Introduction to Polyurethane Injection Molding Machine - Metering System

Polyurethane injection molding machines typically use a two-component material system, employing two metering pumps. One pump is used for measuring the isocyanate component, while the other measures the polyol component, which is a blend of polyols and various foaming agents. Polyurethane injection molding machines may also install separate additive pumps when specific product requirements are necessary, such as pumps for blowing agents, pigments, or fillers.

The metering pumps used in polyurethane injection molding machines include common types such as gear pumps, annular piston pumps, axial plunger pumps, vertical plunger pumps, and notably, single-stroke plunger metering pumps.

To ensure stable and accurate metering, polyurethane injection molding machines are equipped with metering plunger cylinders that have temperature control devices. These devices maintain the temperature of both the cylinder and material. The single-stroke plunger pump, powered by hydraulic energy, can be used in both high-pressure and low-pressure systems. It can reach a maximum working pressure of 25MPa, and its material viscosity range is 3-50,000mPa·س. This type of pump can handle materials with a high content of fillers, including abrasive fillers such as glass fibers or other organic and inorganic abrasives. This feature is particularly important in the production of RIM (Reaction Injection Molding) and RRIM (Reinforced Reaction Injection Molding) products, where the single-stroke plunger metering pump is crucial.

The single-stroke plunger metering pump is suitable for non-continuous production processes. Its maximum discharge volume per stroke is determined by the volume of the metering plunger and cylinder, typically ranging from 2 to 15L, with an injection volume ranging from 7 to 13,000cm3/s. Several specifications are available for selection.

A single-stroke plunger metering pump powered by compressed air is used for low-pressure machines, producing small molded products with or without fillers, and can also be used for small-scale spraying equipment. When driven by hydraulic or mechanical connections, the single-stroke plunger metering pump is applicable to various low-pressure or high-pressure systems.