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PETG adhesion woes  

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Kate
 Kate
(@kate-4)
Active Member
PETG adhesion woes

Hi all.

So after my previous post about PETG over adhesion with the PEI smooth print sheet, i ordered the powder coated sheet from Prusa. After it arrived i was excited to print with it, so i wiped it with isopropyl and tried a print and found quickly that now my adhesion problem was an under adhesion one. I adjusted the Z level, down to the point where the filament line was beginning to fade. I backed it off from there and as far as i can tell i am at a proper level... the prints just dont stick! The last 2 prints i tried the glue stick. I used Makers Muse's suggestion of the glue stick wiped with a paper towel coated in isopropyl. The results were okay, like once? It was a successful print but the overall quality is awful, covered in little strings and such. The filament brand is Inland, its a Micro Center brand, just some generic quality but I am using the Prusament PETG settings, maybe thats wrong?

I took a picture of my latest attempt. After the last print that succeeded, i did even more glue and tried again, and the results are pictured. I just dont know where to start, the filament seems to want to stick to the nozzle just as much as the bed. Is there a such thing as too much glue? Im at the end of my rope with this stuff, i switched to PETG for printing these face shields because people say its easier to sanitize but i just cant get it to print well to save my life. Thanks in advance.

Posted : 22/04/2020 2:58 am
Peter M
(@peter-m)
Noble Member
RE: PETG adhesion woes

Hoe to do a first layer.

Then clean bed with dish soap 2 times, with hot water. That is all.

Extra normally not needed:

first layer sloe down to 10 mm

first layer extruder heat 5 or 10 C higher

 

Posted : 22/04/2020 8:50 am
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

@peter-m26

Ok but thats not even the sheet im using? Like i said ive tinkered with it a little and put it down to where it looks like its pretty low but it keeps sticking to the nozzle. Ive calibrated the machine properly for the smooth sheet on PLA so i know what a good first layer looks like. I did find a video on the textured sheet where it says you need to go extra low on your first layer so the material squishes into the texturing on the sheet. I will try that.

Posted : 22/04/2020 7:08 pm
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

OK well I did what you suggested, i washed the sheet with some dish soap. I then played around with temperatures, i raised the nozzle and bed temps to 250 and 90 respectively. I also ended up raising the Z level quite a bit, because at that point i was getting some adhesion at least and i could tell i was way too low. Below was my latest print attempt. Some sections of it adhered OK, but then you see those lighter sections that dont adhere at all. Whats with the inconsistency? Do i need to wash it some more?

This post was modified 2 years ago by Kate
Posted : 23/04/2020 2:19 pm
GutenBar
(@gutenbar)
Eminent Member
RE: PETG adhesion woes

Try to do the first layer calibration.
It could be this because the image looks like a very high nozzle altitude.
Each plate has its own height and, if I am not mistaken, the machine can store each adjust for multiple plate use.

If persist, you could try the strongest hairspray you can find.
I do not invent this technic but since my stick glue finished, I use it and it has been very, very efficient. Also, it could enter the powder-coated relief.

Posted : 23/04/2020 6:04 pm
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

Yeah, ive been doing first layer calibrations, over and over again. I just cant find that happy medium where it is sticking to the bed and still forming a good solid line of filament.

Heres where it gets interesting. I switched back to PLA, and swapped the textured bed for the smooth bed. Same issue! And yes, i adjusted my Z height for the smooth sheet to what it was before. This used to work, im so confused. Could it be my nozzle? I swear its like the prints just really want to stick to that nozzle.

This post was modified 2 years ago by Kate
Posted : 24/04/2020 5:24 pm
Peter M
(@peter-m)
Noble Member
RE: PETG adhesion woes

Do you have 7x7 bed leveling/mesh, in the setting from the printer you can set this to 7x7.

 

Posted : 24/04/2020 7:58 pm
GutenBar
(@gutenbar)
Eminent Member
RE: PETG adhesion woes

@mckeanke

Did you try to calibrate the extrusion multiplier?
If you suspect the nozzle, it would be good to inspect this.

https://help.prusa3d.com/en/article/extrusion-multiplier-calibration_2257

This post was modified 2 years ago by GutenBar
Posted : 24/04/2020 11:11 pm
steve
(@steve-29)
Trusted Member
RE: PETG adhesion woes

Your 1st layer is WAY, WAY off, not even close - look at the major gaps you have, and the bead of filament is round. Nothing is going to stick to the bed with your 1st layer so high.

