Silicone injection molding is an excellent process for producing a variety of high quality silicone rubber components. There are many factors to consider and account for in the process of making silicone rubber products. One of the most important factors is temperature, the changes that occur under different temperatures, and the effects these changes have on the final product. Heat can alter shot size, cure time, pressure, speed and velocity of injection. With the proper technology and knowledge, heat can be properly and accurately controlled.
Liquid Silicone Molding Components
Liquid silicone rubber is manufactured in two parts. They are divided into the “A” and “B” component. The “A” component contains the catalyst, either liquid platinum or a peroxide-based catalyst, and the “B” component contains a crosslink, allowing the two parts to mix uniformly and cure when heat is introduced. Silicone rubber is designed to cure quickly when heat is introduced, allowing for short cycle times and low production cost. The resulting component is very durable and resistant to most environmental factors, making it one of the most durable materials available.
Thickness and Heat
The exact temperature needed to produce the component varies, depending on many factors. The thickness of the part also determines the cure time; the thicker the part, the longer the cycle time. The heat changes the flow, as well as the viscosity of the silicone during injection. These factors will alter the exact amount of time need for the silicone to cure. The expected percentage of shrinkage can be slightly affected by the heat used during injection and pressure used in the mold.
Injection Factors
Liquid silicone rubber has a low viscosity, allowing it to be injected at relatively low pressures, even in a hot mold. The exact pressures required are determined by the heat, as well as the number of gate locations and dimensions. For most silicone rubber products and components, the injection time would be within five seconds. This helps to ensure that all crevices are filled before the silicone begins to cure. The higher the heat used, the higher the pressure needed to hold the silicone in the mold, preventing the material from leaking out of the gate. Adjusting the temperature and hold pressure simultaneously can help to avoid this problem and produce components more efficiently.
At Si-Tech, we use the latest in silicone rubber technology, which can adjust and hold temperatures consistently. All of our molds are designed with heat, pressure and speed taken into account to produce accurate components for the life of your product. All of our silicone components are designed and created in-house and domestically, to ensure the highest quality products available. For all of your silicone rubber needs, you can trust the experience Si-Tech has to offer.
