Under contract from a Tier 1 automotive supplier, Minnesota Rubber injection has moulded a thermoplastic elastomer (TPE) butterfly valve that regulates heated radiator coolant flow from the engine to the passenger compartment heater core. These butterfly valves replace a previous design, which consisted of two stamped steel components welded together and overmoulded with a rubber elastomer. Component production and assembly was slow, costly and quality was not always consistent. Minnesota Rubber and QMR Plastics designed a one-piece butterfly valve with the correct sealing and strength features that would function trouble-free for hundreds of thousands of cycles. The goal was to develop a single step process using one material and eliminate assembly and welding operations. The material used had to withstand radiator coolant temperature extremes of 190 F over extended periods. Tight part tolerances also were required so valve sealing was assured with each open and close cycle. Minnesota Rubber and QMR Plastics one-piece butterfly valve design eliminated metallic parts with secondary over-moulding operations. Injection moulded of a specialised TPE, prototypes proved the soundness of both design configuration and material selection. Choosing the right material was crucial because it provided both high and low temperature resistance, excellent flex fatigue resistance, excellent compression set and most important, low cost. The successful new butterfly valve design not only replaced the metal assembly with the over-moulded elastomer sealing flange, the part design has become a standard used in a line of cars sold world-wide. By producing in high-speed automated injection-moulding presses, just-in-time volume requirements can be met while part cost has been reduced by nearly 80%. Delivery time has been shortened while part quality and repeatability has been enhanced.
