Rubber parts blog

Custom Fabrication: Molded Rubber Parts

Custom molded rubber parts are an excellent way for manufacturers to get the exact component that...

Custom molded rubber parts are an excellent way for manufacturers to get the exact component that they need. Whether a part has been discontinued or no longer works for the product, sometimes it's necessary to turn to customization. With custom parts, manufacturers can choose color, dimensions, materials, design, durability, properties, and more. It’s often more economical than you think - in the long run, it’s often more cost-effective - ask us how!

The fabrication of custom molded rubber parts is one of the most interesting parts of the custom design process. This is where manufacturers can let us know what conditions the part will be exposed to and how they intend to function - we can help determine the right material. Continue reading to learn more about materials, rubber to metal bonding, types of designs, and the process of custom rubber molding.

Custom Molded Rubber Part Materials

Manufacturers may choose a material based on the properties that they need their part to have. There are many different polymer materials that manufacturers can choose from. The most common are silicone and neoprene. However, there are many other kinds:

Each of these polymers have different properties that make them preferable for certain applications. For example, silicone is often used in the food industry because it is FDA-approved and is great for high heat applications. On the other hand, for shock and vibration absorption, manufacturers often choose Natural rubber for its excellent resiliency and rebound characteristics.  Natural rubber also has excellent energy absorption and damping characteristics.

In almost all industrial applications, rubber to metal bonding is an essential stage in the process of creating durable molded rubber parts.   However, don’t be fooled by inexpensive parts - the quality of the bond is everything and low cost generally means cutting corners.

Access The Ultimate Guide to Custom Rubber Molding

Our free resource covers everything you need to know about custom rubber parts, including top molding methods, the manufacturing process, and more. 


Rubber to Metal Bonding

Custom rubber molded parts can be optimized for things like vibration isolation when they are bonded to metal. OEMs will know how they want the part to function, but the real value is in determining what is the best elastomer (rubber) and substrate (metal).   Knowing this and understanding how important the bond is between the two is where we come in.. The metal should have the properties that are necessary to make a high-quality product that will last. Metal types that manufacturers can choose from include:

  • Aluminum
  • Steel
  • Beryllium 
  • Copper
  • Brass

The rubber to metal bonding process takes place during molding. Often, the elastomer will be coated in some kind of adhesive so that the metal can fully bond to the rubber during the vulcanization process. The bonding process is typically completed through over-molding or encapsulation.

The quality of a rubber molded part is easily identifiable based on the adhesive application. For instance, inferior molded rubber parts will have inconsistent (even hand applied) adhesives, as opposed to perfectly consistent, mechanically applied adhesives. The latter is vastly superior and will create high-quality parts that last.  Low-cost parts typically have inferior adhesives and bonding processes - meaning the part and your equipment will likely see failure - which will cost a lot more than the part!

Prototyping vs. Reverse Engineering

There are a few reasons why a manufacturer may choose to purchase custom molded rubber:

  • The previous part was discontinued
  • The product is being updated
  • Need a completely unique part
  • The previous part was changed
  • Can’t find the necessary part

The reason a manufacturer chooses custom rubber parts will affect whether the part will be prototyped or reverse engineered. 

Prototyping is the only choice when a part is unique or cannot be found elsewhere. The prototyping process will consist of designing and engineering the part, followed by prototypes. These are tested and adjusted as needed. Once the prototype has been approved, the part will be produced at full volume.

Reverse engineering is different in that it is mostly used for parts that have been discontinued or changed. The customer may bring the old part in and the rubber supplier will essentially create a replica of the old part through reverse engineering.


Custom Rubber Molding Processes

Whether the part is prototyped or reverse engineered, the molding processes are the same. 

There are three types of molding methods that are used for custom rubber molding:

1. Injection Molding

This is the most common molding process for rubber parts. With injection molding, the rubber elastomer is filled into the injection unit. The material is then injected into the mold and then vulcanized and cured at high pressure and temperature. It is one of the best methods for highly intricate parts as it ensures high accuracy and precision. This method is best for high-volume parts produced at high speed.

2. Compression Molding

The process of compression molding begins with the charge placed into the mold. The charge is then compressed at high pressure to fit into the mold's shape. Once the part is in the mold, it is vulcanized and cured. This method has a lengthier production time due to the additional work of removing flash from cured parts. Compression molding is typically used for low volume production and prototyping. 

3. Transfer Molding

Transfer molding is another method for custom rubber part molding. It begins with the charge placed in the molding part. The charge is then heated and plunged through the sprue into the mold cavity. Once it is in the mold cavity it is cured and vulcanized at high pressure and temperature. This method is mostly used for prototyping and low volume production.

Have 7 minutes?

The Engineer’s 7-minute Guide to Rubber Molded Parts

Our free resource is a quick-reference guide to help you determine if exploring a rubber part is right for your application.



Custom Molded Rubber Part Service

For high-quality custom rubber part molding services, contact RPM Industrial Rubber Parts. Our team at RPM is dedicated to providing high-quality standard and custom rubber parts with excellent customer service. Some of the standard parts that we provide include:

  • Grommets
  • Bushings
  • Bumpers
  • Mounts
  • Anti-Vibration Pads
  • Industrial Casters
  • Bearings
  • Gears

At RPM Industrial Rubber Parts, we make it our top priority to find the exact part that you need. If we can’t find it, we’ll make it for you. With our custom molded rubber part service, you will work with our team of designers and engineers to turn your idea into reality.

For a more in-depth look at the custom rubber molding process, you can view our free guide by clicking here

To get in touch with our team at RPM Industrial Rubber Parts, give us a call at (888) 842-5668 or contact us online.

If you need rubber, we’ll have it. If we don’t have it, we’ll find it. If we can’t find it, we’ll make it.