Session: 07-14-01 Measurement and Analysis Techniques in Nonlinear Dynamic Systems I

Paper Number: 69393

Start Time: Tuesday, 03:50 PM

69393 - Approach for Modelling the Dynamic Transmission Behavior of Grinding Discs Using Transfer Functions 

Knowledge of the forces applied on the drive train of a machine is important for dimensioning and testing. For fast-rotating power tools, such as angle grinders, the dynamic forces applied on the drive train, including the frequency of the rotational speed, are not known. In the case of angle grinders, these forces arise primarily at the contact between workpiece and grinding disc. Previous state-of-the-art approaches can determine the dynamic tool force in the contact between workpiece and grinding disc for angle grinders. Thereby it remains unclear whether the dynamic tool forces also correspond to the dynamic forces on the drive train since the dynamic force transmission via the grinding disc is not taken into account.

In the field of stationary machine tools, the transmission behavior of tools is modeled by transfer functions. When transferring the approach to grinding discs, it is unclear whether a transfer function is valid for all operating points (pressure force and rotational speed) of a grinding disc or only valid for individual constant operating points. Therefore, two research questions arise for this paper:

- Can transfer functions of constant operating points (pressure force and rotational speed) of a grinding disc be determined and merged to one transfer function?

- How much do the dynamic forces on the drive train determined with transfer functions differ from the tool forces in the contact between workpiece and grinding disc?

To determine the transmission behavior of grinding discs, a new test bench is presented that can measure the multiaxial dynamic forces on the drive train side and the workpiece side. On the test bench, 120 tests were carried out with three different types of grinding discs. From these tests, transfer functions were calculated in all three spatial directions. To answer the first research question, it was investigated how much the transfer functions of the individual working points differ from each other. To answer the second research question, it was investigated how much the dynamic tool forces measured in a real application differ from the dynamic forces on the drive train calculated with the obtained transfer function of a grinding disc.

It is shown that transfer functions of different constant operating points (pressure force and rotational speed) can be generated on a test bench and that these transfer functions differ slightly. Therefore, it is feasible to merge them into one transfer function. It is also shown that the dynamic forces on the drive train in individual spatial directions differ strongly from the measured tool forces in the dynamic range. For example, the mean value of the force oscillations differs by 15 N (100%) in the Y-direction and by 10 N (50%) in the Z-direction for the examined flap disc.

This means that the dynamic forces on the drive train are different from the tool forces for certain spatial directions and disc types. Therefore, they need to be taken into account for dimensioning and testing. With the chosen approach, a solution was shown how the dynamic forces on the drive train can be determined from the tool forces via the transmission behavior of grinding discs. The influence of the transmission behavior was quantified for the three examined grinding disc types in each spatial direction. The knowledge of the transmission behavior of the grinding discs can also be used to reduce vibrations in the overall system and on the user.

 

Presenting Author: Matthias Dörr Karlsruher Institut für Technologie (KIT)

Authors:

Matthias Dörr Karlsruhe Institute of Technology (KIT)
Alexander Dürkopp Forschungsgemeinschaft Werkzeuge und Werkstoffe e. V. - FGW
Sebastian Zimprich Karlsruhe Institute of Technology (KIT)
Thomas Gwosch Karlsruhe Institute of Technology (KIT)
Hans-Jürgen Gittel Forschungsgemeinschaft Werkzeuge und Werkstoffe e. V. - FGW
Christian Pelshenke Forschungsgemeinschaft Werkzeuge und Werkstoffe e. V. - FGW
Peter Dültgen Forschungsgemeinschaft Werkzeuge und Werkstoffe e. V. - FGW
Sven Matthiesen Karlsruhe Institute of Technology (KIT)