Innovative Solutions for High-class Prototypes and Short Runs

Plastic parts in large series are generally produced by injection molding. The building of the steel mold for this production method is complex and costly and should therefore only be used when a large number of parts warrants its use.

The RIM technology can be used to produce a smaller number of units up to 1,000 parts in a fast and cost-efficient way. In the case of reaction injection molding (RIM), a two-component PUR mixture is injected into a mold with a 2K mixing and dosing system and cured in an exothermic reaction, to produce a detailed part with defined properties, simulating thermoplastic materials.

Compared to thermoplastic injection molding, the PUR resins have better flow behaviour due to their lower viscosity and can achieve greater flow paths at the same wall thickness. Typical RIM applications include bumpers, sills and spoilers.

Rjcmold offers a wide range of RIM systems, covering the properties of thermoplastic systems. The 2K PUR resins have a low viscosity and enable the production of large size, complex components with low wall thicknesses. The processing time of most RIM systems lies between 1 to 3 minutes. Due to this fast reaction time, the parts can be demolded after 5 to 20 minutes, which makes the production of small number of units more profitable. Furthermore the Rjcmold RIM portfolio offers special RIM products with high impact resistance, high temperature resistance, long pot life for production of large parts as well as special certifications for the automotive industry.

What is Reaction Injection Molding (RIM)?

Reaction injection molding (RIM) is a molding process to manufacture plastic molded parts.

Polyolefin and Isocyanides (as well as some other ingredients) are mixed in a mixing device in a fluid state and then injected as a liquid mass into a mold. The solidification of the liquid mass occurs in the mold as the mixed liquids react with the heated surface of the tool surface.

The advantage of this process is a low clamping force needed for the mold, long material travel paths and the low pressure conditions of the molding process. The necessary molds can be manufactured quickly and cost effectively using aluminium.

Molded parts produced in the RIM process compete with parts from injection molding, thermo forming and fibreglass lay up. The liquid masses of the RIM process have a more advantageous flow behaviour in comparison to injection molding due to the low viscosity of the material since they are not a thermo plastic. Therefore, much longer flow paths can be achieved with the same wall thickness than other traditional molding processes.

Why Reactive Injection Molding?

Reactive injection molding (RIM) is similar to the conventional injection molding (IM) except thermosetting materials are used. The chemical curing reaction occurs simultaneously as the resin flows during the molding process. The polymerization of RIM is usually activated after mixing under heating with or without high pressure. The advantage of RIM is that with its relatively low viscosity, resins can readily fill the cavities with large L/D ratio. The RIM can produce plastic parts with high mechanical strength because of the crosslinking in polymer structures.

However, the thermosetting polymers are usually difficult to be recycled, and the potential problems of flashing, scorching and longer cycle time have been the main challenges of RIM. Moreover, the complicated interplay between chemical reaction, fluid flow and heat transfer bring more uncertainty on process control and optimization for RIM. Rjcmold RIM offers true 3D solutions to analyze RIM processes for thermosetting materials including unsaturated polyester, polyurethane, rubber compound, liquid silicone rubber, and epoxy molding compound. The software simulates cavity filling, curing, part warpage, fiber orientation, multi-component molding, and many other customized methods and processes.

Advantages of Choosing Reaction Injection Molding

The RIM molding process holds an array of valuable benefits. Here are a few that our customers have found beneficial:

(Due to the liquid injection RIM process and nature of the PUR foaming process, unique, difficult, deep drawn and cylindrical parts can be achieved.)

Where can RIM moulding be used?

RIM mouldings can be used across a variety of industries and sectors. From medical to marine, transportation, and everything in-between. These robust mouldings play a crucial role in industries where reliability and durability can be life-saving.

Polyurethane housings are used within the medical and scientific industries to provide parts for innovative cancer treatment, robotic surgery, and laboratory testing equipment. These safety-conscious industries demand compliance against all regulatory standards as well as UL94 V0 flammability ratings and the option for EMC shielding. Electric vehicle charging units, personal dive units, and solar canopies on the other hand require robustness and UV stability so they can stand up to the rigors of external use. RIM mouldings can create precision parts that offer structure and confidence when it counts.