Plastic moulding is a process in which the desired shape of a plastic product is obtained by heating and pressing the plastic into a mould. The main role in this complex process is: the pressing temperature, the pressure and the cure time. The high costs and time requirements for the entire process can be reduced by preheating the plastic before pressing. This is an energy-intensive procedure, but it can significantly shorten the cure time, reduce moulding pressure by as much as half, and achieve greater uniformity in cure. The Workswell ThermoInspector – an inspection system for contactless monitoring, analysis and temperature evaluation, developed by Czech company Workswell sro, is successfully used to control the temperature of preheated semi-finished products.
For example, one application uses the ThermoInspector TI160-25 system to inspect the temperatures of the pre-heated semi-product before pressing. The whole manufacturing-inspection process starts with the manual insertion of the semi-product into the mould. The semi-product is then pre-heated to the required temperature of 130°C. The control area is monitored throughout the whole time by the Workswell WIC 336 thermal camera with 19mm lens and a resolution of 336×256 pixels – the working distance is approximately 800mm. The camera is compact and, therefore is easy to fix above the manufacturing line when handling products or during the movement of the press. The whole measuring process is controlled by a central unit that receives a signal from the operator when the semi-product has been inserted and starts to measure the temperature at eight points on the semi-product surface. If, during the pre-heating before the pressing, the temperature reduces at any measured point below the correct level (E.g. 75°C) the ThermoInspector sends a signal that the semi-product is unsatisfactory. If this happens then the part is not transported into the press. In this case, the manufacturing line waits until the operator inserts a new pre-heated part, and then presses the button again so the inspection and production process can continue.