Engineer Reveals Easy Way to Strengthen PLA Through Annealing In Heat Bath

June 14, 2017

PLA is probably the most used thermoplastic for 3D printing but one of its downsides is the lack of strength. Therefor many users employ strengthening techniques to get the most out of it. Some users employ epoxy resin, while others resort to metal casting. These are fine techniques, but engineer Justin Lam may have a simpler one.

The method employs a temperature controlled bath where you have to soak the PLA pieces. In a lengthy post on his website, he outlines how the method works. The process allows users to create potentially stronger parts and get smoother prints with less warping through heating.

The Process

Justin Lam’s technique was rather simple and can be carried out with home appliances. At most, you will require a place where you can bathe the prints and the size will depend on what you plan to make. The process itself involved simply submerging prints in a controlled temperature water container. He used a Sous Vide controller and a kettle to act as the vessels.

The water needs to achieve a temperature of 70°C. Once warm enough, dip the prints in for 30 mins, although in the case of the experiment he used small blocks, so depending on the size, time may vary. While simple, the experiment showed a visible increase in crystallinity of the prints. Improved crystallinity is indicative of other attributes as well. It can mean that, on the microscale, the PLA is more evenly aligned and therefore stronger.

While the tests were inconclusive as to what extent the strength was improved, they made some other findings. For one, samples cooled at room temperature suffered from higher internal stress than ones left in the heat bath. Samples printed at a 0.175 mm layer height had higher internal stress than those at 0.2625 mm.

In the end this is a very simple way to improve certain qualities in PLA prints. While it takes half an hour for simple blocks, it is still cheap and less resource intensive than many other options. Future tests may yield further results and improvements to the process.