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Monitoring the cutting process in multi-spindle lathes.

Schnittkraftüberwachung an mehrspindligen Drehmaschinen
: Spur, G.; Schüle, A.; Kirchheim, A.

Proceedings of the 1st International Machinery and Diagnostics Conference
International Machinery and Diagnostics Conference <1>
Fraunhofer IPK ()
cutting force; measurement of cutting forces; monitoring; Überwachung; Zerspankraft; Zerspankraftmessung

In machining with multi-spindle-lathes, signal analysis is impaired by the mutual influence of several simultaneous cutting processes. The mathematical expression describing a signal is based on the assumption that a continuous system having various external forces exists. The natural vibrations developed are intrinsic properties of the structure of the machine tool, dynamic measurements thus often provide more information about the structure than about the forces arising in the machine operation. The basic equation describing the measured signal is a product of the exciting force and system behaviour. It is therefore virtually impossible to solve this equation for more than one force of the same frequency. This situation may be overcome if there are as many independent signals as unknown components of the forces to be monitored. Force evaluation is then accomplished by solution of the inverted equation system. Monitoring of machining forces can be undertaken either by strain analysis of by vibration measurement. Force measurement by strain analysis is far less susceptible to interference from external sources than vibration measurement: Furthermore, the solution of system equations is simplified by the fact that the terms of the force-strain transfer matrix are non-imaginary and constant over a certain frequency range, so that a simple factor can be used for evaluation purposes. Force monitoring by the analysis of vibration signals is more interesting for scientific purposes than for use under production conditions, due to the ability to evaluate amplitudes and resultant directions of the machining forces as a function of frequency. This also applies in the high frequency range.