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The Choice Between Compression Molding and LSI Molding

by Nice Rapid | Sep 23,2022 | Silicone Molding

If you have a project requiring liquid silicone rubber, there are two ways to go about it. You can work with compression molding or liquid silicone injection. Your workshop of choice usually lets you in the details that fit your project better, but you need to understand the reasons behind their thinking. The basics are always the first ones to rear their heads: dimension, design complexity, the volume of the order, and others. But there are more specific factors, and you should also know them.

Compression Molding

Compression molding is an old-school manufacturing technique. It uses heat-curated, weighed-out pieces of silicone rubber to make products. The rubber needs to be heated to the point of malleability required for the part. The heated molds are pressed and assisted by a silicone elastomer that help fills all the cavities on the mold.

The silicone must undergo crystallization by adding other materials and pigments if you want colored parts. By the time the mix is done, it must be shaped and cut into small pieces that fit the weight criteria of your project. You can handle the process in the open, but contaminants can do a number on the parts you’re crafting. Compression molding has been slowly phased out by its more famous cousin.

Food grade silicone cube trays

Liquid Silicone Injection Molding

LSR injection molding is the best way to handle liquid silicone rubber in the market these days. It relies on a binary system that supplies material into a closed echo chamber or mold without too many risks. LSR injection molding is a process that has to be handled by machinery. As such, the hardware can take raw, sealed silicone that can include all the extras required to make your part a reality, even pigmentation.

The first part of the process is the pouring of silicone, and the second is the pouring of the catalysts that seal the deal. These catalysts include an inhibitor agent that makes the curing process easier and faster. All these materials must be dispensed through pumps and nozzles, and the cooling process takes seconds. It’s no wonder this manufacturing process has become so popular. You can get large orders done in a single day.

Comparing the Two Manufacturing Techniques

Suppose you choose to work with silicone rubber injection. In that case, you’ll work in a fully enclosed, semi-automatic system that lays little to no waste and blocks all debris and particles that could contaminate your mold or products. Injecting liquid silicone rubber reduces the cycles of production while increasing your input. You can program lower injection pressures by the viscosity of the silicone you’re working with. You get tight tolerances, consistent quality, and a clean finish.

Compression molding requires a lot more logistics and a lot of handy work with specialized technicians. It involves more people, which could risk the final build of your part. Measuring the raw materials to get things done is a drag since all the pre-chemistry work needs to be sorted before any molten plastics are poured into the casts. If you get a single fraction of the numbers off the mark, you risk getting parts lacking their desired properties which translates into a loss of revenue for your business.

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