The Burnishing Process

In this article, the burnishing process as a finishing operation of flat die surfaces for improving not only surface quality, but also mechanical properties of milled die surfaces is recommended. This technique can be applied after milling operations in CNC milling centers with a single fastening that increases the accuracy of die geometry. To determine both the usability of the process on flat die surfaces, and the influence of process parameters, a simple burnishing tool, with a fixed deformation element was designed and constructed. The CNC milling center was used for burnishing operations. The burnishing process was employed using a constant spindle speed on a flat surface. Burnishing feed rate, stepover, penetration depth, number of

leave their own marks that cause friction and damage on the surface of the work piece [1]. These complications influence not only surface roughness, but also the mechanical properties of the workpiece surface. Surface finishing processes have been employed in order to increase the capability of machined components which depend on the surface roughness, topography, hardness, nature of stress, corrosion, and wear resistance [2]. There are many surfaces finishing methods that are used to improve surface quality. These methods could be examined under two main categories. The first is chip removal process such as grinding, and the second is the chipless process [3]. However, neither of these methods meets the requirements mentioned above. This is becoming more and more difficult to achieve, especially for complex surface geometries such as die and mold surfaces. Therefore, development studies are being continued on surface finishing

CNC work centres are used for the machining of dies and moulds. This method does not need any other machine tool, and machining and then burnishing could be done with a single fixing that increased the accuracy of mould geometry as well. The CNC control unit and CAM softwares can be used for the burnishing of complex surfaces properly. In ball burnishing operations, a ball that is manufactured from special materials is placed in the special tool and the ball revolves in the tool freely and the system pushes the ball by constant forces. However, the special tool increases the machining costs. For decreasing the cost, a simple tool with fixed burnishing ball was designed and used in the study. AA7075 aluminium alloy is used as a workpiece material. It is well known that this material used as mould material and finishing operation of the material is relatively difficult. The process carried out using a CNC milling machine. The surface roughness, the microstructure of the burnished surfaces and the microhardness were observed so as to obtain the influence of the process