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Rubber Compression

Expert Rubber Compression at Beaver State Plastics

Another assistance we are confident we can offer is our specialized rubber compression services. These methods are perfect for applications that still call for traditional processes as the most efficient and reliable choice. We can utilize diverse grades of silicone, thermoset rubber, and components with heavy cross-sections to create durable, high-quality rubber parts.

Another assistance we are confident we can offer is our specialized rubber compression services. These methods are perfect for applications that still call for traditional processes as the most efficient and reliable choice. We can utilize diverse grades of silicone, thermoset rubber, and components with heavy cross-sections to create durable, high-quality rubber parts.
We can handle large, intricate molds with precision because our rubber department is equipped with presses featuring 30” x 30” platens and a 24” ram. When you need compression molding, , we can make it happen. We can also help you decide the best approach for your specific needs.

Launch your project with fast, reliable, and high-quality plastic injection molding services.

Why Choose Rubber Compression Molding & Transfer Molding?

Your best option is rubber compression and transfer molding when you need to produce parts that strictly require consistency in material distribution. Great examples are items with complex shapes or heavy sections.

You must determine what rubber molding application a particular project needs. In some instances, a product needs high temperature and high pressure conditions to maintain its consistent integrity and performance no matter what environmental elements it faces. Excess material is managed during the compression molding process by filling the mold’s overflow grooves after uncured rubber is placed in the mold, ensuring proper demolding and preventing issues such as flashing.

The Compression Molding Process

The compression molding process is a widely used method for producing molded rubber products. It involves placing a pre-form of uncured rubber into a mold cavity and applying heat and pressure to cure the rubber. This molding process is versatile, capable of producing a wide range of rubber products, from simple gaskets and seals to complex components for industrial and automotive applications.

The compression molding process typically involves the following steps:

  1. Pre-form Preparation: The uncured rubber is prepared into a pre-form, which is a chunk of rubber that is roughly the shape of the final product.
  2. Mold Preparation: The mold is prepared by applying a release agent to the mold cavity to prevent the rubber from sticking.
  3. Pre-form Placement: The pre-form is placed into the mold cavity.
  4. Compression: The mold is closed, and pressure is applied to the pre-form to force it into the mold cavity.
  5. Curing: The rubber is cured under heat and pressure, causing it to take the shape of the mold cavity.
  6. Demolding: The mold is opened, and the cured rubber product is removed.

This method is particularly effective for producing durable, high-quality molded rubber products with consistent material distribution.

Compression Molding Tolerances

Compression molding tolerances refer to the allowable variations in the dimensions of a molded rubber product. These tolerances are crucial for ensuring the final product meets the required specifications and performs as expected. Several factors can affect compression molding tolerances:

  1. Shrinkage: Rubber materials can shrink during the curing process, which can affect the dimensions of the final product.
  2. Mold Design: The design of the mold can influence the tolerances of the final product. For instance, a mold with a complex shape may require tighter tolerances than a simpler mold.
  3. Curing Process: The curing process can also impact the tolerances. A longer curing time may result in a more accurate product.

Understanding and controlling these factors is essential for producing high-quality rubber parts with precise dimensions.

Measuring Compression Set of Solid Elastomers

The compression set of a solid elastomer is a measure of its ability to resist permanent deformation under compressive stress. This property is critical for many industrial and automotive applications, where the rubber product may be subjected to compressive stress over an extended period. The compression set can be measured using the following procedure:
  1. Prepare a Specimen: Typically in the form of a disk or a cylinder.
  2. Compress the Specimen: To a specified thickness, usually 0.177 inches.
  3. Hold at Specified Temperature: Typically 158°F, for a specified period, usually 22 hours.
  4. Release the Stress: Allow the specimen to recover for a specified period, typically 24 hours.
  5. Measure the Thickness: After recovery, calculate the compression set using the formula:

Compression set = (original thickness - final thickness) / (original thickness - space bar thickness) x 100

This measurement helps determine the material’s ability to maintain its shape and functionality under prolonged stress.

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What’s the Difference Between Rubber Compression and Transfer Molding From Injection Molding?

Although these three methods—rubber compression, transfer molding, and injection molding processes—are all used to produce rubber products, they all have different pros and cons. One may be superior to the other in its capacity to create products for different applications.

