PETG lifting up on large prints

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psd
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Joined: Tue Mar 08, 2016 9:09 pm

PETG lifting up on large prints

Post by psd » Mon May 01, 2017 8:54 pm

Hello,
I have my PETG settings and calibration all dialed in and I am printing small objects without problems.

However, when I start printing larger objects it seems the first layer doesn't bond well and when the head passes over the previous filament it lifts it and starts collecting globs on the print head.
I have tried lowering the bed height (is there a simpler way to move it down by .02 at a time than just re running the M2EZ Adjust software and resetting starting point each time?)
its strange because for smaller parts I don't have this issue. Bed is leveled and machine calibrated.

Is this a problem with:
PETG not sticking down enough?
Bed height too high?
Under extruding?

video of disaster: https://www.dropbox.com/s/13fr8y3d38g9e ... g.m4v?dl=0
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

Phil
Posts: 214
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Re: PETG lifting up on large prints

Post by Phil » Mon May 01, 2017 10:28 pm

What is your bed? Kapton tape on glass? Is it possibly not clean enough?
Off hand, it appears your initial gap between bed and nozzle is too large. The threads of filament appear more round than they should be if they were being squished enough. You might try adjusting your Z-axis knob to reduce/fine tune the gap as you are printing. It only takes a 'click' or two to really squish the output against the bed.

psd
Posts: 203
Joined: Tue Mar 08, 2016 9:09 pm

Re: PETG lifting up on large prints

Post by psd » Mon May 01, 2017 10:44 pm

thanks Phil,
I am printing on PEI.

So you say while printing try to adjust the knob and see if I can squish the filament more?

thanks!
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

psd
Posts: 203
Joined: Tue Mar 08, 2016 9:09 pm

Re: PETG lifting up on large prints

Post by psd » Tue May 02, 2017 4:09 pm

OK, so I have turned the z-axis knob a few clicks when laying down first laye, and it flattens nicely and bonds to plate nicely,
then I leave the large part printing and inevitably it fails after about 20 layers or more, the nozzle gets covered with material and the extruder jams.

Not sure what I need to do.

I am guessing that as Jules says that PETG needs to AirPrint, so the layers after the first should be higher than the first, maybe the nozzle is too close and therefore it drags against material and picks up stray hairs, (maybe it is too far away and the hairs are being created due to this) not sure where the failure is happening.

Is there any way I can dial this in more precisely to check?

How can I play with heights of 1st layer and subsequent layers?

This only happens on large prints and not on small ones. Very puzzling, my bed is level.

This has happened to me many times in the past as well.

Is the M2 able to print large prints in PETG well?

this particular print has very much support covering because its form is an inverted tray.

any help appreciated
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

psd
Posts: 203
Joined: Tue Mar 08, 2016 9:09 pm

Re: PETG lifting up on large prints

Post by psd » Tue May 02, 2017 9:03 pm

here is the large print attempt 5 (with translucent red PETG on PEI bed)

I got it to start well by squishing down first layer pretty nicely, even added an ABS acetone slurry to the PEI to ensure grip.

It printed well for about 2 hours, I left and when I came back it was air printing with nothing coming out of the nozzle and some raised defect areas on the rear.

what can I do to have a stable large format print????

https://www.dropbox.com/s/sjkle5crcqy01 ... p.m4v?dl=0
Attachments
missprint.jpg
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

Phil
Posts: 214
Joined: Mon Sep 19, 2016 7:49 pm

Re: PETG lifting up on large prints

Post by Phil » Wed May 03, 2017 9:05 pm

psd wrote:what can I do to have a stable large format print????
I have had some materials let loose of the bed, but only on tall, skinny parts. Your broad, flat part should not be an issue. Two possibilities I can think of: Your bed is not clean; Your nozzle is clogged.
I have rarely had a problem with PETG sticking to clean PEI. Some people scuff the surface with fine-grit sandpaper to increase adhesion. I always clean mine with acetone and/or ammonia solution, but have never sanded it.
I use a torch to burn-out a clogged nozzle. The technique has never failed me.

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zemlin
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Location: Indianapolis, Indiana

Re: PETG lifting up on large prints

Post by zemlin » Mon May 15, 2017 5:52 pm

The surface of your PEI looks like a mess. Is it clean?
Give it a good wipe-down with acetone when it's cool. I have zero issues with PETG lifting on PEI, and I have printed full-bed parts.

psd
Posts: 203
Joined: Tue Mar 08, 2016 9:09 pm

Re: PETG lifting up on large prints

Post by psd » Mon May 15, 2017 6:20 pm

I usually print on a clean super perfect PEI surface. In the photo above I was trying with and ABS Acetone slurry to see if I can resolve.

I am finding issues with PETG on large areas which never were an issue months ago.

There are a few things happening:
A. very first 1-2 seconds of print don't seem to come out as abundantly as needed and don't stick down as well.
next few seconds print well.

B. there is usually an area of the print where there is a hiccup and the print makes a blob or upward hair. this blob is then picked up later and exponentially gets worse.

C. sometimes there is a print that begins in one direction then backs up and goes in the other direction, when this happens it frequently pulls up the thread.

I am not sure if my gap is too much or too little, I guess I need to experiment more.

Wondering if my settings need some help......

I just bought an MI6 plate and applied a PEI sheet and having trouble printing large scale on that too......


Do you think I need an enclosure?
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

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ednisley
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Re: PETG lifting up on large prints

Post by ednisley » Mon May 15, 2017 8:25 pm

psd wrote:Wondering if my settings need some help
Overall, the symptoms suggest the nozzle moves too fast on (at least) the first layer: PETG must print slowly.

I ooze the first layer at 15 mm/s onto a 90 °C platform and the parts stick like they were glued (*). The first layer is 0.25 mm thick, just like all the other layers, with no squishing or whatever. That's achingly slow compared to what everybody else seems to use, but it produces great results and, hey, I'm not in any particular rush to get failed prints.

(*) Which they are: hair spray on glass. The parts stay firmly affixed until the platform cools to room temperature, whereupon they free themselves and lift off without any drama at all.
very first 1-2 seconds of print don't seem to come out as abundantly as needed
That suggests the skirt extrusion needs more plastic. I run three loops or 15 mm of filament, whichever is greater, to get the hot end properly pressurized before starting the actual part.

psd
Posts: 203
Joined: Tue Mar 08, 2016 9:09 pm

Re: PETG lifting up on large prints

Post by psd » Mon May 15, 2017 9:20 pm

thanks Ed,
do you mind posting your settings?
I am curious what I have to change to have the first layer at 15 mm/s onto a 90 °C platform and the parts stick like they were glued (*). The first layer is 0.25 mm thick, just like all the other layers, with no squishing?

also I do print skirt with 3 loops, its usually the first loop of the skirt which causes the problem, sorry for the confusion.


btw. another issue when I tried to print with raft was that first few layers of raft went well, and middle of raft became a hairy globby nightmare.....
- peter,

innovative product designer and tinkerer

www.petersolomondesign.com

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