Injection Molding Process Guide for PE Plastics

Injection molding is one of the most widely used manufacturing processes for producing plastic parts in large volumes. Polyethylene (PE) is one of the most common materials.

1. Barrel Temperature

(1)LDPE (MFR 1–6g/10min)

• Feed zone: 50–130°C

• Plasticizing zone: 140–220°C

• Nozzle: 160–220°C

• Melt temperature: 180–220°C (decomposition temp ≈ 300°C)

(2)HDPE (MFR 2–10g/10min)

• Feed zone: 50–140°C

• Plasticizing zone: 160–250°C

• Nozzle: 180–240°C

• Melt temperature: 200–220°C (decomposition temp ≈ 350°C)

2. Mold Temperature

· LDPE parts: 35–60°C

· HDPE parts: 50–80°C

3. Injection pressure: 60–140 MPa (higher for thin-walled parts, lower for simple, thick-walled parts)

4. Packing pressure: 30–60% of injection pressure, held for 5–40 seconds

Screw back pressure: 5–20 MPa (use high screw speed for better melting)

5. Shot size: 0.5–4.0 times the screw diameter (D)

6. Mold Design & Preprocessing

· Use pinpoint gates, with a runner-to-wall thickness ratio of (50–100):1. Heated or insulated hot runner systems are recommended.

· Dry HDPE at 70–80°C for 1–2 hours if moisture is present.

· Clean the barrel by purging with PE, and recycle scrap material by grinding and blending it into new batches.