Understanding the injection molded rubber


Understanding the injection molded rubber

If you're interested in making rubber parts, you may want to learn more about the injection molding process. Understanding the basics of this manufact

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If you’re interested in making rubber parts, you may want to learn more about the injection molding process. Understanding the basics of this manufacturing process will make it easier to produce high-quality parts for your customers.

There are three main types of molding processes for rubber materials: compression, transfer and injection. Each method has its own strengths and weaknesses.


injection molded rubber is a common production process for rubber materials. It is mainly used for products that need to be manufactured with tight tolerances and high accuracy.

The first phase of the injection molded rubber involves preparation. This includes efficient material preparation and pre-form design.

This step is important for reducing waste and improving overall productivity. It also ensures that you will have a complete and finished product at the end of the process.

Before any molded part is placed into the mold, it should be completely dry and free from voids or internal moisture. This is a critical step in the production of injection molded plastic parts, as moisture can cause deterioration in appearance and performance.

One way to ensure that the molded product is completely dry and free of moisture is to use a humidification treatment. The purpose of this treatment is to eliminate airborne moisture, stabilize color, and prevent oxidation.

Another important factor in ensuring that your molded parts are completely dry is to use a good quality vulcanizing agent. This is an additive that can help to improve the strength of your molded rubber parts.

Types of vulcanizing agents

There are many different types of vulcanizing agents available.

  • Some are more effective than others, so it is important to consider which type will work best for your needs.
  • Some of the most popular vulcanizing agents include silicones, elastomers, and thermoplastics. There are even specialty compounds that can be injected into the molding process for specific applications.
  • A very versatile vulcanizing agent is liquid silicone (LSR).
  • This material is a great choice for plastic parts that need to be manufactured at high temperatures since it can withstand extreme temperature changes without losing its shape or performance.
  • It also offers the added advantage of being able to create parts that are highly flexible and durable, which makes it a very popular choice for a wide range of applications.

Another material that is a good choice for rubber products is TPE (Thermoplastic Elastomer). It can be easily molded into shapes and has a very high tolerance to temperature changes, which makes it an excellent option for a wide range of products.


In the injection molded rubber, rubber compounds are injected into a mold cavity under high pressure. This allows for a variety of applications, including custom shapes and intricate designs.

The injection molded rubber can be performed with a wide range of rubber materials, including silicone, neoprene, nitrile, and EPDM. It can also be used to produce rubber parts that are bonded to metal surfaces.

Before a part can be made, the rubber needs to be prepped and mixed. These steps allow the material to be delivered to a machine in a consistent blend. Typically, the blend includes virgin pellets, pelletized post-consumer rubber, scrap regrind, colorant, and performance or property additives.

Raw materials are usually weighed by a gravimetric weighing system before entering the mold. In this way, consistency is ensured, and the part can be manufactured at a uniform thickness, which minimizes errors during production.

During the injection molded rubber phase of the molding process, a heated rubber compound is pumped into the mold cavities by a barrel and nozzle assembly. This provides a continuous flow and reduces the risk of air entering the mold cavities.

Another option is transfer molding, which can be a good choice for parts that have multiple cavities or intricate designs. The pre-form is placed in a pot between the top plate and plunger, and the material is transferred through sprues to fill the mold cavity.

Benefits of this process

One benefit of this process is that only one pre-form is needed to fill multiple cavities, reducing waste and cost. However, this method may require more tooling and can take longer to complete.

It’s also important to keep in mind that the curing time is much longer than other processes. This means it’s crucial to choose the right material for your application.

For example, if you’re creating a medical product, you might consider liquid injection molding (LIM). This type of process utilizes a two-part compound of rubber that is mixed and then cured in a mixer. This process also eliminates the need for pre-forms and preheats the material, which can significantly increase cycle times.

Another key to minimizing cycle times is reducing the wall thickness of your design. This can significantly speed up the cooling and solidification phase of the injection molded rubber and cut costs.


Injection molding is a process used to create plastic parts. The process is a complex one and requires highly trained workers to operate the machines. There are several factors that affect the quality of the molded product, including the type of material used and the injection machine itself.

In addition, injection molded rubber is very energy-intensive. This is because the machine must run continuously, and it must use a lot of power to melt and then inject the raw polymer into the mold. This is a major cost driver for the manufacturing process, and it can make it difficult to keep costs down.

However, there are a number of ways that you can make your project more efficient and cost-effective. For instance, reducing the thickness of your design can reduce cooling and solidification cycles, which cut back on costs.

You can also reduce your mold’s complexity and maintenance requirements by avoiding undercuts, which can be costly to deal with. For example, if you’re producing a part with a snap-fit connector or handle that’s designed to fit into an area, you can avoid creating an undercut in the mould by redesigning the part to prevent it from forming there.

Production volume

Finally, you can also reduce your production volume by choosing a less expensive mold material. For example, you can use a thermoplastic that has lower strength than an epoxy, so it won’t require as much heat during the curing process.

When choosing an injection molding material, it’s important to consider its flexural modulus of elasticity and water absorption properties. These qualities will determine how well the molded part is able to resist wear and tear, and how long it will last.

Thermoplastics have higher elasticity than their thermoset counterparts. This enables them to form complex geometries. They also have excellent ductility and can be bent without tearing, making them ideal for applications like outdoor-equipment webbing.

During the injection molded rubber, two chemical components are introduced to the barrel and screw, which immediately begin irreversible chemical reactions that crosslink the material. During this phase, the pressure inside the barrel and screw increases gradually due to the temperature and expansion caused by the curing. Then, the pressure is decreased to a fraction of the injection pressure for a duration of between 1 and 6 seconds. This step is called the hold and packing stage, and it completes the mold-filling process.


Finishing is the phase of manufacturing that occurs after the rubber parts have been molded. This can include a variety of processes, including coating and assembling the finished products. It can also involve printing and bindery operations, such as die cutting and inserting.

The finishing phase of the injection molded rubber for rubber materials can vary by manufacturer and product type. However, it is typically an important part of the process because it allows for the creation of durable parts that can stand up to the rigors of production.

There are a few different types of finishing that can be used during the final stages of the molding process, depending on the needs and desires of the client. The most common are surface finishes, which can be a combination of smooth or textured surfaces.

During the processing of the rubber product, chemicals are used that can create chemical fumes and residues. This can also be a source of inhalation hazards and respiratory problems for those working with the product.

These chemicals may come from the vulcanization of the raw rubber, the chemical reactions during the curing process, or from the solvents used during the manufacturing process. They can also be generated by the heat from presses or autoclaves used to cure the rubber.

The resulting products are then heated again in a curing mold or press to ensure that the final product is completely cured. This can be dangerous for those who are not fully trained to handle a hot vulcanized rubber product.

Another factor that affects the final rubber product is the level of shrinkage. All rubber compounds will experience some amount of shrinkage, although some will be more pronounced than others. Shrinkage levels are estimated and incorporated into the mold design and cavity size.

One way to reduce the level of shrinkage in a rubber product is to minimize the number of holes or inserts. It is also possible to use a different compound than what was originally intended to be injected into the mold. This can help to keep the product from over-shrinking or leaking during the curing process.