The surface integrity of titanium part is poor after milling; it is unable to meet the accuracy requirements for use. To solve this problem, the ultrasonic vibration-assisted magnetic abrasive finishing was proposed to be used for the surface finishing treatment. The finishing experimental result shows that the efficiency of ultrasonic magnetic abrasive finishing is 40 % higher than magnetic abrasive finishing. The milling texture on part surface faded or disappeared after ultrasonic magnetic abrasive finishing. The surface original micro-cracks have been completely removed. The surface stress state changed from the residual tensile stress 280 MPa before finishing to residual compressive stress 20 MPa after finishing. It verified that the ultrasonic magnetic abrasive finishing can efficiently promote the surface integrity of titanium parts and ultimately gain the best surface quality and performance.

Surface integrity of titanium part by ultrasonic magnetic abrasive finishing

Surface finish greatly affects the friction, wear, corrosion, heat transfer and lubrication properties of internal surfaces which find wide applications in medical, automobile, aerospace and mould and die industries. However, improving the internal surface finish is extremely challenging due to the restricted tool accessibility of conventional manufacturing processes. This paper develops a novel magnetic polishing tool to deterministically polish internal surfaces. Repeatability tests, single point polishing experiments and gap variation experiments are conducted to evaluate the performance of the proposed polishing tool. Experimental results substantiate the good repeatability and localized polishing capability with a material removal rate of 15 μm/min and achievable surface roughness of 0.258 μm Ra. Furthermore, a theoretical model is developed to reveal the material removal mechanism based on the contact mechanics model and sliding wear theory. The developed model can successfully predict the two-dimensional and three-dimensional polished profiles under different gaps which are defined by the distance between the externally driven magnet and the outer surface of the workpiece. The localized polishing capability is, for the first time, achieved in internal surface finishing and the theoretical study establishes a novel framework for modelling the polished profile evolution in pressure-copying polishing processes.

Experimental and theoretical study of internal finishing by a novel magnetically driven polishing tool

Magnetic abrasive finishing (MAF) is one of the nontraditional machining processes that have been studied to improve the surface quality and deburr the workpiece. The magnetic abrasive particles (MAPs) as the machining tool of MAF influence the finishing efficiency and the final surface quality. In this study, in order to evaluate the comprehensive performance of the sintered MAPs with the simply mixed MAPs, the surface morphologic structure and the particulate compositions of the sintered MAPs were observed and tested by scanning electron microscopy with energy spectrum analysis. The M–H curves of the two kinds of MAPs were tested through a superconducting quantum interference device. The actual magnetic flux density in the working gap was measured by Gauss meter, and the results showed that the magnetic properties of the sintered MAPs are superior to the simply mixed MAPs. At last, through the different finished surface texture and motion analysis combining with all the measurements, results proved that the finishing ability of sintered MAPs is greater than simply mixed MAPs.

Comprehensive performance evaluation of the magnetic abrasive particles

This paper aims to improve the surface integrity and surface homogeneity with various trajectories by a newly self-designed experiment device. In the experiments, three kinds of polishing trajectories were studied with attached revolution motion to magnetic abrasive brush (MAB) based on conventional magnetic abrasive finishing (MAF) process. The surface roughness, the cross-sectional shape, and the 3D micro-morphology were chosen as the response variables to explore the feasibility and benefits of the proposed improving polishing method. The results show that the plane homogeneity and surface quality improved in varying degrees after improving the polishing trajectory. In addition, combining MAF theory to analyze related reasons, the trajectory expression of the magnetic abrasive particles (MAPs) was established and was simulated by Graph software. The theoretical analysis is consistent with the experimental results which indicated that analysis of polishing trajectory can be used to predict polishing results. Thus, it is feasible to plan polishing trajectory reasonable according to workpiece profile and surface quality requirements.

Study on improving the trajectory to elevate the surface quality of plane magnetic abrasive finishing

Modeling of material removal in magnetic abrasive finishing process with spherical magnetic abrasive powder

Modern aerospace and electronic industries make frequent use of the difficult to machine materials. The micro machining of these materials with conventional edged tool is uneconomical with poor quality of the surface. A relatively new micromachining technology based on magnetic assistance has been used in the recent past to produce quality surface finish on these materials. The magnetic abrasives play an essential role of cutting tools in these processes. However, the magnetic abrasives are not easily available as these are produced by special techniques. This paper highlights major existing technologies that are used to manufacture magnetic abrasives. Main performance characteristics of magnetic abrasives have also been reviewed as regards to micromachining of various surfaces.

P.S. Mishra

Papers

Performance of abrasives used in magnetically assisted finishing: a state of the art review