The transfer molding process involves transferring pre-measured rubber into a mold cavity using a plunger. This method is known for its high cavity count and design flexibility, making it suitable for complex and detailed rubber parts. However, the process can be complex and may involve higher costs due to the need for precise control and additional equipment. Despite these complexities, the transfer molding process is advantageous for producing high-quality rubber components with intricate designs.

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Compression molding

Compression molding process is suitable for molding simple shapes and rubber parts that need low to medium production volumes. It is durable and an economical process because the molds used in compression molding can be reused for more production runs.
Compression molding uses pressure forces to shape a material to fit a mold cavity. This rubber molding process presses the two halves of the mold together, thus creating the cavity. Mold cavities cause the rubber materials to take on the desired form. The molding material and the mold ensure that the compression set can easily be ejected once the material has been positioned and cured.
These are the main stages of the compression molding process:

Compression Mold Preparation

  • Set the mold by cleaning it first
  • Apply the release agent.
  • Heat the charge to increase the viscosity in preparation for the loading

Charge Preparation

Charge preparation is the most laborious phase in compression molding because its process is not mostly automated unlike the other processes.

You can apply compression molding method to a variety of compression-set materials, simple compressed mold designs or complex ones, varied cavity sizes, formattings, and conditions. Preparation sets the material ready for the compression process and this includes: Unpacking, cleaning, cutting, sizing, weighing, and heating.
Rubber compression and transfer molding

This process is good for simple shapes and low to medium production volumes. It involves placing a pre-heated mass into a mold and then closing the upper mold to shape the material. Compression molding is a time-tested method that can handle a wide range of rubbers. It’s also low maintenance and inexpensive to tool, with production costs falling as volume increases.

During the compression molding process, excess material is managed by filling the mold’s overflow grooves after uncured rubber is placed in the mold. This ensures proper demolding and prevents issues such as flashing.

Transfer molding

This process is good for complex shapes and higher production volumes. It involves injecting material into a mold through a sprue using a plunger. The transfer molding process includes several procedural steps: preheating the material, placing it into a chamber, and then using a plunger to transfer the material into the mold cavities. This method offers advantages such as high cavity count and design flexibility, making it suitable for manufacturing intricate rubber parts. Transfer molding can have faster cycle times than compression molding, but injection molding typically has shorter cycle times than transfer molding. However, the complexities and disadvantages of using this specific molding technique include the potential for excess flash, or rubber left in the pot after the transfer is cured, and the need for precise control over the material flow to avoid defects.

Injection molding

This process is good for complex shapes with tight tolerances and high production volumes. It involves melting thermoplastic pellets and injecting them under high pressure into a mold.

Injection molding has a very short process cycle, but it’s more expensive and takes longer to set up than transfer molding. The right molding process depends on the complexity of the product, the desired production volume, and cost considerations.

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Materials and Applications for Molded Rubber Products

Molded rubber products can be made from a wide range of rubber materials, each with unique properties and applications. Some common rubber materials used for molded rubber products include:

Natural Rubber

A natural, biodegradable rubber material often used for applications requiring high elasticity and flexibility.

Synthetic Rubber

Man-made rubber material used for applications needing high durability and resistance to chemicals.

Silicone Rubber

A synthetic rubber material known for its high temperature resistance and flexibility, ideal for various industrial applications.

Neoprene

A synthetic rubber material with high resistance to oil and chemicals, commonly used in demanding environments.

These materials are used in a wide range of applications, including:

  1. Industrial Applications: Such as gaskets, seals, and vibration mounts.
  2. Automotive Applications: Including engine mounts, suspension components, and seals.
  3. Aerospace Applications: For seals, gaskets, and vibration mounts.
  4. Medical Applications: Including seals, gaskets, and implantable devices.

Each material offers specific benefits, making them suitable for different molded rubber products and applications.

Custom Solutions and Quality Assurance in Molded Rubber Products

We continuously improve our processes to deliver custom rubber components that meet strict performance and durability standards. We are particular with the details, ensuring they meet your specifications and serve the products’ purpose. Our team handles quality checking at every step of the molding process to provide the highest quality.

Additional Benefits of Partnering with Us

  • We have the equipment that can accommodate your rubber injection molding specifications.
  • We prioritize you to ensure on-time product delivery.
  • We propose cost-effective solutions so we can both have a win-win solution.
Rubber compression and transfer molding

Be Our Partner With Your Rubber Injection Molding

Be our partner in the rubber injection molding solutions you wish for your business. Our more than five decades of experience have helped us learn what works and what does not. Talk to us to learn more about what we can do or get a quote for your next project.

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