin line stretched in between.
Any suggestions for improvement would be greatly appreciated.


Bonus Question

The observant among you may have noticed a very odd looking skirt. I just installed Cura v21.02.
This erratic shape does go under the print in quite a few areas (prints right over it).
The normal view of the model looks fine -

The Layers View show the messed up skirt -

Any ideas about why this is happening?



Best regards,
PCH

2

The messed-up skirt is most likely because the bottom of your 3D object is not entirely flat.
You could try printing it on a raft.

3

The model is so disjointed that it’s hard to tell when it’s printing. I looked at the first layer in Cura and you are spot on. It’s a bunch of small points scatters around the print field. Sheesh, who does that?



Best regards,
PCH

4

I can’t 100% tell from the photos but when I had PETG loaded (think it’s my fave material now!) i had some what I thought to be stringing issues, turns out PETG can be pulled like hot sugar. I’m wondering if the blob elements you describe at the infill are part of that issue. I can see some stringing in the photo so here’s how I would describe the difference for PETG.

“thicker” stringing, this is the nozzle set too low in temp by only a few degrees, where the strings put up a bit of resistance to breaking when pushed by your finger and when doing long curves you get a little bit of a layer popping loose. This is not a retraction thing.

“ultra fine” stringing, almost hair like, very little resistance to breaking think ultra fine fibre like a strand of very fine synthetic hair, could move around in a light breeze. This means your temp is likely right and just need to play with retraction a little bit if excessive.

Other issues per the other great comments in this thread.

5

I’ve been playing with PETG again this weekend and have gotten some encouraging results.
My biggest problem was with wall thickness. Once that was sorted out things things were working better.
I think a profile I was trying wasn’t for the .5mm nozzle or something.
The issues with the model above was from the non-flat bottom. It caused lots of bridging and rough surfaces.
There is a setting in Cura to Sink the model into the bed (start several layers up from the bottom).
Sinking it .5mm worked perfectly.

This snowflake is a Quilling Design - http://www.thingiverse.com/thing:1181496
The Blue inside parts are PETG and the outside White part is ABS.





PCH