Low-pressure overmolding is a highly advantageous process that can benefit a wide range of different industries thanks to different rim applications like encapsulation. If you are unfamiliar with the process and want to learn more, consult this comprehensive guide to low-pressure overmolding. Below, we will address what low-pressure overmolding is, what the key benefits are, what items you can mold, and more.


Low-pressure overmolding refers to the process of molding a component directly into a polyurethane part under relatively low temperatures and pressures. The molded in component can be either fully or partially surrounded by the molded part depending on the desired appearance and application of the final product. By molding a component directly into a part, you eliminate the need to use primers or adhesives for bonding. The component chemically adheres to the polyurethane part, creating an exceptionally strong bond.

The reaction injection molding process makes low-pressure overmolding possible. The blend of polyol and isocyanate used to make reaction injection molded parts has a low viscosity that resembles motor oil. The motor oil-like substance is easily injected into a tool without the need for high temperatures or pressures to force the material into all of the nooks and crannies.


Low-pressure overmolding provides numerous advantages from both a functional and aesthetic standpoint. These include:

  • Enhanced protection for fragile items: Due to the low pressure involved in low-pressure overmolding, sensitive components such as antennas or circuit boards can be overmolded without being damaged. Once the fragile item is molded into the part, it possesses enhanced protection due to the layer of durable polyurethane surrounding it. This allows the component to function safely even in harsh environments such as wind, water, and vibration.
  • Reduced parting lines: By molding an item into a part rather than using primers and adhesives to fuse two parts together, unattractive seams and parting lines are completely eliminated. Low-pressure overmolding facilitates the creation of a sleek and seamless part.
  • Wireless capabilities: The process of overmolding can create parts that have strong wireless capabilities. The lower density of overmolded materials can improve the radio signal of wireless components in comparison to other encapsulation methods such as potting.
  • Prevention of theft and tampering: Low-pressure overmolding can also prevent both physical and intellectual property theft. By seamlessly molding an item into a part, extracting or tampering with the component proves far more difficult. The only way to access the over-molded item is to break it. This means sensitive electronics or otherwise IP valuable items have greater protection from theft and malicious hackers.


The reduced amount of pressure applied during the low-pressure overmolding process provides the ability to mold fragile components of items like electronics or medical devices into a part. Examples of the many different situations used for low-pressure overmolding include:

  • Antennas: Due to the low pressure and temperature involved in low-pressure overmolding, sensitive antennas will not incur damage or suffer reduced functionality. Instead, they can experience an improved radio signal due to the low density and enhanced protection of the overmolding material.
  • Circuit boards: Fragile electronic devices such as circuit boards can be molded directly into a part through the process of low-pressure overmolding. Like antennas, circuit boards will have better protection against outside elements and their sensitive components will not be damaged with the low-viscosity material that flows into the mold.
  • Magnets: The low density of low-pressure overmolding material such as polyurethane allows you to mold magnets into a part without a significant reduction in their magnetic capability.
  • Batteries: Low-pressure overmolding also provides the ability to mold batteries into a part without reducing their capacity. The surrounding material will serve as a protective casing against shock, vibration, moisture, and corrosive agents which can help maintain the battery’s lifespan.
  • Threaded inserts: For the production of parts that require attachments or assembly, low-pressure overmolding can mold threaded inserts directly into the part for easy and stronger attachment.
  • Metal rods, bolts, and clips: For added structure and stability, low-pressure overmolding can mold components such as metal rods, bolts, and clips directly into a part.


To determine whether the process would benefit your project, here are some key considerations.


The sensitivity of the components involved in your project will play a significant role in determining whether to consider implementing a low-pressure overmolding process. When deciding, ask yourself if the equipment is sensitive to dirt, oil, chemicals, or grease.

Upon determining the sensitivity of your equipment, consider the potential operating environment of your final product. Will people use the product underwater or in otherwise wet or moist conditions? Will the product be used in a harsh environment where it is subject to dirt, wind, or other types of impact?

If your equipment is sensitive or may be used in a harsh or moist environment, the seamless, protective coating created during the low-pressure overmolding process will likely prove highly beneficial.


Another consideration to keep in mind when determining whether you want to implement low-pressure overmolding into your part production process is if you want to incorporate additional functions into your part. If you realize that your part will require additional functions, implementing low-pressure overmolding will eliminate the need for a lengthy and potentially costly secondary assembly process. It could also lower your total manufacturing cost by eliminating manufacturing steps and reducing the total number of vendors in the supply chain.


You should also consider the desired simplicity of your manufacturing process when choosing whether to utilize low-pressure overmolding. Low-pressure overmolding can erase the need for additional steps in the secondary assembly process. Those who would like to simplify their manufacturing process with a single-piece solution should consider low-pressure overmolding.

Rimnetics is the best and most reliable provider of reaction injection molding services in North America. For over three decades, we have provided exceptional low-pressure overmolding and encapsulating services. To learn more about how we can help make your project a success, contact us today. We are ready to answer any of your questions.

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