This article contains information about annealing parts printed with PET CF. Annealing is a heat treatment process for 3D printed parts that involves heating the object and then cooling it slowly. UltiMaker PET CF is already a high-performance material, but its properties can be further improved by annealing.
Benefits of annealing
There are two main benefits of annealing your PET CF parts:
- The mechanical properties will increase (stiffness + 10% and strength + 30%).
- Temperature resistance increases from HDT of ~ 80 °C to a HDT of ~ 180 °C. Annealing basically transforms your PET CF to a fully semicrystalline state.
Annealing instructions
Here, you can find instructions for correctly preparing your model with annealing in mind, and the annealing process itself.
Print preparation
A downside of annealing is that your printed part will shrink slightly. In UltiMaker Cura, this shrinkage can be compensated for by slightly enlarging your part (typical shrinkage for PET CF is - 0.3% in XY and - 0.9% in Z). This is done automatically when choosing the annealing intent profiles.
Make sure to select a support material, as this will prevent sagging of your part during printing and annealing. You can choose to use self-support (PET CF support) or Breakaway support for annealing.
Annealing oven
Place your PET CF parts still attached to the build plate in the Binder (or other brand) oven. It is crucial that the parts have the same orientation in Z as during printing (so do not rotate or flip the parts in the oven). This will negatively affect the shrinkage.
Tip: Professional programmable annealing ovens such as Binder FP115 and Memmert UFP75plus are validated by UltiMaker and therefore recommended.
To determine the annealing time, measure the thickest section of your part. The annealing time in hours is the thickness in mm / 2. Let's say your part is 4 mm thick, then you would need to anneal the part for 2 hours at the annealing temperature.
Program your oven
A verified annealing profile for a PET-CF sample of 4 mm thickness is depicted below. Different annealing temperatures (Tc) can be decided upon based on property preferences, but it is advised to maintain heating/cooling ramps for optimal results. High-temperature annealing will therefore result in longer annealing times.
Tip: A profile for the Binder FP115 can be downloaded here.
| Process | Duration (h) | Temp (°C) | Ramp (°C/h) |
|---|
| Start | (N/A) | 20 | (N/A) |
|---|
| Heat to Tg | 1 | 75 | 55 |
|---|
| Unstress | 1 | 80 | 5 |
|---|
| Heat to Tc | 1 | 120 | 40 |
|---|
| Anneal | 2 | 120 | (N/A) |
|---|
| Cool to Tg | 2 | 80 | - 20 |
|---|
| Cool to RT | 1 | 50 | - 30 |
|---|
| Total | 8 |
|---|
Once the object is cooled down and retrieved from the oven, the annealing process is completed, and the part is ready for use. Regular post processing methods like sanding, polishing, and coating can be applied if desired.
