Knowledge Base

Which Common Products Are Made by the Compression Molding Process?

May 1, 2023, 15:59 PM by The Stoner Molding Solutions Team
If you’ve ever driven in a car or used a plastic utensil to cook food in the kitchen, then you likely have used compression molded parts. Compression molding takes a raw material and uses an appropriate heating technique and pressure to create a molded part. It’s best for parts with complex geometries but few details.

Various products made from compression molding.If you’ve ever driven in a car or used a plastic utensil to cook food in the kitchen, then you likely have used compression molded parts. Compression molding takes a raw material and uses an appropriate heating technique and pressure to create a molded part. It’s best for parts with complex geometries but few details.

If you are considering adding this type of molding to your industrial molding operations, there are some things you need to know. Various products made from compression molding make it a lucrative addition to your operations, and the tooling is relatively low cost compared to other molding techniques. However, it’s not as efficient as other types of molding. Read on to explore this molding method and, as always, get expert advice from our mold release experts on the best products to choose for your operations.

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What Is Compression Molding?

Compression molding is an industrial molding process that uses heat and pressure. A measured amount of molding material that is generally preheated is usually referred to as a charge. The charge is placed into a heated mold cavity, and another mold compresses it to form the desired shape.

Compression molding is sometimes compared to thermoplastic injection molding. In this process, the charge is injected into a closed mold. After, it goes through a curing process to harden into the desired shape. When considering compression molding vs. injection molding, compression typically has lower tooling costs, but injection molding is better suited for high-volume production.

Compression molding was developed for synthetic materials and is the least expensive molding method for thermosetting plastics. There are four types of compression molds: flash, landed positive, positive, and semi-positive-type molds.

How Does the Compression Molding Process Work?

Products made from compression molding typically follow four primary steps, from raw material to a completed composite component. While each compression molding manufacturing process is unique and may include customized steps in between or after these four steps, the following process will give you a good indication of the basics of this molding method.

1. Setting up the Machine

First, the machine needs to be cleaned using the right mold cleaners for the type of molding being done. Then the mold cavity’s surface must be prepped with a mold release to ensure the part releases quickly and easily after the molding process is completed. The compressing molding machines are then turned on to begin preheating, and then the process parameters are set for the correct molding technique.

2. Preparing and Inserting the Charge

Next, mold operators will prepare the charge. First, the proper amount of charge is measured because excess material will seep out of the machine, resulting in a flash that you must cut off manually. Usually, the charge is then preheated using a specified heating technique for the molding project. Then it’s placed in the center of the bottom half of the heated molds.

3. Compressing the Material

The third step is compressing the mold. An operator will close the top heated cavity onto the bottom half and apply pressure. Sometimes more heat is added at this stage to soften the raw materials and make molding quicker. This compression forces the material to fill the entirety of the mold cavity to ensure the desired density of the product and accelerate curing.

4. Releasing the Part

The part is then released from the molding machine, sometimes with the help of ejector pins. The molding technician will also finish the part by removing excess resin flash around the edges and cleaning up the part before heading to secondary processes or final assembly.

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What Products Are Made from Compression Molding?

Because the compression molding process is cost-effective, produces strong parts, and has design flexibility, many industries turn to it for various parts. Some of the products made from compression molding include:

  • Automotive Industry
    • Large automotive parts, like fenders
    • Car panels
    • Engine components
    • Interior automotive components
  • Technology
    • Video game controllers
    • Keyboards
    • Mouse
    • Joystick covers
  • Household
    • Kitchen tools
    • Utensils
    • Appliances
    • Bowls, cups, plates
    • Mirror handles
  • Electrical Components
    • Electrical sockets
    • Switches
    • Faceplates
    • Metering devices
  • Medical
    • Syringe stoppers
    • Respirator masks
    • Rubber clothing

What Materials Are Used to Create These Products?

With so many different products made from compression molding, various types of composite resins and plastic materials are used in the process. Some of these include:

  • Bulk molding compound (BMC – a mixture of resins, chopped fibers, and a hardening agent, resulting in a pliable material similar to sheet molding compound)
  • Carbon fiber (can make a more rigid composite material)
  • Diallyl phthalate (DAP)
  • Epoxy resin
  • Glass fibers (can be added to resins to form composite materials to make stronger parts, such as sheet molding compounds)
  • High-density polyethylene (HDPE – Can be mixed with natural rubber to make composite parts)
  • Melamine
  • Nylon
  • Polyamide-imides (PAIs)
  • Polyether ether ketone (PEEK – can be used to replace metals in certain applications)
  • Polyurethane (PU)
  • Polyphenylene sulfide (PPS)
  • Phenolic molding compound (thermoset plastics, which have high temperature-resistant properties and dimensional stability)
  • Polytetrafluoroethylene (PTFE – has a very high viscosity and good non-stick properties)
  • Sheet molding compounds (SMC – typically consists of two layers of polymer resin with a layer of glass fibers in between)
  • Silicone rubber
  • Urea-formaldehyde (UF)

How Can You Make the Compression Molding Process Easier?

Using a release agent to cure the mold before the molding process begins makes compression molding processes easier. Various types of mold release are available, and the best ones on the market are the ones we make.

When choosing the best mold release agent for your product, considering factors such as the type of polymer you are molding, whether it requires post-cure, and the maximum temperature required for operation can help you make an informed decision. We specialize in guiding molding professionals to the right product for their needs, and offering a range of sacrificial and semi-permanent products tailored to epoxy, phenolic, polyester, vinyl ester, and polyurethane systems. Our specialized products can help reduce sticking parts and wasted time in production processes while producing superior parts with less waste.

Get Customized Support for Your Compression Molding Operation

Compression molding is an industrial molding process used to create various products, from automotive parts to household items. The process involves several steps, including preparing the charge, compressing the material, and releasing the part. This type of molding is cost-effective, produces substantial parts, and offers design flexibility, making it a popular choice among many industries.

Whether you’re looking to start manufacturing some of the many products made from compression molding or need to improve your existing operations, we can help! Talk to one of our experts to learn more about compression molding and how we could help your business succeed.

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