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PETG Filament - Overview, Step-by-Step Settings & Problems Resolved

Tom's PETG Benchy

(Image courtesy of Tom's Filaween review of our Orange PETG at toms3d.org)

In this guide you'll learn why PET-G filament is fast becoming a favorite. We'll explain what it is and what's it's used for.

Then we'll cover the best practices to printing with it perfectly, including how to avoid any pitfalls when using it. 

Is PLA or ABS not cutting it anymore? Perhaps you need something more durable, or something that can handle higher temperatures than PLA, but is easier to print than ABS?

After reading this guide you will be confident in getting the best possible prints using PETG and able to advise on when best to use this great material.

What is PETG Filament?

PETG is a durable copolyester (a combination). The PET stands for polyethylene terephthalate (think plastic bottles) and the G means it’s been glycol modified for extra durability.

One great thing about PETG is that it is very recyclable so as long as the material is processed correctly, it can be repurposed fairly easily. The flip side of that however, is that PETG is (mostly) non-biodegradable, meaning it isn’t broken down by bacteria or living organisms. This, depending on how the plastic is being used, can be seen as a pro or a con.

And what is PETG Filament used for?

In short this is a really tough material, it's extremely durable and prints without odour. Once you’ve dialed in the correct print settings, it prints nicely too. Users report similar finish quality to PLA. 

Here are the main benefits to printing with this material and common PETG filament properties:

  • Very durable, it’s more flexible than PLA or ABS, but also a little softer. You’d have a hard job breaking it in half, so if an ‘unbreakable’ case or enclosure is what you need, PETG trumps pretty much everything (except, Nylon 12).
  • It has very low shrinkage, and therefore no warping. Ideal for printing big stuff.
  • PETG is also very strong, it’s not brittle but can be scratched more easily than ABS which is harder.
  • PETG plastic makes a terrible support structure, because it sticks so well. But because it sticks so well, layer adhesion is fantastic, so prints come out strong.
  • It sticks well to the print bed too, so be careful when you’re removing it after printing.
  • It has a great chemical resistance, along with alkali, acid and water resistance.
  • Odourless when printing.

Typically Polyethylene filament is supplied in a range of translucent colours, and prints with a nice glossy finish.

It makes it ideal for printing anything that needs to be shatterproof or translucent. Many are taking the leap from using PLA or ABS to just using PETG.

 

Click here for our filament recommendation

 

PETG has quickly become an extremely popular material due to its advanced properties, ease of printing and colour range. It usually is the next step in material experimentation after PLA due to its increased temperature resistance and toughness, and it can be printed on most printers, from desktop to professional.

Compared to other popular, slightly more difficult materials to print (I’m looking at you, ABS!), PETG can provide a great solution to prints that need to be functional. One of these is high impact resistance, meaning it can be dropped, hit and generally take a bit of a battering without breaking. If you’re not convinced, try and break a plastic water bottle and see for yourself how durable this material truly is!

Tom's PETG Weighted Strength Test 

But what does this mean for practical applications? What objects are ideal for you to be printing with PETG?

Because of how easy PETG is to print nowadays, there aren’t many situations that we would turn down the material but there are some solid examples of when we would say “ah yes PETG is the one to use”. The main argument for PETG is that it is strong and sturdy and has very low shrinkage - meaning you can get very accurate, large prints. It also comes with good heat and chemical resistance, making it great for the following projects: 

  • Medical items 
  • Engineering pieces 
  • Electric cases 
  • Functional items 
  • Jewellery 
  • Models with moving part

But we don't recommend printing everything with it, due to it's flexibility (which isn't always desirable, depending on your application)

What's PETG Glass Transition Temperature?

It's 80C - so that's worth taking into consideration when deciding what material to make your next project out of. This is significantly lower than ABS's Tg of 105C, but higher than PLA which is as low as 55C. 

Below is one of our customer's applications, which is a bumper for his micro quadcopter. As you can imagine, the bumped needs reasonable  stiffness to resist impacts, but yet plenty of durability to absorb the force of any severer crashes. 

We think, this is a perfect example of the types of prints you may wish to print with this material. Essentially, it's a great addition to your existing 3D printing filament arsenal. 

PETG_filament

Great example of the practical use for PETG's durability. Crash bumper by Otto.

Here are a few data stats about PETG. Please note, these stats are from our own PETG and are not representative of the average:

  • Density of 1.27g/cc, that’s just higher than PLA and about 20% more dense than ABS.
  • Rockwell hardness of R 106, which is pretty high for PETG. (Our ABS, which is very hard is rated R 110).
  • Our raw pellets for PETG have been GREENGUARD INDOOR AIR QUALITY CERTIFIED®. This is a certification under license from the GREENGUARD Environmental Institute (GEI), who are an independent, non-profit organisation that test low-emitting products and materials for indoor environments.


 Now you know why you’re likely to go for PET-G filament, vs the more traditional materials. It’s nice to print with and produces excellently tough prints that will last.

Let’s look at how to get the best results from this underutilized filament, so that you can spend the least amount of time setting up, and the more time producing ultra-durable high use prototypes, models or end-use parts.

Tom's Screenshot PETG Review

(another screenshot from Tom's epic 90 second PETG review)

Here’s how to print PETG:

As with all 3d printing materials, you need to take note of the specific traits that material adheres to – which issues are caused by what?

