Rubber Overmolding: Process, Design, and Applications

Rubber Overmolding

Rubber Overmolding will put you ahead in the design of products. You can use rigid plastic or metal integrated with a soft rubber finish. This fusion increases grip and adds comfort and high durability. At Prolean Tech, we use the rubber molding process to build smarter parts.

You’ll notice better shock resistance in rubber-overmolded parts. The soft layer generates a shield under pressure. It is perfect for tool grips or precision seals in sensitive assemblies. In one smooth step, you obtain ergonomic and protective value.

Our self-sealing parts make an excellent example. They combine the sealing power of silicone with a rigid core. This couldn’t be achieved with a single raw material. That’s why overmolding is a good option for performance.

Prolean Tech pays special attention to metal overmolding and rubber overmolding projects. We use sophisticated techniques to align ourselves with your product needs. Our process provides strength and comfort for electronics, tools, and seals. You get fit, function, and high-value impact from one solution.

Rubber Overmolding Processes

Rubber Overmolded Product

We provide high-tech plastic overmolding solutions to your specific design and performance needs. Your parts meet exact, rugged, and durable standards. The choice of overmolding process depends on your demands.

Injection Molding: 

Plastic Injection Molded Product

Injection molding ensures that your product receives a perfect fit and consistency. We fill heated rubber over a metal and plastic base. After the material is cooled, the shape of the last geometrical figure is defined. This technique is ideal for large orders with high quality control.

In all parts, you will find nice finishes and superior durability. It’s quick, dependable, and can be repeated. Therefore, it delivers the same results every time with consistency. We adopt it if volume and accuracy are critical.

Compression Molding:

Compression Molding

Compression Molding helps create larger, simpler parts where intricate details are not required. We work your base material into a mold and heat it. The rubber occupies and locks the space. This process is suitable for custom parts and small volume batches.

Moreover, it is useful when dealing with a strange design. It works exquisitely if size or shape makes injection impossible. Prolean Tech applies this approach to realize the complicated goals of your projects. We bring your designs to life, with no further waste.

Transfer Molding: 

Rubber Transfer Molding

Close tolerances in subtle shapes can be achieved through transfer molding. First, we fill up a transfer pot with rubber. High-pressure application makes it go into a channel in the mold. This achieves a clean, sealed, and non-air gap finish.

Transfer molding is perfect for seals and close parts. It also provides for exact alignment inserts. At Prolean Tech, we use it in high-detail jobs. It’s notable for performance-oriented overmolded components.

Liquid Injection Molding: 

Liquid Silicone Rubber Injection Molding

Liquid Injection Molding employs soft and flexible material. It is ideal if your substrate is heat-sensitive or fragile. The fast-curing, free-flowing liquid silicone material provides excellent adhesion without damaging the base. At every cycle, it’s a beneficiary of speed and accuracy.

Our team uses the LIM process on electronics and soft-touch parts. It gives you a satin cover without ruining your base. If safety and style are critical in your case, LIM is the ideal solution. Prolean Tech has brought this solution to the marketplace for brittle applications.

Two-Shot Molding: 

Two-Shot Overmolding Process

In two-shot molding, two different material layers are integrated in a single cycle of the mold. The first layer builds the structure; the second puts comfort in it. It provides grips and ergonomic goods. 

Two-Shot Molding is the go-to choice when your part requires multiple materials or colors. It requires minimal post-processing steps and saves your time. You’ll have consistent performance on everything.

There is a need for a holistic approach to the choice of the overmolding method. Your material, design, and final use will be a factor.

At Prolean Tech, we collaborate closely with you to understand your product’s unique requirements. Our staff ensures that your parts meet precise performance specifications, from durability to comfort and function. Our tools, experience, and support will take you forward and make you feel confident. We help you build a better piece by piece.

