At the Fall API show, Linden Industries presented a new equipment innovation to achieve variable filler content when processing RRIM (Reinforced Reaction Injection Molding). 

Reinforced Reactive Injection Molding (RRIM) is a process whereby a filler, such as milled glass, mica or wollastonite is blended into the polyol stream to provide stiffness and dimensional stability to the product. This process is typically used to manufacture products such as automotive fascia, body panels and trim components.

Linden Industries, Inc. has a developed a new line of equipment that allows processors to quickly vary the percentage content of filler and polyol / isocyanate ratios on the fly. This technology is of particular importance to processors whose production volumes do not justify the purchase of dedicated machines for each requirement.

Historically, the filler is blended in 500 to 1000 gallon batches. The machine is committed to that percentage of filler. The percentage cannot be changed without reblending.

The Linden technology utilizes multiple polyol cylinders and day tanks to vary the filler percentage instantaneously. With the addition of hydraulic orifices to the mix head, pressures can be tuned relative to the programmed cylinder speed. This technology allows the processor to vary the percentage of filler and ratios from mold to mold, shot to shot.

This type of system is ideal for manufacturer¡¦s producing a variety of parts that require varying levels or types of fillers, but do not have the volumes to justify a dedicated machine. The system incorporates two resin cylinders which can meter either two different types of filler or two different ratios of filler.

One cylinder may be used for unfilled resin providing the ability to switch from a filled to an unfilled system depending upon the part requirements. An example of two different types of filler would be one cylinder meters glass fiber while the other mica. Glass filled, mica filled or glass-mica filled parts with varying filler ratios can be produced from a single machine.

This system provides a cost effective method to manufacture parts requiring varying ratios or types of filler such as agricultural equipment, bath and kitchen fixtures, and automotive service parts.

As mentioned in the previous paragraph, the system uses two resin lance-type cylinders containing either different fillers or percentages of the same filler. Depending upon the level of filler required and viscosity of the system, either a cylinder or variable frequency drive metering pump can be supplied for the isocyanate metering.

At the heart of the system is a Linden MHS four stream mix head with hydraulically controlled orifices.

The mix head is manufactured from abrasion resistant alloys. Hydraulic control can vary the stream or shutoff the stream thus modifying ratios/density and filler percentages from part to part. This advanced head comes equipped with proximity switch for the control plunger to provide a signal for process control and ensure consistent shot-time accuracy. Like all other Linden mix heads, the MHS-4 features a shot counter.

The shot counter provides a reliable measurement of the quantity of shots a mix head has made. Based upon the historical failure of a mix head with a particular system, a preventive maintenance program can be established whereby a mix head can be replaced and sent for service prior to a major failure.

A major failure can involve one component burrowing through the mix head plunger and foaming or gelling in the machine. Since the plunger is encapsulated within the mix head, wear in the components cannot be seen without disassembling the mix head.

With the shot counter, a wear pattern, life expectancy, and thus replacement schedule can be established for the components of the mix head. The shot counter is of particular importance in the application of RRIM processing due to abrasive fillers which can wear components of the mix head.

The variable filler system utilizes an Allen Bradley PLC. Standard hydraulic orifices can be replaced by servo controlled hydraulic orifices for applications that require large throughput changes. Data collection, equipment set-up and monitoring capabilities are available through Linden's MicroProcessVu software.