Reaction Injection Molding using SOLIDWORKS Plastics

Reaction injection molding (RIM) is a specialized molding technique in which two reagents (e.g., a resin) are mixed and injected into a mold cavity to react and solidify.

While reaction injection molding is a low-pressure, low-temperature application, it ultimately results in a high-strength bond. SOLIDWORKS Plastics can help simulate reaction injection molding with thermoset material to identify common molding issues.

What Materials Are Used For Reaction Injection Molding?

The polymer material used in the reaction injection molding process is classified as a thermoset plastic. Thermosetting plastic material irreversibly cures, meaning it cannot be reground or remelted.

Unlike traditional injection molding, RIM relies on a chemical reaction inside the mold to form the final part. Once the resin is cured or solidified in the mold, the thermoset plastic has impressive heat and chemical resistance.

Who Uses Reaction Injection Molding?

This process is widely used in automotive, aerospace, and consumer goods industries for producing large, complex parts with excellent surface finish and dimensional stability.  Typical examples of thermoset plastics include epoxy resins, vulcanized rubber, and silicones.

Despite its benefits, reaction injection molding introduces unique challenges such as non-linear viscosity changes during curing of reagents, uneven cooling, warpage, dimensional inaccuracies, and balancing reaction kinetics with mold temperature.

How to Simulate Reaction Injection Molding with SOLIDWORKS Plastics

While SOLIDWORKS Plastics is typically used for higher-pressure injection molding, the study and material settings can be adjusted to support RIM. With just a few simple tweaks, you can be on your way to accurately simulating thermoplastics.

1. Create a SOLIDWORKS Plastics Study: Start with your part design in SOLIDWORKS to create a new Plastics study, selecting either shell or solid mesh under analysis.
2. Define Material Properties: Select thermoset plastic from the database or custom define the material.
   

   Setting the material properties for a SOLIDWORKS Plastics study

3. Define Process Parameters: The fill and pack settings are defined for the injection unit. In the Fill-Pack parameters for SOLIDWORKS Plastics 2026, Thermoset Material Ejection Criteria can be defined. This could be Time or Curing-based criteria.
   

   Using Curing-based study parameters

4.  Mesh and Run the Analysis: The analysis can be run for Fill, Pack, Cool, or Warp, depending on your desired study.
5. Review the Results: Analysis results related to thermoset plastics in SOLIDWORKS Plastics 2026 include time to reach curing level, material’s curing level at end of fill, time to reach curing level, material’s curing level at ejection, and volume above target curing level at ejection.
   

   SOLIDWORKS Plastics results for a RIM analysis

Considerations for RIM Analysis

Accurately simulating reaction injection molding means you need to keep a few things in mind as you are setting up your injection molding analysis.

Material Properties

The following parameters need to be defined for the material:

• Melt, mold, and ejection temperatures, as well as the glass transition temperature
• Specific heat
• Conductivity
• Viscosity: Defined by one of 3 models
  • Constant viscosity
  • 5 Parameters model
  • 7 Parameters model

Defining reaction injection molding materials

Process Parameters

When defining the Fill-Pack parameters, you have options based on the material model:

• Curing-based directs the solver to continue the curing simulation until the material reaches the specified target curing level, eliminating the guesswork of determining the curing time.  In this case, the program ignores the Pressure Holding Time and the Pure Cooling Time parameters in the Pack Settings.
• Time-based sets a specific curing time for the solver to complete the thermoset curing simulation. After the simulation is run, the results show the percentage of curing achieved across the model. Users can adjust the curing time to either shorten or extend the process. The time specified in the Pack Settings is used to calculate the level of curing the part achieves for that specified time.

Curing, or conversion, in this case, is the change of state of the material. This can be either hardening of the polymer for thermoset materials or cross-linking of the molecules of the material for elastomers, which results in elastic behavior of the materials.

Simulation Results

For accurate simulation results, the necessary material characteristics and process parameters need to be defined. Additionally, the temperature plot at post-filling helps evaluate if the part can be ejected or needs more time to cure in the mold.

Accurate Injection Molding Analysis with SOLIDWORKS Plastics

With SOLIDWORKS Plastics, you can seamlessly design lightweight, high-strength physical products that not only meet stringent performance standards but also reduce overall product development cost and time. No matter if you use traditional injection molding techniques or need low-pressure, low-temperature reaction injection molding analysis, SOLIDWORKS Plastics is the key to your company’s success.

To learn more about adding SOLIDWORKS Plastics to your workflow, click here.