Papers by Keyword: Machining Quality

Abstract: Abrasive Water Jet (AWJ) machining has proven to be an effective and versatile technique for milling various kinds of materials, even with low machinability such as aerospace grade titanium alloy Ti6Al4V. Many studies have been performed in order to master this technology and produce geometrically accurate shapes. However, in the context of bonding repairs which require surfaces free from foreign bodies, AWJ machining presents a significant drawback in form of abrasive grit embedment. The goal of this present work is then to investigate the effect of a post-AWJ machining cleaning operation using Plain Water Jet process (PWJ – i.e. without abrasive particles) on the surface quality and material properties. For this, several characterization techniques were employed. It was concluded that the contamination has been reduced by 65% without noticeable changes in depth of cut and crater volume. The AWJ milling operation produced surface and subsurface hardening as well as biaxial compressive residual stress, mostly piloted by the jet pressure. PWJ cleaning reduced the depth of hardening without clear modification in surface hardness.

Abstract: Modern methods of machining of bed slideways with the required parameters of accuracy and quality of the processed surfaces are considered in order to increase productivity in the treatment of the surface of machine stands. To improve productivity, the finishing sanding operation has been replaced with finishing milling to ensure the required roughness, flatness and parallelism. The method of replacement of technological operations as exemplified by processing of a bed made of gray cast iron of grade “СЧ-20” is studied. The priority method of increasing the productivity of the processing of machine slideways of metal-cutting equipment, based on the use of cutting ceramics during the processing of the bed as a final technological operation, is determined. Based on the microstructural characteristics of oxide-carbide cutting ceramics, a uniform method of equipping cutters with cutting inserts with equal lifespan is used to increase productivity and achieve the required surface finish. This method of the milling cutter layout allows for longer life and provides the required margin of tool accuracy as well as allows predicting premature wear of the cutting tool. The results of the work are the identification of the patterns of influence of structural parameters of cutting ceramics on the quality of machine slideways of metal-cutting equipment in the selective formation of instrumentation. Studies have shown that the quality of machining depends on the microstructure characteristics of each insert used in the machining process when using interchangeable multi-sided oxide carbide ceramic inserts. The increase in productivity and quality of machining is achieved by monitoring the microstructure of the cutting oxide-carbide ceramics.

Abstract: Longitudinal-bending complex vibration can be realized by opening chute on the amplitude amplifier pole. Different longitudinal and bending amplitudes can be obtained under different angles and the number of the chutes. Based on the theory of two-dimensional ultrasonic cutting, the effects of the two dimensional amplitude on the cutting characteristics were analyzed experimentally in the paper. Research results show that the amplitudes of longitudinal and bending vibration have a great effect on cutting force and machining quality in two-dimensional ultrasonic vibration cutting of hard and brittle materials. When keeping constant longitudinal amplitude and increasing bending amplitude in a certain extent, the cutting force could be reduced and the machining quality of workpiece could be improved effectively. The research provides relevant basis for designing two-dimensional longitudinal bending vibration cutting system.

Abstract: Surface integrity is widely used for evaluating the quality of machined components. It has a set of various parameters which can be grouped as: (a) topography parameters such as surface roughness, textures and waviness (b) mechanical parameters such as residual stresses and hardness, and (c) metallurgical state such as microstructure, phase transformation, grain size and shape, inclusions etc. Surface roughness and residual stresses are among the most significant parameters of surface integrity, so that it is worth investigating them particularly. Many factors affect the surface integrity of machined components, including cutting parameters, tool parameters, material properties and vibrations. We can make prediction and optimization for surface integrity by taking advantage of these factors. This paper reviews previous studies and gives a comprehensive summary of surface integrity in the following order: introduction of surface integrity, main parameters of surface integrity, factors affecting surface integrity, prediction and optimization for surface integrity.

Abstract: Carbon fiber reinforced plastics (CFRP) are highly promising materials for the applications in the aerospace industries, but they are typical difficult-to-cut material. In order to improve the quality, helical milling technology was developed. In this study, helical milling experiments were conducted in the machining center about CFRP materials. The hole quality including the surface roughness, the diameter error and the roundness error are analyzed. The result shows that the hole quality was improved corresponding to drilling technology.

Abstract: Surface integrity is widely used for evaluating the quality of machined components. It has a set of various parameters which can be grouped as: (a) topography parameters (b) mechanical parameters and (c) metallurgical state. Many factors affect surface integrity including cutting parameters, tool geometry, material properties and vibrations. We can make prediction and optimization for surface integrity by taking advantages of these factors. This paper reviews previous studies and offers a comprehensive summary of surface integrity in the following order: introduction of surface integrity, main parameters of surface integrity, factors affecting surface integrity, prediction and optimization for surface integrity.

Abstract: Engineering Ceramics is a inorganic nonmetal material, which is sintered at high-temperature. ceramics have promising potential as high-temperature strength.erosion-resistant, wear-resistant and hot impact-resistant.However, because they have high hardness and brittleness as well as nonconductive, it is very difficult to machine them using conventional machining. Their use-area is restricted. At presently, the machining technology of Engineering Ceramics by abrasive waterjet become more and more important for humankind. In this paper, the influence of technical parameters on machining quality has been studied and analyzed. A better changing method of technical parameters is given.

Abstract: Surface roughness influences the performance of a finished part. In machining operations, the surface roughness generated is influenced by an enormous set of factors. In ball end milling operations, the geometric characteristics of the cut clearly affect the surface crests generated. This paper presents an experimental methodology that permits engineering students to identify and analyze the surface roughness. The methodology is applicable to training courses and surface texture generation as well.

Abstract: This paper presents the method of calculating roller spacing and press amount of straightening roll. based on rigid-flexible virtual prototype technology, the entities model of straightening block was established by Pro/E, then it was imported into the ADAMS environment and constraints were added to create a rigid model, the model neutral file generated by ANSYS, thereby the rigid-flexible coupling virtual prototype was established. The distance of the point in the steel-bar relative to the end in Y direction is obtained through simulation, the acceleration curve and the range of roller spacing and press amount which consist with theory and the straightness of the ribbed bar after being straightened are obtained, which are reference to the dynamic simulation of the same complicated mechanical system and the theory of steel-bar straightening.

Abstract: The Zr-C:H coatings with various C2H2 flow rate were deposited on micro-drills (a diameter of 0.2 mm) used a closed field unbalanced magnetron sputtering system. The ultrahigh speed (drilling speed of 160000 rpm) through-hole drilling printed circuit board tests used to evaluate the drilling performance of the coated micro-drills. The rejection criteria of service lives of the coated micro-drills were evaluated using two different criteria: (1) a nail head ratio greater than 1.5; (2) a drilled hole surface roughness greater than 25.4 μm. Adopting a service life criterion of a nail head ratio of 1.5, the Zr-C:H-5 coating possesses the optimal high-speed machining performance, which yields a micro-drill lifetime of above 6000 drilled holes. It represents a three-fold improvement on that of an uncoated micro-drill and it also improves machining quality.