To adjust your Z-layer print (just the first layer) a 150mm x 150mm x 5mm cube with a 5mm brim. First - the brim should be solid and strongly attach to the cube, no gaps. With your 1st layer height I will tell you right now you will have gaps and the brim may not even attach to the cube! As it prints the cube you will have lots of time to experiment with the Z-layer. Keep moving it down until you start to get "scarring", meaning the nozzle is too low and the filament is coming up and around the nozzle, then raise it until the scarring goes away and you have nice, flat, uniform strips that form a solid layer. Note with a textured plate you should have a very very strong texture pattern on the bottom (after you remove the piece); a lightly textured pattern means your 1st layer is still too high and again you won't get proper adhesion. After all that then print the test cube again and make sure 1) the brim is perfectly solid and attaches to the cube strongly and 2) the first layer of the cube is solid and flat.

Also regarding PETG you obviously didn't read the PRUSA manual or online advice - you should NEVER clean with isopropyl and then print PETG, you can (and sounds like you did) get over-adhesion and will ruin the PEI. Prusa recommends something to reduce the adhesion like Windex or glue stick. I personally use Windex and its fine.

If you suspect the nozzle then you should try a cold-pull, preferably with specific nylon filament. Again Prusa gives advice on how to do this.

You will save yourself a lot of time and energy if you just spend some time on the Prusa site reading their advice and guidance.

...
Posted : 25/04/2020 2:56 am
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

@steve-e3

Are you sure you're looking at the second image? I definitely had it lower that time, and it did NOT look or feel round in person. I already said this, I was lowering it to the point where the filament line was coming out broken and uneven, and only then did I see really good, repeatable adhesion. At that height the little cube it makes during the first layer calibration has huge ripples in it which, as the video above shows, is not right. I can't stress this enough, there were NO GAPS in the Prusa calibration. Is there something different about this 150x150x5 cube you're talking about??

Yes, I'm aware I failed to read documentation about the PEI sheet. I went over this in my last post, it's not relevant to the current discussion or very helpful. I've read lots and lots of Prusa documents and forum posts since my mistake, but for the record, I really hate how makers everywhere emphasize how "easy" PETG is to print. It really misled me when I started down this path. Now I have a broken printer. And another thing... I used Windex. I got more holes. I will not let my PETG touch my PEI sheet again.

This post was modified 2 years ago 2 times by Kate
Posted : 27/04/2020 3:14 pm
steve
(@steve-29)
Trusted Member
RE: PETG adhesion woes

@mckeanke

Hey sry missed the second photo. Looks like you're trying to print a COVID headband.

So just to level set, you are now trying PLA on a sheet that did not have PETG printed on it, correct? If not, that's where I would start.

At this point it sounds like you are an expert at Z-layer calibration and you're fully aware of when it's too high (comes out as a round bead, doesn't adhere to the bed, doesn't provide coverage) and when it's too low (leaves "scraping" marks). I doubt it's a Z-layer adjustment at this point.

FYI the MK3 does need calibration when you switch between the textured and smooth plates. It's counter-intuitive to me but I needed to adjust the nozzle down quite a bit when switching from the smooth to textured plate. (I thought it would be the other way around).

Just some obvious comments - make sure 1) you're running the latest MK3 firmware and 2) using the latest PRUSA slicer software.

Q: Did you do a full calibration from the ground up? If not, take the 20 minutes to do this (with the sheet of paper process).

Also, what filament are you using? Ideally you would be trying this with Prusament or Prusa filament, just to eliminate another variable. But if not, note that different filaments may use very different temperatures. For instance Prusa PLA uses 215, however Hatchbox PLA specifies 180-210. I see people printing Hatchbox all the time at 215 because they never read the box and think all filament is the same.

