Surface integrity and chip formation in abrasive flow machining

Abstract

Due to rising requirements workpieces become more complex. After machining operations in which the geometry is produced, the claims of surface roughness, deburring and edge rounding aren't often satisfied. This leads to necessary finishing processes. A widely used solution for those challenges on inner contours is abrasive flow machining. It is used for reducing surface roughness, deburring and edge rounding in workpieces made of steel and even difficult to machine materials. As result the surface roughness can be decreased down to Ra = 0.04 μm. The rate of deburring, edge rounding and edges' shapes can be adjusted in correlation to a suitable choice of machining parameters. Besides results of surface roughness and edge rounding there are many more parameters for characterizing the surface integrity. For these purposes values of residual stress, micro hardness and changes in metallic structure could be given, too. To make the investigations useful for industrial applications, surface integrity is researched for several processing parameters like geometry, process time, piston stroke length and flow rate. Presented results are surface roughness, edge rounding including edges' shape and residual stress. All these quantities are examined in machining processes with heat treatable steel and a media for abrasive flow machining in mass production. Moreover, a new approach of proving the existing theory of chip formation is presented in this paper. Due to the new findings about the surface integrity, it is possible to draw conclusions referring the physical processes at the point of chip formation. In the long run, these conclusions can be used for a friction model, which will be part of a comprehensive process model. On the basis of this process model a process simulation will be possible, which can be used to reduce the required time of process design and to increase the quality of process design.