How to Apply Annealing to PETG for 3D Printed Models?

With functional prints getting more and more popular with each passing day, an increased level of strength in 3D printed models is something most enthusiasts wouldn’t mind having.

The annealing process comes in at this point, allowing you to increase both the strength and the heat resistance of your 3D printed model by reorganizing the molecular structure of the plastic.

As PETG is a highly popular filament in the functional printing world, many members of the 3D printing community are curious about the best way to apply annealing to PETG to strengthen it and make it more durable.

So, how to apply annealing to PETG for 3D printed models?

To apply annealing to PETG, you will need to heat the model slightly above the glass transition temperature of 80 to 85 degrees Celsius in a controlled environment and then let it cool down gradually.

The two main methods for the process are heating the model in an electric oven or hot water, as they both provide the controlled and equally distributed heat annealing requires.

While annealing is a simple process at its core, there are also plenty of things that can go wrong and cause your model to become completely unusable due to warping.

In the next section, we will take a deeper look at the process of applying annealing to PETG with both the oven and the hot water method and outline the steps we recommend taking.

How to Apply Annealing to PETG for 3D Printed Models?

Since applying annealing to PETG is all about equally heating it slightly above its glass transition temperature, both an electric oven and hot water are fantastic tools for our purposes.

Annealing PETG with an Electric Oven

Annealing PETG with an electric oven is the best way to conduct the process, as an electric oven allows you to control the temperature easily at all times.

  1. Start by heating the oven to a value between 90 and 95 degrees Celsius, which is slightly higher than the glass transition temperature of PETG. If the manufacturer lists the glass transition temperature of the filament, set the oven to 10 degrees higher than that value instead.
  2. Wait until the oven heats up. If your oven does not feature a display that shows the progress, wait around 30 minutes to ensure that it’s fully heated.
  3. (Optional) If you want to ensure that everything is in order in the temperature department, use an oven thermometer to confirm that the temperature is accurate.
  4. Place your model on an oven-safe tray, place it in the oven, and turn the oven off. The internal temperature of the oven will be enough to anneal the PETG, and leaving it on might cause it to go above the desired temperature.
  5. Let the object slowly cool down in the oven for a few hours.
  6. Take the model from the oven, which should be successfully annealed.

As an oven allows you to fine-tune the temperature, you can always experiment with it depending on the results to find the optimal values.

Annealing PETG in Hot Water

Annealing PETG in hot water is also perfectly acceptable in cases where you don’t have access to an electric oven, but the process can be slightly harder to conduct optimally.

  1. Place your object in a heat-resistant plastic bag alongside some dense objects that will weigh the bag down in the water.
  2. Heat water to a temperature 10 degrees higher than the glass transition temperature of the PETG filament you have. If the glass transition temperature is not listed, you can go for a temperature range between 90 and 95 degrees Celsius.
  3. Submerge the object into the water, and let it stay there for around 30 to 40 minutes. The water temperature needs to be constant during this period.
  4. Remove the water from heat, and let the water (and the object) gradually cool down.
  5. When the water has cooled down to room temperature, you can safely remove the object, which should be annealed.

As it’s harder to control the temperature with this process, it requires a higher degree of caution compared to the oven method to get the optimal results.

Advantages and Disadvantages of Annealing PETG

Annealing is a process that comes with both advantages and disadvantages, but you can often minimize the negatives by conducting the process as optimally as possible.

First, let’s start with the advantages of annealing PETG:

  • Annealing dramatically increases the strength of the model and makes it more durable against stress.
  • Annealing makes the model more resistant to high temperatures, giving it the ability to preserve its rigidity.

On the other hand, here are the disadvantages of annealing PETG:

  • Annealing can cause the model to warp and deform.
  • Annealing will cause the model to shrink in size.

Note that it’s possible to combat these disadvantages by performing the annealing process optimally and compensating for the shrinkage, which makes annealing an overall beneficial process.

How to Avoid Warping While Annealing PETG?

Warping is a widespread issue that many enthusiasts face after annealing PETG – but it’s possible to avoid it or at least minimize it to a point where it’s not glaringly obvious.

Avoiding warping while annealing PETG comes down to three primary factors:

  • Ensuring that the heat is distributed evenly across the model – Failing to distribute the heat evenly will immediately cause the model to warp due to the significant difference in temperature between parts of the model.
  • Ensuring that the temperature you apply isn’t too much higher than the glass transition temperature of the filament – Using a too high temperature will cause the model to quickly deform and lose its rigidity, which will present itself in the form of warping.
  • Allowing the model to cool down gradually after the annealing process – If you attempt to cool the object down too quickly, the sudden temperature change will likely cause the model to warp.

Paying attention to these three factors will prevent or at least minimize warping to negligible levels in your model after annealing.

Does Annealing Cause PETG Shrinkage?

Whether PETG shrinks due to annealing is a common question, as the possibility of a shrinkage requires the model’s size to be calculated accordingly.

Annealing will unavoidably cause PETG to shrink, which is why it’s vital to account for the amount of shrinkage before you print your model if you are planning on annealing it.

As a rule of thumb, you should assume shrinkage to be in the range of 1 to 5 percent and do your calculations accordingly.

Wrapping Up

While the process of annealing PETG is mostly a straightforward task, the essential part is to perform it without letting the model warp too much to a point where it’s unusable.

To quickly recap, all you have to do to anneal PETG is heat it slightly above its glass transition temperature of 80 to 85 degrees Celsius in a controlled environment where the heat is distributed equally, such as an electric oven.

After the model reaches the desired temperature, let it slowly cool down, which will conclude the annealing process.

As annealing PETG without warping comes down to the equal distribution of heat and careful control of the temperature, using the right tools, being vigilant, and having some experience is usually more than enough to conduct the process optimally.