TPE Injection Molding Advances Boost Production Efficiency

In manufacturing, even a minor error can lead to thousands of defective products, creating significant inefficiencies. For companies using thermoplastic elastomers (TPE) in injection molding, understanding how to mitigate risks and achieve stable, high-quality production is critical. This article explores key factors in TPE injection molding to optimize processes and enhance product quality.

TPE combines rubber-like elasticity with the processability of plastics, making it ideal for automotive, medical, and consumer applications. Injection molding is one of the most common methods for producing TPE components. The process involves feeding TPE pellets into a hopper, melting them into a liquid resin in a heated barrel, and injecting the material under high pressure into a closed mold. After cooling, the finished TPE part is ejected. While injection molding is suitable for mass production, initial mold costs can be high. High-performance TPE materials can shorten cycle times, improving overall efficiency.

The following parameters provide a general framework for TPE injection molding. Specific settings should be adjusted based on material grade and application requirements.

• Equipment Selection: Standard injection molding machines are suitable for TPE. Key considerations include matching machine specifications (clamping force, shot size) to part dimensions and production volume.
• Screw Design: A minimum 2:1 compression ratio ensures uniform melting. For low-speed operations, high-compression (3:1 to 4:1) screws with short pitches improve plastification and reduce material degradation.
• Shrinkage Control: TPE shrinkage varies by material grade, part design, and processing conditions. Mold designs must account for shrinkage, and adjustments to mold temperature or packing pressure can enhance dimensional stability.
• Mold Surface Finish: EDM or sandblasting optimizes surface texture for filling and release. EDM provides finer finishes, while sandblasting increases friction to prevent sticking.
• Ejection Methods: Soft TPEs require careful ejection to avoid deformation. Ejector plates distribute force evenly, while larger ejector pins should target rigid sections. Draft angles and air-assisted ejection may also help.
• Gate Design: Gate type impacts filling and quality. Diaphragm gates suit thin-walled parts, fan gates reduce flow resistance, submarine gates enable automatic degating, and multi-valve gates control complex flows.
• Venting: Proper venting (0.01–0.02 mm depth) prevents air traps and defects. Vents should be placed at flow endpoints or gas-prone areas, with additional options like vent pins or vacuum systems.
• Temperature Management: Precise control of runner, barrel, and mold temperatures ensures proper melt flow. Higher mold temperatures improve surface finish but extend cycle times.
• Injection Speed: SEBS benefits from high speeds to reduce viscosity, while SBS requires moderate speeds to avoid excessive shear.

In addition to injection molding, TPE can be processed via extrusion or two-component (2K) molding, including overmolding and co-extrusion.

Technical resources are available for these methods, providing guidance on material selection and process optimization.