Thanks Nick. I'll give it a try.
Here are my conclusions so far:
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.
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.
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.
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.metalmuncher wrote: ↑Tue Sep 21, 2021 3:17 pmRegarding 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.
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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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.
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 ..... 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.
PS - Anyone want to buy two unused reels of Eryone PETG?
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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.
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