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Overview and introduction
Published in Tom Denton, Automobile Mechanical and Electrical Systems, 2018
Machinists usually work to very small tolerances, for example ±0.1 mm, and deal with all aspects of shaping and cutting. The operations most often carried out by machinists are milling, drilling, turning and grinding. To carry out fitting or machining operations you should be familiar with: measuring tools, e.g. a micrometerhand tools, as found in a standard tool kitmachine tools, e.g. a bench drillwork holders, e.g. a vicetool holders, e.g. the chuck of a drillcutting tools, e.g. saws and files.
Numerical Control and Computer Numerical Control
Published in Helmi Youssef, Hassan El-Hofy, Traditional Machining Technology, 2020
In conventional or manually operated machine tools, the process starts from the part drawing, and the machinist is responsible for the entire job. The machinist determines the machining strategy, sets up the machine, selects proper tooling, chooses machining feeds and speeds, and manipulates machine controls to cut a part that will pass inspection. It is clear that using this method of machining involves a considerable number of decisions that influence the accuracy and surface finish of the machined part.
Reliability analysis of chatter stability for milling process system with uncertainties based on neural network and fourth moment method
Published in International Journal of Production Research, 2020
Congying Deng, Jianguo Miao, Ying Ma, Bo Wei, Yi Feng
For the random structure system, the reliability analysis contains the probability analysis and design based on the random variables, which can provide a quantitative index to represent the influence of uncertainty. Until recently, the application of reliability analysis in turning chatter vibration have made much progress (Huang et al. 2016). Liu et al. (2016a) established a probability model for the turning process system considering the structure parameters and spindle speed as the random variables, and adopted the fourth-moment method to obtain a reliability lobe diagram (RLD). The RLD gives a direct approach to evaluate the probability of a stable machining, and benefit a machinist in determining chatter-free machining parameters.
Effect of cryogenic CO2 and LN2 coolants in milling of aluminum alloy
Published in Materials and Manufacturing Processes, 2019
In the modern era, a major research work focuses on the evolving field of green technology and sustainability engineering. The most important sustainability concern is the use of cutting fluids in the machining operations [9]. The use of conventional cutting fluids in the machining operations leads to numerous health, ecological pollution and high expenditure for cutting fluids compared to the tool expense [10]. The flood cooling system also requires additional floor area, pumping system, storing container, purification, recycling, etc. [11]. The effectiveness of the conventional fluid coolant fails for the reason of two aspects: failure to spread into cutting region and movement of the chip for the period of machining [12]. Therefore, use of a biodegradable coolant in every machining industry is crucial and it would be an optimistic impact on the surroundings and green technology. Cryogenic machining is a green technology and one of the alternate techniques for wet machining. The cryogenic machining system has no hazardous effects on the machinist and the tool and leaves no deposit to destroy the workpiece. It is an absolutely nonpolluting and ecologically acceptable process [10–13]. In addition, the cryogenic coolants offer the good surface finish to the product. Use of cryogen in machining process reduced the Ra values through the reduction in Tc, tool wear, vibration and cutting forces [9]. The heat produced in the metal cutting operation affects the product quality and reduces tool life [14]. The major heat generation zones in the machining process are elastoplastic deformation zone (primary), plastic deformation zone (secondary) and elastic deformation zone (tertiary) [15,16].
Vibration control techniques during turning process: a review
Published in Australian Journal of Mechanical Engineering, 2021
X. Ajay Vasanth, P. Sam Paul, G. Lawrance, A.S. Varadarajan
Investigations on machine tool vibration started during the early twentieth century when machine tool industries experienced tremendous development in technology. The work of Taylor (1907) was the genesis that put forth that vibration was a limiting factor during machining, and it was the most obscure and delicate problems faced by machinist. Later, Arnold (1946) both analytically and experimentally explained the mechanism of chatter generation and proposed cutting force as a function of speed. It was also stated that the most important characteristic property of tool vibration was not produced by the external forces, but rather by the forces related to the dynamic cutting process. Further many researchers stated that the instability during the cutting process caused chatter. Tlusty and Polacek (1963) proposed that depth of cut was the major process parameter that causes the instability during the machining process. Tobias and Fishwick (1958) stated that depth of cut had a direct relation with the modulated chip thickness which in turn affected the dynamic cutting force and increased the amplitude of vibration. Also it was observed that in turning the rigidity of tool was proportional to tool vibration (Tobias 1961). Selvam (1975) concluded that frequency above 500 Hz which are catastrophic were produced because of the dynamic interaction between tool and workpiece and further it was also stated that parameters such cutting speed, workpiece rigidity and surface roughness had greater impact on tool vibration. Bonifacio and Diniz (1994) proposed that values of tool life was depended based both on criteria of surface roughness and tool vibration. It was further stated that during the initial stages of machining both surface roughness and tool vibration behave in the same pattern as both increases steeply. Chiou, Chung, and Liang (1995) in their work tried to establish a relation between tool wear and chatter stability using Laplace transform. It was further stated that overhanging length of tool was a critical parameter for determining chatter stability and as overhanging length increase they were found to affect the stability, and it was proposed that vibration was basically caused by the lack of dynamic stiffness (Figure 1).