10-port water outlet molded without parting lines

A combination of tooling and engineering plastics expertise has come to the fore in a complex 10-port water outlet for 1.6-2.5-L engines used in Nissan Motor vehicles. The component, molded of Amodel polyphthalamide (PPA) from Solvay Specialty Polymers (Alpharetta, GA) by MPC Inc. (Walworth, WI) on a Van Dorn 500-ton hydraulic press, was recently recognized with the powertrain award at the 42nd Annual Society of Plastics Engineers (SPE) Automotive Innovation Awards Competition.

This water outlet assembly was made possible through the development of a complex injection mold, incorporating multiple sequential valve gates to prevent material over-pack and gas entrapment. The ten male ports are created without a parting line usually required with conventional injection molding. Seamless hose joints are made possible through precision timing of multiple valve gates and multiple slide actions to properly form this complex product in one-piece. Scientific molding was used to activate the valve gates and monitor product quality. The molding process was combined with a traverse robot to monitor and remove non-conforming product.

Amodel PPA's high elongation permits elimination of the parting line commonly required for injection molding and part extraction to produce this complex part at 450g weight reduction versus metal (the part weighs 275g with dimensions of 209 mm W x 107 mm D x 123 mm T). One of the key differentiating factors for Amodel PPA and an important reason for its selection for Nissan's water outlet is its ability to be injection molded without producing a parting line on the barb of the 10 outlet and inlet tubes. In a typical plastic part, the parting line could be very sharp and could create a cut during installation, resulting in a coolant leak path. To avoid such a quality issue, auto OEMs specify no parting line in the barbed area.

Solvay's AmodelAS-1933 (335 glass fiber reinforced) has superior elongation at the recommended mold temperature of 135°C (275°F) compared to other PPAs and polyphenylene sulfide (PPS). The material's elongation allows injection molders to eject the parts from the mold without producing a parting line in the barbed area, unlike conventional injection molding.

"The bottom line is that Amodel PPA made possible the molding of this highly complex part," said Andre Carvalho, global automotive market manager for Solvay Specialty Polymers. "Amodel PPA's unique properties are clearly superior to the competition and they were the deciding factor in the successful production of this complex assembly."

AS grades of Amodel PPA reportedly reduce cost, use simple tooling, and speed cycle times. They have been successfully used by many auto OEMs in numerous heating and cooling components. Among the key design guidelines and recommendations: the maximum undercut ratio should be around 8-9% and the ejection angle should be greater than 150 degrees. In case of outlets with a small diameter, it is possible to mold the undercut in the range of 12-13% with a special provision.

The water outlet assembly was a metal to plastic conversion which integrated two components into one assembly. The thermoplastic replacement is a single molded product, delivering greater than 25% cost savings. There is also a labor savings at the engine plant by removing one assembly operation due to component integration.

The plastic water outlet eliminates the need for 18 machining operations and eliminates 20 potential leak paths. It achieves machined metal tolerance right out of the mold without any secondary machining. Tooling for competitive cast aluminum parts should be replaced after about 100,000 cycles which adds to the cost. In comparison, tooling for Amodel PPA injection molded parts will last the life of the Nissan engine program, with annual volumes of approximately 800,000 pieces.

The main function of the water outlet is to act as a manifold for the cooling system. The outlet features 10 seamless barb ports that feed coolant to and from the transmission cooler, throttle cooler, heater core, oil cooler, and provides coolant to the radiator. The outlet also includes a press-in place seal inserted post-molding, a sealed threaded insert, a wire harness bracket, an oil drip rail, and houses the thermostat.

This same part earned an award earlier this year, taking home the ‘Single Part’ prize in the Society of the Plastics Industry’s International Plastics Design Competition held during NPE2012 in Orlando, FL on April 5. Industrial Molds Group, a mold manufacturer specializing in precision molds with multiple complex actions, supplied the tooling for the part to MPC.