Annealing PLA: Improve Heat Resistance and Strength
How annealing works
Standard PLA is mostly amorphous (random polymer chain arrangement), which is why it softens at 55 C. Heating PLA above its glass transition lets the polymer chains rearrange into crystalline structures. Crystalline PLA is much more heat resistant and stiffer than amorphous PLA.
Standard PLA vs HTPLA
- Standard PLA: anneals but shrinks unpredictably (3 to 5 percent typical, sometimes warps)
- HTPLA (heat-treatable PLA): designed for annealing, contains nucleating agents that crystallise predictably (1 to 3 percent shrink)
The annealing process
- Print at standard PLA settings
- Let the part cool to room temp
- Place the part on a flat oven tray, ideally supported by sand or salt to prevent sagging
- Bake at 100 to 110 C for 15 to 30 minutes depending on part size
- Use an oven thermometer, many ovens overshoot
- Cool slowly inside the oven; rapid cooling causes warping
- Measure the part after cooling to verify dimensions
Designing for annealing
- Print 1 to 3 percent oversize (HTPLA) or test with sacrificial print first (standard PLA)
- Support the part with sand or salt fills to prevent sagging
- Avoid thin walls, they warp more than thick ones
- Symmetrical designs warp less than asymmetric
What annealed PLA can do
- Survive in a hot car interior (was 55 C, now 100 C+)
- Hold dimension in sunlight-exposed indoor mounts
- Serve as a near-PC-grade engineering plastic at PLA prices
- Run hotter applications: light fittings, near electronics, occasional kettle proximity
Browse the range
HTPLA, Protopasta HTPLA, All PLA (for experimental annealing).