Methodology for the Design of Cooling Channels in Thermoplastic Injection Moulding Process

Injection is one of the most used processes to manufacture thermoplastic parts. The design of the cooling channels in this process is of great importance during the mould design. Indeed, an inappropriate cooling will lead to defects in the part and a low production rate. In this paper, a new approach for the design of the cooling channels is assessed. Based on morphological concepts, the idea of regulation by cooling surface is introduced. The thermal behaviour of the mould can be restricted on the spatial domain delimited by the cooling surface on which a spatial temperature distribution is imposed. The first step of the methodology leads to the optimal determination of the fluid temperature distribution along the cooling surface in order to minimize a cost function composed of two terms linked to the quality of the part and the productivity of the process. The conjugate gradient algorithm coupled with a Lagrangian technique is implemented for the determination of fluid temperature parameters. However, the obtained solution is not workable in practice. The second step consists then in building real channels from this optimal distribution. The shape, location and fluid temperature level of these channels are determined a posteriori from the thermal analysis of the temperature field in the mould domain located between the plastic part and the cooling surface. Channels are builded by using the contours of isotherms in the thermal steady-state area of the mould. It becomes then possible to design the cooling channels with no a priori on the numbers, the location of these channels and on the temperature of the coolant fluid. The methodology is first illustrated with a 2D part. Results are compared with literature.