A machine for spraying polyurethane skins for automotive door interiors, seats, and instrument panels is new from Cannon USA, Cranberry Township, N.J. The spray-skin system uses a PUR elastomer that is sprayed into heated open molds to give a leather-like look and feel to the finished parts.
The machine has a compact single-frame design, pressurized day tanks, radial piston pumps with magnetic couplings for both isocyanate and polyol components, closed-loop controls with volumetric flowmeters and frequency drives, low- and high-pressure chemical filters, flow-rate display, and a compact hydraulic mixhead.
Chemical temperatures are controlled independently by water-jacketed day tanks and in-line heat exchangers. The chemicals can be heated at the mixhead while keeping them cooler in the day tanks. Mixed components flow through a hollow tube or wand (with no static-mixing elements) to a spray tip. Between shots, a high-pressure solvent flush cleans the mixing nozzle, wand, and tip.
Spray skins have been produced at mixing pressures and flow rates that varied by up to 20% during the shot. This is an advantage as it is often necessary to vary material flow during the pour to accommodate the varying features of intricate automotive parts. One version of the head allows introduction of a third stream for pigment that can be turned on and off at will.