How to switch from PLA to PET-G?  

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pedja
(@pedja)
Eminent Member

PLA is said to be most forgiving and easy to use for inexperienced users.

When one decides to try PET-G what reconfiguration of machine and PrusaSlicer is needed (other than using different filament profile)?

Posted : 03/06/2020 9:07 pm
bobstro
(@bobstro)
Illustrious Member

Different temperatures, bed prep and minor adjustment to Live-Z are common.

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 : 04/06/2020 6:35 am
h.waibel
(@h-waibel)
Trusted Member

And if available use the powder coated sheet, saves you all the trouble with glue sticks or other separator magic like window cleaner or hair spray...

But don't forget to use a different sheet profile 😉

Posted : 04/06/2020 8:43 am
pedja
(@pedja)
Eminent Member

Here is what I did (as novice, after reading a lot about this).

I have only smooth PEI sheet.

First time I did PETG print i just changed filament profile to PETG in PrusaSlicer and generated G-code. Also I used glue stick I got with printer. Then I printed small object for test. O boy how it sticked to the plate! I thought I would rip sheet apart.

Then I learned that first layer has to be bit higher for PETG to prevent it sticking to hard to the sheet. Although some advised doing First Layer Calibration I decided go different also recommended route: setting Z offset.

I started with Z offset 0.4 and decreased gradually until filament started to stick firmly to the sheet. I ended up setting Z offset to 0.1. Filament sticks to sheet to hard for my liking, but with greater Z offsets I get nonuniform first layer prints.

Why Z offset instead of First Layer calibration? Well, just for comfort.

First Layer calibration requires me to remember value for each type of filament (or create Sheet profiles in printer) and check and change it each time I run some G-code with high probability that I would miss to do that.

Z offset I set in PrusaSlicer Printer Settings and save as custom printer profile. That is more comfortable, as when I do slicing I just set proper filament and printer profiles and get G-code that I then can run whenever I want without thinking of setting up printer. That means I just have to assure First Layer Calibration is properly done for PLA and PETG prints will do fine as they use proper Z offset relative to PLA setting.

This post was modified 2 months ago by pedja
Posted : 04/06/2020 4:32 pm
pedja
(@pedja)
Eminent Member

Just to add, I did PLA First Layer Calibration using this method https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/ before switching to using PETG and Z offset.

(I cannot edit previous post)

Posted : 04/06/2020 4:41 pm
chocki
(@chocki)
Prominent Member

If you have been printing with PLA on the textured sheet, your best of washing the sheet with hot water and washing up liquid using a non stick pan scourer, rinse with plenty of running hot water (Washing up liquid like Dawn and Fairy liquid contains a lot of salt and there's nothing worse than salt to cause corrosion (OK maybe acid!)), dry thoroughly with kitchen paper then heat on the printer to the maximum heated bed temperature (120) the printer will do for at least 5 minutes to make sure ALL trace of water is gone.

The reason for this is that PLA can leave sugary deposits which will prevent PETG from sticking and sugar does not dissolve in IPA and some brands of PLA have mixed in oily additives to improve printing.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 04/06/2020 5:11 pm
pedja
(@pedja)
Eminent Member
Posted by: @bobstro

My notes and disclaimers on 3D printing

Man this is really good resource. I am surprised it never came up in numerous web searches. Check your site SEO. It should be more prominent.

Posted : 04/06/2020 9:19 pm
pedja
(@pedja)
Eminent Member

@chocki

I actually have smooth sheet and I use one side for PLA and other for PETG printing.

Posted : 04/06/2020 9:21 pm
Robert-mm200
(@robert-rmm200)
Noble Member

There have been a fair number of people complaining that PETG stuck too firmly to the smooth PEI sheet, and damaged the surface. A common fix was to spray the sheet with Windex and let it dry before printing. Seems to act as a release agent.

Posted : 04/06/2020 10:40 pm
michele.b3
(@michele-b3)
Eminent Member

I strongly recommend to get one powder coated sheet for petg.

It makes petg printing  very simple, no need for glue or hairspray. All you need is to set zero layer z offset to a specific profile.

Once the print is finished you just need to wait till it cools down and it will detach without any issue.

You do not need to clean either (indeed once every 5, 10 printing task you will have to) petg will stick without any problem.

For pla I still recommend Pei sheet instead with hairspray.

Bests

Posted : 05/06/2020 12:37 am
jsw
 jsw
(@jsw)
Reputable Member

I've had good luck using PETg, specifically the Prusa 'stuff they use in the farm' on the smooth sheet.

The only thing I changed in the slicer was to use the Prusament PETG selection, in addition to the stuff used for the specific print, such as skirt/brim/raft, support and such.

I've had no problems using the same smooth sheet for PLA, ABS and PETg.

Cleanings, of course, mostly IPA and denatured alcohol, occasionally acetone and/or a wash in the kitchen sink after cleaning with solvents.

I'll often use a SMALL amount of glue stick on smaller PETg items and those which have small support first layers.  Otherwise, PETg seems to have good (too good) adhesion to the smooth sheet.  A few weeks ago I printed a tool tray to keep beside the printer and I did it in the Prusa orange PETg to match.  It took some assertive flexing to get it to release, but it did pop off with flexing at 45 and 90 degree angles.

Early on I ruined one side of the stock sheet with an ABS print that was not releasing.  I got impatient and used tools and a few little pieces of the coating pulled away.  It's still usable on that side for smaller parts toward the front, but I do want to avoid that again in the future.

Posted : 05/06/2020 2:54 am
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