What are the molding methods in the silicone industry?

Silicone, as a widely used material in various fields, has various molding methods, each with its unique advantages and applicable scope.

Compression Molding

Compression molding is the most common and fundamental process in the production of silicone products. The core of this process lies in the use of molds, and the shape of the molds directly determines the shape of the final product. The specific process of compression molding is as follows:

1. Raw material preparation: Mix raw materials such as silicone rubber, vulcanizing agent, color masterbatch, etc. in a certain proportion, and then mix them evenly through a rubber mixing machine. The blended silicone raw materials should have appropriate viscosity and flowability for subsequent molding operations.

2. Mold design and production: Design and produce corresponding molds based on the shape and size of silicone products. Molds are usually made of steel with high hardness and precision to ensure the dimensional accuracy and surface smoothness of the formed products.

3. Molding operation: Place the mixed silicone raw material into the mold, and then place the mold into the vulcanizing machine for heating and pressure. At a certain temperature and pressure, silicone raw materials undergo sulfurization reactions to form the desired shape. The temperature for compression molding is usually within the high temperature range to ensure that the silicone raw material can be fully vulcanized.

4. Demolding and post-processing: After vulcanization is completed, remove the mold from the vulcanizing machine and perform demolding operations. After demolding, silicone products still need some post-processing, such as trimming burrs, cleaning, inspection, etc., to ensure the quality of the product.

The compression molding process has the advantages of high production efficiency, high product size accuracy, and suitability for large-scale production. However, this process also has some drawbacks, such as high mold costs and limited product shape. Therefore, when choosing compression molding, it is necessary to comprehensively consider factors such as specific product requirements, production conditions, and costs.

Injection molding

The injection molding process has higher quality requirements. It combines the advantages of liquid silicone and plastic, making the product have excellent thermal stability, cold resistance, excellent electrical insulation performance, and will not produce toxic substances during combustion. This characteristic makes injection molded silicone products occupy an irreplaceable position in fields such as health products, automobiles, baby products, medical supplies, diving products, kitchen utensils, and seals.

The specific process of injection molding is as follows:

1. Raw material preparation: Store the liquid silicone raw material in two components, A and B. Before molding, mix the raw materials of components A and B in a certain proportion to ensure stable product performance.
2. Mold design and production: Similar to compression molding, design and produce corresponding molds based on the shape and size of silicone products. The mold needs to have high precision and temperature resistance to adapt to the high temperature and high pressure environment of injection molding.
3. Injection molding: Inject the mixed liquid silicone raw materials into the mold through an injection molding machine. Injection molding machines are usually composed of injection systems, mold clamping systems, heating systems, cooling systems, etc. At a certain temperature and pressure, liquid silicone gel undergoes vulcanization reaction to form the desired shape.
4. Demolding and post-processing: After vulcanization is completed, remove the mold from the injection molding machine and perform demolding operations. The silicone products after demolding also need to undergo post-treatment to ensure product quality.
The injection molding process has the advantages of high precision, high smoothness, and high production efficiency. However, this process requires high equipment and molds, and the cost is relatively high. Therefore, when choosing injection molding, it is necessary to comprehensively consider factors such as product quality requirements, production scale, and cost.

Extrusion molding

Extrusion molding is the process of using a silicone extruder to extrude silicone raw materials into shape. This process is commonly used to produce tubular silicone products with longer shapes that can be cut freely, such as silicone tubes, silicone strips, etc. The specific process of extrusion molding is as follows:

1. Raw material preparation: Similar to compression molding and injection molding, raw materials such as silicone rubber, vulcanizing agents, colorants, etc. are mixed and blended to meet the requirements of extrusion molding.
2. Extruder debugging: Select a suitable extruder based on the shape and size of the silicone product and debug it. Extruders are usually composed of screws, barrels, heads, heating devices, etc. During the debugging process, it is necessary to ensure that the parameters such as screw speed and heating temperature meet the product requirements.
3. Extrusion molding: The blended silicone raw material is added to the extruder, and under the rotation of the screw, the silicone raw material is gradually pushed towards the machine head. At the machine head, silicone raw materials are extruded into the desired shape through a mold. During the extrusion molding process, it is necessary to control the speed of the screw and the heating temperature of the extruder to ensure the dimensional accuracy and surface quality of the product.
4. Cooling and cutting: The extruded silicone products need to go through processes such as cooling and cutting. Cooling can be achieved through water or air cooling to quickly solidify silicone products. Cutting can be done manually or automatically to cut silicone products into the desired length.

The extrusion molding process has the advantages of high production efficiency, regular product shape, and suitability for continuous production. However, this process also has some drawbacks, such as relatively low product size accuracy and high mold costs. Therefore, when choosing extrusion molding, it is necessary to comprehensively consider factors such as product shape requirements, production scale, and cost.

summary

The three main molding methods in the silicone industry – compression molding, injection molding, and extrusion molding – each have unique advantages and applicability. Compression molding is suitable for the production of various silicone products and has the advantages of high production efficiency and high product size accuracy; Injection molding requires higher quality and is suitable for fields such as health products and automobiles, with characteristics such as high precision and high smoothness; Extrusion molding is suitable for producing tubular silicone products with longer shapes that can be cut freely, and has the advantages of high production efficiency and regular product shapes.