RIM Products & Parts: A Review of Projects

back of white rim molded products

Commercial Tractor Hood

32.5L x 21.5W x 22H     (7 lbs.)

The chemical reaction that distinguishes Reaction Injection Molding from typical injection molding makes all the difference in how your products perform. RIM Manufacturing uses low viscosity liquid polymers which expand and harden in the mold at much lower temperatures than those of plastic injection molding or thermoforming. Plus, your RIM designs can be much more intricate with a greater range of weight, strength, density, and hardness.

RIM is ideal for large parts that need to be lightweight, like the above tractor hood, which is only 7 pounds.

Medical Device Swivel Tray

18L x 18W x 5H     (2.5 lbs.)

RIM, and Structural Reaction Injection Molding, give you design options otherwise impossible. RIM is able to accommodate small to very large parts, impart structural integrity, tight tolerances, and greater ranges of wall thickness within the same part. Plus, several parts can be combined into one.

Consider the intricacy of the above design, with RIM, the medical device swivel tray doesn’t need as many post-production additions or assembly steps as other manufacturing options.

Laboratory Device Base

58L x 27W x 3.25H     (26 lbs.)

Since our RIM process requires lower temperatures and pressures than other manufacturing processes, RIM polymers can be injected into cost-efficient aluminum molds. These cost up to 70% less than steel molds and last longer. They may never need to be replaced and can be modified much less expensively.

For the laboratory device base above, the size, weight, and number of products needed, along with the intricacy of the design, made RIM an ideal process for the project.

Medical Device Cover

18L x 11W x 4H     (1.5 lbs.)

Whatever your specifications, we will work with you to check that RIM is the optimal process for your project. Depending on wall thickness and strength, ribs, draft, bosses, holes, grooves, and vent needs, we will help you select the right system and chemistry to achieve the correct process and end product.

RIM Manufacturing Will Help You Find the Best RIM Design for Your Project 

  • Elastomeric– for RIM parts with superior impact strength, durability, dimensional stability, and resistance to corrosion, abrasion, and wear.
  • Solid– produces RIM parts similar to those created with thermoforming or thermoplastic systems, but these allow variation in wall thickness throughout a part without visible sink marks. Typically, the minimum wall thickness is 1/8” to 1/2”.
  • Rigid Foam– a blowing agent creates a high-density skin around a low-density microcellular core. This skin gives the RIM part firmness and durability, while the low-density core reduces the part design’s weight. Wall thickness can vary from 1/4” to 11/2”.
  • Flexible Foam– this system’s blowing agents create self-skinning foams. The thickness of the skin and density of the foams can be adjusted to achieve the precise flexibility, firmness, and support characteristics your RIM part design requires.
  • Reinforced RIM (RRIM)– the Elastomeric system with glass or mineral fillers introduced to produce parts with greater rigidity.
  • Structural RIM (SRIM)– Solid or Foam chemistries can incorporate long-fiber reinforcements, like glass mats, to increase stiffness and impact resistance for your RIM design.

Contact RIM Manufacturing for a Quote

Our Reaction Injection Molding (RIM) Process

Reaction Injection Molding part
Reaction injection molding and plastic injection molding have almost the same name, so even experienced engineers and designers may think they are the same. But the ‘reaction’ creates a big difference.

The Reaction Injection Molding Process: Pressure & Temperature

Step 1: Polymer Liquids

The RIM molding process begins with polymer liquids (polyol and isocyanate) stored in large storage tanks and dispensed by large, high-pressure industrial pumps. The polymers are recirculated from the storage tanks to a multi-stream mix-head on the machined aluminum mold and back to the storage tanks in a continuous loop.

Step 2: Mixing

When each part is made, a piston or plunger inside the mix-head retracts, breaking the continuous loop, and the polymers mix at a high velocity (approximately 1200 psi) to ensure the proper combination and mixture of the polymers. The resulting polyurethane enters the mold through the after-mixer, which maintains the mixture’s properties while reducing its velocity to 95-100 psi, a much lower pressure.

