Polymer Injection Parameters & Mold Design Guidelines

Polymer Injection Parameters & Mold Design Guidelines optimize melt temp, pressure, and cooling for precision molding. Covers thermoplastics, thermosets, and elastomers selection and gate design tips.

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Polymer Injection Parameters & Mold Design Guidelines
Polymer Type	Material	Abbr.	Melt Temp (°C)	Mold Temp (°C)	Inj. Pressure (MPa)	Hold Pressure (MPa)	Cool Time (s)	Key Mold Design Recommendations
General Thermoplastics	Polypropylene	PP	200-280	20-80	70-120	30-60	15-30	① Short/wide runners to reduce pressure loss. ② Vent depth: 0.02-0.03mm to avoid gas traps.

	ABS	ABS	210-250	50-80	80-130	40-70	20-40	① Mirror-finish cavities to prevent gloss. ② Use fan or submarine gates to minimize weld lines.

Engineering Plastics	Polycarbonate	PC	280-320	80-120	90-150	50-80	30-50	① H13 steel molds (HRC48-52). ② Avoid sharp corners to prevent stress cracking.

	Nylon 66	PA66	260-290	60-100	80-140	40-75	15-30	① Include overflow wells for high shrinkage (1.5-2%). ② Gate away from load-bearing areas.

High-Temp Plastics	PPS	PPS	300-350	130-160	100-160	60-90	40-60	① Heated molds to prevent premature solidification. ② Tungsten carbide inserts for wear resistance.

	PEEK	PEEK	360-400	160-200	120-180	70-100	60-120	① Titanium/alloy steel molds required. ② Heated runners to prevent cold slugging.

Thermosets	Phenolic Resin	PF	160-190	170-190	100-150	60-100	60-120	① Corrosion-resistant (chrome-plated/stainless steel). ② Rapid venting to avoid scorching.

	Epoxy Resin	EP	120-160	150-180	80-120	50-80	90-180	① Tight parting line tolerance (≤0.02mm). ② Smooth ejection to prevent brittleness.

Elastomers	TPE	TPE	180-230	30-60	50-100	20-50	20-40	① High-polish runners to reduce sticking. ② Avoid pin-point gates (stringing risk).

	LSR	LSR	20-40 (material)	20-40	10-30	5-15	30-90	① Cold runner systems with chilled molds (20-40°C). ② Vent depth: 0.01-0.02mm for bubble-free parts.

Key Process and Mold Design Guidelines

Temperature Control:

Thermoplastics: Melt and mold temperatures directly affect crystallinity (e.g., low mold temp for PP increases shrinkage).
Thermosets: High mold temperatures are critical for curing, requiring electric heating systems.

Pressure Parameters:

Injection Pressure: High-viscosity materials (e.g., PC, PEEK) need high-pressure filling.
Hold Pressure: Engineering plastics (e.g., PA, PPS) require extended hold times to compensate for shrinkage.

Mold Steel Selection:

Standard Plastics: P20 steel (nitrided surface).
High-Temp/Corrosive Materials: H13 steel, S136 stainless steel, or titanium alloys.

Special Design Requirements:

Venting System: Thermosets and LSR need intensive venting (0.01-0.03mm groove depth).
Cooling Channels: Fast-cooling materials (e.g., PP) require conformal cooling, while high-temp materials (e.g., PEEK) may omit cooling.

Gate Design:

Thermoplastics: Submarine gates (self-degating) are preferred.
Elastomers: Open gates are recommended to avoid shear-induced overheating.

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