Sugio, D., Okazaki, S., and Kaneko, M., "Application of Rapid Heat and Cool Molding to High Strength Outer Parts without Painting Treatment," SAE Int. J. Mater. Manf. 10(1):52-71, 2017, doi:10.4271/2016-32-0024.
Glass fiber reinforced plastic of polyamide is applied as one of the materials used for the high strength exterior parts of a motorcycle, such as a rear grab rail or a carrier, to which both strength and good exterior appearance are required. However, Glass Fiber reinforced Polypropylene (PPGF), which is relatively inexpensive material, has a property that the contained glass fibers are prone to be exposed at the surface and, therefore, the requirements for good appearance are hardly met by using PPGF. In this study, Heat and Cool molding method (H&C molding) was employed to realize a cost reduction by using PPGF yet without applying painting process, and the established method was applied to mass production while fulfilling the requirements for a good exterior appearance. In H&C molding, the metal molds are heated up by steam and cooled down by water after molding. This process works for making superior surface appearances and the appearance quality is determined by the temperature control of the molds. H&C molding has been generally applied to the parts with a flat shape and straight piping with a diameter of around 10 mm is arranged close to the surface of a metal mold cavity to get a good efficiency of temperature control. However, when this method is applied to a motorcycle part that is structured by three dimensional surfaces, these conventional piping arrangements cannot satisfy the requirements for a short molding cycle time and an even distribution of mold surface temperatures at the same time. In our study, a piping arrangement design by which the pipes are located along the three dimensional cavity surfaces was investigated. The piping arrangement design was determined based on the measurement results on test pieces and the molding cycle time of 100 seconds was eventually achieved. Furthermore, a proof testing to examine the material strength and the weather resistances is conducted as well.