PETG or not PETG?

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ge_rik
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PETG or not PETG?

Post by ge_rik » Sun May 16, 2021 8:40 am

Has anyone had experience of printing with PETG?
Am I worrying unnecessarily about using PLA for outdoor models do you think?
I've tried printing with ABS with spectacularly poor results. I know Trevor is a great advocate and his models look great, but I just can't get the settings right on my printer.

PETG seems to offer many of the advantages of PLA (eg bed adhesion, lack of odour when printing) without the disadvantages (ie biodegradability).
https://www.simplify3d.com/support/mate ... uide/petg/

Thoughts anyone?

Rik
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Re: PETG or not PETG?

Post by ge_rik » Sun May 16, 2021 10:49 am

I've decided to give it a try. A reel is on its way. I'll let you know how I get on.

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Re: PETG or not PETG?

Post by metalmuncher » Sun May 16, 2021 10:54 am

Biodegradability is not something you have to worry about regarding PLA prints. Its only really biodegradable in industrial composting plants at high temperatures.

PETG has better heat resistance than PLA, which might be helpful for model that is a dark colour and gets direct sun so it heats up significantly. PETG is also a bit better when exposed to UV.

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Re: PETG or not PETG?

Post by philipy » Sun May 16, 2021 11:59 am

I've never tried PetG myself, aside from anything else I'm not sure how to glue it?

I've not had any real issues with PLA outside, my earliest PLA prints have been outside 24/7/365 for about 3 years. I did worry about it to begin with, but only had one problem that could be blamed on the weather ( the dog walking on a platform seat would break it whatever it was made of!). On my stately home, the high level decorative stone work is made in 4 or 5 pieces glued end to end. One of them for some reason decided to shrink and curve slightly and I have no idea why, they were all printed one after the other from the same reel and with the same settings! The building faces the afternoon sun, summer and winter.

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Re: PETG or not PETG?

Post by ge_rik » Sun May 16, 2021 1:10 pm

metalmuncher wrote:
Sun May 16, 2021 10:54 am
Biodegradability is not something you have to worry about regarding PLA prints. Its only really biodegradable in industrial composting plants at high temperatures.

PETG has better heat resistance than PLA, which might be helpful for model that is a dark colour and gets direct sun so it heats up significantly. PETG is also a bit better when exposed to UV.
That's useful to know (and reassuring) thanks

Rik
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Re: PETG or not PETG?

Post by Trevor Thompson » Tue Aug 10, 2021 9:48 pm

How are you getting on with it? Are you having more success than with ABS?

Trevor

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Re: PETG or not PETG?

Post by ge_rik » Wed Aug 11, 2021 7:25 am

Trevor Thompson wrote:
Tue Aug 10, 2021 9:48 pm
How are you getting on with it? Are you having more success than with ABS?

Trevor
Unfortunately, life has got in the way and I've not had a chance to do any modelling for around the past two months. So, nothing to report as yet. I managed to get back into the workshop yesterday, but am clearing a backlog of other jobs before firing up the printer again.

I'll let you know how I get on.

Rik
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Re: PETG or not PETG?

Post by -steves- » Wed Aug 11, 2021 7:17 pm

ge_rik wrote:
Wed Aug 11, 2021 7:25 am
Trevor Thompson wrote:
Tue Aug 10, 2021 9:48 pm
How are you getting on with it? Are you having more success than with ABS?

Trevor
Unfortunately, life has got in the way and I've not had a chance to do any modelling for around the past two months. So, nothing to report as yet. I managed to get back into the workshop yesterday, but am clearing a backlog of other jobs before firing up the printer again.

I'll let you know how I get on.

Rik
Yes please do let us know as I have been considering using PETG for the last couple of months myself, namely because I had sprayed two pieces of PLA+ in black and left the outside in the sun drying. When I got back to them a couple of hours later, they were "very" warped (about 6mm of warpage on a 2mm thick roof) and I had to throw them in the bin, reprint and respray. Never had it happen before, but that has definitely worried me.
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Re: PETG or not PETG?

Post by ge_rik » Fri Aug 13, 2021 8:04 am

Well, so far, so good. I've done a few small test pieces using the default settings for "Generic PETG" in Cura. However, although the parts have printed ok, research on tinternet suggests I will need to make some adjustments to those settings for larger pieces. The most significant seems to be reducing fan cooling to around 25% (some even suggest 0%) to help with layer adhesion. I'll try a few larger pieces and then let you know how I get on.

