5 Tips for 3D Printing with PETG

One of the wonderful things about 3D Printing is the ability to print models in a constantly expanding range of filaments depending on your needs. One of the most popular filaments is PLA however it is not the best for every situation. This is where filaments such as ABS, TPU, PETG, PC, ASA, and various other types come in. Each type of filament offers different benefits just as they require different print settings. In this post we will be looking at PETG filament and 5 tips to help when printing with it.

PETG (Polyethylene terephthalate glycol) is a modified version PET. In industry PETG is used to make items such as bottles, medical braces, electronics, and various other items. In 3D Printing it is a popular type of filament for several reasons. Models printed with PETG benefit from durability, flexibility, chemical resistance, heat resistance, and moisture resistance. The glass transition temperature of PETG is also in-between PLA and ABS at 80-82°C. It is considered easier to print with than ABS as it doesn’t require a direct drive extruder, enclosure, or hardened steel nozzle but can still be troublesome if you have only used PLA in the past.

Bed adhesion

Damaged PETG print as a result from bed adhesion
Damaged PETG print as a result from bed adhesion

First layer adhesion is the first step towards a successful print. While getting that perfect first layer is an issue for some filament this is not always the case with PETG. Different brands of PETG as behave slightly differently so it is not a case of one solution for all.

Various Makers have reported that PETG adheres too well to some surfaces and can cause damage, so it is important to use the best possible build surface.

PETG can adhere too well to surfaces such as glass, Buildtak, and PEI, so when you try to remove a print, it is possible that some of the bed may be damaged or have pieces pulled up with the print. To avoid this, it is recommended that you use some form of adhesion aid such as a glue stick or hairspray. These aids aren’t to help with first layer adhesion but rather act as an adhesive surface between the PETG and the build surface. This helps with removing the printed model without removing chunks of your build surface as well.

Tune your retraction

Poor retraction can result in stringing
Poor retraction can result in stringing (Image by Saumitra Jagdale. Source)

PETG has a high tendency to string and ooze. And the material’s toughness and eagerness to adhere to itself makes strings of molten plastic difficult to break. This can lead to fine strands of filament and wisps on your prints or worse cause a failure of your print.

The best way to combat this issue is to increase retraction distance, retraction speed, and travel speed, within reasonable limits. Retraction is when the printer pulls the filament up into the hotend in order to reduce or prevent oozing from the nozzle while moving between printed parts or layer changes. Increasing retraction will pull the PETG further into the hotend and drastically reducing the possibility of oozing form the nozzle.

It is important to keep in mind that changing retraction distance may mean you need to adjust the retraction speed to accommodate the change. This is because retracting filament too far and at too low a speed will result in under extrusion as the nozzle may not get primed in time for the next extrusion.

Avoid cracking/layer separation

Example of layer cracking/separation
Example of layer cracking/separation (Image by Barret. Source)

This tip is especially important if you are making the switch from PLA to PETG. When making the switch you may find that the PETG cracks of has layer separation. This is cause by the PETG being cooled too quickly due to the use of a part cooling fan.

If you discover cracking or layer separation on your PETG prints, then consider reducing the fan speed. PETG retains its shape at higher temperatures than PLA, so overhangs and complex shapes will still turn out well. The reason for reducing the fan speed is to lower the amount of cooling that occurs and give the extruded plastic time to fully bond with the rest of the model.

Be careful with supports

Supports can cause issue with PETG
Supports can cause issue with PETG (Image by farley911. Source)

As we have mentioned before PETG likes to adhere to itself and this can cause issues especially when printing with supports. As supports can often be a pain to remove even when using PLA having the supports fuse with the printed model can cause a serious headache for more delicate parts. Fused supports can also impact the quality of the finished print as removing them can leave behind small pieces of support or imprints on the model.

One way to reduce the possibility of fused supports is to adjust settings in your slicing software. Using the setting Support Z Distance in Cura, or similar with other slicers, allows you to increase the distance between the model and the top or bottom of the support material. This will make it easier to remove supports but keep in mind that increasing the distance too much will result in inadequate support for the print and print quality may suffer.

Keep filament dry

Comparison between dry and wet PETG filament
Comparison between dry and wet PETG filament (Image by Thomas Sanladerer. Source)

The last tip on this list can be applied to any type of filament but especially PETG. If you have been using a roll of PETG for a while or left a roll of PETG open before use, then you may start to experience deteriorating print quality. The reason for this drop in quality is a result of PETG being hygroscopic. This means it will absorb moisture from the surrounding environment. All filament types absorb moisture but at different levels with PETG being well known to absorb moisture.

To avoid this issue, it is important to take steps to prevent your roll of PETG from absorbing moisture. The easiest way to do this is to keep your filament in the vacuum sealed bag it comes in until needed. The desiccant bag that is often included in the sealed bag will help prevent the filament from absorbing any moisture. Once the filament has been opened, we recommend storing it in a dry airtight box with desiccant bags/gel at the bottom to remove any moisture in the container.

If you want to dry out a roll of PETG that you suspect has absorbed moisture then there are other methods available. The first would be to purchase a filament dryer. These use a heat element to warm up the filament and remove any moisture, some dryer boxes even allow you to print using the filament while it is kept dry. The second method is using an oven or food dehydrator. Both are popular choices with Makers who don’t have a filament dryer however you need to know what the glass transition temperature is of the filament otherwise you will end up with a useless roll of filament. They also take quite a bit of time to dry out a roll of filament.

We hope that these tips have helped you improve the quality of your PETG prints. If you have other tips that you would like to share then please drop a comment below so that others might benefit as well.

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