Thermoset 101: How Are Thermosets Molded?
Thermosets are processed in similar functions to thermoplastics such as nylon, ABS, polypropylene, etc. Thermosets may be injection molded, compression molded, injection-compression molded, or transfer molded. Additionally thermosets can utilize molded-in inserts within the molding process.
Injection MoldingInjection molding offers a cost-efficient option for large volume applications that require a high throughput. Injection molding offers a faster cycle time, allowing more parts to be produced per hour vs. a compression or transfer molding process. In addition to higher throughput, the faster cycle times of injection molding provides a low unit part cost. Injection molding also offers better opportunity for multi-cavity tooling.
Injection-Compression MoldingInjection-compression is a hybrid molding process similar to injection, but where the mold opens slightly to degas after injection, and then closes as a compression type process. Injection-compression molding provides higher throughput similar to injection, but offers additional strength properties. Whereas straight injection molding will create a knit-line opposite the gate, injection-compression does not use gating to flow material directly to the parts, so there are no knit-lines or witness marks created.
Compression molding optimizes high strength characteristics. As with injection-compression, no knit-lines or witness marks are created. While straight compression offers the most compressive strength properties, the cycle times are much slower than injection processes, creating higher part costs and lower throughput. Compression molding is generally geared towards low volume applications requiring very high strength characteristics.