PETG Woes  

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xayoz
(@xayoz)
Eminent Member

I finally feel confident enough to move away from PLA and try something else, so I'm trying PETG.

I'm using Prusa MK3S and slicing in Prusa Slicer with the Prusament PETG default settings. And yes, I am using Prusament PETG.

I'm having a couple issues. The first is that it wouldn't stick to the textured sheet. No problem, I tried the smooth sheet. Stick too much to smooth sheet. No problem, tried glue stick on the smooth sheet. Solved, no I can get my prints loose. Would ideally still like to use the textured sheet with no glue.

Problem 2 is more important. Base layers are great, but randomly, further up the print, I get a glob. Then it keeps running over the glob and triggers crash detection. How do I stop getting globs?

Posted : 02/06/2020 7:25 pm
Kevin Reid
(@kpreid)
Trusted Member

For adhesion on the textured sheet, try setting your Live Z lower. Good adhesion on the textured sheet requires smashing the extrusion into the crevices.

Also, try preheating and/or increasing the ambient air temperature. A few degrees can make a big difference between corners peeling up off the bed and not.

As to the globs, PETG is in general more curly and sticky. Expect "bridge infill" parts of prints to be troublesome, and to have to clean the outside of your nozzle after prints. I've seen a lot of sticking-up bits in prints and the nozzle running over them, but it usually isn't a problem unless the print is also peeling off the bed. You can also use flush cutters to snip off particularly bad parts during the print.

Posted : 02/06/2020 8:05 pm
Graham25Fox
(@graham25fox)
Trusted Member

Hi  I had all this problems with PETG

i found out that the text plate is about 1/2 the thickness of the smooth plate,  only found out after much head scratching.

it would just roll up in a ball, wash the plate with hot water. then keep going with the live Z adjustment.

i had to go a lot lower on the Z, i was not going far enough.

What i did was to get a good layer with PLA, before going to PETG

i did not get on very well with the prusa calibration. i found it too fast to get a good height set.

look on Thingyverse for a bed level. i used a 25 mm calibration cube scaled up to fill the plate, as you are only doing 1 layer it dont really matter how long it says in the slicer

hope this helps

Posted : 02/06/2020 8:07 pm
charles.h13
(@charles-h13)
Famed Member

Concur - Correct Z level is the key to success with PETG - too low or too high will lead to failure.  

Posted : 02/06/2020 11:37 pm
krb liked
scottsh
(@scottsh)
Active Member

It took me a week or so to dial in PETG correctly.  Here are the tips I'd offer.

I have the MK3S and print PETG with the textured PEI sheet.  I clean the textured sheet with isopropyl alcohol every so often.  Removing prints from the textured sheet is trivial after it cools down.  I think the textured sheet was designed for PETG. 

I found these settings worked if I used Prusa PETG or other.  Mostly I've been using a PETG I got off Amazon named Overture.  

I found the textured sheet needs to be heated hotter than other sheets.  For PETG, I use 90C first layer, with 85C other layers.  If you don't have the temp right, getting everything else was a huge headache.  Note that 90C is much hotter than the default and the smooth sheet but I'm convinced the textured sheet transfers heat poorly and thus you have to use a higher temp at the PCB to have the right temp on top of the sheet.

For the extruder, I'm using 245C for the first layer and 250C for the remaining.  I didn't find this setting to be critical for success and I could probably dial this down a bit but I haven't experimented because what I have is working.  I do get some stringing so I feel I could work on this more.

Live Z-level - with the temps right, I used a Z calibration pattern from Thingiverse.  I found the best was a simple cube about 100mm square.  With that, I was able to dial it in right.  As others have said, the textured sheet has a higher Z level than the smooth sheet which is why the FW lets you configure it uniquely for each sheet.  

I know this can be super frustrating.  It sure was for me.

Posted : 03/06/2020 2:31 pm
xayoz
(@xayoz)
Eminent Member

ok, looks like the globs were from a leak...I didn't tighten the nozzle enough when I replaced it.  Now just z to adjust...too close or too far?

 

Posted : 04/06/2020 7:28 am
vsobr
(@vsobr)
Active Member

I have had quite a similar problem, it seems to me that these thinner sheets are more prone to warping... and such they have some issues...

I think I wasted more material and time on attempting to calibrate it by wizzard then just printing this:
I have found out the easiest way how to get decent layer is to make a 1 layer thick 3D object over whole printing area and then attempting to get decent layer all over the board. with also making sure the nozzle does not drag into the print.

I still have some issues though - in one corner I am getting much thinner layer then elsewhere and I am not sure how to remedy that by going up and not mess up other print side of the sheet.

also - having such a single layer print (even if it takes hour to print) is magic boon how to clean this sheet. it removes all leftover filament, and I believe every other rubbish, I have amazing adhesion even for support base after I did this.

However I still have a "section" where the print is bad.

I did not have such issue on a normal sheet. But as I say I believe thats mostly because its less warped.
(Though I did not test this on regular sheet, so I am not sure but since that sticks much better its less sensitive to issue I guess)

So my question - is there some compensation in software or in settings I could apply to this corner somehow? I can print around it but it in essence looses me like 1/8 of the sheet space (I still can print there but it needlesly accumulates rubbish on the nozzle and its more difficult to remove)

(the top one is going to bit higher layer)

 

This post was modified 4 months ago by vsobr
Posted : 04/06/2020 9:30 pm
scottsh
(@scottsh)
Active Member

@xayoz

In my limited experience, what you are seeing indicates the LiveZ is too high.  My LiveZ ended up much lower than I expected at -1.00 but of course that's an offset so who knows where your starting point is.

Posted : 04/06/2020 10:46 pm
guy.k2
(@guy-k2)
Noble Member

1. Changing between different materials you MUST wash the plate with Dawn or 1s layer adhesion will be quite poor.

2. Agree that the LIFE Z MY WAY test print is far better than Prusa's built-in test. 

3. Even with 7 x 7 mesh working perfectly, if the PEI layer varies in thickness, the printer cannot compensate. The PINDA mesh only measures distance to metal plate. Work arounds are to abrade plate where its PEI is thicker or keep nozzle high enough to clear highest point. Neither is a very satisfactory solution when PEI coating is uneven.

4. Higher bed temperature can help. Ideal is near the glass transition point for the filament to be sticky enough to adhere to bed and retain some thixotropy. My PETG temp starts at 85C for 1st layer and goes up to 90C for subsequent.

 

Posted : 04/06/2020 11:03 pm
Graham25Fox
(@graham25fox)
Trusted Member

My best way to use petg is to have different plates, textured and a smooth.

you have pointed out something i have seen but not fully understood and that is;

85 first layer and then 90 after, what is the reasoning behind it,

i have just been using 85 all the way, with no problems.

could it be better layer adhesion ?

Posted : 04/06/2020 11:15 pm
vsobr
(@vsobr)
Active Member

@graham25fox

there are two schools of though regarding this - making it solid faster with lower temperature so it gains some rigidity or heat it up so it bonds a bit better...

people tend to have mixed results with either.

for me the print drasticaly improved after essentialy calibrating whole printing area... (plus as I said it likely removed all the rubbish from within the texture so it bonds even better)

Posted : 05/06/2020 10:10 am
xayoz
(@xayoz)
Eminent Member

ok, problem solved.

The globs were from a leak. I accidentally loosened the heatbreak when changing the nozzle, tightened everything up, it no longer leaks.

As far as the textured sheet, I was given the suggestion to rub the hell out of the sheet with a mr clean magic eraser. I did so, and now it works great, so I can use both sheets without issue now.

Posted : 09/06/2020 4:23 am
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