Enhanced Mixhead Improves PUR Spray Molding Of Sandwich Components

A new spray adapter for a high-pressure mixhead is said to boost output up to threefold in production of polyurethane sandwich components using the polyurethane spray molding (PSM) process.

A new spray adapter for a high-pressure mixhead is said to boost output up to threefold in production of polyurethane sandwich components using the polyurethane spray molding (PSM) process. Krauss-Maffei Corp., Florence, Ky., now offers its MK 10 P-2KV linear mixing head with the new spray adapter to overcome some limitations of the PSM process. In this open-mold process for producing multilayer PUR parts, the highly viscous PUR reaction blend is typically pressurized with compressed air in order to fluidize it. In most cases, air channels are routed directly to the mixing chamber for that purpose. These are easily clogged, however, increasing the risk of downtime. This design also restricts the efficiency of these spray-type mixheads to an output rate of at most 30 g/sec. With the new PSM combination, the compressed air is metered into the viscous PUR blend in a chamber mounted on the mixhead. As a result, the fluidizing takes place in front of the spray-nozzle’s discharge gap instead of in the mixhead itself. This is said to remove the risk of air-channel clogging, and there is also more space available for the air supply so that larger amounts of air can be delivered to provide higher output. Krauss-Maffei also offers a new wear-resistant version of the mixhead for spraying highly filled compounds, such as barium-sulfate-filled acoustic shields.