Cracks, narrow fissures appearing on injection-molded parts, can stem from issues with the injection molding machine, mold, molding process, and raw materials.

1. Injection Molding Machine: The Test of Plasticizing Capacity

Insufficient plasticizing capacity, resulting in incomplete melting, is a primary cause of cracks. Upgrading to a machine with greater plasticizing capacity is crucial.

2. Mold: Where Details Make or Break

• Poor ventilation leads to flow marks, weakening part strength.

• Oversized gates cause overpressure in molded parts.

• Leaks in cavities or cores; check for micro-cracks.

• Excessively thin part design requires reinforcing ribs.

• Ensure mold cavities and cores have adequate draft angles.

• Mold maintenance is needed to prevent ejector pin oil from contaminating surfaces.

• Increase ejector pin diameter and reduce ejection speed.

3. Injection Molding Process: The Art of Precise Control

• Adjust barrel temperature to avoid material decomposition at high temps or insufficient welding strength at low temps.

• Manage injection pressure; elevate temperature for smooth mold filling and reduced viscosity; reduce pressure to avoid internal stress-induced cracks.

• Decrease preform back pressure and screw speed to prevent material degradation.

• Appropriately increase injection speed.

• Extend cooling time to ensure proper solidification, preventing jetting cracks or marks.

4. Raw Materials: Ensuring Purity and Dryness

• Completely dry raw materials to prevent moisture-related cracks.

• Identify and control impurities in raw materials.

• Determine the appropriate proportion of recycled material through testing to avoid excessive addition.