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The mechanical shaping of metal
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
Coining is a cold-forging process in which the deformation takes place entirely by compression. It is confined mainly to the manufacture of coins, medals, keys and small metal plaques. Frequently, pressures in excess of 1500 MPa are necessary to produce sharp impressions, and this limits the size of work which is possible.
Granular Materials Powder Metallurgy
Published in Leo Alting, Geoffrey Boothroyd, Manufacturing Engineering Processes, 2020
The coining operation serves two purposes: improving the mechanical properties of the product and improving the dimensional tolerances. The mechanical properties can be improved only by increasing the density of the compact, which means high compacting pressures (higher than or equal to the primary compacting pressures). Thus, in general, coining requires a special die for the purpose, often of a higher quality than the primary die, because of the higher pressures and the adverse wear conditions.
Forming and Shaping Processes
Published in Richard L. Shell, Ernest L. Hall, Handbook of Industrial Automation, 2000
Closed-die forging (Fig. 2) is performed within a die cavity through the application of load by a punch. Wherever possible, large changes in shapes are not achieved in a single step. Instead, the processing is broken down into intermediate activities, such as edging, where material is drawn into a localized area, and fullering, where material is distributed away from an area. Blocking is another intermediate operation that is essentially a prefinish-forging stage. Large changes in shapes require significant pressures that can cause breakage in the work material and the dies. Insufficient pressures lead to the improper filling of the die cavities. In each case the determination of the forces and the areas of deformation is very critical. The determination of forces is also important to the calculation of the power consumed. In flashless forging, little to no squeezing of material between the die halves or flash is experienced. Precision forging is an advanced type of net-shape closed-die forging operation whereby high pressures are used to replicate very fine details on parts that require little postprocessing. Operations such as heading and coining are also basic variations of the common closed-die forging process. The coining operation is characterized by the fine detailing and excellent surface finish obtained. Heading is one of very few manufacturing operations used for increasing the cross-section of a workpart in solid state. Bolt and screw heads are often processed this way, without material wastage. Roll forging combines the rolling and forging operations in a simple, but, unique way for part processing.
An Advanced Anti-Tarnish Process for Silver Coins and Silverware—Monomolecular Octadecanethiol Protective Film
Published in Tribology Transactions, 2021
During the ultrasonic bath, octadecanethiol molecules were continuously absorbed on the silver surface but were constantly removed by the extra layer remover. As a result, after a few minutes only the monomolecular film that reacted with the silver surface was formed. The results did not change with the bath time or concentration in the solution. The process is easily implemented in the production line with fewer parameters to control. Because only one layer of molecules was coated on the surface, the appearance, color, and reflectivity of the 1993, 2018, and 2019 coins did not have visible or measurable changes. However, the 1922 Peace silver coin became shinier, as shown in Fig. 5. The photo was taken at a tilt angle to show the reflectivity difference. As mentioned above, during the ultrasonic bath, the extra layer remover could remove some physically adsorbed molecules and the thick silver oxide layer on the surface was removed. Therefore, the surface became shiner. With a high-magnification lens, the plastic flow marks during coining reappeared.
Influence of single phase NiS nanoparticles as lubricant additive in microscale deformation of copper gear
Published in Australian Journal of Mechanical Engineering, 2023
Scaled-down items undergo further material hardening due to miniaturisation. As a result, the material’s strength decreases as the sample size decreases ((Chan, Fu, and Lu 2011)-)10]. According to the tensile, bulging, and bending tests, the material’s microstructure significantly affects the size effect (Diehl, Engel, and Geiger 2010). FEM simulation and micro-hardness tests help to investigate the size effect on material properties, and the results reveal that as the specimen size increases, the flow stress and hardness decrease (Chen and Tsai 2006). The Coining test usually investigates the micro-formability of materials. It was discovered that die geometry, and material grain size are strongly associated with micro-formability (Wang et al. 2007).
Optimum design and analysis of a novel planar eight-bar linkage mechanism
Published in Mechanics Based Design of Structures and Machines, 2023
Recep Halicioglu, Assylbek Jomartov, Moldir Kuatova
Stopping the ram at BDC is an essential feature of the servo presses. The coining pressure can be applied to the sheet metal at BDC by using the stationary function. This type of motion, called “dwell motion,” has three segments: rising, long dwell, and descent. For a metal forming process, the long dwell time results in uniform metal deformation. Thus, the shape and dimensional accuracy of the formed product is ensured. This feature cannot be performed on conventional mechanical presses. In a conventional mechanical press, the slider cannot stop at BDC due to the forming load. To be able to perform the dwell motion, specially designed mechanisms or servo motor usage are necessary (Halicioglu, Dulger, and Bozdana 2016, 2017, 2018).