Rolling

Rolling is the process of deforming a workpiece by moving it between two steel rolls. The operations are performed at high speeds, which reduces both production time and cost. This technique is essentially based on the deformation of the material, without removing it. It thus strengthens the workpiece, gives it a better mechanical resistance and a greater resistance to wear and fatigue. The rolling is keen to milling (operation of forming ridges on the surface of a cylinder in order to increase adhesion, for example) and to burnishing. Burnishing is an industrial process carried out during finishing and super finishing. There exist shaping burnishing (pebbles are rolled on the metal to repel, leaving a thickness relative to the nominal side), the superfinishing burnishing, and strengthening burnishing. The latter is mainly used to increase the fatigue resistance of a workpiece such as the crankshaft; the burnishing is performed at the edges of the crankpins and the main journals in order to reduce the risk of cracking. Moreover, this process improves the state of the surface and the surface hardness, while being less expensive than grinding. The crankshafts burnishing machine is specifically designed for this type of operation. Other equipment relevant to the rolling category, the thread rolling machine allows the cold deforming of the shell of cylindrical parts. It is the deformation of the workpiece under the effect of two rolling tools in rotation which produces the thread. The profile of the tool penetrates the surface of the workpiece and the material is thus repulsed into the bottom of the rolling wheels. The brands Escofier, Pee-Wee, Seny, and Unify are known for the quality of their thread rolling machines. As far as it is concerned, the pivot rolling machine is mainly used in the clock industry, since it allows reducing the pivots to the required dimensions while obtaining optimum polishing. Hauser is one of the leading manufacturers of pivot rolling machines. The second-hand machines used in rolling operations and gone through RDMO workshops offer a quality level close to the new.