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Grinding Operations and Machines
Published in Zainul Huda, Machining Processes and Machines, 2020
A grinding wheel is a disk comprising abrasive grains and bonded material; the abrasive grains act as cutting teeth during grinding machining operation. Grinding wheels must be precisely balanced for their high rotational speed so as to avoid vibration during the grinding operation (see Figure 11.2a). A grinding wheel is a cutting tool that contains millions of microscopic abrasive grains that are bonded together; here, each abrasive grain acts like a spiky cutting tool. The abrasive grains are held together in the porous structure of the grinding wheel by a bonding polymeric material. When these grains come in contact with the surface to be cut, their sharp edges can cut and remove the material on the surface (see Figure 11.2b). The abrasive grains lose their sharpness after each cutting action; they are regularly removed to allow fresh new grains to come forward.
Cutting Tools
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
Conventional grinding wheels are characterized by their grit size; for example, 80-grit size means that the average size of the abrasive grains is approximately 80 particles per inch. Grit sizes below 50 are considered coarse, those between 50 and 90 are considered medium, and grit sizes above 90 are classified as fine. Generally, the percentage of grains coarser than the specified average grain size is smaller than the percentage of smaller grains.
Make engineered products
Published in Mike Tooley, Engineering GNVQ: Intermediate, 2012
A grinding wheel consists of abrasive particles bonded together. It does not ‘rub’ the metal away, it cuts the metal like any other cutting tool. Each abrasive particle is a cutting tooth. Imagine an abrasive wheel to be a milling cutter with thousands of teeth. Wheels are made in a variety of shapes and sizes. They are also available with a variety of abrasive particle materials and a variety of bonds. It is essential to choose the correct wheel for any given job.
Workplace exposure to particulate matter, bio-accessible, and non-soluble metal compounds during hot work processes
Published in Journal of Occupational and Environmental Hygiene, 2019
Balázs Berlinger, Ulf Skogen, Conny Meijer, Yngvar Thomassen
“Hot work” is a term used for working with ignition sources near flammable materials, and to the extent that surface grinding of metals may cause sparks, it can also be classified as hot work. Thus, welding, flame and plasma cutting, air carbon arc gouging, and surface grinding are examples of hot work. During an arc welding process, an electric arc is created and maintained between a welding electrode and the base material to melt the metals at the point-of-contact.[1] In flame cutting, the part of the material to be cut is raised to ignition temperature by an oxygen-fuel (e.g., acetylene) gas flame.[2] During plasma cutting, an arc is formed between the electrode and the workpiece, which is constricted by a fine bore, copper nozzle. The plasma gas flow is increased so that the deeply penetrating plasma jet cuts through the material, and molten material is removed in the efflux plasma.[3] During air carbon arc gouging, an electric arc is generated between the tip of a copper-coated graphite electrode and the workpiece. The molten metal is blown away by high velocity air jet streams. This is an effective process to clean metal surfaces.[4] Surface grinding is used to plane the surface of a workpiece, remove surface coatings, mistakes, or excess material. A grinding wheel of aluminum oxide or silicon carbide is usually used in this process.[5]
Optimization of the parameters for the rotary diamond dressing of grinding wheels
Published in Smart Science, 2019
Chin-Chia Liu, Dyi-Cheng Chen, Tsung-Ying Kuo
The parameters used to dress a grinding wheel have a critical and direct influence on grinding quality. With use, a grinding wheel becomes dull due to wear. The surface porosity is also reduced by an accumulation of metal particles and other material. This greatly hinders grinding efficiency and may even cause burn or chatter on the ground surface of a workpiece [1]. These wear-induced changes do not appear in a surface roughness measurement, but cause poor grinding quality and may even damage the surface of a workpiece and reduce its surface strength.
Experimental investigation on enhancing grindability using alkaline-based fluid for grinding Ti-6Al-4V
Published in Materials and Manufacturing Processes, 2018
Manish Mukhopadhyay, Pranab Kumar Kundu, Santanu Das
Several researchers have investigated grinding of titanium alloys and about the increased complexity of the operation because of their high chemical reactivity, low thermal conductivity and high strength at elevated temperature [4,5,11,16]. Sticking of the materials in form of tiny chips to the grits of the grinding wheel leads to subsequent wheel loading and is followed by excessive wheel wear with gradual deterioration of ground substrate. Chemical incompatibility between the grinding wheel and workpiece substrate results in low grindability even using super abrasive grinding tools and otherwise effective cryogenic liquid nitrogen as a cutting fluid [4,5,17]. A large proportion of heat, generated during grinding Ti-6Al-4V is conducted into the grinding wheel as heat is restricted to conduct through titanium alloys due to their poor thermal conductivity and the fast flowing tiny chips have low heat capacity, which leads to the development of thermal shock and fatigue [3,18]. Generation of high temperature during grinding results in development of tensile residual stresses in the ground surface due to thermal cycling. This is further augmented by the microstructural transformations and plastic deformations [17]. Problems associated with grinding, especially grinding of titanium alloys can effectively be controlled by the selection of proper dressing infeed and dressing technique, proper process parameters, suitable wheel, and by applying cutting fluid using effective coolant delivery system [3,16,19–22]. Use of special techniques like multi-nozzle cooling, scrapper board, rexine-pasted wheel, painted wheel also influence the grinding performance to a great extent as these stimulate effective cooling during grinding [23,24]. Biswas and his coworkers [25] investigated grinding of titanium grade 1 in dry and multi-nozzle cooling conditions using silicon carbide wheel. They observed much lower grinding forces in multi-nozzle cooling conditions compared to dry grinding. They found several adverse effects like generation of high grinding forces, surface burns, high wheel loading, etc. during grinding under dry condition can effectively be reduced by applying multi-nozzle cooling technique. Das and his coresearchers [26] studied the stress distribution on same material during grinding in wet condition with pneumatic barrier and reported that induced stress depends on both the temperature gradient and the maximum temperature rise at the surface. Guo and his coresearchers [17] reported reduction in grinding force ratio (ratio of tangential to normal force) and specific energy at elevated feed rate while performing conventional grinding on Ti-6Al-4V using silicon carbide wheel. Xu and his coworkers [27] performed experimental analysis on grinding Ti-6Al-4V using cBN, and wheels and observed that cBN wheel results in less surface damage on Ti-6Al-4V compared to the other wheels as cBN shows greater chemical stability at elevated temperature.