Related To: overmolding vs insert molding

Key Design Considerations for Rubber Overmolding

Smart design is the key to successful overmolding at Prolean Tech. Before starting a production process, we consider several physical and technical considerations. Patterns of how you form, measure, and place things can make a difference. These elements influence the way components operate and perform for some time. (Get more insights on our Overmolding Design Guide)

Rubber Thickness Guidelines

Thin Layer Rubber Overmold Product

You should maintain your rubber layer in a proper equilibrium. Too skinny may rip under pressure. Too thick may not be cured. Our recommendation specifies a standard range from 1.5 mm to 4 mm. It guarantees strength, flexibility, and soft bonding. Moreover, standard thickness allows for avoiding shrinkage and distortion. At Prolean Tech, we direct you to the best dimensions. This consistently achieves performance and a clean surface finish.

Undercuts and Draft Angles

Draft Angles Illustration

You’ll have to deal with undercuts to prevent damage while pulling out. Undercuts permit locking shapes, though the planning has to be exact. We usually propose mechanical release features or split molds. This helps maintain function without increasing the dangers of tooling.

Draft angles help promote mold release and part shape as well. We recommend 1-3 degrees for rubber surfaces and inserts. This allows the rubber to come out clean after it’s cured. Each mold is designed by Prolean Tech with draft and undercut in focus.

Insert Retention and Bonding Strategies

Molded Insert Retention Illustration

Your insert should lock itself in position before the rubber flows. We use mechanical locks, surface treatments, or holes to grip better. Clean, dry surfaces enhance chemical bonding and minimize failure. Rubber adhesion is improved by textured inserts as well.

Our evaluation of every project involves using the right type of material for the required geometry. Metals, plastics, or composites need to be prepped specially. Prolean Tech employs bonding that is proven to yield rigid and stable results. Your insert remains affixed during handling and use.

Tolerance and Dimensional Control

Rubber may be used to shrink during cooling and curing. You have to think of tolerance right from the beginning of a design. We size molds based on the rubber material’s shrinkage rate, as well as other factors like part geometry and tolerance requirements. 

Dimensional variation may also result from uneven curing or poor venting. That’s why we test every tool for heat flow and pressure balance. With Prolean Tech, your parts arrive molded up to your standard. It is all tied together, piece by piece, batch after batch.

Types and Grades of Rubber are used in Overmolding

Rubber Types Used In Overmolding

Rubber overmolding services use different kinds of rubber depending on the application needs. When selecting a type and a grade of rubber, the appropriate performance and durability of the final product are determined.

Silicone Rubber is usually selected for overmolding due to its high flexibility, temperature stability, and chemical resistance. It is widely applied in medical devices because of its biocompatibility and nontoxicity.

EPDM Rubber or Ethylene Propylene Diene Monomer is famous for its outstanding resistance to UV rays, ozone, and weathering. It is therefore suitable for outdoor exposed applications such as automotive seals and gaskets.

Neoprene rubber has a remarkable ability to resist oils, heat, and chemicals. It is common for industrial applications, where environmental protection is of prime importance, such as parts that must endure demanding conditions.

Natural Rubber is very elastic and firm; therefore, it is suitable for those products that must be flexible and resistant to tears, such as seals and hoses.

Nitrile Rubber, in particular, is quite effective in automotive and industrial uses because it resists oils, fuels, and chemicals. It gives hardiness and dependability when exposed to harsh substances every day.

Rubber grades are usually established by standards such as ASTM D2000; this standard tests factors such as tensile strength and compression set. Higher-grade rubbers are preferred for applications in high-demand conditions. In contrast, low-grade rubbers are for less critical applications.

Common Applications of Rubber Overmolding

Overmolded Plastic and Rubber Seal

Here are the common application areas of rubber overmolding:

Benefits of Rubber Overmolding

Rubber overmolding allows you to simplify builds and create more functionality. It consists of rigid substrates- metals, plastics, or soft rubber layers. Doing so decreases parts, eliminates assemblies, and makes it more durable. Prolean Tech helps you design more innovative and more efficient components.

