Compression molding uses a heated mold in combination with precise amounts of material and applied pressure to create solid components from a wide range of available and custom formulated materials. In this blog, we offer a concise overview of the compression molding process, its benefits, and its uses for various industries.
What is Compression Molding?
Compression molding is a highly specialized manufacturing process that uses heated reusable molds and melted thermoset materials to create highly accurate and exceptionally strong components. The process applies intense pressure to force the molten material firmly into all mold cavities, which makes it ideal for producing components with complex geometries or fine details. Compression-molded materials also exhibit an exceptionally high level of strength due to the permanent cross-linking of molecules in the material during the molding process.
The Compression Molding Process
The compression molding process can be broken down as follows:
- Design and fabricate a mold around the exact specifications of the desired component.
- Heat the mold and and place the specified material into the preheated mold, and close the mold.
- Apply extremely high pressure to the material in the mold to remove air and fill all available space, so that even the most detailed components are completed to a high degree of accuracy.
- Allow the material to cure and solidify, then remove from the mold cavity.
Compression Molding Uses and Applications
Thermoset materials used in the compression molding process exhibit a favorable strength-to-weight ratio, which facilitates the production of parts that are precise, strong, and low weight. This makes compression molded components ideal for a variety of applications, touching every market segment including:
- Automotive parts
- Aerospace components
- Material handling tools
- Industrial equipment
- Medical components
- Construction and architectural components
Advantages and Disadvantages of Compression Molding
Compression molding offers some unique advantages over other molding processes:
- Enhanced component material strength. The combination of heat and pressure result in exceptionally strong components.
- Superior detail and accuracy. The application of pressure ensures that every detailed cavity of the mold is filled, resulting in components with a high degree of detail and precision.
- Cost-effectiveness. Compression molding creates exceptionally durable, accurate components at a lower overall cost than other production methods. Because the mold is reusable, the process can be used for production runs at relatively low costs.
- Metal replacement. Due to their high strength and lightweight nature, compression molded thermosets are often used to replace metal components in various aerospace, industrial, and automotive assemblies and medical components are molded with this method as well.
Although compression molding offers a wide range of benefits, it is not necessarily the best option for all parts. The cycle times are often longer than comparable molding processes, and the cost offset by additional cavities in a mold to make more parts per process cycle which will increase the cost of tooling.
Common Rubber Materials in Compression Molding
Compression molding can be used to create components from a wide range of polymers, including:
- Fiber-reinforced materials
- Natural Rubber
What is the Difference Between Injection Molding and Compression Molding?
Although injection molding and compression molding are similar, they exhibit some distinct differences:
- Injection molding is ideal for small parts, while compression molding can be used for much larger components.
- Injection molding is faster, as it does not require the same amount of finishing work.
- Compression molding equipment has excellent production capacity and gains economies of scale through multi cavity tooling, which makes it better for high-volume production runs.
- Compression molding equipment is easier to repair and maintain than injection molding.
Compression Molding Services at Elastomer Technologies
With more than 40 years of experience, Elastomer Technologies is a leading expert in compression molding and fabrication services. We pride ourselves on providing quality manufactured products using equipment and processes that meet and exceed even the most stringent industry standards.
Contact us today for more information about our compression molding services!
Silicone rubber is a highly versatile material used in the manufacture of a wide range of industrial, commercial, and consumer products. In this blog, we provide an overview of the material, including what it is, the types available, typical applications, and the difference between liquid and solid silicone rubber.
What Is Silicone Rubber?
Silicone rubber is a high-performance synthetic elastomer composed of silicone and other molecules (e.g., carbon, hydrogen, and oxygen). It is characterized by high viscosity and elasticity, as well as better abrasion resistance, chemical stability, insulating properties, heat and cold temperature resistance, and weatherability than organic rubber.
The exact properties of a given piece of silicone rubber depend on the material’s chemical composition and structure. However, some of the generally applicable characteristics are as follows:
- Operating temperature range: -100° C to 350° C (depending on the length of exposure) and in some cases can be formulated for higher temperature ranges.
- Weatherability: resistant to wind, rain, UV radiation, and ozone
- Moisture resistance: for extended periods with 1% water absorption (for cold, warm, and boiling water)
- Steam resistance: indefinitely (for unpressurized steam)
- Chemical resistance: oils, solvents, polar organic compounds, and diluted acidic or alkaline substances
- Electrical insulation: 1TΩ·m–100TΩ·m over a wide temperature range and frequency spectrum
- Thermal conductivity: 0.2 W/mΩ·K
- Compression set: consistent from -60° C to 250° C
- Tear strength: 9.8 kN/m
Types of Silicone Rubber
As indicated above, different silicone rubber formulations result in different material behaviors. These variations can be categorized in several ways, including by molecular structure and form.
The former categorization method classifies silicone rubber by the organic group employed in its synthesis. The main types are:
- Methyl Group: dimethyl silicone rubbers (also referred to as methyl silicone or MQ silicone rubbers)
- Methyl and Phenyl Group: methyl phenyl silicone rubbers (also referred to as phenylsilicone or PMQ silicone rubbers)
- Methyl and Vinyl Group: methyl vinyl silicone rubbers (also referred to as VMQ silicone rubbers)
- Methyl, Phenyl, and Vinyl Group: PVMQ silicone rubber
- Fluoro, Vinyl, and Methyl Group: fluorinated rubber (also referred to as fluorosilicone or FVMQ silicone rubber)
The latter categorization method classifies silicone rubber by viscosity and processing method. The main types are:
- Solid Silicone Rubber: Solid silicone rubber—also sometimes called high-temperature vulcanized (HTV) rubber—has long chains of polymers with high molecular weight. It can be processed by conventional rubber processing methods.
- Liquid Silicone Rubber (LSR): LSR has shorter chains of polymers with lower molecular weight. It must be processed by specialized injection molding and extrusion methods.
- Room Temperature Vulcanized (RTV) Rubber: RTV rubber is a one- or two-component system that falls between very soft to medium on the material hardness scale. It is typically used for sealing, encapsulation, or potting applications.
Applications of Silicone Rubber
Due to its numerous advantageous properties, silicone rubber finds application in a wide range of industries, including, but not limited to, the following:
- Aerospace (e.g., space suit elements)
- Automotive (e.g., gaskets and seals)
- Construction (e.g., coatings and sealants)
- Electrical and electronics (e.g., adhesives and encapsulants)
- Food processing (e.g., food molds)
- Medical (e.g., medical instruments components such as seals, tubes, and valves)
- Recreation (e.g., goggles and mouthpieces)
Liquid Silicone Rubber vs. Solid Silicone Rubber
As mentioned above, silicone rubber is available in several variations, including in liquid and solid forms. Below we outline the main differences between the two materials:
- Liquid silicone rubber exhibits high fluidity. The parts and products manufactured from it are generally transparent, odorless, and safe for use in applications involving direct contact with food or the skin. However, they typically require the use of expensive specialized processing equipment.
- Solid silicone rubber exhibits low fluidity. It is cheaper to purchase and process than liquid silicone rubber as it can be used alongside conventional equipment.
Silicone Rubber Capabilities at ETI
At Elastomer Technologies, we have provided exceptional elastomer processing services for over 30 years. Our team has the knowledge and skills to fulfill virtually any rubber molding or die cutting request.
For additional information about the materials and methods used in custom part fabrication, check out our blog.