Well, This Happened

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FellCrustacean8
Posts: 7
Joined: Sun Jun 18, 2017 12:05 am

Well, This Happened

Post by FellCrustacean8 » Sun Jun 18, 2017 12:09 am

This was my first attempt at using PETG. I've only had experience using PLA before. I had no problems with bed adhesion or the first layer but later on my Benchy turned out like this. Does anyone have any idea of what is happening, or more, how to fix it? Image

Any help is appreciated! Thanks in advance.

LKM
Posts: 27
Joined: Wed May 24, 2017 9:05 pm

Re: Well, This Happened

Post by LKM » Sun Jun 18, 2017 6:04 pm

FellCrustacean8 wrote:
Sun Jun 18, 2017 12:09 am
This was my first attempt at using PETG. I've only had experience using PLA before.
It kinda looks as if you printed this with PLA settings?

What were your printer settings (particularly hotend temperature) for this print?

FellCrustacean8
Posts: 7
Joined: Sun Jun 18, 2017 12:05 am

Re: Well, This Happened

Post by FellCrustacean8 » Sun Jun 18, 2017 9:13 pm

I was printing at 250C for the first layer then cut it down to 240C for the others. The bed was at 54C. Perimiters at 60mm/s and infill at 130mm/s.

gertlind
Posts: 3
Joined: Mon May 22, 2017 12:55 pm

Re: Well, This Happened

Post by gertlind » Mon Jun 19, 2017 8:39 am

Try to print slower, i print PETg at 40mm/s, first layer 50%.

FellCrustacean8
Posts: 7
Joined: Sun Jun 18, 2017 12:05 am

Re: Well, This Happened

Post by FellCrustacean8 » Thu Jul 06, 2017 2:43 am

So I've been working on this problem for the past few days and it is still happening. I saw that the nozzle looked distorted at the tip so I replaced it, things are extruding smoother but now I'm getting thisImage
Image
This issue also is happening on PLA prints. I didn't notice this before because I haven't used it in the past 3 days before the initial post.
I also upgraded to a blower like cooling fan. The previous one died.

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Well, This Happened

Post by chumm » Thu Jul 06, 2017 6:39 am

My first thought seeing that would be that the nozzle is dragging across the print. This typically would happen if your Z steps per mm are off, so the printer tries to move up .2mm to the next layer, but because the steps are off it only makes it 1.8mm up and prints too close to the previous layer. This isn't a big problem at first, but once you're on layer 10 in that example you're printing at 18mm when you're supposed to be at 20, so there's way too much material and it's being dragged around. This could also be consistent with that benchy, which does look like it could be a bit short and gets progressively worse the higher it goes. That would also potentially cause issues with the nozzle like you had.

You can test this by taking manual control of your printer and moving the Z axis a determined amount, then measuring how much it actually moved. If the amount is wrong, you can fix it in firmware (though you'd probably want to try to figure out how this happened if it worked fine before).

Alternatively I'd just print something like a 10mm x 10mm x 30mm test piece and watch it carefully to see exactly where the point of failure is. If you can get a good pic if where it starts to fail that would be way easier to diagnose.

voyager
Posts: 4
Joined: Thu Jul 06, 2017 11:21 pm

Re: Well, This Happened

Post by voyager » Thu Jul 06, 2017 11:23 pm

Tom will ban me for saying this but, just print a calibration cube. :D

FellCrustacean8
Posts: 7
Joined: Sun Jun 18, 2017 12:05 am

Re: Well, This Happened

Post by FellCrustacean8 » Fri Jul 07, 2017 4:40 am

I got PLA printing well now. I made a couple of prints without any flaws. But now I see that the PETG is rising after it is extruded. It gains height and the nozzle smacks back into it, even on the same layer! I didn't know PETG would expand like that. Any clues of how to fix it?

voyager
Posts: 4
Joined: Thu Jul 06, 2017 11:21 pm

Re: Well, This Happened

Post by voyager » Fri Jul 07, 2017 1:10 pm

I never have seen PETG doing that. And again I suspect your Z steps are off. I think PLA reacts different in comparison with PETG. If I put a first layer of PLA on the bed really low you can see it being squash down, its laying down somewhat wide lines but it's fine, If I do the same thing with PETG it starts to get bubbly with small bumps in the brim etc.

So If you say that its expanding, that is the first thing that comes to mind. It to close to the previous layer.

Again please print a calibration cube to know for sure.

FellCrustacean8
Posts: 7
Joined: Sun Jun 18, 2017 12:05 am

Re: Well, This Happened

Post by FellCrustacean8 » Thu Jul 13, 2017 5:39 am

I figured out what caused it. For some reason on default settings cura was forcing way to much filament through. It was kind of odd. Considering it always worked fine before, there weren't any of the usual signs like extruder stepper motor stalling. But it was doing it to the extreme. I cut the extrusion down to 42% of regular speed and now it is working fine.

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