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I was just shopping for filament, and saw some glowing claims about PETG being as easy to work with as PLA, but as strong as ABS, and less brittle. Anyone know if that's actually true, or what the tradeoffs are?

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PETG is great stuff to work with. It is stronger than ABS also. It prints slower than ABS and PLA. The formulas vary quite a bit from vendor to vendor. I have used 3 brands, and each of their properties vary.

From my experience you do have to be careful with moisture. You'll be able to tell you have moisture in your filament if you start hearing a slight hissing and popping and an increased number of structural zits on the object. Moisture will also increase the problem listed in Mark's post below regarding the accumulation of filament on the nozzle.

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    $\begingroup$ I absolutely agree with you on all points, @Asa. However, be careful about making subjective recommendations about products, as that is generally frowned upon in the Stack Exchange community. In this case, you could try to describe the difference between different kinds of PETG based on their properties rather than simply saying that one is "better and cheaper" - if you can! (Also, adding a reference that says the subjective opinions for you could help argue in such cases.) $\endgroup$ – Tormod Haugene Jan 21 '16 at 6:20
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    $\begingroup$ Thanks for comment and I will make shure I put more substantive information. In my replies. $\endgroup$ – Asa D DeBuck Jan 21 '16 at 22:55
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    $\begingroup$ The post is now much better. Thank you for taking your time! $\endgroup$ – Tormod Haugene Jan 22 '16 at 8:01
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I have never used ABS, because I have a young child at home and no ventilation system (just to be safe). I have however used PETG, a crystal clear brand competitively priced on AMA-ssive online retailer, I loved it and will probably only buy it in the future.

Advantages Noted:

  • There is no odor I could detect

  • It is remarkably clear, like glass using a large nozzle (1.2) and layer diameter.

  • It flexes without breaking I'm guessing what seems like about 10-15% more than PLA. In other words if I print a large circular ring I can squeeze the ring about 10 to 15% farther without the ring cracking or breaking.
  • The material itself is more dense, identically printed items have more weight to them and feel sturdy.
  • It has a higher glass transition temperature

Disadvantages noted:

  • It's a little more expensive, but not prohibitively so (like carbon fiber).

  • It requires a higher printing temperature, so uses more power.

  • I havent perfected my retraction settings, and I have read others having similar issues with excess stringing. IOW it oozes more than PLA.

  • Switching between this and PLA requires extra care and time to ensure the nozzle is clear. I guess that is the same with any other alternate material as well.

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PETG is great, but definitely not as easy to print as PLA. However the advantages of higher impact resistance, temperature resistance and longevity make it superior to PLA for parts that require those properties. ABS is even harder to print than PETG and has worse strength and layer adhesion so no reason to bother with it in my opinion.

I print PETG at 80°C bed temp on PEI bed material, with 250°C nozzle temp. At first I was trying my old BuildTak bed material and it works at 40°C but the base of my parts was warping up some, it still worked but they didn't come out flat.

If you raise the temp on BuildTak to 80°C bed then the PETG permanently bonds to the BuildTak and rips up pieces of it upon removal.

PEI at 80°C keeps the base of printed parts perfectly flat (up to a certain part size/thickness) and has good adhesion and release properties with no wear showing on the bed after many prints.

If your parts are 100% infill and over about 3/4" (20 mm) tall you may still have problems with the base not ending up completely flat. In such large rigid parts the upper area that does not stay properly heated through conduction from the bed will shrink some and pull the lower sections up with it. Lower fill density like 50%, 20% help with this problem.

PETG build up on the nozzle was a real problem for me until I got a silicone sleeved hotend, E3D is the only one who makes them that I know of right now, but I am sure there will be others shortly. This completely fixed the problem of filament sticking to the hot nozzle and later being deposited as black charred blobs.

Another thing to consider is moisture, after even a day in high humidity PETG absorbs enough moisture to undergo hydrolysis upon extrusion at 250°C and become very brittle. To avoid this I use a conventional food dehydrator with the plastic being fed from inside, you can lookup designs on Thingiverse.

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In addition to what @AsaDeDeBuck said, PETG is also more flexible than PLA, and less stinky than ABS. Furthermore, some PETG variants like to accumulate on the nozzle (particulate build up) and then char a bit before being deposited at some random spot on the object.

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    $\begingroup$ I've experienced this accumulation of material on the nozzle also on my first builds with PETG. But after raising the temperature to 260 degrees and the print speed to 70 mm/s it never happened any more. Of course I only have experience with one particular type of PETG (Real-Filament). $\endgroup$ – Cees Meijer Jun 13 '16 at 20:00
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I love PETG. When I first started I always used ABS because I thought it was the best and didn't see the point in using PLA. However, after a few years of playing around I no longer use ABS. I use PLA for when I am testing and PETG when I want to print something that will be used, ike parts or models.

PETG is a little more expensive, however worth it, as it is strong and easy to use. I normally print at 220°C on the nozzle and 80°C for the bed.

PETG has more flex to it so when you are printing parts it is less likely to break under pressure like ABS.

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