Sheet-metal based molds for low-pressure processing of thermoplastics

摘要

Current mold technology, used in thermoforming processes such as vacuum forming, often lack in material and energy efficiency during their lifecycle. These molds, mostly milled out of solid blocks of al-uminium, take long to produce and come at a high cost. Moreover the tempering of the vast mass of these molds requires more energy than that of sheet metal ones. These drawbacks result in a high cost of the formed product. The goal of this research is the development and the technical and economical validation of faster producible, cheaper, and material and energy efficient molds based on plastically deformed metal sheets. Design guide-lines have been developed to ensure that (a) appropriate sheet metal forming techniques can be used, (b) the required structural stiffness is obtained and (c) the desired thermal pattern can be achieved. One technique in particular is considered to produce the deformed metal sheets, namely Single Point Incre-mental Forming (SPIF). This technique can produce generic, freeform shapes using a standard, spherical, CNC controlled tool and is characterized by its short lead times. The manufactured deformed metal plates are thin, resulting in very low thermal inertia and thus good thermal efficiency, but they cannot cope with the forces during the thermoforming process and must be supported.