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Thursday September 12th, 2019

Compression Molding vs Injection Molding

Compression molding or injection molding? There is no right answer. Read our article and learn about the pros and cons of both technologies and where they might perform best.

What is compression molding

The compression molding tool makes even stiff and high durometer rubber materials perfectly vulcanized and dimensionally stable. Compression molding is basically curing in a heated mould cavity under pressure. The preheated material is inserted into mould, closed and then cured under pressure. The result is always a high-quality, long-lasting rubber product that can be used in various industries. Watch the following video about how compression molding is done at SIC Hungary:

Its greatest advantage is that using this technology, larger parts can be easily molded. We use one of the largest compression molding machines in the CE region, which can create cost-efficient rubber products in a maximal size of 1200x1200x500 mm. Our range of compression molded products contain various sizes, from small to extra large.

What is injection molding

Injection molding is one of the most popular ways to manufacture molded rubber products.

The methodology of injection molding is very straightforward: the hot liquid compound is injected into a closed cavity where it is vulcanized. The result is a dimensionally stable, perfectly cured rubber with no need of much aftercare. Injection molding is ideal for producing high volumes of the same product such as cones, automotive parts and components, balls, gaskets and other rubber items. Watch out for the hot material being injected into the molds in our video about injection molding at SIC Hungary:

Injection molding excels in waste reduction and can have an incredibly fast production cycle, therefore, it is one of the most cost-efficient technologies. The injection molding machine we use allows manufacturing a large number of rubber products at the same time that meet the requirements of several industries.

Common characteristics

Custom colour – Both technologies make it possible to create custom coloured rubber that will be used to manufacture the parts.

Low tooling costs – Both technologies are extremely common, therefore, mold costs are usually low.

Reduced part costs – With an increasing number of manufactured parts the average cost decreases significantly with both technologies.

Main differences

Size of product – Compression molding allows creating large rubber products, whereas, injection molding is ideal for smaller rubber parts with tight tolerances. Compression molding also enables manufacturing products that vary in wall thickness from 1.3 mm to an inch.

Production time – The production time of compression molding is significantly longer than that of injection molding. Moreover, the excess flesh around the parts must be trimmed manually in case of compression molding, slowing down the production cycle even more, making the process more labor intensive. Timewise injection molding is the more efficient technology because full automation of the process is possible.

Quantity – When the automation of the molding process meets short cycle times, a high-quantity production is possible. Therefore, high-quantity series can be created with injection molding, while compression molding is used rather for low and medium series of large products.

Quality – Injection molding results in an increased strength of the parts.

Shape of final product – Compression molded products are rather blocky and simple. The raw material is cut into a shape resembling the final, generally simple product and will be compressed. Whereas, injection molding enables manufacturing more complex rubber parts such as cones. These products can have various wall thicknesses and can be a combination of different shapes.

Simple, blocky part using compression molding
Injection molded complex product

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