PETG is an incredibly versatile 3d printing filament. From engineering prototypes to production-ready parts, polyethylene terephthalate glycol is one of the best all-around filaments on the market today. It can be difficult to print with though – Some of the issues I’ve run into with it include bed adhesion, stringing, and moisture. I’m here to share my lessons learned after a year of printing with PETG and to help you kick-start your journey into the world of PETG!
Why I chose to print PETG
You may be asking yourself – What are the actual benefits of using PETG over a more common filament, such as PLA? After all, PLA prints hold up well and are much easier to print than PETG. Here are the reasons I like PETG:
- The temperature resistance of PETG is higher (PLA’s glass transition temperature is around 60 degrees celsius, while PETG clocks in with a glass transition temperature of 85 degrees Celsius)
- Another reason I chose PETG over PLA that is not often talked about is the smell. I’ve noticed, through personal experience, that PLA has a much more distinct and strong odor than PETG. If you’re working in a cramped space and you’re worried about smelling up your work area, consider PETG as a substitute to PLA.
- Obviously, the biggest reason to use PETG is that it has superior mechanical properties. For example, printing with PETG has helped me design more rigid parts for my projects, including fixing up an old electric scooter!
Now, with all of these benefits, what are the drawbacks of printing with PETG? Unfortunately, this feisty filament is not all sunshine and rainbows. There are several pitfalls that I had to deal with when printing with PETG, to avoid the dreaded spaghetti monster and severe stringing during printing. From poor-quality filament to moisture absorption, there is a lot to cover.
Drying out your PETG filament
One of the biggest problems, especially after my filament was sitting out for a few weeks, was moisture. Soon after you receive your first spool of PETG, you’ll realize this filament is incredibly hydroscopic. This means it’s going to absorb a lot of moisture from the environment. Because of this, it is very important that you store your PETG filament in a moisture-free area, such as an airtight container or vacuum-sealed bags. I didn’t know this at first, and went through weeks of poor printing before I realized moisture was the issue. To remove moisture from filament, consider a dedicated filament dehydrator, and for storage, consider airtight containers or vacuum-sealed bags.
I use the EIBOS Cyclops, and it works beautifully for my purposes. It can dry two spools of filament at once, and it does a great job.
My first mistake – PETG stringing
If you’re used to printing with PLA, you won’t be prepared for the possible mess PETG can cause. PETG has a horrible tendency to “string” during printing, causing a spider-web like effect between different parts of your print. This is due to the higher temperature and slower cooling time required for PETG compared to PLA. This can also be due to moisture in the filament.
To solve this issue, I increased retraction in my slicer. Activating the “Lift Z during travel” feature raises the nozzle prior to its movement between different points, helping break off that dreaded stringing.
Build plate adhesion when printing
If you’re big on printing with PETG, you may have trouble with build plate adhesion (getting the first layer of your print to stick to the build plate). Despite what other sources say, I’ve had a lot of trouble getting PETG to stick to the build plate when printing my first layer. A few tips if you’re running into the same kinds of issues –
- Tune the temperature of the build plate – If your build plate is too cool or too hot, this can lead to issues with bed adhesion. Usually, PETG should be printed with a bed temperature of about 65-75 degrees Celsius.
- Change the material used on the build plate – If you’re using a smooth build plate, consider switching to a textured PEI build plate. Making this switch on my Prusa MK3S+ helped bed adhesion considerably. You can buy a textured PEI plate directly from Prusa’s website, but I recommend buying a third party build plate on Amazon. These plates are cheaper, and work the same as Prusa’s official plates do.
- Change your first layer height – Contrary to PLA, PETG does not like being squished on the first layer. If you’re used to PLA and have your first layer height set fairly low, experiment with larger first layer heights. You’d be surprised at how much of a difference this simple setting can make to the first layer of your PETG prints!
Investing in quality filament
A significant factor that can’t be overlooked when printing with PETG is the quality of the filament you purchase. The saying ‘you get what you pay for’ certainly rings true when it comes to 3D printing filament. Opting for cheaper, worse-quality filament might seem like a great way to save some money, but it will lead to headaches, poor quality prints, and possibly damage to your printer.
Poor quality filament tends to have an inconsistent diameter, which leads to uneven extrusion, causing issues such as under-extrusion or over-extrusion. In extreme cases, this can even lead to extruder clogs or jams. I once made the mistake of buying poor quality filament for cheap. My prints would constantly string, and the extruder would clog almost every print. Higher quality filament has a much more consistent diameter, which helps achieve better results, with higher quality prints and less risk of a clog or jam.
Another critical aspect is the filament’s packaging. Reputable brands take great care in packaging their products, ensuring they are vacuum-sealed with desiccants to reduce moisture absorption, a particular concern for PETG. Budget filaments may lack these protections, leaving them prone to moisture absorption even before you’ve loaded them into your printer.
Personally, I use Hatchbox PETG and it works very well.
It’s going to be a lot different
Transitioning from PLA to PETG may seem difficult due to the differences between the two materials. PETG is a challenging filament, especially for beginners who are comfortable with PLA. However, the uniqueness of PETG is exactly what makes it such a valuable tool.
Remember, we are not trying to treat PETG like PLA. It will be different, and you’re going to have to embrace these differences and understand the nuance of this unique filament.
You can probably tell that I strongly believe PETG is an incredibly versatile and useful filament. It balances ease of use with mechanical strength. If you’re an engineer prototyping high-stress parts, this is absolutely the filament for you. It’s worth keeping in mind the differences between PLA and PETG before committing to either one. PETG is going to be a different experience to print with, so if you’re used to PLA, it’s going to be a big change. However, in my opinion and in many applications, this change is absolutely worth making.
