Molded or injected? Advantages and disadvantages of the rubber seal molding process
Molding machines (compression molding) and injection machines (injection molding) are two molding processes commonly used in the production of rubber products. Each of them has unique advantages and disadvantages and is suitable for the production of different types of rubber products. The following will make a detailed comparison of the aspects of process flow, production efficiency, product quality, cost, etc., and provide relevant data support.
Process
Compression molding
Compression molding is to put the pre-weighed rubber compound into the heated mold cavity, applying pressure and temperature through the plate vulcanizing machine, make the rubber flow in the mold and fill the cavity, and after a certain period of vulcanization reaction, form the rubber products of the desired shape. This process is suitable for products with simple shapes and large sizes, such as gaskets, sealing rings, etc.
Injection molding
Injection molding is to send the rubber compound into the heated barrel of the injection machine through the feeding device, and after the rubber material is heated and plasticized in the barrel, the melted rubber material is quickly injected into the closed mold cavity through the high-pressure action of the screw or plunger, and the product is formed by vulcanization. This process is suitable for products with complex shapes and high dimensional accuracy requirements, such as seals, shock-absorbing pads, etc.
Productivity
Compression molding
The production cycle of compression molding is relatively long, including the steps of placing the rubber compound, clamping the mold, heating and vulcanizing, opening the mold, and taking the parts. The time of each cycle depends on the thickness and complexity of the product and generally ranges from a few minutes to tens of minutes. Therefore, compression molding is more suitable for low-volume production.
Injection molding
Injection molding has a high production efficiency. Because the rubber has been heated and plasticized before injection, the injection time into the mold cavity is only 1~5 seconds, and the vulcanization time is also shorter. Therefore, the production efficiency of injection molding is 4~7 times higher than that of compression molding, which is suitable for mass production.
Product Quality
Compression molding
The quality of the molded product depends on the fluidity of the compound and the mold design. Due to the short flow distance of the rubber in the mold, it is easy to produce bubbles, inclusions, and other defects, which affect the compactness and mechanical properties of the product. In addition, the dimensional accuracy of compression-molded products is relatively low, and subsequent trimming is required.
Injection molding
Injection-molded products are of high quality. Because the rubber fills the mold cavity under high pressure, it can reproduce complex details, the dimensional accuracy of the product is high, and the surface finish is good. At the same time, the injection-molded products have high compactness, excellent mechanical properties, and less flash, which reduces the follow-up dressing work.
Cost
Compression molding
The cost of equipment and molds for compression molding is relatively low, which is suitable for small batches and multi-variety production. However, due to the low production efficiency, the labor cost is high, and the product needs to be repaired later, which increases the production cost.
Injection molding
The cost of equipment and molds for injection molding is high, especially the complex structure of the mold and the high manufacturing cost. However, due to the high production efficiency, the cost of a single product is low, which is suitable for mass production. In addition, injection molding reduces flash, saves rubber, and lowers material costs.
Scope of application
Compression molding
It is suitable for products with simple shapes and large sizes, or production occasions with small batches. For example, large gaskets, thick-walled products, etc.
Injection molding
It is suitable for products with complex shapes, high dimensional accuracy requirements, and large batches. For example, complex seals, shock-absorbing pads, shoe soles, etc.
According to relevant data, the production efficiency of injection molding is 4~7 times higher than that of compression molding, the energy consumption is reduced by about 10%, and the qualification rate and dimensional accuracy of the product are also significantly improved. In addition, injection-molded products have less flash, which saves rubber and reduces material costs.
Compression molding and injection molding have their advantages and disadvantages, and the selection of the appropriate molding process should be comprehensively considered according to the shape, size, batch, quality requirements, and other factors of the product. For products with simple shapes and small batches, compression molding has the advantages of low cost and simple equipment; For products with complex shapes and large batches, injection molding has the advantages of high production efficiency and good product quality.
