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Characterization of band sawing based on cutting forces

Thaler T., Bric I., Bric R., Potocnik P., Muzic P., Govekar E.

Journal of Machine Engineering

2012

Vol. 12, No. 1

41--54

Band sawing is one of the most efficient methods for which in general it is known that uneven tool wear, chatter and cutting blade defects can affect cutting performance significantly. A data acquisition system was arranged on an industrial band saw machine in order to characterize the band sawing process based on measurements of forces. In this paper, the cutting force signals are analyzed in order to demonstrate important relations to workpiece and cutting blade properties. It is shown that cutting forces contain information about in homogeneity of a cut workpiece. Signals of cutting forces also reveal important properties of blade geometry that is related to uneven blade wear. Discontinuities such as blade welding are clearly evident in force signals and it is shown that unevenness of blade backing geometry can cause a significant variation in forces due to wedging between the workpiece and a blade support. An original method for blade shape extraction from force signals is presented in detail. Paper also reports on chatter phenomena observed at specific cutting conditions. Possible solutions to the addressed problems and phenomena are discussed in the conclusion.

Faculty Of Mechanical Engineering, University of Ljubljana, Slovenia

Gradisek J., Govekar E., Grabec I.

Prace Naukowe Instytutu Technologii Maszyn i Automatyzacji Politechniki Wrocławskiej. Konferencje

1998

Vol. 69, nr 31

163-172

A method for chatter detection in turning is presented. It utilizes significant differences in dynamics of chatter - free cutting and chatter. Experimentally, chatter was achieved by a change of the cutting depth. The measured time series of cutting forces were characterized by the coarse - grained entropy rate. A high value of the entropy rate is typical of chatter - free cutting, while a low value is typical of chatter. For the purpose of chatter detection, the normalized entropy rate is used and a characteristic threshold is defined. The value of the threshold is independent of cutting conditions.

Przedstawiono nową metodę detekcji drgań narzędzia w skrawaniu. Podstawą metody są duże różnice w dynamice procesu skrawania zależne od tego czy towarzyszą mu, czy też nie, drgania. Niekorzystną dynamikę procesu osiągano przez zmianę głębokości skrawania. Zmierzone szeregi czasowe sił skrawania opisano zmianą entropii. Duża prędkość zmiany entropii jest typowa dla skrawania bezdrganiowego, z drganiami narzędzia natomiast wiąże się mała prędkość zmian entropii. Na potrzeby detekcji wprowadzono prędkość znormalizowaną entropii i zdefiniowano jej wartość progową. Stwierdzono, że wartość progowa nie zależy od warunków skrawania.