Before you choose
- HDT includes a test load and deformation criterion.
- Melting temperature is not a service-temperature rating.
- Time, stress, moisture and post-treatment affect the decision.
Describe the actual heat exposure
Write down the part temperature rather than only the room or air temperature. Include peak and normal conditions, dwell time, load and whether heating repeats. A briefly warmed cover and a continuously clamped hot fixture present different requirements.
Keep the thermal terms separate
Glass transition describes a change in polymer behavior; melting describes the melting of crystalline material. Heat-deflection temperature records a specified deformation under a specified test load. A continuous-use rating needs its own definition and evidence.
| Term | What it helps describe | Buying question |
|---|---|---|
| Tg | Change in polymer mobility/behavior | How does the part behave near this range? |
| Tm | Melting of crystalline material | What processing conditions are required? |
| HDT | Deflection in a defined loaded test | Which stress, specimen and preparation? |
| Service condition | Performance for the actual use | What load, time and environment were validated? |
Check the state behind the published value
Annealing, moisture conditioning and resin post-cure can change reported thermal behavior. Ask whether these steps are required to reach the published result. They may also alter size, shape or residual stress, so leave room for dimensional reinspection.
Make heat part of the sample approval
Trial the relevant geometry under a defined loaded dwell and assess fit after cooling. Also confirm that your printer, drying equipment and any approved thermal treatment can support the grade. If a requirement is critical, agree on a test rather than extrapolating from a headline temperature.
Turn a thermal claim into a testable question
A part next to a warm air stream may also be held by screws or clamps. Define both the exposure and the load path. A short unloaded exposure test can leave sustained deformation unanswered. Also inspect after cooling when fit and repeated installation matter.
For an illustrative project brief, a buyer might specify a part-temperature range, a 20-minute loaded dwell and a maximum permitted movement at a locating feature. Those values would be the buyer’s chosen requirements, not a recommendation that any listed polymer passes them. The supplier can then identify the relevant evidence and remaining trial work.
| Keep in the brief | Reason |
|---|---|
| Part temperature and measurement point | Air, machine setpoint and part temperature can differ. |
| Normal/peak duration and cycles | Time and repetition affect the required evidence. |
| Load, geometry and permitted movement | The service requirement is more specific than a temperature alone. |
| Preparation and final inspection state | Thermal treatment and conditioning can affect dimensions. |
Questions buyers ask
Can I use HDT as the maximum working temperature?
Use the HDT test conditions as a reference, then evaluate the actual load, exposure time and geometry. A single HDT number does not cover every service condition.
Can I anneal every grade with one temperature recipe?
Follow the current instructions for the exact grade. A generic recipe can change dimensions or damage a part without giving the intended result.
Sources
- Prusa — annealing 3D printed parts
Thermal treatment can change both performance and dimensions.
- Polymaker — filament selection guide
Grade-specific equipment, drying and annealing requirements.
- Formlabs — material selection and mechanical properties
How stiffness, elongation and other properties relate to the part's job.