Engineering reference

Injection moulding temperature chart — melt, mould and drying

Typical processing windows for the thermoplastics that dominate technical moulding. Values are compiled from machine-maker guidance and material-supplier practice — your specific grade’s datasheet always governs, especially for filled, flame-retardant and impact-modified variants.

Material	Melt temp (°C)	Mould temp (°C)	Drying (typical)
PP	220–290	20–60	Usually not required (surface moisture only)
HDPE	200–280	20–60	Usually not required
PS / SB	160–230	20–60	SB: 80 °C · ~3 h if streaking
ABS	180–260	40–85	90 °C · ~3 h · to <0.2% moisture
PC	280–320	80–100	120 °C · 2–4 h · dry until streak-free
PA6 / PA66 (nylon)	240–290	60–110	~100 °C · ~4 h · to <0.15% moisture
PBT	240–270	60–100	120 °C · ~4 h · to <0.02% moisture
POM (acetal)	190–230	60–120	120 °C · ~4 h if regrind/moist storage
PET	260–290	20–140 (grade-dependent)	Dry thoroughly — hydrolysis-critical

Compiled from machine-maker processing guidance (ARBURG/Rapra practical literature) and supplier practice. Glass-filled grades typically run at the upper melt range with hotter moulds.

The three rules behind the table

Hygroscopic resins re-wet fast. Nylon, PC, PBT and PET drink moisture from air — dried material left in an open hopper can be wet again within the hour. Dry to spec, keep hopper loadings matched to consumption, and treat moisture streaks as a drying audit, not a machine fault. Semi-crystalline materials want warm moulds. Their crystals need temperature and time to form; a cold mould freezes an unstable structure that finishes shrinking after moulding — in the customer’s warehouse. The window is a window. Running at the bottom of the melt range saves energy and residence-time risk; the top buys flow for thin walls — a choice, not a default.

Companion tools

These temperatures feed the cycle-time estimator directly, and the drying rules explain half the defects in any moulding shop. Choosing the material itself? Start with the materials guide.