A survey amongst the leading thermoforming companies in Belgium revealed a great need for a better understanding and control of the heating stage of the plastic sheets in thermoforming processes. Currently, in most companies, the control temperature of the sheet is set by trial and error depending on the complexity of the product and the adopted material. The required time for such trial and error procedure mostly depends on the experience of the technical staff. The sheet temperature is typically not measured. At most it is only monitored in the center of the sheet at either top and/or bottom of the sheet material. The thermoformers have absolutely no idea about the achieved homogeneity of the temperature across the thickness of the sheet.
The choice of a proper heating strategy is relevant because of two reasons. Firstly it directly influences the wall thickness, and hence the quality of the finished product. Secondly, a bad initial choice of heating strategy will result in a trial and error phase that takes most of the setup time for new products, which affects the time-to-market in a negative way.
This project primarily focusses on thermoformers who mainly produce big, heavy gauge products, and it will also deliver results for thermoformers in the packaging business, suppliers of plastic sheets, machine builders and distributors of heating elements.
The goal of the project is to deliver a guideline to the target group, incorporated in an interactive computer program (wizard), which will enable them to determine the correct (optimal) heating strategy for their own products.
During this first work package the companies of our target group will be questioned in order to make the inventory of the type of machine, type of heating elements, types of process control, current methods of approach,... that are operated in the industry. This information allows us to focus the research to the needs of our target group.
This work package focusses on temperature measurements which will be performed by using thermocouples as well as pyrometers, to accurately map the heating process. To be able to obtain results which are as complete as possible, different materials will be tested using different heating methods and strategies.
Simulation of the 'real' heating situation will be used to gather insight in the temperature distribution throughout the thickness and in the plane of the sheet as a function of the material and the process parameters. The main goal of the work package is to develop a thermal model, by means of finite element modelling, which allows it to describe a type of plastic with all his thermal properties in combination with a certain heating type.
The main goal is the development of an interactive wizard. This is part of the optimization phase. This wizard will guide the user to the optimal heating strategy, based on guidelines and with the aid of simulations and case studies.
Technical evaluation and validation of the new heating strategies will be conducted during several case studies on real thermoformed products. These cases will be provided by the companies of our user group. The economic impact of the project results will be evaluated simultaneously.
This work package runs through the entire duration of the project. The main goals of this work package are to manage the project content within time and budget and to integrate the project results in education.
Propolis: KU Leuven, Technology Campus Ostend
Cel Kunststoffen: KU Leuven, Technology Campus Diepenbeek
IWT (Agency for Innovation by Science and Technology)