RIM Molding Motor Home/Bus/Coach Bumpers

Rim Molded Bus Bumper

RIM is a very cost-efficient and effective method to create parts for vehicles like a motorhome bumper. The RIM process can make your motorhome bumper strong and impact-resistant but also lightweight.

It is formed by using an exothermic chemical reaction to produce a strong, impact-resistant, and flexible material substrate. This also gives you options for designing the bumper with large complex geometries, deep draws, and cylindrical features of size.  In many ways, you can customize your molds to your design standards.

Unlike traditional molding, RIM molding uses lightweight, cost-efficient thermoset polymers.

The RIM Molding Process for Bumpers

The RIM process begins with two liquids: isocyanate and polyol. These two materials are fed from individual storage tanks to temperature-controlled day tanks where they are continually recirculated until a shot is called for at the tool mix head.  The mix head allows the material to flow into the tool.  A piston retracts in the head allowing the two liquids to mix and they flow into the tool with little pressure. 

The chemical liquids have to be mixed at a high velocity of at least 1200psi. You must make sure you are using an impinging mixer before moving it into the mold. The liquid polymers will require less pressure as the curing process occurs. The liquids need to be in a low-pressure area, at least around 100psi for the curing process to work. It also will need to have at least a heat level of 180 degrees Fahrenheit (82 degrees Celsius). These are the minimum requirements for the curing of the mold. The time for the mixture to cure is somewhere between 1 minute and several minutes depending on the size and complexity of the tool designed to make a motor home bumper as an example.  Depending on the material selection, many of these parameters can be changed to affect fill, cure time, shot time and overall part quality and cycle time. 

Advantages of RIM Molding for Bumpers

There are also so many advantages to molding Motor Home bumpers with RIM and RIM materials.  These materials are strong, appeal to large part manufacturing and lightweight making them perfect for a motor home application. They are very tough as they can take a hit and still retain their original design state/shape.  They are very impact resistant making them a very strong and longer-lasting product. RIM molding works really well as bumpers because they have many customizable options.  The tooling can incorporate such design details such as inserts to make different versions of a bumper with one tool and various inserts for such things as cut outs or changes in length. 

Motorhome bumpers made out of these polymers are also much more fuel-efficient due to the weight reduction of the vehicle. The polymer and process are very flexible in terms of design freedom.  In addition, RIM is non-corrosive and chemically resistant. This makes RIM perfect for a bumper application where they are continually exposed to chemicals in garages and use environments. 

Learn more about the advantages of RIM Molding with Thieme. Contact us today for a quote.