Annealing PLA prints can help improve their heat resistance and overall stability. Below is guide for annealing PLA:
First, it is important to note that not all PLA filaments are suitable for annealing, as some may have additives or different formulations that may not respond well to the process. Check the filament manufacturer’s recommendations for guidance on how well their product behaves when annealing PLA.
1. Printing considerations: Start by 3D printing your desired model using PLA filament. Use a high level of infill, preferably 100%, the denser the print the better it will resist warping and dimensional changes, it will take extra filament but will greatly increase chances of better outcome. Review geometry of your model, thinner layers will be more prone to warping, consider incorporating stiffeners and supports into your design. Model geometries that are more complicated or have different layer densities will be more prone to warping and dimensional changes. Remove any supports, stringing, and brims prior to annealing. Besides the risk of them becoming fused to model during annealing they can also act as heat sinks that will unevenly distribute heat as model heats up and cools down. Also ensure that the print is clean and free from any debris.
2. Preheat oven: Preheat your oven to the recommended annealing temperature, usually between 60-70°C (140-160°F). Use an oven thermometer to verify the accuracy of the temperature. Once the oven has reached the desired temperature give it an extra 30 minutes or more, this will allow the walls and parts of the oven to reach a uniform temperature. The use of an electric oven is preferred as gas can cause rapid heat fluctuations. The more consist you keep the temperature the better your success will be.
3. Prepare baking tray: There are two primary oven methods for annealing PLA:
· Sand Method: The preferred method, especially for models with more complex geometries, is to bury your PLA print completely in sand using an oven safe tray/container that has adequate volume for your print and the sand. The sand will distribute the heat more uniformly and allow for a slower cooling later which will help minimizing warping. If you have a gas oven, using the sand method will increase your chances of success. Start by applying a 5-10 mm layer of sand to bottom of container. Then proceed to bury your print(s) entirely in sand, making sure to maintain at least 5-10 mm buffer of sand on all sides of the print(s) (top/bottom/sides). If you have multiple prints maintain a 5-10 mm distance of sand between each. Use sand that is uniform in grain size, dry and free of debris such as: TETON supply Co Pure Silica Sand
· Air Method: Start with a room temperature baking tray, line the baking tray with parchment paper or use a silicone baking mat to prevent the PLA from sticking to the tray. Place your print onto the prepared tray, ensuring your print is placed flat and has no contact with other objects.
4. Bake in the oven: Put the baking tray with the PLA print into the preheated oven, avoid contact with the sides of the oven. While it is suggested to keep an eye on the print throughout the annealing PLA process to prevent overexposure to heat, it is also important not to fluctuate the oven temperature by holding oven door open. Avoid handling or movement of the print while it is heating.
5. Annealing time: The annealing time, which is the time the PLA print is left in oven, depends on the thickness and size of your print. A general guideline is to anneal for around 30 minutes to 1 hour. If you used the sand method above, leave the print in oven for at least an hour. Thicker prints or larger amounts of sand may require longer annealing times.
6. Cooling process: Once the annealing time is complete, turn off the oven and allow the PLA print to cool down gradually inside the oven. Depending on the characteristics of your oven, it may take a considerable amount of time (overnight) before the print and oven reach room temperature. Keep oven door close during cooling, avoid sudden temperature changes, as they will cause warping or cracking. If you are using the sand method you may carefully remove the container from the oven after it has cooled for an hour but leave the PLA prints completely buried in sand until the sand and print have both reached room temperature. Be patient, gradual cooling is a critical step of the annealing PLA process.
7. Remove the print: Once the print has cooled to room temperature, carefully remove it from the oven/sand. Inspect the print for any changes in its shape or appearance.
8. Test and evaluate: Test the annealed PLA print to assess any improvements in its mechanical properties, such as heat resistance or dimensional stability. Compare it to an un-annealed PLA print to
determine the impact of the annealing process. Annealing PLA is a process that takes patience and multiple trials to dial-in the variables of your equipment and materials. When the process is successful the PLA print will gain strength and became less brittle.
Remember to follow safety precautions when using and handling hot objects. Always refer to the specific recommendations provided by your PLA filament manufacturer for annealing PLA, as different brands may have varying temperature and time requirements.
May your 3D journey be strong and true.