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.

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The RIM Manufacturing Process

RIM Manufacturing Process

RIM Manufacturing is well-known for helping our customers design molds, or “tools,” for the greatest efficiency, uniformity, and production productivity. During our RIM product design and manufacturing processes, we also consider including after-mixers and gating to maximize your part’s quality.

Planning & Communication

Our experience in the industry means we can help you achieve the ideal mold design by taking multiple factors into consideration:

The Right RIM System

Part size is the primary factor for determining the size of the dispensing machine used to inject the polyurethane into the mold. RIM Manufacturing offers a wide range of capability with three of the largest machines made, two mid-size, and two small machines.

RIM parts are often light but can weigh as much as 100 pounds. The largest part RIM Manufacturing currently produces weighs approximately 50 pounds.

Mold Clamping Pressure

This is determined by the amount of chemical and the type of RIM system injected into the mold. Generally, clamping pressure can range upwards of 200 tons, but typical molding pressure is less than 100 psi.

Mold Cost

RIM molds (aluminum) can be as much as 70% less than injection molding (steel molds). Lower in-mold pressures allow molds to be created from lower-cost materials, and these lower pressures often lead to less wear and tear, allowing the mold to be used for longer, saving more in mold costs.

Part Shrinkage

All plastics, including RIM materials, shrink during molding. The amount of shrinkage characteristic of the particular RIM system is factored into the tool’s design.

Dimensional Tolerances

This is usually geared toward form, fit, and function, allowing molds to be built to absolute dimensions. Because this is more costly, designing parts for more practical dimensional tolerances generally saves money.

Quality & Dependability

RIM Manufacturing is known throughout the industry for producing parts that reduce cost without any reduction in dependability or quality. For decades, our customers have relied on us because they need parts to be defect-free while they strictly conform to form, fit, and function requirements.

Our process goes a long way to ensure that we spend whatever time is necessary with customers assisting with and reviewing the final part design. Collaborative GoTo, WebEx, or in-person meetings are essential to designing parts that exceed everyone’s expectations.

After part drawings are finalized and the mold is designed and constructed, the Production Part Approval Process (PPAP) begins.

  1. First Article parts are produced, and our Quality Department inspects them for conforming to the part drawing. They measure all critical dimensions and callouts and review them for cosmetic conformance.
  2. Once approved, the polyurethane parts are sent to the customer for First Article Approval and sign-off.
  3. Once final approval has been obtained, our Quality Department produces Work Instructions for each relevant area of the part’s production – molding, secondary operations, painting, assembly, quality assurance, and packaging.

Our customers can count on us for quality and consistency, as evidenced by our ISO 9001:2015 and ISO 13485:2016 certifications. And we will continue to improve our processes, capabilities, equipment, facilities, and staff to sustain the highest level of customer satisfaction – that’s our guarantee.

Contact RIM Manufacturing for more information

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!

Combining Multiple Parts into One: A Key Advantage of RIM

Metal part from injection molding (RIM)

Advantage of Reaction Injection Molding

Reaction Injection Molding or RIM is a process used to produce a wide variety of polyurethane parts, including: structural foam, solid RIM, elastomeric, flexible foam, and composite parts. These are used in multiple different industries, ranging from automotive to medical.

RIM involves using polymer liquids – polyol and isocyanate. These liquid polymers are dispensed through high-pressure pumps at low pressure into aluminum molds, which are temperature controlled. injected into heated molds. Inside the mold, the combined chemicals produce an exothermic reaction transforming the liquids into a molded part. This process allows you to easily create products that are customizable according to your desired tolerance, density, weight, thickness, and hardness.

Because the RIM process is perfect for larger, lightweight parts, designing several parts into one part can reduce the need for multiple molds and the labor required for assembling multiple parts. Additionally, over-molding sheet metal or steel can eliminate the need for hinges or attachment points creating additional cost savings.

Contact Us for Your Next RIM Manufactured Part

Understanding the ‘Reaction’ Process in Reaction Injection Molding

Injection Molding machine for RIM process

Some people assume that the difference between traditional injection molding and reaction injection molding (RIM) is purely superficial. But the two processes are considerably different and provide distinctive results. Although both inject raw materials into a mold, RIM is more complex as it uses chemical reactions to create parts.

Educate yourself on RIM’s “reaction” process to understand how it differs from traditional injection molding. Apart from this, you will discover how chemical reactions create stronger, more durable, and more customizable parts.

The Reaction Process

RIM uses low-viscosity liquid polymers, specifically isocyanate and polyol, which are lightweight and cost-efficient. These liquids are stored in large tanks before high-pressure industrial pumps dispense them into the appropriate molds. The injected liquids slowly expand and thicken through a chemical reaction. Once this is complete, the materials harden into the finished parts.

RIM differs from traditional injection molding in its design process. It is highly customizable, making it easier to select which raw materials and molding techniques to use. It results in finished parts that have custom weight, strength, and density characteristics. The RIM process also allows for more intricate designs.

The Advantages of RIM

The chemical reaction utilized in this process has several advantages, including better structural integrity at a low cost. Learn more about it to understand why many businesses prefer the RIM process.

Build Larger Parts

The traditional injection molding process is more expensive, making it difficult to use in manufacturing larger parts. The RIM process for parts molding offers clients a cost-efficient alternative. Additionally, liquid polyurethane is better at filling molds for larger pieces without compromising on its finer details.

Experience Better Durability

The materials used in the RIM process offer better design flexibility, allowing you to design and build parts with varying thicknesses to suit the final product better. Parts created through RIM exhibit better dimensional stability and chemical resistance, letting them withstand internal stress during processing. Polymer-made products are also known for their corrosion resistance, making them ideal for moisture-prone applications and environments.

Enjoy Superior Flexibility

Polymer materials used in RIM are known for their flexibility, especially compared to aluminum and sheet molding compound. Quickly form parts with intricate details without compromising their durability with these materials.

Create In-mold Paintings

RIM provides aesthetic benefits, including in-mold painting. This is achieved by painting the cavity of the mold before it is filled with polymer materials. The paint adheres to the liquid through a chemical bonding process, coating the finished part as it dries. It results in a paint job that is resistant to cracking, flaking, and chipping.

Experience the Advantages of RIM Processes When You Work with RIM Manufacturing

For over four decades, we have worked with businesses across industries, providing them with high-quality parts for their products. We take a hands-on approach to each project, allowing us to create custom parts for any product.

Get in touch with us for more information about our services.