Papers by Keyword: High Speed Machining (HSM)

Abstract: Micro ball-end milling process features the ability of machining complex surfaces, precision machining accuracy, and excellent machined surface roughness. However, because the diameter of a micro milling tool is very small, a rapid progress of tool wear or even tool breakage usually happens when machining a high-strength hardened mold steel using improper machining parameters. As a result, the machining cost would rise due to the quality defect in machined workpiece. In this study, to investigate how the machining parameters affect the cutting behaviors, a series of experiments using micro CBN ball-end mills with a diameter of 0.5 mm were performed to cut the SKD11 mold steel with hardness of HRC 61. The machining parameters are selected as the feeding speed (f) being 840, 960 and 1,080 mm/min, depth of cut (ap) being 30, 45, 60 μm, and spindle speed (vs) being fixed as 30,000 rpm. According to the experimental results, the measured three-axis cutting forces, flank wears, and surface roughness of machined workpiece are highly related to the cutting length. It is expected that the measured results can be used to construct a performance function of a micro ball-end tool. With referring to the performance function, the tool life can be well expected, and thus a progress in machining efficiency without tool failure can be achieved.

Abstract: The paper is devoted to vibration monitoring of rotating tools in modern milling machines. Dynamic analysis of slender ball-end milling process was performed and dynamics of the controlled structure was described. Instantaneous change in the spindle speed is applied in order to reduce vibration level. The method of vibration monitoring by means of spindle speed optimal-linear control was developed and implemented with success. Vibration monitoring during high speed milling was performed on the basis of results of computer simulation. These results were verified during experimental investigation on the Alcera Gambin 120CR milling machine.

Abstract: The development of surface high-speed machining has put forward higher demands for uniform cutting load and smooth cutting tool path. Most current tool-path planning methods are based on constant scallop height, but they have the disadvantage of path point redundancy during the path discretization process. To overcome the problem, a tool path generation method of equal approximation error in each step for free-form surface is presented based on geodesic principle and curvature judgment. In this method, the NURBS curve is employed to realize smooth transition for adjacent two tool paths in high-speed machining. A certain angle of inclination of flat-end milling cutter during multi-axis machining improves the machining efficiency. Because of the advantage of this machining condition, the cutter location point generation algorithm during the machining condition is given by the method. The method is verified and simulated by C++. Experiment results proved that it can obtain uniform cutting load and continuous smooth cutting tool path during surface high-speed machining by the proposed method.

Abstract: Under the circumstances of 7/24 taper tooling system being widely replaced by 1/10 taper tooling system in the high-speed machining, using 1/10 taper HSK- A63 tools as the research object, this article, adopting the method of finite element method, analyzes the parameters such as clamp force, surplus magnitude and rotary speed which affect the connecting performances of 1/10 taper spindle/ tool-holder. The results of this study provide basic and useful guidance for the parameters’ selection of 1/10 taper tooling system in practical machining.

Abstract: The high-speed metal cutting process is analyzed by finite element (FE) method in order to understand the effects of the cutting speed on the thermomechanical responses of workpiece materials. The reliability of numerical simulation is firstly validated by comparing the simulated cutting force with experimental data. Then a series of FE simulations are carried out to reveal the effects of the cutting speed on three key cutting state variables. The cutting force varies with the cutting speed and shows a minimum inflexion at 10 m/s. The maximum temperature in the secondary deformation zone increases gradually with the cutting speed and finally tends to a steady value. The residual stress decreases with the cutting speed as a whole. Thus high speed cutting can improve surface machining precision of product. Besides, it is found that the high residual stress mainly concentrates in the topmost surface layer with a depth of 0.1 mm and sharply decreases to a low level beyond the layer.

Abstract: Green manufacturing is the theme of manufacturing industry in the 21st century. The environment can be seriously polluted by a large quantity of waste cutting fluid .In manufacturing industry, it’s critical to restrict the quantity of waste cutting fluid poured in the environment in order to assure a green earth. Cutting temperature has a major impact on processing quality. A stable cutting temperature means a high quality process. Cutting temperature is also a comprehensive embodiment of process state. In order to control cutting temperature in an appropriate level, an adaptive fuzzy control system is developed to control the flow of cutting fluid injected to machining tool and workpiece which can not only reduce the consumption of cutting fluid but also ensure process quality. Simulation and experiment results show that this control system can achieve the desired purpose.

Abstract: The microstructure observation and microhardness measurement were performed on the adiabatic shear bands in primary shear zone in the serrated chips formed during high speed machining of two tempering hardness of hardened high strength steel under different cutting speeds by optical microscope, SEM, TEM and microhardness tester. The investigation results show that two types of adiabatic shear bands are formed as cutting speed increases. One is deformed band with heavy elongated microstructures generated under lower cutting speed, another is transformed band with fine grains under higher cutting speed. The increase of the cutting speed little influences on the microhardness in the transformed bands, and the microhardness in deformed band results from strain hardening, whereas transformation hardening leads to very high microhardness in transformed band.

Abstract: Over one hundred types of commercial CAD/CAM systems are currently used in various industries. To meet the increasing demand for high speed machining (HSM) from shop floors most of these systems have integrated functions for the generation of HSM tool path. However, the strategies they adopted and the qualities of HSM tool path generated by these packages differ significantly from system to system. This paper reviews the state-of-the-art HSM strategies adopted by industrial CAD/CAM systems. The review is based on sixteen widely used software packages which include both advanced systems and the relatively concise packages. HSM features of each system are summarized; HSM strategies adopted by those systems are presented; the advantages and disadvantages are discussed as well.

Abstract: Owning to the ultra high feed rate and spindle speed, tool path patterns which are less important in conventional metal cutting processes becomes critical in High Speed Machining (HSM). Without an appropriate tool path strategy HSM can not be fully implemented even though the CNC machine has HSM potentials. In practice attentions are usually drawn to advanced hardware components; tool path pattern catering to HSM is often overlooked. This paper introduces the principles of tool path generation for HSM. Essential properties of HSM and its technical requirements on the CAD/CAM system are summarized. The state-of-the-art technologies and practice-oriented tool path generation methodologies are presented.

Abstract: The analysis of the rigidity of an Al-Cu alloy lathe bed to be used for high speed machining (HSM) is presented in this work. Mechanical design optimization by means of simulations based on the finite element method (FEM) was applied in order to calculate the lathe bed deflections, the natural frequencies and the corresponding vibration amplitudes. For the parametric modeling, a prototype lathe to be used in conventional speed machining (CSM) with a cast iron bed was considered. The optimized parameter was the stress in the lathe bed, considering as a restriction the allowable deflection in a node of the machine-tool structure. The design variables were the height, the thickness, and the length of the wall of the lathe bed. The lathe bed was loaded with cutting and inertial forces due to HSM in order to demonstrate that the evaluated stresses and vibration amplitudes are in an acceptable level according to ISO Standards (system of limits and fits in workpieces). The results show the feasibility of using an Al-Cu alloy instead of cast iron in the fabrication of lathe beds. This increases the flexibility of manufacture.