Corner shaping is a necessary operation in manufacturing of most mechanical components. Edge radiusing is the principal way to reduce stress concentration in components like gear, crank shaft, ball bearing, to permit assembly and disassembly of parts, to avoid local damage and to reduce the possibility of hurting the operators. Often precise values of corner radius are specified in component design. Deterministic operations such as chipping, plastic deformation and non traditional ones such as electro discharge machining, abrasive jet deburring are well established technology. Yet, sometimes, it results not economic or even impossible to perform these operations due to the complicated part geometry, difficulty in part clamping and tool path, large number of parts to be produced. Barrel finishing is technique able to improve the roughness of parts of complicated shape by means of a soft mechanical action over the surface performed by abrasive media. The main features of this technology is that the parts do not need to be fixed. Radiusing is, in turn, a potential application area for barrel finishing which has been investigated in this paper. Experimental tests were conducted on finished specimens with sharp corners in order to achieve information about corner radius evolution as a function of the time for different set parameters. The radius values have been assessed by analyzing the acquired profiles with a proprietary fitting procedure. It has been found a square root relation between radius and working time and, by assessing the influence of single parameter, a radiusing model has been proposed.
In sheet metal processes the burrs cannot be completely eliminated during the process but can be minimized by optimization of the process parameters. Hence the deburring often becomes an essential secondary operation. Most of the deburring operations are hand-made and therefore several manufacturers tend to eliminate these tedious and labor-intensive operations due to time and cost issues. Moreover, clamping problems can arise which, together with the deburring forces, can induce dimension alterations and local deformations, particularly for thin sheets. Barrel finishing is an old technique commonly used to improve the surface roughness of complicated parts, but can find interesting applications also in the deburring. Aim of this work is to present an experimental investigation on the deburring of sheet metal performed by barreling. A technological model has been developed in order to assess the height of the burr as a function of the initial burr and of the working time.
Ball milling is a material processing method that allows near room temperature process of elements in powder and permits to synthesize materials with peculiar properties otherwise difficult or impossible to obtain. Due to the repeated fractures and cold welding of the reactants particles, solid solutions, amorphous alloys and equilibrium nanostructured materials can be obtained. Products coming from mechanosynthesis process can be advantageously applied as high performance structural and functional materials. Different milling devices can be utilized for the powder processing: planetary mill, attritor, horizontal ball mill, 1D and 3D vibrating machines. The wide differentiation in configuration of the mills obstacles the development of a unified model on powder transformation kinetics in the milling process and then most of processing procedures are still developed by using a trial and error method. The focus of this paper is on a horizontal fixed vial ball mill; in this configuration a high speed rotor launches several tumbling against the vial wall. During hits, a quantity of energy is released to the trapped powder and the solid state reactions are promoted. To characterize the powder transformation process, knowledge of the kinematics of the balls system must be inferred. For this purpose an experimental setup based on digital image acquisition was constructed and the movement of balls inside the vial was filmed. Particle trace analysis methodology permitted to obtain balls trajectories, velocity vector field and total hit frequency. The kinetic energy of the impacting balls inside the vial was quantified, so that the energy released to the powder in a milling experiment can be estimated.
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