BTW, Steve. With thinnish plastic parts such as roofs, I usually paint both sides to discourage warping. As I understand it, a paint layer can shrink as it dries so if both sides are painted the shrinkage occurs on both sides equally. I've had that paint induced warping with plasticard so I imagine it will probably happen with most plastics. It sounds like PLA is actually stiffer than PETG and so such warping might be even more likely with PETG.

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Re: PETG or not PETG?

Post by Jimmyb » Fri Aug 13, 2021 10:47 am

ge_rik wrote:
Fri Aug 13, 2021 8:04 am
As I understand it, a paint layer can shrink as it dries so if both sides are painted the shrinkage occurs on both sides equally. I've had that paint induced warping with plasticard so I imagine it will probably happen with most plastics.
Rik
Rik, good point, and though I had not appreciated it with plastics, I do know this to be a fact with MDF, 6mm and thicker.

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Re: PETG or not PETG?

Post by ge_rik » Sat Aug 14, 2021 7:58 pm

OK - so, I'm still getting to grips with PETG.

The test pieces actually worked out better than the more recent 'proper' pieces. The default temperature for PETG in Cura (210C) was less than the temperature recommended on the spool (220-240) so I upped it to 225 thinking this would improve the quality of the printing.

In actual fact, this seems to have exacerbated the problems of stringing and blobbing which were much less apparent on the test pieces
DSCF0960.JPG

I tried using 'ironing' to improve the smoothness of finish on the final layer but it looks like I'll need to reduce the temperature as well
DSCF0964.JPG
Higher temperatures (and minimal fan speeds) are recommended to ensure good adhesion between layers. It seems to have worked on the roof section which was printed vertically, but as you can see there's a lot of stringing.
DSCF0962.JPG

Bed adhesion is not a problem. In fact, it's suggested that Pritt stick is used, not to enhance adhesion but to help with the removal of parts from the glass print bed. The printhead keeps getting smothered in filament - I'm told PETG is more like glue than plastic filament so I might invest in a silicone cover for the printhead.

I'll persevere with PETG (I've got two spools to work through) but I'm already beginning to miss the relative simplicity of PLA. Another issue associated with PETG is that it is hygroscopic, which means that once it's unwrapped, the spool will gradually absorb moisture from the atmosphere which adversely affects its ability to print reliably. It can be dried out in the oven (on a low heat) but it's beginning to feel like PETG is more trouble than it's worth!

Rik
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Re: PETG or not PETG?

Post by philipy » Sat Aug 14, 2021 8:12 pm

All very interesting Rik. Please keep us updated as you experiment further.

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Re: PETG or not PETG?

Post by Nickclarke » Sat Aug 21, 2021 11:51 am

PET-G all the way for me, stronger than PLA and just as easy to use. Great for making maching fixtures and jigs, patten making and all sorts of tooling applications. I made over a thousand face shields at the start of the pandemic and not one failure. I do not use cooling at all, with one exception, if the job has pinacles or thin projections that will not have time to cool without. In Simplify 3D the fan can be turned on and off layer by layer...

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Re: PETG or not PETG?

Post by -steves- » Sun Aug 22, 2021 7:59 am

Nickclarke wrote:
Sat Aug 21, 2021 11:51 am
PET-G all the way for me, stronger than PLA and just as easy to use. Great for making maching fixtures and jigs, patten making and all sorts of tooling applications. I made over a thousand face shields at the start of the pandemic and not one failure. I do not use cooling at all, with one exception, if the job has pinacles or thin projections that will not have time to cool without. In Simplify 3D the fan can be turned on and off layer by layer...
Now that is very interesting information. Thank you, looks like I will be giving PETG a go once I get through the 4 rolls of PLA+ that I have on the go :thumbup:
The buck stops here .......

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http://peterborough.16mm.org.uk/

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Re: PETG or not PETG?

Post by ge_rik » Mon Aug 23, 2021 2:51 pm

Gradually getting to grips with PETG. I keep tweaking the settings. The greatest problem seems to be overcoming stringing.
DSCF0976.JPG

It's surprising what a difference dropping the print temperature by 5 degrees makes
DSCF0977.JPG

I'm now working on the retraction settings to see if I can get an even neater finish.

Rik
PS - Dropping the temperature by too much leads to blobs - so it seems to be quite a fine window to aim for
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