Introduction
Liquid Silicone Rubber is an elastomer that has high fluidity at high temperature. Base Cross-linker polymer and catalyst are the two important components of liquid silicone rubber and their composition plays an essential role in the moulding process.
Methods of LSR Moulding
The process of injecting material at a specific pressure and converting it into a pre-made mould is the first step of the LSR moulding process. It allows the material to flow inside cavities. Some of the effective methods to follow this procedure are as follows:
- Injection Moulding
- Compression Moulding
- Rotational Moulding
- Over Moulding
It is important to note that these different methods require different equipment and procedures.
Injection Moulding:
The process of injection moulding for LSR consists of injecting liquid silicone rubber into the mould of injection. The process is similar to all other injection moulding processes but there is a difference in the set up and tooling of this process. In this process, cross-linked polymers and catalysts are stored in two different units. Even pigments and additives are also stored in separate units. These four elements are mixed uniformly to form a mixture before the injecting process and then nozzle is used to inject the mixture into the mould. The temperature range of LSR moulding is between 180 to 200℃ whereas the pressure of injection is between 200 to 1200 psi. Following is the list of steps, used for LSR injection molding process:
- Mold Creation which includes designing of silicone injection mold.
- Preparing LSR Material which includes preparation of base polymers, additives and catalysts.
- Injection Molding which includes injecting LSR mixture into the mold while controlling the pressure.
- Curing which includes curing of LSR into solid or elastic state due to heat of the mold.
- Demolding which includes safely ejecting the cured parts.
- Post-Curing which includes baking those parts and completing the cross-linking process.
- Quality control which includes inspection and testing of parts.
- Finishing Touches which includes finishing the secondary operations.
Compression Molding
Compression Molding is considered the easiest method for LSR molding. Its process includes molding of liquid silicone into a pre-heated open mold. The range of pre-heating temperature lies between 170-200℃, according to the size and thickness of the desired part. Once the part is placed correctly, a press mechanism is used to compress the material which allows the material to flow and capture the parts of mold cavities. This process is considered best for small and medium level production as it contributes to long production cycles.
Rotational Molding
Rotational Molding is specially used to make hollow-shaped parts from liquid silicone rubber. Its process includes heating of silicone rubber in a hollow mold and then rotate it in the oven. The mold should be rotated until it is coated and is formed into the desired shape. However, its curing process is quite different from the curing process of other methods due to which it is a less prevalent method.
Over Molding
Process of over molding the LSR is a combination of its high performance and its structural properties to attain the required functionality. It is important to keep the insert on mold before the filling of LSR material.
Applications of Liquid Silicone Rubber Molding
Liquid Silicone Rubber is used in various industries and for various purposes due to its diverse properties. Following is some of the sectors where LSR is used prominently:
- Medical Sector: LSR molding is used in various instruments of medical sectors such as surgical tools, endoscopic caps, components of insulin pump, respiratory masks, etc.
- Automotive Sector: In the automotive sector, LSR molding is used for engine seals, gaskets, O-ring seals, transmission parts, Air intake systems, etc.
- Electronics Sector: LSR molding is used in the production of tablet cases, keyboard covers, smartwatch bands, etc.
- Sports and Leisure Sector: In the sports and leisure sector, LSR molding is used for diving masks, fitness equipment, sports shoe inserts, knee and elbow guards, etc.
- Aerospace Sector: LSR molding is used in fuel houses, insulation seals, hydraulic seals, window seals, etc.
- Dental Products: LSR molding is also used in various dental products such as mouthguards, dental picks, denture adhesives, etc.
Advantages of LSR Moulding
Some of the advantages of LSR mouldings are as follows:
- Precision and Detail: LSR mouldings help in the production of highly complex and precise parts.
- Consistency: A uniformity and reproducibility are seen in the end products, made with this process which reduces the chances of variations.
- Versatility: Products made from LSR moulding consist of various properties such as flexibility, transparency and durability.
- Biocompatibility: Due to its non-toxic nature, LSR is also used in the medical and healthcare sector.
- Efficiency: LSR mouldings lead to production of large volumes in short term cycles.
- Durability: Parts made with the process of LSR mouldings have outstanding wear resistance which extends its life for long term.
- Temperature Resistance: LSR materials have a strong temperature resistance due to its stability over a wide range of temperatures.
- Reduced Waste: Precision in the moulding process comes due to the minimization of waste. LSR moulding also helps in protecting our environment and cost reduction.
- Colour Customization: LSR materials are easy to colour which provides a wide range of colour options.
- Minimum Finishing Requirements: The products made through the LSR moulding process requires less finishing.
Take Away
This is the brief explanation about different methods, applications and advantages of Liquid Silicone Rubber Molding. We hope those tips will be effective for you. Please let us know through your valuable feedback and the suggestion in the drop box.