How Much Cooling (Fan Speed) Does PETG Need? (Detailed)

Due to the differences in chemical composition, each filament type has different attributes, which means that they also require separate configurations.

Factors such as melting point, adhesion strength, and the likelihood of stringing and oozing all show differences among different filament types, requiring you to tweak the settings of your slicer accordingly.

One such factor is cooling, which, while usually overlooked, is a significant component that highly contributes to the quality of a print.

Since many 3D printing enthusiasts encounter cooling-related issues when they switch to PETG from PLA for the first time, we decided to cover this topic extensively.

So, how much cooling does PETG need, or in other words, what should you set the fan speed for PETG?

You can print PETG with any fan speed between 0% and 100%, as the optimal fan speed depends on your use case.

While higher fan speeds will allow your prints to have a greater level of detail, lower fan speeds will strengthen the layer adhesion and make the object more durable.

As cooling is a complicated subject with no definitive answer that applies perfectly to every scenario, we will take a deeper look into it and analyze the effects of different cooling levels on PETG filament to find the optimal cooling settings for each case.

How Much Cooling (Fan Speed) Does PETG Need?

Cooling PETG filament is a subject with no correct answer that works in every case.

A lower level of cooling (lower fan speeds) allows the PETG to dry naturally, and as a result, the object ends up having stronger layer adhesion and better durability.

On the other hand, a higher level of cooling (higher fan speeds) causes the PETG to dry faster, giving it a better level of detail aesthetically.

As a result, choosing the fan speed for cooling PETG mostly comes down to preference, with anything between 0% and 100% fan speed being acceptable depending on the scenario.

Since it may be hard to make the right choice if you have no prior experience, we will go over some common scenarios and our cooling recommendations to give you a better idea.

  • Thin (and tall) models, such as figurines (short layer times) – Models with shorter layer times require some cooling, as it becomes harder for them to hold their shape the longer it takes for the PETG to dry. We recommend using a fan speed between 30% and 50% in this case. While it’s true that using higher fan speeds would give you better surface resolution, models with short layer times will easily snap without sufficient layer adhesion.
  • Thick models, such as a box (longer layer times) – Models with longer layer times won’t have issues holding their shape, which is why you’re free to choose any fan speed you want in most scenarios. While higher fan speeds will give you better surface resolution, lower fan speeds will provide better layer adhesion. We recommend staying close to 0% fan speed for objects that will see physical use and close to 100% for purely aesthetical ones.
  • Overhangs – Overhangs require cooling to dry quickly and stabilize. As overcooling the overhangs will give you issues with layer adhesion, we recommend using fan speeds between 70% and 80% and adjust depending on the signs you observe.
  • Bridges – Bridges are similar to overhangs when it comes to cooling. While a cooling speed that is too low will cause the bridge to become droopy, a cooling speed that is too high will present layer adhesion issues. We recommend using fan speeds between 70% and 80% for bridges, but feel free to adjust according to the signs you see on the object.

How Does Cooling Affect PETG?

As changing the cooling level impacts the temperature of the PETG directly, you will notice significant changes in the models you print with different cooling levels.

Layer Adhesion

Layer adhesion is the first thing that comes to mind when anything temperature or cooling-related is the subject, as poor layer adhesion can easily ruin your print and cause it to fall apart.

The lower the level of cooling is, the stronger layer adhesion becomes.

As the layers of PETG require sufficient time to form strong bonds with each other, cooling them way too quickly will prevent these bonds from forming, causing the model to become very prone to falling apart.

In severe cases, poor layer adhesion will cause delamination, a phenomenon where layers separate from each other and completely ruin the print.


Durability is closely related to layer adhesion, as an object requires its layers to have strong adhesion to be durable. Durability is a significant factor for prints that you will primarily use for their function.

Since durability increases with the strength of layer adhesion, a lower level of cooling also means the model becomes more durable.

When the PETG layers have enough time to form strong bonds, there won’t be any weak points on the object due to all the layers merging into each other.

On the other hand, a high level of cooling will cause the model to have weaknesses between layers, making the model brittle and prone to cracking and physical damage.

We recommend keeping durability as high as possible for prints that you will be using for their function.

Model Detail

Model detail is vital for prints where aesthetics are more significant than the function.

The detail (surface resolution) of the model increases with a higher level of cooling.

When the PETG dries as quickly as possible, the fine details of the model remain intact. As the filament does not get enough time to flow freely, it can’t cause warping, stringing, or drooping.

We recommend going for the best model detail possible for prints that are purely aesthetical.

Signs of Cooling PETG Too Much

If your printer is cooling the PETG way too much, below are the signs you would notice:

  • Adhesion between layers is weak.
  • The print feels way too brittle.
  • The object is not durable and cracks easily.
  • The bridges (if any) on the model are especially prone to breakage.
  • The overhangs (if any) on the object are especially prone to breakage.

Signs of Cooling PETG Too Little

If your printer is not cooling the PETG filament enough, you will notice signs such as:

  • There is visible warping on some areas of the print.
  • There is extreme stringing on the model.
  • The surface resolution of the object is poor.
  • Bridges (if any) on the object are droopy.
  • Overhangs (if any) on the model are droopy.

Wrapping Up

Getting cooling right with PETG filament can be a tricky one, especially compared to PLA, where most enthusiasts have an overall easier time correctly configuring the settings.

As choosing between different cooling levels creates trade-offs in areas such as layer adhesion and aesthetics, a large part of making the right decision is running your experiments and fine-tuning the cooling on a print-by-print basis depending on the purpose of the print.

While the journey to finding the optimal PETG cooling settings can be slightly frustrating, it will be well worth it when it all clicks.

We hope it has been an enjoyable and helpful read, and we wish you a great day!