Product

In an exclusive agreement with Ballistics Research, Inc.,  Melleck is the sole manufacturer of RIM-produced ballistic blocks.  This product is geared toward the defense and security industries.  The ballistic block can be used at:

• forward operating bases
• firing ranges
• check points
• defensive perimeters
• between air craft at airfields 
• as well as  in many other defensive postures. 

The RIM process allows us to manufacture a  light, mobile block which can be easily deployed in the field.     Our blocks have been tested  by the U. S. government and will stop a 50 caliber API round from 20 feet. 

We ensure the highest quality and the most efficient manufacturing process possible.

About RIM

Overview

Polyurethane reaction injection molding (RIM) technology was developed in the late 1960s by Bayer AG.  Since then, the technology has evolved dramatically as more and more product designers and manufacturers have learned to tap the unique capabilities and benefits of RIM for an evergrowing range of products.  The universal physical characteristics of polyurethane RIM parts are high strength and low weight.

What is RIM?

Like thermoplastic injection molding, RIM is a plastics-forming process that uses molds to form parts.  But the similarity ends there.

It's helpful to view RIM not as a specific resin with narrowly defined properties, but as a process capable of achieving a broad range of properties.  As its name implies, the polyurethane RIM process uses polyurethane to produce molded parts.  The polyurethanes begin as two liquid components, compared with the pellet form of most thermoplastics.  These liquid components - an isocyanate  and a polyol - are developed in two-part formulations, which are often called polyurethane RIM systems.

Depending on how the polyurethane RIM system is formulated, the parts molded with it can be a foam or a solid, and they can vary from flexible to extremely rigid.  Thus, polyurethane RIM processing can produce virtually anything from a very flexible foam-core part to a rigid solid part.  Part density can vary widely, too, with specific gravities ranging from 0.2 to 1.6.

Some Advantages of RIM

The RIM process utilizes very low viscosity liquids ranging from 500 to 1500 centipoise(cps), low processing temperatures of 90 to 105 F,  low mold temperatures of 90 to 105 F and low internal molding pressures between 50 and 150 psi.   The low viscosity, low temperatures and low pressures provide some very distinct benefits or advantages for the RIM process compared with other plastic processing methods.

1. Very Large Parts

The flowability of the liquid polyurethane components enables them to fill molds for very large parts.  The rigid structural foam roof for a Deere & Company combine measures 62 inches by 69  inches and weighs approximately 55 pounds.  The size of the part that can be molded depends on the speed of the reactivity profile of the polyurethane formulation and the throughput of the metering unit - the pounds per minute that can be dispensed.

2. Encapsulation of Inserts

Inserts of many types can be placed into a mold prior to injection of the RIM material.  And the RIM material can encapsulate many inserts during molding.  In one example, an aluminum frame is placed into the mold and an elastomeric RIM system is injected and encapsulates the frame to form the decking for a snowshoe.  Steel, aluminum shapes and frames, window glass, glass preforms, electronic sensors, PC boards and wiring harnesses are some examples of materials that have been encapsulated using the RIM process.

3. Thick and Thin Walls

Producing variable wall sections within the same molded part are a definite problem with many plastic processing methods and materials, such as thermoplastic injection molding,  blow molding,  sheet molding compound (SMC) and other polymers.  But the RIM process offers you the flexibility to design parts with significant wall thickness variations.  Wall thickness ranges between .25 inches and 1.125 inches are possible cross-sections in the same molded part.

4. Class-A Surfaces

The surface  finish  of parts molded with the RIM process allows manufacturers to produce Class A painted parts.  For example, automotive manufacturers are able to produce fenders, spoilers  and fascia parts that can match the high-gloss painted metal parts they are mounted to in the final assembly.

In Detail:  How Does RIM Work?

At the heart of the polyurethane RIM process is a chemical reaction between the two  liquid components, which are held in separate, temperature-controlled feed tanks equipped with agitators.  From these tanks, the isocyanate and polyol feed through supply lines to metering units that precisely meter both components, at high pressure, to a mixhead device. 

When injection of the liquids into the mold begins, the valves in the mixhead open.  The liquid reactants enter a chamber in the mixhead at pressures between 1,500 and 3,000 psi, and they are intensively mixed by high-velocity impingement.  From the mix chamber, the liquid then flows into the mold at approximately atmospheric pressure.  Inside the mold,  the liquid undergoes an exothermic chemical reaction, which forms the polyurethane polymer in the mold.

Shot and cycle times vary, depending on the part size and the polyurethane system used.  An average mold for an elastomeric part may be filled in one second or lesss and be ready for demolding in 30-60 seconds.  Special extended gel-time polyurethane RIM systems allow the processor enough time to fill very large molds using  equipment originally designed for smaller molds.

Portions copyright Bayer MaterialScience LLC.

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Links:  Ballistics Research, Inc