I think at this point you're doing everything right - I am suspicious of your nozzle, I don't think you're getting the proper flow. Even your first outside loop before the print is not printing correctly. I wonder if your nozzle is clogged up? PETG uses a higher temp than PLA; If there was some PETG in the nozzle when you unloaded the PETG filament and then you a) cooled down completely or b) lowered the nozzle temp to 215 (or lower for other filaments) when loading the PLA then you could have some PETG remnants in there jamming things up and affecting flow. Two things I would try is:

  1. If you have a spare nozzle, swap it out. (Note that the nozzle needs to be heated - search PRUSA site for instructions).
  2. Do a "cold pull" - ideally with filament specifically for this (I think its a type of nylon) but I think you can do it with other filaments as a second choice. (Again PRUSA gives advice on this).

As a last resort, perhaps there are some calibration factors in the firmware that are corrupt and/or not resetting. I believe there's a way to do a factory-reset that deletes all calibration info (but I'm not positive here so do some research). If there is I would to a factory reset and start over.

There's really no magic to this physically working correctly so it has to be something simple at this point.

And yeah PETG should come with some warning labels. However I printed dozens of COVID19 headbands in PETG and dozens more in PLA and I will say that the PETG is noticeably a) stronger and b) more flexible, although its "stringy". I won't print it on my MK2 because if I ruin the bed it's major surgery, but on the MK3 I switch between it and PLA no problem - again I use Windex on the sheet before PETG and I use the smooth sheet. (It should be fine on the textured sheet but that sheet does have more surface area so I'm a bit more nervous about that).

Good luck and keep us updated.

 

 

...
Posted : 27/04/2020 11:34 pm
Matt Boyer
(@matt-boyer)
Estimable Member
RE: PETG adhesion woes
Posted by: @mckeanke

Hi all.

Im at the end of my rope with this stuff, i switched to PETG for printing these face shields because people say its easier to sanitize but i just cant get it to print well to save my life. Thanks in advance.

Don't leave us hanging.  Have you printed successfully?  My money's on the clogged nozzle fixing the PLA problem and suspect filament for the PETG problem.  Outstanding breakdown above. I'm sure you'll be up and printing shortly.

Posted : 30/04/2020 12:14 am
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

@smoking_rubber

Haha, sorry about that 🙂 honestly I was pretty put off after switching the filament and bed back and still seeing issues... I played around with it last night, and I think I got it working!

I actually started a couple prints with PETG temperature settings with the assumption that there were PETG particles clogging the nozzle. And actually, after a few first layer calibrations, suddenly the extruded globs stopped, and I was back to consistent flow with my PLA. I did my first successful print in quite awhile finally last night.

I think you guys may be right about the PETG filament I bought. It did seem like, no matter what I did, it kept coming out in globs, very inconsistent. I can try to order some Prusament PETG and see if I get some more consistent results. I'm a little miffed that I can't figure out this other filament, since I bought several rolls 🙁 but what can you do.

One other thing, this is perhaps totally off on a tangent. I noticed last night while observing a first layer calibration on the textured sheet (I did get PLA to adhere to it as well, BTW) that the Z axis seemed off-balance, by which I mean that, as the gantry moved to the right, the extrusion seemed ever so slightly more squished. I notice it on the textured sheet, and maybe a tiny bit on the smooth sheet. Is it possible I have a bad sheet? I did notice that the right side Z axis had a tiny bit of up and down play, not much but noticeable. The left side had a tiny bit but I had to apply more force, if that makes sense? Anyway, maybe this is normal, I don't know, but I think I at least have my printer back for now.

Posted : 04/05/2020 1:53 pm
Matt Boyer
(@matt-boyer)
Estimable Member
RE: PETG adhesion woes

Up and down play isnt useful at all.  Go through it and tighten it up. That will effect 1st layer for sure.

 

Posted : 04/05/2020 2:15 pm
Kate
 Kate
(@kate-4)
Active Member
Topic starter answered:
RE: PETG adhesion woes

@smoking_rubber

Well I guess what doesn't make sense about it is, why isn't the firmware detecting this? I did a proper Z axis calibration, and it's not picking up any irregularities.

What do I tighten to fix play between the axis screw and the threaded piece? That's where I see the play. And it's very slight, maybe it's not even an issue, but I don't know how to measure it.

Posted : 04/05/2020 3:33 pm
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