Rubber to Metal Joining

Rubber-to-Metal Bonded Components

If the part needs strength and flexibility, rubber overmolding results in forming a single molded part. You have the strength of structure in the metal and grip in the rubber. It is highly used as a tool, and for brackets and parts of the industrial seals.

At Prolean Tech, we use accurate bonding pressures and cure times. This helps keep the rubber from staying in place without adhesives and fittings. The result is strong, wear-resistant elements for everyday use.

Adhesion to Plastic Substrate and Inserts

Plastic substrates offer space for designs for light parts. When combined with rubber, they become easier to handle and use. Think about soft hand-held gadgets, grips, or housings.

We first make the plastic part, then overmold the rubber layer onto the substrate. This process helps you to cut costs, but at the same time, it escalates product function. Our configuration matches small runs and high volume production at a low price.

Bonded Rubber-to-Metal Seals

High-performance seals require a good bond at high pressure. Precision sealing is what you get when rubber is over molded on metal. The rubber forms the seal; the metal supports the structure.

We construct these seals for close-tolerance systems such as valves and pumps. The overmold provides protection against leaks, absorption of vibration, and retains shape. Prolean Tech guarantees your parts are up to even the most severe field conditions each time.

Challenges of Rubber Overmolding

Here are the common challenges encountered during rubber 

Delamination Issues

Layer Delamination Issue In Injection Molding

Delamination occurs when the rubber layer peels away from the substrate, compromising product life. This particularly applies to parts under high stress, such as seals or handles.

Solution: To avoid delamination, the surface of the substrate should be well prepared, such as by cleaning or using bonding agents. Choosing the appropriate rubber for the material assists in guaranteeing a good bond. In addition, changing the moulding parameters, temperature, and pressure can also enhance adhesion.

Flash Control

Flash Control In Injection Molding

Flash is what happens if additional rubber oozes out of the mold, producing undesirable material that may cause problems with the look and operation of the part.

Solution: Optimization of mold design and the injection pressure control can minimize flash. Precise cavity dimensions and the proper material are also crucial to curbing the flash. Post-production trimming machines can trim unnecessary flash rationally.

Cycle Time vs. Quality Trade-offs

Quite often, manufacturers need to balance faster cycle times and product quality. Shorter cycles can decrease the quality, and longer cycles can reduce production speed.

Solution: To balance and optimize molding parameters such as temperature and pressure. Using state-of-the-art Molding cooling systems and automation makes it possible to minimize cycle time without compromising quality. Real-time process alterations can also stop defects.

Summary

Rubber overmolding is a valuable process that allows for the rigidity associated with metal and plastic without sacrificing the comfort of rubber. It’s pretty popular across industries to make stronger and ergonomic products. By selecting the proper rubber type and overmolding process, the manufacturers can increase the performance of their products, user satisfaction, and the lifespan of their products. 

At Prolean Tech, our Overmolding service provides more efficient and sustainable solutions as we use state-of-the-art technology. Our engineers and designers understand material properties and production methods to achieve the best results concerning your products.

FAQ’s

What is rubber overmolding?

Rubber overmolding is a process where rubber is molded over another part. You often see it used to add grip or seal over hard plastic or metal. It creates a single, bonded product with dual material benefits. This helps improve both function and comfort.

What material is used for overmolding?

Materials like TPE, TPU, silicone, and EPDM are common choices. The base part is usually plastic or metal. The selected rubber must bond well and meet product needs. Heat resistance, flexibility, and adhesion all play a key role.

Can EPDM be overmolded?

Yes, EPDM can be overmolded in many designs. It bonds best when the surface is clean and prepped. This rubber works well in sealing, weather resistance, and durability. It’s widely used in automotive and electrical parts.

What is the purpose of overmolding?

Overmolding adds more than just protection or looks. It helps improve product grip, feel, and safety. You also get better shock resistance and part integration. It turns two materials into one high-performing product.