Manufacturing is evolving inexorably toward "Smart" factories, but many metalcasting plants (and secondary metal operations broadly) are stalled in Industry 2.0, in manufacturing assembly line operations, without IT support. The core elements of a 21st-century manufacturing operation, such as interfacing with a central database server, or an intelligent and yet heat-resistant automation package — including sensor technology enabling all operations to communicate with each other —frequently are not available. Although there are numerous protocols for establishing such communicative operations, the possibility of retrofitting these protocols standards does not exist in many older facilities.
A lack of capital resources and the absence of a vision for the future often have led to missed opportunities. Therefore, research strategies that build on each other are always recommended in order to keep up with the times. This is the only way that a foundry or secondary metal plant can face the multiple, long-term challenges of future manufacturing.
For several years ZPF GmbH has been investing in such a development, with various universities supported by Germany’s Federal Ministry for Economic Affairs and Energy (BMWi) and other research sponsors, in order to meet metalcasters’ current requirements and to create a foundation for further technological developments.
Currently, a major challenge in Industry 4.0 is the automation of predictive maintenance. In this process, manufacturing equipment is monitored on an ongoing basis and throughout the entire process (continuous system monitoring) to perform condition-based maintenance work. In a Smart factory with a melting furnace, for example, cleaning could be carried out by a robot that knows all the parameters of a furnace and can take action in good time already before a critical degree of contamination is reached. Consequently, in just a few minutes the robot automatically prevents a later complete breakdown of the system and a standstill of the entire plant.
However, as long as there is no suitable (and at the same time safe) sensor technology that can withstand the extremely high temperatures, these essential parameters cannot be recorded, even though they are the basis for industry 4.0. In order to master these complex automation tasks, the entire factory needs extensive knowledge of all important plant data - from the furnace filling level to the degree of contamination in the bath area. For this reason, ZPF already has laid the foundation for intelligently networked melting furnaces through various research projects in the past.
From refractory materials to burner technology — ZPF’s "Enoptal" project is an example. As a result of climate policies derived from the E.U.’s Directive 2009/29/EC, aluminum producers and processors with a total rated thermal input of 20 MW had to limit their CO2 emissions starting in 2013 and purchase new certificates, if necessary. This put pressure on the aluminum industry to find timely solutions for lower CO2 emissions. Following this, more investment was made in the development of efficient burner technology to reduce energy costs and to reduce the impact of greenhouse gases on the environment. Furnace charging methods and cleaning intervals, as well as the melting losses, were examined along with the influence these parameters have on the critical emission values.
The Enoptal research was funded by BMWi and conducted together with the Technical University Bergakademie Freiberg, and completed in 2011. With the help of various field tests, the essential parameters of a melting and holding furnace with a melting capacity of 300 kg/h and a holding capacity of 700 kg were determined, and optimization potential was identified for the refractory material and the burner arrangement, resulting in energy savings of up to 10%. These results formed the basis for the next major research project.
From burner technology to sensor technology — As the next step, the melting plant and other plant components were at the center of the task in order to optimize the entire furnace system. The aim was to locate further energy saving potential in aluminum melting to minimize melting loss, to improve process monitoring, and to create the basis for modern and efficient heat recovery.
Because the field of "measurement technology" has large gaps, the possibilities for a system for monitoring and control were examined in cooperation with the BMWi, T.U. Bergakademie Freiberg and the Leibniz University of Hanover. The focus of the Edusal I and II projects was mainly on the development of a measuring technique for the sensory detection of the furnace chamber.
In some areas, water-cooled, optical systems are used for furnace interior monitoring - for example after the repair of glass troughs. Although these provide an insight into the condition of the refractory lining and other process parameters, for safety reasons they cannot be used in everyday operation or must not be used by operators of aluminum melting plants.
If such a system is damaged and the water is unintentionally heated from 20°C to 900°C, the sudden change in the volume of the water can lead to explosions and thus to serious damage to property and individuals. For the first time, the measurement method developed with the associated software made it possible to determine precisely the amount and position of material on the melting bridge during melting operation. In this context, a dynamic burner system was developed that can be regularly aligned to the melting charge via the recorded measurement data, and thus increase the efficiency of the overall system.
In addition, the plant was equipped with a heat exchanger system. With the help of the exhaust gas, the required burner air is heated in the heat exchanger and directed to the burners. This heating results in a higher temperature level during the combustion process and leads to significant gas savings. Due to the design of the system, a series product could be generated directly from research. The research project ended successfully in 2016 and enabled a further increase in energy efficiency of up to 15% in the melting plant. On this basis, assemblies were revised for series use. Today there are already plants for trial operation, which have been successfully used there. The measured values from the research project are confirmed at these plants in the rough melting operation.
From sensor technology to automation — Thanks to the Edusal II project findings on sensor technology, a non-contact optical test method was developed for detecting a change in the state of the aluminum block.
This is a camera system with a special evaluation logic that is able to detect non-molten aluminum on the bridge during the melting process. This new sensor technology enables an objective evaluation of the melting process in the aluminum furnace and the user can automatically determine the current quantities of the material that are molten. In this way, characteristic values can be derived for objective evaluation of the melting performance, guaranteeing continuous monitoring throughout the entire melting process. It also opens up further possibilities for automatic control processes in a Smart factory.
All results of these research projects serve as a basis for the current project called AlSO 4.0 (Aluminum Melting Furnace 4.0).
Research into the control and evaluation options for automation, required for further steps in the process chain, is conducted in close cooperation with the T.U. Bergakademie Freiberg, the University of Bremen, and the Leibniz University of Hanover as well as aluminum melting furnace operator and is funded by the BMWi.
In this process, the areas to be examined are extended to the entire furnace system and the first prerequisites are created for integrating adjacent peripherals and achieving the desired increase in efficiency. The frequently described scarcity of resources will drive further technical development, which cannot be achieved without research work. Long-term and systematic research brings effective results.
Sven-Olaf Sauke is the director of R&D at ZPF GmbH. Contact him at [email protected]; or visit www.zpf-gmbh.de for more information.