What is the trick with PETG?  

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SteyrTMP
(@steyrtmp)
Active Member

I've been printing on and off since 2017.  PLA, PLA+, no problems.  ABS, no major issues.  I have gauge plates in my car that were printed in ABS.  I started printing with TPU, and after a little bit of a struggle, was able to get it to print pretty well, printing masks and holster paddles.

PETG, that's another story.  I can get some smaller things to print without an issue, but large prints, with a lot of supports, go nowhere.  I'm on my 6th or 7th try, most of a spool later, and it still looks like it's going to fail again.

I'm going to attach a lot of photos, showing the part, my next fix for it, and the settings I am currently running.  I've tried .3 first layer with .15 Z modification, and that was a flop.  I went back to standard setup, with my Z zeroed in pretty well, from the look of things. 

Apparently, I can only link one file at a time, so the responses will be other photos, if it'll allow.

Posted : 22/06/2020 5:06 pm
SteyrTMP
(@steyrtmp)
Active Member

An earlier failed first pass.  I run them very slow.  While they're already slowed down to 20mm/s on Slic3r, I dial them down even further down to 60% or less on the printer, as well.  I tend to crank up the extrusion percentage, from 95% to 100% or 105%/

Posted : 22/06/2020 5:09 pm
SteyrTMP
(@steyrtmp)
Active Member

This is a contact surface, on top of some supports.  This is an issue, not just limited to PETG, but I have this with everything.  I have yet to have a decent, smooth supported surface.  The best I can get is a semi-stringy surface.  That would be with a .15 separation between support and part surface.

Posted : 22/06/2020 5:11 pm
SteyrTMP
(@steyrtmp)
Active Member

This is another part for the same project I'm working on.  This was supported, and still came out like this.  I really struggle with supports, but mostly with PETG.  Usually, something angled like this, would come out decent with PLA+.

Posted : 22/06/2020 5:13 pm
SteyrTMP
(@steyrtmp)
Active Member

Here's a CAD screen shot of the fix I'm about to try, if the current print fails (about 12 hours into a 60 hour print).  I went and made a block that fits .05 beneath the existing part.  That will leave a support surface between the two, and not much else.  There will be supports in the radiused front, but I can deal with a little support, usually.

Posted : 22/06/2020 5:17 pm
SteyrTMP
(@steyrtmp)
Active Member

As much as I'd prefer to not have supports, Slic3r seems to think it's necessary, even with the support block underneath.

Posted : 22/06/2020 5:18 pm
SteyrTMP
(@steyrtmp)
Active Member

Here are my Slic3r settings.

Posted : 22/06/2020 5:24 pm
SteyrTMP
(@steyrtmp)
Active Member

More settings

Posted : 22/06/2020 5:24 pm
SteyrTMP
(@steyrtmp)
Active Member

And more.

Posted : 22/06/2020 5:24 pm
SteyrTMP
(@steyrtmp)
Active Member

And last settings page.  

Any info would be great.  Thanks

Posted : 22/06/2020 5:25 pm
SteyrTMP
(@steyrtmp)
Active Member

Finished the print, over 50 hours, and it looks like crap.  The bottom supports don't want to separate, and had to be cut off.  I'll try to lightly sand to try to save it, but it looks terrible.  I'm reprinting some other parts, and dropped from 245/240 to 230/230, with hopes that it might not melt the parts.  I don't know what to do past the .15 space between supports and parts, as any higher than that tends to make the supported finish look like ramen noodles.

Posted : 24/06/2020 3:04 pm
SteyrTMP
(@steyrtmp)
Active Member

Another view.  Heat distortion.

Posted : 24/06/2020 3:05 pm
Neophyl
(@neophyl)
Noble Member

Instead of posting screen shots of settings and models save your problem project (file>save as) , which will save as a .3mf file.  The 3mf saves the model and all of your settings for print, filament and printer. Zip it up as the forum doesn’t accept the file type. 
That way people can scroll around and see what the slice is like and also see the previews for speed etc. It’s a much easier way to receive help. 

btw for posting multiple pictures use the add media button to add it to a library on your account and then you can add them by ticking them. 

Posted : 24/06/2020 4:12 pm
wook
 wook
(@wook)
Active Member

I'm following.  I'm new to printing and just started with PETG.  I've noticed a huge difference compared to PLA.  And most of the issue is the supports (and some minor blobs from time to time). The print looks like junk above a support - especially if it is a curved or irregular shape.  I've also adjusted the z calibration of the first layer and I've played around with the support settings.  The sweet spot is still elusive to me. 

Posted : 25/06/2020 4:06 am
peter.m26
(@peter-m26)
Honorable Member

@steyrtmp

First layer to high, and possible not clean.

Pei sheet, clean with dish soap, clean with window cleaner(this leaves a layer so it does not stick to much).

Get a 100% first layer, sticking will then be optimal.

 

A new sheet will stick less then a used one.

PLA sticks more difficult on a powder coated sheet. Is still possible settings need to be more preciese.

This how I work on a pei sheet(there are always exceptions):
Most important to 3d printing is:

1. 3d print will never be like start and i have the print, there will always be problems!!!!!!

2. A clean sheet, use dish soap, then you can print on it. A few prints you can use alcohol, then again dish soap,
big flat models and models with small footprint on sheet- use glue stick(and not every glue stick is the same,
use one that makes a thin layer), and big flat models and small footprint, use a big brim attach to model so footprint is bigger.

Petg sticks to much on the pei sheet, use window cleaner, this leaves a layer on the bed, so it does not stick to much.

3. To get it stick very good, a 100% first layer is very important, see youtube for movie on this.
Every new print watch the first layer, and look if it is 100%, this will also prevent a big ball of filament on your nozzle wenn model let loose during printing.

Extra: (normally not needed).

First layer, print hotter.
First layer slower.
Bed more heat.

Most problems are first layer to get this 100%.

Bad filament is possible, or filament with water inside.

Move extruder to the top and extrude filament, it should go straight down(if not, nozzle possible blocked),
it should be thick enough(if not, nozzle possible blocked), (do a cold pull),
if Bubbling during extrusion then it has to much water inside.
Check after the first layer is ready, then you see if it sticking enough, and not releasing and sticking to the nozzle.

Posted : 25/06/2020 7:03 am
peter.m26
(@peter-m26)
Honorable Member

Go back to presets settings, for petg there are 2 to try.

Do a temp tower.

Do a stringing test.

Measure filament thicknis, and do a cube test to measure how big models gets, this is a cube with roof open,and 1 layer thick.

Could also be bad filament, or less quality.

Small objects. or a part of the objects, if this is only printing it could be a cooling problem, if you print more parts(small parts) then the first part could cool down.

Posted : 25/06/2020 7:11 am
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