Mold-Making.com is a professional liquid silicone rubber(LSR) injection molding and liquid silicone rubber parts manufacturer from china.
Our liquid silicone rubber molding process produces custom prototypes and end-use production parts in 15 days or less. We use aluminum molds that offer cost-efficient tooling and accelerated manufacturing cycles, and stock various grades and durometers of LSR materials.
What is liquid silicone rubber(LSR)?
Liquid Silicone Rubber (LSR) has existed since the late 1970s and has become the material of choice for manufacturing rubber parts and products. The distinctive qualities of liquid silicone rubber injection molding make it different from molding conventional high-consistency silicone and other thermoplastic injection molding processes.
Liquid Silicone Rubber injection molding has thousands of applications across a variety of industries, including medical, automotive, infant care, general industrial markets, aerospace, electronics, and many other specialized industries. While liquid silicone rubber injection molding works best for short- and long-run part production, customers can employ the process in the final stages of prototyping. The process is also suitable for the evaluation of different material configurations before green-lighting a project for full production.
As one of the global premier injection molding companies, MOLD-MAKING works with liquid silicone rubber injection molding many years. We have produced billions of liquid silicone rubber parts for leading businesses partners worldwide. We have the manufacturing expertise to provide services that range from prototyping to serial production of high-precision components.
MOLD-MAKING’s ability to provide fast, high-quality service has led to a global reputation for commitment to customer satisfaction and our team of liquid silicone rubber injection molding experts can assist you through the entire process. Contact your MOLD-MAKING representative today and learn how we can help you with your liquid silicone rubber injection molding needs.
How Does Liquid Silicone Rubber Molding Work?
LSR molding differs slightly from thermoplastic injection molding due to its flexibility. Like a standard aluminum tool, an LSR molding tool is fabricated using CNC machining to create a high-temperature tool built to withstand the LSR molding process. After milling, the tool is polished by hand to customer specifications, which allows six standard surface finish options.
From there, the finished tool is loaded into an advanced LSR-specific injection molding press that is precision geared for accurate control of shot size to produce the most consistent LSR parts. At Mold-Making, LSR parts are manually removed from the mold, as injector pins can impact part quality. LSR materials include standard silicones and specific grades to fit various part applications and industries like medical, automotive, and lighting. Since LSR is a thermosetting polymer, its molded state is permanent—once it is set, it can’t be melted again like a thermoplastic. When the run is complete, parts (or the initial sample run) are boxed and shipped shortly thereafter.
LSR Liquid Silicone Rubber Injection Molding Process
Our liquid silicone rubber injection molding machine appears to look just like thermoplastic injection molding machines. Both types of presses use the same basic machine parts, clamp unit, and injection unit.
The LSR injection molding machine clamp unit is identical for liquid silicone rubber and thermoplastic machines. The silicone injection molding machines typically have a hydraulic ram and may have a hydraulic toggle. Some presses are designed with an electric ram with toggle. Unlike the high pressures used to mold thermoplastic parts, liquid silicone injection pressure is in the range of 800 PSI. The purpose of the clamp is to contain the expansion force of the silicone material, by keeping the mold closed as the silicone cures.
The injection unit for liquid silicone runs cool with a water cooled barrel and nozzle to prevent the liquid silicone from curing. Thermoplastic injection units run the opposite way, they need the barrel and nozzle to be heated to 300F or more to keep the material moving. Liquid injection molding units also run at lower pressures (under 1,000 PSI), while their thermoplastic counterparts run at tens of thousands of PSI.
Liquid silicone is typically provided in 5 gallon pail or 55 gallon drums. There is a part A and Part B. Colorants come in the form of dispersions and are normally 1-3% by weight of mixed silicone. The silicone dousing unit pumps one part A silicone and one part B silicone via separate hoses to the static mixer. In addition, color is pumped to the static mixer via another hose. The mixed components are then fed into the throat of the injection molding barrel by way of a shut-off valve.
Once the silicone material is inside the barrel, a shot of the cool mixed silicone advances to the mold as the nozzle seals firmly against the mold. The nozzle shut-off valve opens and a measured shot of cool liquid silicone is injected into a hot (275F to 390F) clamped mold. Then the nozzle shut-off valve opens and the barrel retracts from the mold, while the screw begins to build another measured shot of cold liquid silicone.
After the silicone vulcanizes in the heated mold, the clamp will open and parts are then manually removed or automatically ejected. Cycle times for liquid silicone molded parts are often similar to their thermoplastic counterparts.
As the production molding run comes to a close, the liquid silicone injection molding press must be readied for a new material for a different part design. It is not acceptable to purge out the system with the new silicone, which will result in the new parts having the last production runs’ silicone in them. Therefore, everything must be cleaned out, which can easily take a day to clean, depending on which injection molding press is used.
Our workshop for LSR Production:
Some of LSR products we have producd before: