Читать книгу Plastics Process Analysis, Instrumentation, and Control - Группа авторов - Страница 37

During a conventional injection molding process, plastic granules are melted by heating and then injected into a mold to form a plastic product (53). However, the plastic granules may be contaminated so as to cause the molded product to have defects, which lowers the product yield. Therefore, there is a need to provide a system that can perform defect analysis of a molded plastic product at an early stage.

Such a molding machine, which is operated to mold plastic granules into a plastic piece, includes a machine body, a platform, a heater, and a pressing unit (53).

The platform is installed at the machine body and defines a molding cavity adapted to receive the plastic granules. The heater is installed at the machine body adjacent to the platform and is adapted for heating the platform.

The pressing unit is installed at the machine body and disposed above the platform. The pressing unit includes a pressure cylinder, a telescopic rod connected to and driven by the pressure cylinder to extend downward and retract upward, and a pressing plate coupled to the telescopic rod and disposed to correspond in position with the molding cavity.

The pressure cylinder drives the pressing plate via the telescopic rod to move the pressing plate relative to the platform between an initial position, where the pressing plate is away from the molding cavity of the platform, and a molding position, where the pressing plate is close to the molding cavity of the platform so as to cooperate with the platform to form a mold for molding the plastic granules into the plastic piece.

Another system for defect analysis of the plastic piece includes the molding machine, an optical sensing unit, and a computing unit. The optical sensing unit is configured to detect the plastic piece formed using the molding machine. The computing unit is coupled to the optical sensing unit and is operable for defect analysis of the plastic piece.

Here, the method for forming a plastic piece includes the following steps (53):

1 Heating a raw plastic material,

2 Pressing and molding the heated raw plastic material to form a light-transmissive molded plastic piece,

3 Cooling the molded plastic piece, and

4 Based on defects of the molded plastic piece, determining whether or not the molded plastic piece conforms with predetermined criteria.