Manufacturing Methods For Silicone Rubber Parts
Silicone rubber parts offer a high level of quality and durability. Its resistance to extreme weather and temperatures, as well as its electrical insulation properties make it a highly sought-after material for many applications.
Whether you use compression, transfer or liquid silicone injection molding (LSR) to create your products, there are several steps that are involved in the manufacturing process. These include mixing the LSR materials, catalyst and casting mold on a 1:1 volume basis.
Injection Molding
Injection molding is one of the most popular methods for producing silicone rubber parts. It is used for products like gaskets, O-rings and seals as well as a variety of other applications. This process involves injecting liquid silicone rubber (LSR) into a Silicone rubber parts mold to form the desired shape. The injection molding process requires specialized equipment designed to handle the unique properties of LSR. This is because standard injection molders are equipped to work with thermoplastics, not LSR.
The LSR injection molding process begins with proper part design. This includes the use of correct tolerances to account for the high shrink rate of silicone rubber and the tendency for it to flash during the molding process. It is important to consider these factors when designing your product, as the proper tolerances can help avoid costly production errors.
Once your prototype is complete, you will need to prepare the LSR materials. Calculate the amount of material required to fill your mold and add 20% for loss. This will help ensure that you have enough material to fill your mold without overfilling it. The raw silicone material is supplied in barrels – Barrel A holds the base forming silicone and Barrel B contains a catalyst. A metering unit is used to release these two materials in a consistent one-to-one ratio. A static mixer is then used to combine the two ingredients before they are injected into a designated mold via a nozzle.
Extrusion
Rubber extrusion is a form of manufacturing that involves forcing silicone into a shaped die. This allows for a wide range of products to be produced quickly, efficiently, and with a high degree of precision. It is a popular process for producing things like tubing, hoses, and pipes of various sizes. These products are used in hydraulic and pneumatic equipment to transport gases and liquids. They are also useful for insulating electronic components and electrical cables.
A silicone extrusion can be made using a variety of different materials, including polysiloxanes and various plastics. It can also be made with multiple cross-sections, allowing for the creation of complex parts. The choice of which type of material to use depends on the final product requirements.
The raw material that is loaded into a extrusion machine can be in the form of granules, powders, or pellets. Once the mold is closed and heated, it forces the silicone into the desired shape.
The pressure that is exerted on the silicone is usually sufficient to achieve a complete seal with the mold. In some cases, additional post-cure steps may be necessary to improve mechanical performance and reduce the amount of leachables or extractables in the finished part.
3D Printing
In recent years, 3D printing has become a popular method for producing silicone rubber parts. This process reduces production time and costs by eliminating the need to create molds, allowing parts to be printed in hours or days instead of weeks. 3D printing also gives designers more freedom when designing their product, resulting in superior final products.
The most commonly used silicone material for 3D printing is liquid silicon rubber (LSR). This type of silicone offers many advantages, including its resistance to extreme temperatures and environments. It also has a range of mechanical properties that can be tailored for specific applications, such as hardness and tensile strength. LSR is often used for medical, automotive and aerospace components.
There are several ways to make LSR parts using 3D printers. One way is to use a drop jet system, which prints layers of LSR with a UV-activating binder. This system allows for high printing density, allowing the machine to print multiple parts at once without affecting the quality of each part. A specialized nozzle allows for precise placement of the LSR and ensures consistent printing.
Another method is to use a resin system, which is similar to traditional injection molding. This system prints a rigid mold in a heat-resistant material, such as ABS, which is then filled with the LSR. The silicone is then cured in a vacuum chamber, ensuring that air bubbles do not form.
Duplication
The duplication process is a great way to quickly create a high quality silicone rubber mold of any shape or size. The process allows for a variety of materials and colors to be cast into the silicone molds. This can include polyurethane resins such as urethane, epoxy or polyester, gypsum and wax.
The first step in duplication is to build a master pattern of the part to be copied. This can be done in Silicone Rubber Parts – Supplier pattern shops with traditional clay, wood or plastics or with rapid prototyping technologies such as selective laser sintering from 3D Systems and Stratasys, PolyJet from Objet Geometries, or CNC machining.
Once the master pattern has been constructed, a silicone mold can be made. Many different silicones are available with a range of specifications such as hardness (durometer rating), tensile strength, elongation, heat deflection temperature and clarity. In addition, it is important to select a silicone that is resistant to inhibition. Inhibition is caused by contaminants on or in the master that can prevent the crosslinking of the silicone and result in a tacky master, uncured rubber or failure to produce a quality duplicate.
Fluorosilicone has been shown to be compatible with a wide variety of thermoplastic and thermosetting materials including PS, PLLA, SEBS, SMP and Sylgard-184. It also provides a good level of mechanical durability for soft lithography applications.
