In the process chain from granulate to the finished molding, mold temperature control is of great significance during polymer processing, which has been substantiated that it determines the quality features of the components and guarantees correct reproduction of the surface. In view of the existing inherent problems associated with the constant temperature mold in injection molding process, the rapid heat cycle molding process can facilitate rapid temperature change at the mold surface thereby improving quality of molded parts without increasing cycle time. So an integrated heater and sensor consisting of one metallic heating layer and one oxide insulation layer was investigated in this thesis and developed for thermoplastic injection molding applications.

The entire researc...[ Read more ]

In the process chain from granulate to the finished molding, mold temperature control is of great significance during polymer processing, which has been substantiated that it determines the quality features of the components and guarantees correct reproduction of the surface. In view of the existing inherent problems associated with the constant temperature mold in injection molding process, the rapid heat cycle molding process can facilitate rapid temperature change at the mold surface thereby improving quality of molded parts without increasing cycle time. So an integrated heater and sensor consisting of one metallic heating layer and one oxide insulation layer was investigated in this thesis and developed for thermoplastic injection molding applications.

The entire research consists of three parts: theoretical part, fabrication part and experimental part.

In the theoretical part, a transient heat transfer model is built to help understand the mechanism of heat transfer in an injection mold, and thus derives an important parameter for the designed heater and sensor- the thickness of thermal insulation layer, which can be neither too thick nor too thin, too thick an insulation layer increase the cooling time too much, whereas with a too thin layer the mold surface temperature will stay too low. Design issues towards developing a mold capable of raising temperature 200°C in one second and cooling to room temperature very fast were discussed.

In the fabrication part, materials with closely matched low thermal expansion coefficient were used for all layers to reduce thermal stresses between layers during heating and cooling period. Several rapid heat cycle mold inserts prototype were constructed by using MEMS technology.

In the experimental section, the heating and cooling response shows differences with the analytical solution of the heat transfer model and results are discussed and verified by performing numerical simulation using FEM. Shear force test proves the integrated heater and sensor is durable and wear-resistant, which is capable for practical appIications.