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Silicone Compression Molding

Silicone Compression Molding


I. What is Silicone Compression Molding?

Compression molding is a well-established method for manufacturing simple silicone rubber components. It is a straightforward process that involves high pressure and heat to transform vulcanized silicone rubber into a durable, functional rubber part. The silicone rubber is placed in an open mold, closed, and subjected to significant heat and pressure. This forces the casting material to fill all areas of the mold and expel any trapped air. The heat and pressure are maintained until the material is fully cured. Once the parts have been cured, the silicone products are removed from the mold.

Compression molding suits applications requiring low durometer and tight tolerances, especially when injection molding costs are prohibitive. With over a decade of experience, our team possesses the expertise to create relatively intricate parts using compression molding techniques.


II. How Does Silicone Compression Molding Work?

Compression molding uses heat and pressure to shape silicone rubber into a desired form. When all the necessary components are in place, vulcanized silicone rubber undergoes compression in the prepared molds.

Here are the steps involved in the silicone rubber compression molding process:

Step 1. The mold is preheated and sealed, preparing it for molding.


Step 2. Uncured rubber (preform) is placed in the mold cavity, ready to be shaped. Each mold has an optimal preform shape and size, which must be determined for the best results. It is essential to maintain a tolerance for both the size and shape of the performance to ensure proper part formation. Excess material can be wasteful and lead to thick flash, while insufficient material can partially cause voids.


Step 3. The mold is closed, and heat and pressure are applied using a compression molding press. Production presses employ a programmable logic controller to monitor and control critical parameters, such as temperature, pressure, and time, ensuring molding occurs within a prescribed tolerance window.


Step 4. With the mold closed, heat and pressure are applied according to the programmable logic controls and in compliance with the specified temperature and pressure parameters.

Step 5. The mold is opened, and the cured silicone rubber and its flash are removed.



Step 6. The silicone rubber products proceed through manufacturing, undergoing post-molding operations such as deflashing, inspection, and post-curing.


The compression molding process efficiently produces high-quality silicone rubber components following these steps.

III.Advantages and Disadvantages of Silicone Compression Molding

Compression molding is widely used for gaskets, seals, and grommets. Still, it may not be the best choice for all molding processes due to its advantages and disadvantages.

Advantages of Compression Molding:

Minimal lead time: Short setup time allows for quicker production.

Easy to prototype: Minimal waste during the prototyping process.

Wide range of part sizes: Ideal for manufacturing parts with large cross-sections.

Dimensional stability: The ability to process stiff, high-durometer materials is excellent for low quantities of parts requiring long cure times.

Low tooling and equipment costs: Tooling is simpler and more cost effective than injection molding. Although the technique has a longer cycle time, it uses low-pressure molds, making it more affordable to produce various cavities without high tooling costs.

Disadvantages of Compression Molding:

Produces only intermediate tolerances: Parts may be less consistent in quality.

Parts may require deflashing: When a flash (the resin that escapes between two parts) occurs, it must be manually trimmed, reducing productivity. The excess material cannot be reground, resulting in more waste.

Higher human capital investments: As mentioned earlier, flash is removed manually on compression molds, leading to higher labor costs.

Longer cure times: The time needed to initiate and repeat the sequence of operations for compression molds ranges from 1 to 6 minutes, significantly slower than injection molding.

Not suitable for complex part configurations: This technique best suits simpler parts.

Colored silicone can be easily contaminated, requiring transfer or injection molds.

Potential for contamination of colored silicone during the process.

Considering the advantages and disadvantages of compression molding is crucial when deciding whether this technique is appropriate for a specific application.

IV. Details to Note During Silicone Compression Molding

1. Shrinkage and product stability: Careful calculations and coordination of mold design and formula are required to ensure stable product size and quality.

2. Temperature and environmental factors: Manufacturing conditions, including temperature and humidity, must be adjusted appropriately to prevent product quality deviations.

3. Material preparation and processing: Design formulas based on product requirements and use plate vulcanization equipment for molding to ensure smooth surfaces and no burrs.

4. Vulcanization and molding issues: Adjust mold temperature, exhaust time, and mold pressure to address issues like mold sticking, warping edges, air bubbles, and uncured white spots.

Manufacturers can maintain a streamlined process and produce high-quality products by considering these key factors in solid silicone compression molding.

V. Industries and Applications of Silicone Compression Molding

Silicone compression molding is widely used in various industries requiring high levels of safety and environmental protection. These include:

1. Home and Housewares: Kitchen and dining products, drinkware, and household items.

2. Baby and Toys: Baby products, feeding products, and learning toys.

3. Health, Beauty, and Personal Care: Oral, beauty tools, accessories, and hair care products.

4. Stationery and Office Products: Arts and crafts, school supplies, and office products.

5. Sports, Outdoor, and Garden: Fitness equipment, travel accessories, silicone water bottles, and outdoor gear.

6. Pet Supplies: Accessories and products for pets.

7. Electronics and Cell Phone Accessories: Protective covers, cases, and holders.

8. Automotive, Aerospace, and Military: Components for vehicles, aircraft, and defense applications.

9. Smoking Products: Accessories for smoking and vaping.

10. Promotional Products: Licensed merchandise, mascots, and blind box items.

Manufacturers can produce high-quality, custom silicone products for various industries and applications by utilizing silicone compression molding.


VI. Conclusion

Silicone compression molding is a versatile and cost-effective manufacturing method for producing high-quality, custom silicone products across various industries. Its simplicity, adaptability, and ability to accommodate various design requirements make it ideal for applications requiring safety and environmental protection. Discover our unique molding techniques! Call Mitour at (+86)13352910077. We're a top supplier of custom silicone bottles and silicone rubber products, using an innovative injection molding process for cost-effective, tailored solutions.

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