Reaction Injection Molding Service

Injection Molding Process


3Diligent's Reaction Injection Molding Service provides customers a cost-effective avenue for pursuing productions runs in the thousands or higher and/or for large part creation. 


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Process Overview

With Reaction Injection Molding, instead of injecting molten thermoplastic material, thermoset polymer resins are used.  Mixing in the tool, a "reaction" actually takes place that drives the polymerization of the input materials, resulting in a solidified part in the mold.

The lower viscosity of resin, relative to thermoplastic, allows for larger parts to be fabricated using this process, which would often otherwise suffer from imperfections when attempted at larger sizes.

For all the benefits of reaction molding, it does have a few drawbacks.  First, the range of materials available to the process is smaller than thermoplastics, and resins generally cannot deliver the same kinds of material performance that is achievable with thermoplastics.  Additionally, the relative wait time for parts to set means that this process is slower on a per-part basis than traditional injection molding.  As a result, it is typically most useful for quantities in the 1000-5000 piece range.

Process At A Glance

Common Materials


Standard Tolerance


Usual Batch Size

Preferably 500+ (for unit cost savings)

Minimum Wall Thickness



  • Affordable - Lower costs for aluminum tooling and production runs above 500
  • Strong - Filler options can increase density, strength, and other material properties
  • Large and lightweight - Low viscosity allows for large and lightweight parts



  • Longer lead times - Time is added per part made because of resin setting
  • More expensive raw materials - Compared to regular injection molding