|Project title||Intelligent grinding tool (IW 1)|
|Project duration||01.07.2008 – 30.06.2010|
The aim of the research project was to develop an intelligent grinding tool, which allows the use of thin walled grinding blades and reduces the probability of tool deflection. Therefore, a measurement system for tool deflection detection was developed. The main components of the measurement system are piezoelectric sensors which are included in a grinding tool and a wireless microcontroller unit (included in the drive spindle). Axial vibrations are an indicator for tool deflection. The measurement system is able to detect increasing axial vibrations. Thus, deficient production can be reduced.
Publications about the project
Due to their diverse properties and versatile aesthetics, natural stones are used as construction materials, i.e. for floor coverings, stair steps and as facade cladding. The production of slabs and tiles made of natural stone is mainly performed with rotating diamond cutting discs. In the production of slabs and tiles the cutting rate is more than 60%, leading to a loss of raw material as well as high energy consumption, and tool costs. By using thin cutting discs the width of the cutting kerf can be reduced and the efficiency of the abrasive cutting process can be increased. However, the reduced stiffness of the thin cutting disc may lead to higher tool deflection and reduced cut quality. The objective of this work is to investigate a closed loop control for an abrasive cutting process using thin cutting discs. The used diamond cutting disc is 40% thinner than normally used tools in the industry. For the implementation of a closed loop control a monitoring system is being developed. It allows monitoring the axial tool vibrations throughout the grinding process. Integrating piezoelectric elements in the grinding tool, the vibrations can be detected directly at their source. This ensures a high accuracy of the detecting process. Based on studies, a closed loop cut-off control is being developed and studied. The closed loop control varies the feed rate depending on the axial tool vibrations. Through the developed closed loop control further information on the vibration characteristics of a cutting disc during a process are obtained. Furthermore, approaches to increase the cutting quality of thin cutting discs by a closed loop control are presented.
cut-off grinding, natural stone, process monitoring, process control
Industry 4.0 Astitouh, M.; Overmeyer, L.; Tönshoff, H. K.: Sensor-integrated tools for grinding process monitoring. In: Proceedings of the 1st International Conference on Stone and Concrete Machining (ICSCM), Editors: Denkena, B.; Bach, F.-W.; Tillmann, W.; Theisen, W., PZH, Produktionstechnisches Zentrum GmbH, Garbsen 2011, pp.71-78.
Thin diamond cutting discs help to increase efficiency in the production of slabs and tiles out of natural stone. The reduced stiffness of the discs, however, may lead to higher tool deflection and reduced cutting quality. This can be compensated by using higher cutting speeds. So far, such an intervention needs to be supervised by an operator. For ergonomic and economic reasons this is not an option for the industry. Up to now, no system able to monitor the tool vibrations near the source during the cutting process exists. On this account, such a system has been developed. Due to the integration of piezoelectric elements in the grinding tool, the vibrations can be measured right at the source. This ensures the high accuracy of the measuring process. The measured data will be transmitted wirelessly to a computer evaluating the results. Cutting tests show that the sensor integrated tool is able to monitor the tool vibration during the grinding process. This paper describes the sensorintegrated grinding tool and shows the results of cutting tests.
cutting disc, monitoring, grinding, granite
To produce slabs and tiles out of natural stone abrasive cutting with circular tools is of primary importance compared to gang or rope saws. To improve the economy and ecology of abrasive cutting processes various approaches exist, such as the reduction of the tool width or the increase of the material removal rate via creep-feed grinding. Those approaches reach their limits due to tool deflection. Knowledge of the tool behavior within the process can improve the profitability of the grinding process. This information can be gained with the help of a tool monitoring system. The paper describes an approach to monitor the axial tool vibrations throughout the grinding process.
grinding process, abrasive cutting, processing quality, grinding-performance, material removal
The abrasive cutting with thin diamond tools is a common method for the production of plate-like components, such as tiles, made of hard stone. Hard rocks are suitable as construction materials due to their material properties. They are used for e. g. cladding buildings or interior design. In addition to mining granite rough blocks in quarries especially metal-cutting production lies at the heart of value creation. Alone for the abrasive cutting, which is often referred to in practice as a circular sawing, 67% of the production costs are bound. The reason for this very high cost portion is the ratio of removal volume to board volume of more than 60% leading to a loss of raw material and high tool and energy costs.
abrasive cutting, metal removal rate, metal removal volume