Seam on PETG parts

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terrymcc
Posts: 22
Joined: Thu May 29, 2014 12:23 am

Seam on PETG parts

Post by terrymcc » Wed Dec 07, 2022 4:08 pm

In the past, I have only printed PLA. My M3-ID has always printed it great with very little tweaking. I know, its the easy stuff....

I have started using some black PETG for some parts. I've got the temperature where I'm getting good adhesion and stringing is manageable for these parts at 235. However, I can't get rid of the seam on the side of the part from ooze where it starts and ends the outer perimeter on each layer. Also, a bit of bulging on sharp corners. Looks like a nasty scar going up the part. I've tried dialing up the retrack distance to 6mm with no affect and also the retract speed to 2400.

Can someone tell me what parameters I need to tweak and/or share their successful print settings for PETG. I am going to try the ooze shield next, but it's a pretty good size part and I need to print a lot of them. I'm also doing one at a time to eliminate strings between parts but would like to print multiples in the future.
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IMG_3359.jpg

airscapes
Posts: 573
Joined: Wed Jan 31, 2018 11:36 pm

Re: Seam on PETG parts

Post by airscapes » Wed Dec 07, 2022 8:54 pm

Hi! That looks like the Z seam and you really can't get rid of it. You can tell the slicer to put it in a certain location, like a corner rather than the middle of the curve. You may be over extruding a bit as well. You may want to drop the temp to 230, at least that is where I get best pet prints with my M2. I will not change the z seam but my give you a better surface.

The seam is just part of the process, I have never been able to eliminated it and still keep the integrity of the part. You can't move melted plastic to the side and then up and not have a seam..
This is an abs part laying on it's side to show the seam better.. this is a good print as far as I am concerned.
Z seam.jpg

Gwhite
Posts: 359
Joined: Tue Jul 11, 2017 3:38 pm

Re: Seam on PETG parts

Post by Gwhite » Thu Dec 08, 2022 4:46 am

If you are patient & fussy, you can fine tune the seam quality by adjusting your retraction and extra restart distance. A small negative restart distance will do a lot to clean up the seam. That compensates for how much molten filament wants to dribble out the nozzle during the move to the next layer. PETG tends to be extra oozy, so you may need a slightly more negative value than what PLA would require. I just checked one PETG profile I fine tuned, and I used a retraction of 2 mm, and an extra restart distance of -0.06 mm. That was with HatchBox white PETG. I used Simplify3D for that job. For some reason, the retraction values and I need in PrusaSlicer are often quite different.

airscapes
Posts: 573
Joined: Wed Jan 31, 2018 11:36 pm

Re: Seam on PETG parts

Post by airscapes » Thu Dec 08, 2022 2:08 pm

One other thing to mention is the retraction and restart will not have any affect on that seam if you have "only retract when crossing open space" turned on (s3d last tab). With that check box checked, there is no retraction on the Z change. To me, the least amount of stops and starts the more solid the part so I don't normally have any retraction during the Z change with that option checked.. It is a tradeoff but I think you probably need to calibrate you EM at the very least, also my want to try a taller layer with PETG

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