Step 3: Molding

Since these liquid polymers require less pressure and lower temperatures than typical ingredients, they can be injected into cost-efficient aluminum molds, lowering tooling costs. The molds are then moderately heated (~190°), but the resulting exothermic reaction quickly brings the materials to (~325°) and promptly cures the part inside the mold.

Step 4: Curing & Cooling

Cure times vary from less than a minute to several minutes, depending on the part’s size, geometry, function, and thickness. Polymers and RIM processes can be chosen to produce solid, elastomeric, rigid-foam, or flexible-foam finished polyurethane parts.

Differences Between Reaction Injection Molding & Plastic Injection Molding

Unlike plastic injection molding, reaction injection molding (or RIM molding techniques) utilizes low-viscosity liquid polymers in thermoset – not thermoplastic or thermoforming – processes.

Through a variety of chemical reactions, these polymers expand, thicken, and harden only after they’re injected into a heated mold, accommodating much more intricate designs than ordinary plastic injection molding.

Raw materials and polyurethane reaction techniques can be selected and even customized to precisely deliver desired weight, strength, density, and hardness characteristics. The result is large polyurethane parts with a much lighter weight than those created by more commonplace processes.

Learn the Advantages of the Reaction Injection Molding Process from RIM Manufacturing

Reaction injection molding not only offers certain advantages over injection molding, but also vacuum-forming, pressure-forming, and cast molding.

The admittedly longer production time of reaction injection molding is more than offset by its benefits to design, flexibility, and cost-efficiency, not to mention the wide ranges of part size, design uniqueness, and colors.

Contact RIM Manufacturing to Learn More!

How Reaction Injection Molding Can Reduce Manufacturing Costs

VanDerLande product from Reaction injection molding

Companies continually strive to improve production costs. Whether you need a large, lightweight, or complex, 3-D part, or a limited tooling budget, RIM can be the solution you’re looking for.

Reaction Injection Molding (RIM)  is an example of an innovative manufacturing process that lends to high-quality polyurethane parts.

What Is Reaction Injection Molding (RIM)?

RIM creates end-use products or parts by combining two liquid polyurethane chemicals – an isocyanate and a polyol. These chemicals are isolated as they re-circulate through a sophisticated dispensing machine until a part is produced. 

Parts are produced when the chemicals enter the mixing chamber of the mix-head, which is attached to a machined aluminum mold with heated water lines.  The chemicals impinge at high-pressure (3000 psi) and flow into the mold at low pressure (150 psi).  An exothermic reaction occurs within the mold as the temperature reaches 350℉.  The mold’s water lines quickly wick away the heat and allow the molder to quickly withdraw parts by hand.

Tooling Cost Advantages of Reaction Injection Molding

By using aluminum molds, instead of steel molds, your overall capital expenditure can be dramatically lower – especially for larger parts.  We still use aluminum molds manufactured over 30 years ago!

Injection molding requires high pressures, high temperatures, and highly viscous materials.  All of these elements place tremendous stress on the mold, which is why steel is required to produce conforming parts and minimize mold maintenance. 

Comparatively, more affordable aluminum molds are perfect for the RIM process and its integration of low pressures, low temperatures, and non-viscous materials.

Additional Benefits of RIM Molding

  • RIM is best suited for larger parts and lower volumes.  However, RIM Manufacturing produces smaller parts by the thousands too. 
  • RIM offers tight tolerances with more cosmetic freedom in part design, variable wall thickness, geometric complexities, and the ability to combine multiple parts into one single, seamless part. 
  • Parts can be solid, elastomeric, structural foam, or flexible foam.
  • RIM parts can be pigmented, in-mold painted, or post-painted to provide the required cosmetic finish at the right price point.

Work with RIM Manufacturing for Your Next Custom Project

Partnering with RIM Manufacturing for custom Reaction Injection Molded parts and products can yield high-quality parts that perform well, are durable, and uniquely designed.

Learn more about reaction injection molding and how it can help your business. Contact RIM Manufacturing today.