EXPERIMENTAL METHOD FOR DEFINING THE STABILITY LOBE DIAGRAM IN MILLING Č4732 (42CrMo4) STEEL
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Датум
2019
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Издавач
University POLITEHNICA Timisoara, Faculty of Engineering Hunedoara
Апстракт
Self-exciting vibration (chatter) is an unwanted phenomenon that can occur in metal cutting. Self-exciting vibration is a phenomenon that has a negative effect on productivity, leads to accelerated wear or breakage of the tool, and in some cases can lead to breakage of elements of jigs and fixtures or elements of the machine tools. In order to predict and control the process of creating self-excited vibration, different methods have been developed. One way of predicting self-excited vibration is defining stability lobe Diagram, which shows the boundary between stable, conditionally stable and unstable cutting process, whereby combinations of cutting depth, cutting speed, i.e. spindle speed and feed rate are observed. Methods for defining the stability lobe diagram can be analytical, and experimental. This paper shows the experimental method of defining the stability lobe diagram, on machining steel Č4732 (42CrMo4). Metal cutting is carried out on a vertical machining center. The methodology for defining the stability lobe diagram implies that a series of experiments were done, were workpiece surface to be milled is made with a slope of 3°. In this way, when moving the tool, the cutting depth gradually increases until the moment of self-excited vibration occurs. The occurrence of the vibration is registered by measuring the acceleration, where the accelerometer was being mounted on the main spindle carrier, as close as possible to the tool. After the self-excited vibration occurred, which is manifested by a sudden jump of acceleration amplitude, and by the change in the sound, the cutting process is stopped and then the axial depth of the cut at which the vibration occurs determined by the tangent method in Matlab. The obtained stability lobe diagram has two dimensions, which means that all measurements were performed for one, a constant value of feed rate per tooth.
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Кључне речи
milling, self-excited vibration, stability lobe diagram