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Machining Processes
Published in Hassan El-Hofy, Fundamentals of Machining Processes, 2018
During abrasion machining, because only a fraction of the abrasives causes material removal and because there are many sources of friction, the energy required to remove a unit volume may be up to 10 times higher than in machining by cutting processes. Unlike most other machining processes, abrasive machining can tackle materials harder than 400 HV, produce smooth surface finishes, and enable close control of the material removal. It is, therefore, normally adopted for finishing operations. Table 1.2 shows the main and feed motions in some abrasive machining processes. Machining by abrasion is classified in Figure 1.11 into grinding (used for finishing cut parts), superfinishing (for ground and reamed surfaces), and modern abrasive methods that have many industrial applications. Figure 1.12 shows a typical ultrasonic machining operation where successive layers are removed from the workpiece material by mechanical chipping using the loose abrasives that are hammered against the workpiece surface at 19–20 kHz. Further examples of modern abrasive processes include the high-velocity abrasive jet in abrasive jet machining, abrasive water jet machining, abrasive flow machining, magnetic abrasive machining, magnetic float polishing, magnetorheological finishing, and magnetorheological abrasive flow finishing.
Introduction
Published in Zainul Huda, Machining Processes and Machines, 2020
An abrasive machining process involves the use of a grinding wheel, an abrasive stick, or an abrasive suspension to remove material from a workpiece. Grinding is a material removal operation by the action of hard and abrasive particles that are bonded usually in the form of a wheel (grinding wheel). As indicated in Figure 1.2, a grinding operation may be surface grinding, cylindrical grinding, or center-less grinding. The abrasive finishing machining operations include honing, lapping, superfinishing, and the like. Grinding and other abrasive machining processes are explained in detail in Part III (Chapters 11 and 12).
Surface Integrity and Fatigue
Published in Eliahu Zahavi, Vladimir Torbilo, Fatigue Design, 2019
Eliahu Zahavi, Vladimir Torbilo
Abrasive machining includes grinding, honing, and polishing. Here the same principles apply: strain hardening increases proportionally to the force exerted on the abrasive grain, and is in accordance with grinding depth, feed, and geometry of the grains.
In-machine data acquisition for evaluating the conditioning efficiency of resin-bonded super-abrasive grinding wheels
Published in International Journal of Computer Integrated Manufacturing, 2023
Leire Godino, Arkaitz Muñoz, Iñigo Pombo, Jose Antonio Sánchez, David Barrenetxea
Therefore, special attention must be paid to the grinding wheel. This is a composite tool in which the abrasive grits, which are responsible for part material removal, are embedded in a bonding agent. Process performance is therefore determined by the state of the abrasive grits, which suffer from wear during abrasive machining. Part tolerances, surface finish and the probability of occurrence of grinding burns (among other effects) depend largely on wheel surface topography. Therefore, wheel truing and dressing is periodically performed to renew the wheel surface to its initial state. Even in the most advanced workshops, the time between dressing operations is decided from a conservative point of view, making sure that part damage is avoided and tolerances are met for all the parts consecutively. This leads to underuse of expensive grinding tools, especially when super-abrasives such as diamond and CBN are used. As a consequence, overall costs increase, making grinding operations less competitive.
Surface Patterning of Cemented Carbides by Means of Nanosecond Laser
Published in Materials and Manufacturing Processes, 2020
Shiqi Fang, Víctor Pérez, Nuria Salán, Dirk Baehre, Luis Llanes
Abrasive machining, such as grinding, honing and lapping, can be described as removal of material by the action of multitude of small hard particles, usually embedded in soft binders.[1–3] It takes place as the sharp edges of these grains – protruding out of the cutting surface – penetrate into the material, due to the pressing force, and shear it as a result of the sliding movement between tool and workpiece. In general, abrasive machining yields higher precision and better tolerance than other surface finishing processes, being the main reason for their extensive implementation in industry. On the other hand, it is considered as an expensive process, and high cost of tool materials is one important intrinsic factor. Hence, increasing cost-effectiveness of abrasive tool materials is a clear industrial need.
A review of cutting tools for ultra-precision machining
Published in Machining Science and Technology, 2022
Ganesan G., Ganesh Malayath, Rakesh G. Mote
Diamond is one of the hardest materials known. It is used as solid tools and loose powders in machining applications, including cutting, drilling and abrasive machining. According to Linares and Doering (1999), the most common material used for UPC is SCD due to its ultimate hardness, abrasion resistance, chemical inertness (toward most of the materials) in high-temperature, high thermal conductivity and extended tool life. Diamonds are either naturally grown or synthesized by a high pressure/high temperature process. The presence or absence of nitrogen impurities segregates SCDs into two types (I and II), which have also been divided up based on the configuration of nitrogen atoms (isolated or aggregated) and the presence of boron impurities. Due to the extreme cost of diamonds, Type IIa is preferred for most industrial applications. However, it may contain impurities (nitrogen), inclusions and other crystalline imperfections which influence the mechanical and optical properties of SCD. Fourier Transform Infrared (FTIR) spectroscopy can identify the type of diamond by analyzing the quantities of impurities present. Each diamond variety has a distinct infrared spectrum of impurities. Laser Raman spectroscopy is another effective method to identify the different forms of carbon by distinguishing each yield characteristic vibration frequencies between them. SCD is known for its ability to be lapped or polished to extremely sharp cutting edges down to the nanometer range. There are two types of diamond tools used in UPC, turning/milling tools which have a circular or elliptical nose, and prism-cutting tools with a V-shape. Lapping, thermo-mechanical polishing (MP), and focused ion beam machining are the popular cutting tool fabrication/edge preparation processes for SCD.