Cavity air flow behavior during filling in microinjection molding

Process monitoring of microinjection molding (µ-IM) is of crucial importance in understanding the effects of different parameter settings on the process, especially on its performance and consistency with regard to parts' quality. Quality factors related to mold cavity air evacuation can provide valuable information about the process dynamics and also about the filling of a cavity by a polymer melt. In this paper, a novel experimental setup is proposed to monitor maximum air flow and air flow work as an integral of the air flow over time by employing a microelectromechanical system gas sensor mounted inside the mold. The influence of four µIM parameters, melt temperature, mold temperature, injection speed, and resistance to air evacuation, on two air flow-related output parameters is investigated by carrying out a design of experiment study. The results provide empirical evidences about the effects of process parameters on cavity air evacuation, and the influence of air evacuation on the part flow length

Micromilling strategies for machining thin features

Micromilling of metal structures with ‘thin’ features represents a major challenge towards broadening the use of this technology in a range of microengineering applications, for example in producing multi-channel microstructures, housing for mechanical microdevices, and surgical instruments. The most common thin features seen in microengineering products are ribs and webs. This research identifies the main factors affecting the reliability of micromilling technology when employed for the machining of microcomponents incorporating thin features. The general principles that should be followed in designing machining strategies for such features are discussed in this article. Taking these general principles into account, new strategies are proposed to reduce the negative effects of identified factors on part quality and, at the same time, to overcome some of the problems associated with the use of conventional machining strategies for micromilling of ribs and webs. To implement and verify them, initially the milling operations were programmed manually, and then a special CAM module was developed for their automatic generation. Finally, this article reports the validation of the proposed strategies for machining thin features, which was carried out on a specially designed test part