A model of lathe dynamic system when cutting hard-to-work materials

Abstract

Background. Ensuring the surface quality of critical products of aviation equipment, chemical, power engineering, transport systems for various purposes presents certain requirements for the equipment on which surface formation is carried out. Most parts, including those made of hard-to-work materials, are turned on CNC machines, which requires you to select cutting modes that provide specified values for accuracy and quality parameters. Machining modes are determined by the interaction of a specific tool-part pair and the dynamic quality of the machine. Machining on lathe machines using automation tools is a complex process that depends on the properties of the dynamic machine system. The forming process on the lathe is accompanied by vibroacoustic vibrations, the spectrum of which is quite wide and is determined by the interaction of the tool and the part, depending on the cutting force, the physical and mechanical properties of the materials of the contacting bodies, the chip formation process, friction in the cutter-part contact and other factors. The overall influence of these factors brings the oscillation spectrum of the cutting force acting on the DS closer to the oscillation spectrum of the “white noise” type. By changing the cutting modes, you can determine the values corresponding to the highest dynamic quality of the machine and the quality of processing from the characteristics of VA oscillations of the ET. Materials and methods. The Gagarin Yu.A. State Technical University has developed a method for assessing the dynamic quality of machines in various cutting modes based on the stability margin of the ET, calculated from its transfer function, identified by the autocorrelation function of VA oscillations. Cutting mode is assigned to maximum stability margin of ET at preservation of preset values of macro- and microgeometric parameters of processing quality. The method has shown high efficiency in turning hard-to-process materials, taking into account the specifics of processing. Results and conclusions. During cutting of hard-to-process materials, values of processing parameters are changed, values of coefficients a0,..., a5 in transfer function are corrected and, accordingly, stability margin of ET is changed. The above is confirmed by the experimental results of research on the cutting process on a CNC lathe. Thus, the stability margin of the ET can serve as an assessment of the dynamic quality of the machine in various cutting modes when processing different groups of hard-to-process materials.

Keywords

• turning
• hard-to-process materials
• cutting modes
• vibroacoustic vibrations
• dynamic lathe system
• surface quality