What is HDT (Heat Deflection Temperature)?

HDT is the temperature at which a material deforms by a specified amount under a standardised load (0.45 MPa for HDT-B). Above the HDT, printed parts will warp, sag, or lose structural integrity under load. It is more relevant than glass transition for load-bearing parts.

Can I increase the heat resistance of PLA?

Yes. Annealing PLA in an oven at 80-110°C for 1-2 hours can increase its HDT to 80-120°C by crystallising the polymer. However, parts shrink 2-5% during annealing and may warp, so design with shrinkage compensation.

Why does PLA warp in cars?

Car dashboards can reach 60-80°C in direct sunlight. This exceeds PLA HDT of 55°C, causing the part to soften and deform under its own weight. Use PETG (75°C HDT), ABS (95°C), or ASA (95°C) for automotive applications.

What material has the highest heat resistance?

Among common FDM materials, Polycarbonate (PC) has the highest HDT at ~130°C. For extreme temperatures, consider PEEK (250°C HDT) or PEI/ULTEM (170°C), though these require specialised high-temperature printers.

3DPrintCalcs

Heat Resistance Calculator — Operating Temperature Check

Check if your printed part will withstand a given operating temperature.

MaterialThe filament your part is printed in — each has a different heat-deflection (HDT) and glass-transition (Tg) temperature.

Operating Temperature

The hottest the finished part will get in use — e.g. ~60-80°C on a sunny dashboard, ~50°C near an enclosure, 100°C for boiling water.

Load-Bearing?Choose Yes if the part carries weight or stress while hot — this uses the lower HDT limit instead of the glass transition.

Exposure DurationHow long the part sits at this temperature. Longer exposure applies a larger safety buffer (15°C continuous, 10°C intermittent, 5°C brief).

How We Calculate This

Heat Resistance Assessment

Effective limit = HDT (load-bearing) or Glass transition (no load)
Safety margin = Effective limit - Operating temp - Safety buffer
Safety buffer: 15°C continuous, 10°C intermittent, 5°C brief

Load-bearing parts are limited by the HDT — the temperature at which the polymer deflects under a 0.45 MPa load. For amorphous polymers (PLA, PETG, ABS, ASA, PC) the HDT sits below the glass transition, so a structural part must stay cooler than a decorative one. Semicrystalline nylons behave differently — their crystalline regions keep them stiff above their low glass transition — so this calculator caps the load-bearing limit at whichever is lower (HDT or Tg) to stay conservative. Non-load-bearing parts may operate up to the glass transition. The safety buffer accounts for hot spots and temperature fluctuations.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.