Up to 50 percent less scrap
Inadequate recording and different setting modalities for process parameters have been among the biggest disadvantages in thermoforming up to now. The production quality was dependent on the knowledge of the employees and the settings on the machine, a real-time recording of the process did not exist until now.
Thanks to the latest measuring technology with specially adapted sensors, developed by Toolvision GmbH, it is now possible to monitor and document production processes in every phase and visualize them as graphics with the aid of customized software. "The inadequate recording of process data is one of the major disadvantages in thermoforming," explains Peter Schöberl, Managing Director of Toolvision GmbH. "The tools and machines are often not equipped with integrated sensor technology for checking temperatures, pressures, paths, forces and condition data." High scrap rates, wear and tear on tools and machines and, as a consequence, a very high unit cost factor can be the consequences. This is a major problem, especially for the food industry, where speed and efficiency are particularly in demand. At the same time, increasing quality demands due to automated processing and a long production chain are part of everyday life. Food producers demand a 100% traceable and documented quality of the continuous production under consideration of special criteria, which is only possible through electronic process control.
Previous solutions do not lead to the desired results
In the past, machine settings relied on the intuition of the employees. "The quality in production was mainly dependent on the presettings and know-how of the workshop staff and technicians. This often led to different product characteristics and quality of the individual pieces. In addition, a satisfactory analysis of the actual thermoforming process in real time was not possible," says Schöberl. Due to this trial and error principle, optimal quality assurance could not be guaranteed either.
Fast reaction in case of deviations
With the solution described here, however, an exact representation of the entire thermoforming process is now possible. The system comprises up to twelve sensors that are integrated directly into the mold or the machine - this is individually adapted to the respective machine and the customer's requirements. Up to 125 measurement data per second are generated per measurement channel, which are recorded on-line and evaluated in real time. Instead of a pyrometer measurement, which is not very informative, the temperature on the tool and film is now visualized and monitored with a precise infrared camera. This camera detects even the slightest deviations and immediately transmits an error message to the system.
The process data obtained is displayed in a clear graphic that includes all important components - the appropriate software is included. "By visualizing the process parameters during the entire process, it is possible to react immediately and correctly to possible quality deviations," explains Schöberl. "Monitoring is carried out with the aid of so-called envelope curves, which are superimposed on the process curves as quality windows, or with the aid of hotspots from the infrared camera. If the quality window is exceeded or not reached, a corresponding reaction can take place in real time." Colored reference graphs perform a similar task: They provide a clear display of actual and target curves in direct comparison. If the results of this analysis are then implemented in the thermoforming process, the start-up of the machine can be accelerated considerably, which has a positive effect on scrap and unit costs.
Practical three-stage error reporting system
In order to ensure comprehensive control, Toolvision has relied on a three-stage error reporting system for its measurement technology: The software allows the user to create a shift report during production over a self-selected period of time. If desired, this report can even be sent by e-mail. Alternatively, the system can be set so that the machine is automatically switched off if errors occur during production. In this way, defective products can be sorted out in good time and any damage to tools or the machine can be prevented in advance. In addition, service intervals and repair work can be better monitored and calculated in advance. Toolvision also plans to add an additional feature to the current measuring system by the fourth quarter of the year: "In the future, comprehensive trend visualization will be possible so that customers can monitor and sustainably improve their thermoforming processes in the long term," explains Schöberl.
