Polishing of Silicon Nitride Ceramic Balls by Clustered Magnetorheological Finish

In this study, a novel finishing method, entitled clustered magnetorheological finish (CMRF), was proposed to improve surface finish of the silicon nitride ( Si 3 N 4 ) balls with ultra fine precision. The effects of different polishing parameters including rotation speeds, eccentricities and the machining gaps on surface finish of Si 3 N 4 balls were investigated by analyzing the roughness, sphericity and the micro morphology of the machined surface. The experimental results showed that the polishing parameters significantly influenced the surface finish. The best surface finish was obtained by using the polishing parameters: the machining gap of 0.8 mm, the eccentricity of 10 mm and the rotation ratio of 3/4. To further investigate the influence of the polishing parameters on the surface finish, an analytical model was also developed to analyze the kinematics of the ceramic ball during CMRF process. The resulting surface finish, as a function of different polishing parameters employed, was evaluated by analyzing the visualized finishing trace and the distribution of the contact points. The simulative results showed that the distribution and trace of the contact points changed with different polishing parameters, which was in accordance with the results of experiments.

Electrically Assisted Compression of Tungsten Carbide and its Implications for Electrically Assisted Machining

It has been shown that electrically assisted machining has the ability to reduce cutting force, change chip type, and improve surface finish. However, the effect of electricity on tungsten carbide has not been examined, a material often used to create cutting tools used in electrically assisted machining. During machining processes, depending on the type of cut, a small amount of the tool may be in contact with the workpiece. This will lead to an increased current density at that point on the tool which could lead to undesired effects with respect to tool wear and life. This paper conducts electrically assisted compression tests on uncoated tungsten carbide rod to examine the effect of electricity on the material and determine if there are any current densities that cause large magnitude weakening of the tungsten carbide. It is concluded that there is a maximum current density that can be passed through tungsten carbide before thermal softening becomes a problem. At a current density lower than this threshold, electricity has little effect on the strength of the carbide. This work is related to past electrically assisted turning experimentation.

On the Development of a Machining Support System to Improve Surface Finish

Finishing processes such as deburring are performed on a wide variety of products in various quantities by workers on a piece-by-piece basis. Accordingly, the accuracy of the product depends on the worker’s skill. The aim of this research is to develop a finish machining support system. The machining is supported by using a haptic device and controlled by a bilateral control system. Here, we propose a original bilateral controller which have the gain components on the line used to transfer the force signal between master and slave robot. These gains change the binding force between master and slave robot to change the construct of the system. The effectiveness of this system is shown in simulations using haptic device and virtual model of slave robot.