Flexibility
Silicone’s flexibility makes it easy to work with. Silicone molds are pliable and lightweight compared to stiffer substances like plastic and they’re also easier to remove once a part is fully formed. Thanks to silicone’s high level of flexibility, both the mold and the fabricated part are less likely to break or chip. You can use custom silicone molds to shape everything from complex engineering components to holiday-themed ice cubes or confections.
Stability
Silicone withstands temperatures from -65° to 400° degrees Celsius. Additionally, it can have an elongation of 700%, depending on the formulation. Highly stable under a broad range of conditions, you can put silicone molds in the oven, freeze them, and stretch them during removal.
Durability
In most cases, you’ll get many runs out of a silicone mold. However, it’s important to note that the life span of molds can vary greatly. The more frequently you cast, and the more complex or detailed your design, the faster your mold might degrade. To maximize the life of your silicone molds, clean them with mild soap and water, dry them thoroughly, and store them flat without stacking.
Liquid silicone rubber molding enables the creation of high-volume, intricate, and consistent components. Injection molding is employed to fabricate products from both thermoplastic and thermoset materials. This method entails loading the material into a heated chamber, blending it, and subsequently propelling it into the mold cavity via a reciprocating screw or plunger. The injection-molded item is then solidified to match the mold cavity's form.
Initially, a liquid silicone rubber molding tool is crafted through CNC machining. This tool must be capable of withstanding high temperatures to endure the LSR injection molding process. The tool can then be polished to offer various finish options.
Subsequently, the completed tool is installed into an injection molding machine specifically designed for LSR, which is finely calibrated to accurately control the injection volume to produce the most consistent LSR parts. Materials utilized include standard silicone and specific grades tailored to different part applications. Since LSRs are thermoset polymers, their molded state is permanent. Unlike thermoplastics, they cannot be remelted. Once an LSR injection molded part is ready, it can be removed from the mold and used as a prototype or production part.
Injection molded silicone rubber is an ideal solution for a variety of industries, including medical, lighting, and automotive.
General-purpose silicone rubber (with hardness levels of 30, 40, 50, 60, and 70)
Medical-grade silicone rubber
Optical-grade silicone rubber
Fluorosilicone (resistant to fuels and oils)
High Production Efficiency: It can produce large quantities of parts in a relatively short time, which is suitable for mass production.
Precision and Consistency: The process can create highly precise and consistent parts with tight tolerances, ensuring uniform quality.
Design Flexibility: It allows for complex and intricate part designs, enabling the production of parts with detailed features and tight specifications.
Material Properties: Liquid silicone rubber has excellent properties such as high temperature resistance, chemical resistance, and good mechanical properties, making it suitable for a wide range of applications.
Cost-effectiveness: Although the initial tooling cost may be high, the cost per part decreases significantly with increased production volume, making it cost-effective for large-scale production.
Reduced Waste: The injection molding process minimizes material waste compared to other manufacturing methods, as the material is precisely metered and injected into the mold.
Versatility: It can be used to produce parts for various industries, including medical, automotive, consumer electronics, and more.
Short Cycle Time: The cycle time for producing each part is relatively short, which further enhances production efficiency.
Color and Additive Options: A wide range of colors and additives can be incorporated into the liquid silicone rubber to meet specific requirements.
Post-processing Minimization: The parts produced are often close to the final product, requiring minimal post-processing.
Medical Devices: Production of components for medical equipment, surgical instruments, and implants, benefiting from silicone's biocompatibility and sterilization resistance.
Automotive Industry: Manufacturing of gaskets, seals, hoses, and other parts that require high temperature and chemical resistance.
Consumer Electronics: Creating seals, gaskets, and protective casings for electronic devices to ensure durability and protection against moisture and dust.
Household Appliances: Used for making seals, gaskets, and flexible components in appliances such as washing machines, refrigerators, and ovens.
Lighting Industry: Production of silicone components for LED lighting, including lenses, diffusers, and protective covers.
Industrial Components: Fabrication of parts for various industrial applications, such as seals, gaskets, and flexible couplings.
Aerospace: Used in the production of components that require high reliability and performance under extreme conditions.
Toys and Consumer Goods: Manufacturing of soft, flexible, and safe components for toys and other consumer products.
Food and Beverage Industry: Production of food-grade silicone products such as baking molds, kitchen utensils, and seals for food processing equipment.
Personal Care Products: Used in the production of components for personal care items such as toothbrushes, razors, and other hygiene products.
Whether used alone or in combination with overmolding, liquid silicone rubber injection molding is the best method for producing complex and high-temperature-resistant items with thermoset liquid silicone rubber. In silicone rubber injection molding, the polymer is injected into the mold under high pressure to form the part. The steps of this process are very brief. Typically, the entire injection molding process takes two to twenty minutes. This cycle consists of four phases. These steps are the clamping, injection, cooling, and ejection phases.
Clamping
Usually, the mold is heated by electric heaters or water flowing through the mold. In addition, a cold runner system can be used to prevent the flowing silicone rubber in or around the runner area from curing prematurely. In the field of liquid silicone rubber molding, the LSRA+B components usually arrive at the appropriate injection molding machine, where they are heated to form the molded rubber parts. The barrel is compressed by a process-controlled pumping unit, which feeds the material into the static mixer and injection device.
Injection
Pipes and tubes can be used to pump the silicone rubber material into the injection molding machine for vulcanization with liquid silicone rubber. The granules are melted by the pressure and heat around the barrel. The term "injection" refers to the amount of material injected. When the mold is filled to 95% to 99% of its capacity, the injection phase is completed.
A stage of continuous pressurization is the injection molding machine's holding pressure step. The density of the silicone rubber also increases with the increase in injection molding machine pressure. During the holding pressure process, the mold cavity is gradually filled with liquid silicone rubber material, causing the injection molding machine's back pressure to gradually rise. The injection molding machine screw advances slowly throughout the holding pressure phase, and the reaction time of the silicone rubber is also slow. Holding pressure flow is the term used to describe this type of flow.
The silicone rubber cools during the holding pressure phase of the injection molding machine, causing it to solidify more quickly, increasing the melt viscosity, and significantly increasing the cavity resistance. The material density continues to rise as the holding pressure progresses, and now silicone rubber products are also produced by injection molding. When the gate hardens, the pressure inside the cavity reaches its highest level, and the holding pressure step ends.
Cooling
The design of the cooling system is crucial for liquid silicone rubber injection molds. This is because the molded silicone rubber product can only cool to a specific hardness before being ejected from the mold to prevent deformation caused by external forces. An intelligent cooling system can significantly reduce the molding time, increase injection molding output, and save costs, as the cooling time accounts for 70% to 80% of the entire molding cycle.
Ejection
Ejector pins are commonly used in thermoplastic molds, but liquid silicone rubber molding does not require them. When the mold is opened at the end of the molding cycle, the complete product remains on one half of the mold. Ideally, the characteristics of the product should be above the parting line surface, making it easier to demold the product.
