Heat Control simulation for variothermal injection moulding moulds using infrared radiation

Abstract

Mould temperature control has a significant influence on component quality and costs in the plastic injection moulding process. In the case of standard applications isothermal temperature control, in which the mould temperature is maintained at one level, is sufficient. For special applications (e.g. plastic optics; long, thin components; moulding of microstructures) variothermal temperature control using cyclically changing temperatures is beneficial. Therefore, the use of infrared radiators offers advantages in terms of achievable temperatures and investment costs but at low heating rates and efficiency. This paper therefore investigates the possibility of increasing the efficiency of energy input by infrared radiation into metals in particular into aluminium. For this purpose, a simulation model is developed. The numeric models used are validated by means of experiments. A short-wave infrared radiator is investigated, consisting of a tungsten filament in a quartz glass tube. The emitter power is varied from 1200 to 400 W. An aluminium sample with a thickness of 10 mm and a square base with an edge length of 60 mm is investigated. The temperature is measured on the non-irradiated side in the centre of the sample surface and at a distance of 20 mm from it while being irradiated. For the numerical model, a ray tracing simulation is carried out in a first step, the result of which is used as a Neumann boundary condition for a thermal simulation in second step. The model created can serve as a basis for the thermal design of more complex geometries.

Prediction of Morphology Distribution within Injection Molded Parts Obtained with Fast Cavity Heating Cycles: Effect of Packing Pressure

“…A scalar measure of the stretch that the molecules experience by the effect of flow during the process, Δ, is given by the largest difference between the eigenvalues of the molecular conformation tensor A. In simple shear, Δ can be expressed as reported in Equation (10).…”

“…[7,8] However, most of the proposed methods show slow heating and cooling rates (10 °C s −1 ), cause excessively long processing time. Induction heating, infrared heating, and high proximity heating [2,9,10] can realize cavity heating with a rate of 50 °C s −1 . [2,11] Although fast, those methods require high investment costs.…”

Rapid Heating of Mold: Effect of Uneven Filling Temperature on Part Morphology and Molecular Orientation

“…For instance, the molded part's surface appearance, strength, and shape accuracy can be significantly enhanced by the increase of the cavity temperature. Moreover, the required injection pressure and clamping force of the molding machine significantly decrease when increasing the cavity temperature, leading to a significant energy saving [2,[7][8][9][10]. However, the increase of the cavity temperature may induce an increase in the processing time, particularly the cooling stage, with a consequent decrease in the productivity of the injection molding process.…”

“…The induction heating is realized by introducing a cavity insert wound with induction coils, which allows temperature modulation [14]. The radiation heating is based on the introduction of a movable insert that can be heated by an infrared source [8]. The proximity heating mainly consists in the flowing of a high-frequency current between the two plates of the mold, and this induces a rapid mold heating, while the cooling channels allow for a mold temperature reduction after the current deactivation [15].…”