The goal of the heating process during thermoforming is to heat the foils as quickly as possible, both in defined areas and across the entire surface. FRIMO has developed a new foil heating process specifically for this reason, called Time Shifted Heat Control (TSHC). The key is a specially-developed calculation algorithm, which switches the emitters on at the right time, taking overlap and peripherals into account.
In place of traditional, relatively slow heater banks that reach up to 400°C and heated filament wires in quartz tubes that reach up to 600°C, we use halogen infrared emitters filled with gas, which heat up to about 2400°C. They are used because they can heat larger areas in a shorter period of time and react much faster. Current heating systems are controlled by the amount of electrical power that is input. The disadvantage in this is that the emitter spectrum and emitter efficiency vary.
FRIMO TSHC uses the optimal efficiency of the emitters to warm the foil. As the name “Time Shifted Heat Control” suggests, the variables used to regulate the temperature are the point in time and duration that the emitters are turned on. The challenge is determining the optimal operating method of the IR emitters, which influence each other and have overlapping radiation fields. Machine operators input the surface temperature (in °C) that the semi-finished film needs to reach, and by using TSHC, an elaborate algorithm determines the optimal point in time for each individual emitter to be turned on. When required, different temperatures can be preset for specific areas of the film. Reflections, such as from a clamp frame, are also accounted for. By turning each individual emitter on at the correct time, the film is evenly heated to the correct temperature, from the edges to the middle. At the end of the heating cycle, the emitters are all turned off at the same time. They cool immediately and therefore do not need to be moved to the side or swiveled upwards, saving floorspace.
Because the optimal efficiency of the emitters is used, both heating time and energy use are reduced by up to 40%. TSHC has already been successfully implemented in series production and has demonstrated energy savings, shorter heating times, simple maintenance, and reduced floorspace requirements.
PDF: Article from special reprint of Kunststoffe international
Contact for questions and additional information:
FRIMO Freilassing GmbH
Tel.: +49 (0) 8654/4985-27