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PETG Print Quality Challenges
 
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PETG Print Quality Challenges  

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ami.l
 ami.l
(@ami-l)
Eminent Member
PETG Print Quality Challenges

Hi again everyone and greetings from California.

I'm having some issues with PETG. It's an Amazon Basics Black PETG spool, it had great reviews.
I'm using the Slicer "Generic PET" setting.

The challenges seems to be non-uniform extrusion, where I will get 'blobs' of material, for example see attached photo.
The first layer seems to be good, and the bottom is smooth so I know Z is good.

I have no such challenges with PLA or ABS. With both I get excellent results.
I also have no adhesion issues, I've been following the recommendations on this forum to use Windex and it works great.

Could it be a faulty spool? Perhaps the settings should be adjusted?

Thanks in advance for any tip.

Ami

Posted : 20/04/2019 7:24 pm
cwbullet
 cwbullet
(@cwbullet)
Member
Re: PETG Print Quality Challenges

It is hard to tell from that image. Under extrusion or Live Z is off.

--------------------
Chuck H
3D Printer Review Blog

Posted : 20/04/2019 7:30 pm
Jerry
 Jerry
(@jerry)
Estimable Member
Re: PETG Print Quality Challenges

How much maintenance do you do to the insides of the extrusion path? I clean very thoroughly when changing types.

Posted : 20/04/2019 8:13 pm
--
 --
(@)
Illustrious Member
Re: PETG Print Quality Challenges

For starters, your layer 1 looks much too low: you are scraping the bed with the nozzle. Other issues look like temperature and/or a nozzle jam induced by being too low.

I use Amazon PETG in black and other colors and find it prints very well, very easily, just needs a clean bed to stick down : unlike every other PETG that normally sticks to even filthy beds like superglue ... Windexs kills a print for me.

Try a cold pull, get any overcooked PLA out of the nozzle.

Posted : 20/04/2019 8:30 pm
Peter M
 Peter M
(@peter-m)
Noble Member
Re: PETG Print Quality Challenges

If you change filament type, check your first layer for z height, this can change if bed a different temperture.
And even better, every print you should check the first layer, it can change.

Posted : 21/04/2019 4:58 pm
ami.l
 ami.l
(@ami-l)
Eminent Member
Topic starter answered:
Re: PETG Print Quality Challenges

Thank you all for your replies.

I calibrated first layer Z based on the results of the bottom layer, which seems to be uniform for all other materials.
I will try to increase live Z a bit and see how that impacts things.

Regarding thorough cleaning - can you provide a link to a good article / video with best practices for deep cleaning the extrusion path?

Thanks again,

Ami

Posted : 21/04/2019 8:25 pm
bobstro
 bobstro
(@bobstro)
Illustrious Member
Re: PETG Print Quality Challenges


[...] Regarding thorough cleaning - can you provide a link to a good article / video with best practices for deep cleaning the extrusion path?
Here's some copypasta to get you started...

Adhesion problems are usually caused by 2 main problems:

  • A dirty PEI print surface. Even if you don't think this is the cause, it's always a good idea to make sure your PEI surface is clean before trying any other fixes. Take it to the kitchen sink and give it a good dunk with Dawn (original formula, no vinegar or hand softener variants) dishwashing soap or your local equivalent (e.g. Fairy in UK). Use a clean paper towel to clean it off, and another to dry it. Avoid using any sponge or cloth that has been in contact with grease. Above all else, avoid touching the PEI print surface. Once it's good and clean, you should be able to use 91%+ isopropyl alcohol between prints, 100% acetone when that fails, and another dunk when acetone fails. Worst-case, use a 3M 7445 ScotchBrite pad or equivalent to give it a very light buff, but only infrequently.

  • If you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-Z setting. It is much easier to use and understand than the on-board routine.

    • And above all else, avoid touching the PEI print surface.

    Try those 2 steps. If you're uncertain of the Live-Z results, post pics here of the 75x75 print bottom and you'll get quick help. In general, start high (less negative) and work lower (more negative) in large increments (e.g. 0.1mm) until the filament starts to stick on its own. When it's right, you should be able to gently rub it without it coming loose. Then start lowering (more negative) the level until there are no gaps between layers.

    As for the extrusion path:

  • A cold pull can do wonders if you have build-up of crud in the nozzle or hotend.

  • Check the extruder gears by opening the cover and examining the area around the bondtech gears and PTFE path. Remove any built-up grit or filament.

  • I like to drop a 15cm/6in 1.5mm rod down through the top of the extruder, past the (open) extruder gears and into the PTFE tube to check for any resistance or plugs.

    • If you want more detail, I've dumped everything I know about adhesion and bed cleaning here and Live-Z calibration here (draft). Note on cold pulls here. Pics and incomplete notes on the feed path check here.

    My notes and disclaimers on 3D printing

    and miscellaneous other tech projects
    He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

    Posted : 21/04/2019 8:36 pm
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