PETG is an immensely popular 3D printing filament, widely used for its high strength, relative flexibility, and temperature resistance compared to the ever-popular PLA.
PETG provides the strength of ABS parts with even more flexibility and a printing experience more akin to the familiar and easy PLA process while being food safe too. It’s perfect for practical prints that need a little bit more give before breaking than PLA can offer. As a result, it displaced ABS as the second most popular 3D printing filament on the market.
But what exactly is PETG? Are there other materials like it? And how the heck can we get this sticky mess printing well? We’re going to answer all those questions and more, so let’s get started with the basics.
What is PETG?
PETG stands for glycol-modified polyethylene terephthalate – similar to PET, which you may know from plastic water bottles – but an additional glycol is included in the polymer structure, hence the letter “G” after PET for “glycol-modified”. The result is a clearer, less temperature-sensitive material that’s easier to extrude than PET. However, it does have the unfortunate side effect of changing the recycling process. Although PET is widely recycled, PETG is not; the subtle differences between these materials create a troublesome contaminant in recycling facilities.
Still, it’s an excellent filament choice for printing objects that need to be sturdy, smooth, and exhibit low shrinkage. It’s also popular because PETG is considered food safe, but you should still read the fine print on any spool you buy to be sure.
Of course, it’s not all good news: PETG isn’t great at bridging because it’s super sticky. However, this does mean it has great layer adhesion. It’s also more prone to both heavy stringing and air-moisture absorption. But still, if you need a high-strength material and PLA or ABS just won’t cut it, standard PETG is a great option.
PETG Variants
Though PETG is perhaps the best known in its family of filaments, it’s a variant of PET plastic – an exceedingly common material often found in water bottles and other single-use plastics. There are more variations of PET in filament than just the familiar glycol-added version, and all of them share many properties but with some important differences.
- PET: Polyethylene terephthalate (PET) is one of the most commonly used plastics in the world and the unmodified parent of PETG. It melts at 260 °C and has the most potential for recycling – local program permitting. PET struggles more with layer adhesion compared to PETG.
- rPET: Exactly the same as its base material, PET, but this filament gets a lowercase “r” in its name because it’s made from recycled PET. Previously recycled materials may not be recyclable again, at least not with the same results.
- CPE: Some brands choose to differentiate PET products with a moniker. Fillamentum and UltiMaker use “CPE” because it stands for copolyester.
- PETT: Polyethylene co-trimethylene terephthalate is slightly more rigid than PETG because it isn’t modified with glycol. It isn’t very common in 3D printing but was popularized by Taulman T-Glase.
Pros & Cons
PETG is a good all-around material but stands out from other filaments given its flexibility, strength, temperature, and impact resistance. This makes it ideal for objects that might experience sustained or sudden stress, like mechanical parts, 3D printer parts, and protective components.
Additionally, since the material is considered food safe, it can be a good option for objects that will encounter food or drink. Just check your particular material to make sure first.
There aren’t many disadvantages to printing with PETG. Of the few, PETG is more prone to scratches and scuffs than PET is. It’s also true that, despite being comparable to PLA for its ease of printing, many makers do find PETG a bit trickier to print than other materials.
It certainly has its quirks, so you’ll need to find the “sweet spot” for your print settings. For example, you’ll likely find more clumping at the nozzle and stringing compared to other filaments.
PETG is also hygroscopic. If left out, it will absorb moisture from the air, which causes all sorts of problems that mostly culminate with a disappointing failed print. Be sure you keep PETG stored in a dry environment, whether it be a DIY or purchasable dry box.
PETG vs PLA vs ABS
PLA (or polylactic acid) is a thermoplastic material and is the most common 3D printing filament. PLA filament is especially easy to 3D print and can be produced from renewable materials. There are many different colors and varieties, and almost every filament producer on the market has a version of PLA. From additives like metal powders, hemp, coffee, or wood, PLA is unbeatable when it comes to variety, even compared to PETG.
Like PLA, PETG is excellent for low-warping, showing only minor shrinkage during cooling. While PETG may exhibit better layer adhesion than its competitor, it may adhere to itself too well, leaving you with more frequent nozzle clogs and stringing.
When it comes to printed parts, PETG is typically more durable, stronger, temperature resistant, and can handle stronger impacts, although it’s more prone to scratching and surface damage compared to PLA. Both materials are considered food safe, although proper precautions are needed regardless. ABS, on the other hand, is not recommended for prints that may come into contact with food.
Acrylonitrile butadiene styrene (better known as ABS) – the other material option that you’ll frequently see – is cheap, durable, lightweight, and easily extruded, making it great for 3D printing. While ABS and PETG are both stronger and more durable than PLA, PETG can offer some flexibility that would snap ABS in half.
There are also come key disadvantages to using ABS filament. For one, a heated build platform is an absolute must, and a printer enclosure is highly recommended to prevent the print from cooling too quickly, leading to warping. Another drawback is the intense fumes that come from printing. They can be dangerous for people (or pets) with breathing difficulties.
The main advantage that ABS can offer is its solubility in acetone, which is great for creating an unbelievably smooth finish. If you’re going for a fresh-off-the-injection-mold look with PETG, you’ll have to opt for some manual methods.
Print Settings
The ideal temperature settings for PETG filament will vary depending on the specific filament and manufacturer. Usually, the material is quite forgiving and can be printed at a wide range of temperatures. Still, there’s a general range of properties that you can expect from every spool of this filament. The print temperature will usually range between 220-250 °C, while manufacturers will also recommend a print bed temperature between 50-80 °C.
A heated bed is not a must for printing with PETG, but it’s certainly a big advantage – especially when it comes to avoiding warping on the bottom of large-scale prints. Although you can attempt the usual hairspray or blue tape tricks, some makers claim that these won’t work with this filament. A glass print bed is great for releasing PETG after cooling, but mind the easy release during your print and make sure your bed temperature is high enough to keep it stuck.
If the manufacturer doesn’t provide a recommended temperature, start with a temperature of 80 °C and see if the first layer sticks to the bed. Like most things involving 3D printing, finding what’s best for your setup will take patience and the willingness to experiment.
Troubleshooting
How do you know if you’re using the best print settings for your PETG filament?
There are a couple of ways to ensure more success and higher quality when printing. First, take a good look at the first layers. If the extruded material doesn’t feel a little greasy, you’ll probably want to raise the temperature a bit. Also, you should always start with a low print speed of around 15 mm/s and work your way up. Printing at this low speed will help you sort the other settings like temperature out, after which you can start increasing it.
Note that printing at the upper end of the temperature range mentioned above for prolonged periods will destructively degrade the PTFE lining in a PTFE hot end. If you plan to print PETG a lot, consider upgrading to an all-metal hot end if you don’t already have one.
Filament Options
Once you’ve settled on using PETG for your print, you’ll need to choose which blend to pick up. There’s a lot on the market, but if you’d rather not slog through the web to find a good one, we’ve narrowed the choice down for you. Here are some great options:
- Eryone: This mid-range PETG filament is a great go-to pick for everyday printing with 10 color options to choose from. We’ve found it to print consistently with good dimensional tolerance.
- FormFutura: This brand offers both a transparent, high-gloss PETG called “HDglass” as well as ReForm rPET, which is made from recycling excess material from the production of HDglass. Despite the recycling, the filament prints easily – it’s almost PLA-like.
- Prusa Research: If you’re after a filament with an exceptional tolerance or large color selection, Prusament PETG may be worth a look. Being a fan favorite, there’s lots of support online if you run into any issues while printing.
License: The text of "PETG Filament: All You Need to Know" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.