PETG or not PETG?

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philipy
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Re: PETG or not PETG?

Post by philipy » Mon Aug 23, 2021 2:56 pm

Full marks for perseverance Rik. :D

Both of those look OK-ish but still a lot of cleaning up needed, not sure it is giving overall better results than PLA though?

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Re: PETG or not PETG?

Post by Nickclarke » Mon Aug 23, 2021 2:59 pm

A hairdryer on hot or very careful use of a heat gun gets shot of all the hairy bits, you could try printing a temperature tower to get ideal heat setting...

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Re: PETG or not PETG?

Post by ge_rik » Mon Sep 20, 2021 12:20 pm

Nickclarke wrote:
Mon Aug 23, 2021 2:59 pm
A hairdryer on hot or very careful use of a heat gun gets shot of all the hairy bits, you could try printing a temperature tower to get ideal heat setting...
Thanks Nick. I'll give it a try.

Rik
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Re: PETG or not PETG?

Post by ge_rik » Mon Sep 20, 2021 12:47 pm

I've now finished my first complete model with PETG. It's taken a while, firstly because I've been busy with non railway related projects (and socialising) and secondly because it took me quite a while to experiment with adhesives and solvents.
IMG_2181.JPG

Here are my conclusions so far:

Bed Adhesion
PETG sticks to the print bed like the proverbial to a blanket. I use a layer of Pritt on the bed, not to help with adhesion but to help with the removal of parts. I coated the bed with a thin layer of Pritt several weeks ago and haven't needed to replace or add to it.

Stringing
I've reduced stringing by lowering the print temperature and reducing the fan speed while printing, but I've not eliminated it. As a consequence, finer details like rivet and bolt heads tend to get gummed up and even with Nick's tip about the hot air gun, are tricky to clean up.
IMG_2176 (1).JPG

Joining parts
As indicated above, I really struggled to join parts together. Superglue didn't! PVC Pipe Weld worked OK when the two large surfaces were joined but was useless with parts with a small surface area. Revell plastic glue didn't make any impression but eventually, I discovered Plastic Weld (Methylene Chloride / Dichloromethane) worked, but it takes a while to harden off and so increases construction time quite markedly compared with PLA and thick Superglue.

I've not yet tried painting this model, but some previous test pieces seem to accept paint quite well.

I don't have problems with excessive sunny temperatures (yet) in this part of the UK and I've been reassured that the biodegradation of PLA won't be an issue (certainly in my lifetime), so I'm not yet convinced that PETG will replace PLA as my filament of choice. Unless, of course, I make a major breakthrough with stringing and joining parts.

Rik
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Re: PETG or not PETG?

Post by philipy » Mon Sep 20, 2021 1:06 pm

Thanks for the update Rik. I've always doubted that PETG would be worth the extra hassle, and atm you seem to be confirming my suspicions.
Having said that, the wagon looks pretty good overall.

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Re: PETG or not PETG?

Post by metalmuncher » Tue Sep 21, 2021 3:17 pm

Good to see the results of your experiment, I think I'm in agreement with Philipy regarding the usefulness of PETG for models. I do have a roll of it, but haven't really had a good reason to use it yet.

Regarding the stringing, I've seen that excessive stringing can be a result of the filament taking up water, it might be able to be reduced by drying the filament prior to use. Then again, I think PETG is just more naturally prone to strings, it might make little difference.

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Re: PETG or not PETG?

Post by ge_rik » Tue Sep 21, 2021 3:42 pm

metalmuncher wrote:
Tue Sep 21, 2021 3:17 pm
Regarding the stringing, I've seen that excessive stringing can be a result of the filament taking up water, it might be able to be reduced by drying the filament prior to use. Then again, I think PETG is just more naturally prone to strings, it might make little difference.
Thanks for the suggestion.

The reel was vacuum sealed in plastic with silica gel bags before I used it, so I think it would have been fairly dry. The stringing was worst before I reduced the print temperature and the fan speed. I might try tweaking both again to see if I can reduce it further but, as you say, PETG does seem to be prone to stringing.

If I can't improve on it, I might try drying it out in the oven before the next print run to see if it makes a difference.

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Re: PETG or not PETG?

Post by Trevor Thompson » Tue Sep 28, 2021 9:51 pm

Rik

That is all very interesting.

Particularly the issue of gluing things together. How you glue things is really an important consideration. It is partly why I started to use ABS - where the solvent glue is acetone. I had acetone in the garage left over from boat repairs.

The print quality on the wagon seems OK.

Trevor

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Re: PETG or not PETG?

Post by ge_rik » Sat Oct 16, 2021 3:16 pm

OK
I've now reached the end of the reel of PETG and reached a conclusion.

I have decided to abandon PETG in favour of PLA+

Here's one reason why .....
IMG_2287.JPG
On the left is the sandbox for my Skylark loco printed with PLA+ and on the right is the same sandbox printed with PETG. OK, maybe I should persevere with PETG to see if I can improve on the settings, but I have come to the conclusion that for fine detailed work and small parts such as these, PLA wins hands-down.

It wasn't until the PLA I'd ordered turned up that I discovered it was PLA+, so I used the default settings in Cura for it and this was the first item I printed. Not sure any further tweaking of the settings will improve it, but you never know.

The second object I printed with PLA+ was the smokebox door handle - which is only 8mm in diameter and took 59 seconds to print. I don't think PETG would have produced anything but a blob of plastic.
IMG_2285.JPG

Rik
PS - Anyone want to buy two unused reels of Eryone PETG?
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Re: PETG or not PETG?

Post by -steves- » Tue Nov 30, 2021 11:21 am

I also purchased some Petg some time ago but have only just got around to trying it. I thought I ought to as I have 3 rolls of the stuff.

Anyway, my first prints were pretty awful, so I did a bit of reading and found some recommendations on how to print it. My main issue it seems was speed, I was printing it way to fast, hence loads of stringing. With a mixture of speed, heat and retraction settings I am now getting very passable prints with it, all be it rather slow compared to what I am used to.

Not much detail on these, but here is a seat and some R1 check rails I printed with it and I am more than happy with the outcome. Hopefully the check tails won't warp like they did in the summer when I used some PLA ones.

So, food for thought, settings can make that difference, or at least they did for me.
Attachments
16382711847294114355836021609984.jpg
IMG_20211130_102951.jpg
IMG_20211130_103000.jpg
The buck stops here .......

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Re: PETG or not PETG?

Post by ge_rik » Tue Nov 30, 2021 12:34 pm

That's useful to know. I still have a reel of PETG, so I might give it another try when my PLA runs out.

Rik
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