Development of Higher Clarity Injection Molded Windscreen for Motorcycles

The windscreen is one of the key elements to enhance passenger comfort of touring motorcycle. The clarity through the windscreen should not discomfort the rider. The discomfort we discuss here mainly refers to three factors: the “distortion,” the “blur,” and the “transparency.” Introduced in this paper is the technical measures to achieve sufficient clarity by the injection molding method. Firstly, with respect to the “distortion,” we determined the main cause was local unevenness of plate thickness. As the uneven thickness were related to the accuracy of the die, we clarified the tolerable zone and carried out higher precision machining of the die to satisfy the requirements. Regarding the “blur,” we analyzed the refractive power of the windscreen and found the main cause of blur is the microscopic roughness on the surface. As the microscopic roughness were attributable to the die surface, we clarified the tolerable zone and established the polishing conditions satisfactory for the requirements. With respect to the “transparency,” it is necessary to maintain transparency after being scratched and degraded by weather in long term use. We determined to use the bio polycarbonate because of its good scratch and weather resistance, which are necessary for maintaining transparency. With all these technical measures applied, we have established the new injection molding method for the windscreens featuring sufficient clarity while taking the environmental protection.