This always saves head-scratching time when you run a material through your printer the first time, and the results aren’t quite what you expected.

This plastic is just like any other, you just need to adhere to the few best practices when printing and you’ll love the results.

Sometimes PET-G can take a little more setting up, fine tuning those filament settings. It's just slightly more particular than something more forgiving, like PLA. That's not to say it's hard to use, just perhaps a little more patience with the setup. 

But once you’re set up correctly, you’ll find printing with PETG a dream. No warp, odorless printing and great layer adhesion are just some of the excellent properties with printing this filament.

Be sure to use a high quality polyethylene filament and it’s likely you’ll just dial in your PETG temperature settings and you’ll be away.

 

Gap setting for PETG filament

 

However, as with any filaments there are some pointers to make the new transition easier.

Let’s look at how to get setup correctly, issues to look out for and our top PETG printing tips that’ll save you time troubleshooting.

PETG Print Settings

  1. We recommend printing our PETG settings at roughly 220C-245C depending on your extruder. The PETG bed temperature works best around 70-75C, a few degrees hotter perhaps for those first few layers.
  2. What's the best surface to print PETG on? Well in our experience, blue painter's tape works the best. A very old method of print surface but, if it ain’t broke, don’t fix it! PETG generally has no trouble sticking to your print surfaces. It can be a bit of a pain when it comes to bed adhesion - but not in the way that you may think! On standard surfaces, the material can stick TOO well! Removing your prints then becomes a tricky game of applying enough force to get the print off but not too much so that it ruins the print surface, or worse, the printer itself.
  3. This material doesn’t need to be squeezed onto your heated bed, you want to leave a slightly larger gap on the Z axis to allow more room for the plastic to lay down. If the extruder nozzle is too close to the bed, or previous layer it will skim and create stringing and build-up around your nozzle. We recommend starting off moving your nozzle away from the bed in 0.02mm increments, until there is no skimming when printing.
  4. The Fan: When setting your print cooling fan, the general rule is the less fan, the better the layers bond and the higher the strength - but the worse the finish will be due to stringing and poor overhang printing. The more fan, the weaker the bond (it will still be good just not great) but the better the finish on perimeters, top surfaces and overhangs. A good compromise is a range between 30% and 60% fan speed. If you have a part that has lots of bridging sections, it is recommended to have a higher fan percentage, for these sections, so you do not allow the molten material to sag too much before cooled. This is easy to set up as most slicers enable you to set a fan speed override for bridges.

 

PETG First Layers

 

PETG Red 1.75mm

These are some of Joseph Casha of 3D Maker Noob's prints in our Red PETG

 

This is the sort of thing you may choose different fan settings for different prints - so that you're set up optimally for what you wanted to print. Experiment to get a good idea for how the filament reacts with your printer's fan settings. 

  1. Print speed is worth mentioning. As with a lot of materials, PETG likes to be printed slow. Slower than 60mm/s is recommended to give the filament time to bond with lower layers and to be cooled sufficiently in overhangs and bridged sections. Any faster and quality and structural integrity may be compromised.
  2. One downside of printing with PETG is that it can end up gathering wayward pieces of filament during the printing process and can build these up to form little clumps of molten material. These little clumps can then be deposited on your print in unexpected places which will at best ruin the overall finish of your print, or at worst, disrupt your print, cause collisions or ruin dimensionally-critical areas. Fortunately, there are a few methods to avoid or reduce these imperfection: • Increase retraction to reduce stringing and leaking material • Enable the “wipe” setting • Under-extrude slightly, but not by a huge amount. 0.1-0.2% is a good starting point(this will also help with stringing) • Increase cooling fan speed (but as mentioned earlier, this does come at a cost of lower strength)

It’s likely you won’t have issues with all of these points, but as you can see – just like other 3d printing filaments, each material has its own set of traits to setup for.

Once you know the cause of each issue, and how to fix you’ll find the printing consistent time and time over.

 

Join the Institute of 3D Printing Facebook Group

Here's a quick rundown of PETG vs ABS:

  • PETG is more durable than ABS, but ABS is harder, and more rigid. 
  • PETG has a lower glass transition temperature, at 80C compared with ABS's 105C
  • ABS is approximately 20% less dense than PETG.
  • PETG won't warp like ABS might (if printed incorrectly) and is generally odourless. 
  • PETG is more chemically resistant, and so cannot be acetone smoothed like ABS. 

Here's a quick rundown of PETG vs PLA:

  • PLA is more brittle than PETG, unless you want to try to anneal it. 
  • PLA and PETG have very similar densities. 
  • PETG will need a heated bed, whereas PLA can be printed cold. 
  • Layer adhesion with PETG is typically unmatched, leaving very strong and durable prints. 
  • PLA prints supports easily to remove, whereas these are harder (but not impossible) to remove with PETG. 

 

TOP TIP: If you switch back and forth between PLA and PETG on your printer, beware that a nozzle that’s contaminated with PLA will not print PETG well - the PLA will interfere with bonding and the layers of PETG won’t stick together. If your PETG prints start out weak and crumbly for the first few layers and then become solid and strong for the rest of the print, contamination is the likely cause. To avoid this, when switching from PLA to PETG make sure you purge the nozzle with enough PETG to get rid of every last remnant of PLA from the printer’s hotend. It’s also a good idea to use a brim, skirt or raft so those risky first few lines aren’t part of your final prints.

 

 Check what rigid.ink is doing now

 

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