Manufacturing processes have greatly evolved over the years. One of them is Liquid Silicone Rubber Molding that forms liquid silicone rubber. Compared with compression molding, in this process, the material is introduced to a closed mold through a system of runners, sub-runners, and sprues. Once the molded parts are set, the mold is opened and the parts removed. This process will be repeated until the requirements are fulfilled.
Here is an in-depth look at how the liquid silicone rubber molding works.
Liquid Silicone Rubber Process
Step 1. The liquid silicone rubber process is the first part of the LSR molding method. It starts with silicone contained in two barrels: one is for the cure, while the other is for the accelerant. These two substances are then combined using an internal mixer in a ratio of one is to one. Colors may be added at this stage if needed.
Step 2. Liquid silicone rubber molding is an automated process and customized for every job. The injection molding settings and the correct size of the shot are programmed into the machine. Other than that, the settings for the cycle, pressure, and temperature are also adjusted accordingly.
Step 3. When the setup is completed, the mold will be heated to a temperature between 300 to 350 Fahrenheit. Once this temperature is achieved, the clamping force will take effect, and the mold will be closed. With the mold closed, the screw will plunge forward and force the material into the mold. It will also fill all the spaces in the cavity.
Step 4. The next step is applying heat and pressure to the liquid silicone rubber material and letting it cure until it reaches the solid-state. When the whole cycle is completed, the mold opens, and the operator can remove the final part with flashes. The mold will close again and repeat the cycle.
Step 5. The parts will proceed to the post-molding processes that include post-curing, de-flashing, inspection, and packaging.
Applications of Liquid Silicone Rubber Molding
The liquid silicone rubber molding process is a highly automated process that benefits the manufacturer because it has a short cycle time and a reduced price on the finished product. One of the benefits of the liquid silicone rubber is it has a high degree of chemical, electrical, and thermal resistance. It makes it compatible with many industries, particularly for medical uses, because it is biocompatible and can undergo sterilization.
The inert qualities of the LSR make it ideal for medical devices. It can cure completely and quickly, which is critical when the medical devices are placed inside the body. This is necessary because that means it will not leach chemicals that could lead to an adverse chemical reaction. Compared to latex that does not completely cure during its production that could lead to adverse reactions from the patients.
The chemical makeup of LSR is also favorable because it does not degrade when heated at high temperatures. That means it can handle the sterilization process that makes it ideal for manufacturing baby care and medical products.