Liquid Silicone Injection Molding, also referred to as LIM, is a process that is widely used to make silicone parts (considered thermosets) for industries that need parts that can withstand extreme temperatures, ozone, weather and chemicals. The key component to this type of molding is the use of a liquid silicone rubber that is pre-catalyzed, pigmented and mixed prior to injection into the mold. This allows for quick cycle times and less raw material handling which makes the process highly efficient.
The injected LSR is cured inside the closed injection mold by heat from the dosing unit, and the pressure that is applied to the molding press. This allows the silicone to fully cure in a matter of seconds, which is much faster than any other process available for making silicone parts. It also allows for a more accurate part size since the silicone is allowed to elongate and expand during the cure process. The LIM process is also very cost-effective as compared to other silicone production methods such as compression molding, which requires labor intensive preparation of the silicone rubber to make it moldable.
ASH produces many different types of silicone parts using the LIM process, including medical grade varieties. Injection of the LSR into a medical-grade mold allows for a quicker and more precise cure time, which is essential to meet the strict requirements that come with manufacturing silicone parts for medical applications. This quick cure time, along with other features such as low outgassing and low compression set, is what makes the LIM process so effective for many different applications.
LIM is a very simple process, and ASH’s team of Production Engineers will work with you to determine the ideal type of silicone for your project and the best method of molding that will deliver the results you are looking for. Silicone LIM is often a much more economical option than the traditional compression molding of gum based silicones. This is due to the fact that it can be produced in a much shorter cycle time, allowing for higher production volumes and quicker delivery of your finished silicone part.
Another benefit to the LIM process is that it can utilize a smaller number of cavities in the mold than compression molding, resulting in lower tooling costs. Injection of the LSR into fewer cavities within the mold also means that there is less chance for air entrapment, which can lead to flawed silicone parts. Venting is critical for this type of silicone injection molding, and ASH’s engineers will work closely with you to ensure that your mold design is properly vented to avoid the risk of hot tearing once your parts are ejected from the mold. This is an important factor to keep in mind as you design your part and will allow ASH to give you the most accurate quotes for production. liquid silicone molding