Difference between Thermal Injection and Compression

Numerous benefits to the qualities of its components and the production process are provided by compression molding. Compared to parts made by injection molding, components made by compression have a longer lifespan. They feature a greater surface quality, extremely less shrink, and no visible injection gate. Changes to the material and color are quite simple.

For small batch sizes, compression molding is therefore perfect. The strong forces of resistance characteristic of thermosets are produced by a chemical reaction between thermosets and pressure at temperatures between 130 and 180°C. Granulates, powders, tablets, SMC mats, and BMC compounds are some of the forms in which thermoset materials can be treated.

Thermoset Molding: Injection vs. Compression

Although selecting the best molding process for your thermoset item might be difficult, there are typically cues provided by the design and program end-use application that point in the direction of a certain molding technique. Thermosets process can be injection or thermoset compression molding. Before procuring a new tool construction, thermoset molders and end users need to weigh the advantages and disadvantages of each molding technique.

Variables such as program yearly quantities, material property requirements, part design geometries, and use of molded-in inserts can all determine whether a component is better suited to be thermoset injection molded or created with another molding method for thermoplastic molding.

Injection

For thermoset components, the injection molding process is widely used in various sectors. In comparison to compression or transfer molding, the thermoset injection molding method has an extremely short cycle time, which enables a thermoset molder to produce more in a day or shift. This method is used by the automobile and home appliance industries to make high-volume thermoset components that can be swiftly sent to customer factories. 

Molders can make large numbers of thermoset components daily in multi-cavity tools thanks to a thermoset injection molding technique that can save up to 50% of machine time each shot and have a faster cycle time than a thermoset compression molding process. Faster cycle times are advantageous for a variety of projects, not only high-volume ones. For example, thermoset injection molded parts require less machine time during a single production run, which lowers unit costs for customers and frees up machine time for other tasks.

Compression

Compared to thermoset injection molding, thermoset compression molding has certain clear benefits and drawbacks. In thermoset injection, the material is forced from a hopper (phenolic material) or hydraulic stuffer (bulk molding compound/BMC material) into a screw and barrel to preheat before being injected into a hot mold. The glass fiber fillers that comprise some thermoset polymers are broken up and distributed even more when the material is forced through the screw and barrel. This would be excellent in some applications since it would provide consistency of the material qualities because the glass is distributed equally across the portion.

Thermoset compression processes have shorter molding cycle times, which result in lower daily production yields and throughputs. As a result, they are less appropriate for high-volume programs than thermoset injection processes. While thermoset injection machines can more frequently mold automatically, requiring no operator to remain at the molding station to "demold," or remove components from the mold, compression molding also requires an operator or robot to manually load material and remove parts from the mold. 

Final Thought

There are broad markers that indicate whether injection molding or thermoset compression molding is a better fit for a thermoset program. The application such as thermoplastic molding and future program needs should always be taken into account and examined when determining which thermoset molding technique is ideal for your product application, even though these are frequent signs.