Development of a new magnetic abrasive finishing process with renewable abrasive particles using the circulatory system

Highlights

• A new ultra-precision MAF process with renewable abrasive particles using the circulatory system was developed.

• Due to the renewable abrasive particles of This process, The machining efficiency will not decrease over time.

• The workpiece surface roughness was improved from 273 nm Ra to 23 nm Ra by this process.

Abstract

In order to improve the finishing efficiency of the Magnetic Abrasive Finishing process, we proposed a new MAF process with renewable abrasive particles using compound magnetic finishing fluid circulatory system in this paper. This new finishing process has a circulating system that uses a conveyor belt to renew the mixed abrasive particles. This not only maintains the stability of the finishing but also ensures that the processing does not need to be interrupted. In this study, we investigated the magnetic field distribution, finishing force, and finishing behavior of the processing area. Furthermore, we designed experimental device to finish the sus304 stainless steel plate, to verify the feasibility of this process and understand its characteristics through processing experiments. Moreover, the influence of important process parameters, including magnetic particles, abrasive particles, conveyor belt line speed and working gap, on the surface quality of the workpiece is studied through the experiment. The experimental results indicate that the present process can achieve stable processing of the material surface without interruption, and the surface roughness of the sus304 stainless steel plate has been improved from 273 nm to 23 nm through this process.

Introduction

Magnetic Abrasive Finishing (MAF) process is a technology that uses flexible magnetic brushes to improve the surface quality of materials. The mixture of abrasive particles and magnetic particles forms the Flexible Magnetic Abrasive Brush (FMAB) between the workpiece and the magnetic pole under the action of the magnetic field. FMAB is flexible and can tightly contact the surface of the material [1]. Therefore, it is considered to be a highly adaptable surface finishing technology that can be used in flat, complex curved surfaces and inside tube [[2], [3], [4], [5], [6]]. At the same time, MAF generates low stress and avoids surface defects or subsurface damage to the workpiece. This technology can not only finish the surface of ferromagnetic materials, but also can effectively finish non-ferromagnetic materials such as stainless steel [[7], [8], [9]], glass [10,11], ceramics [12]and brass [13]. At present, the magnetic field assisted finishing technology has been widely used in many fields such as the processing of medical parts and optical parts [[14], [15], [16], [17], [18]].

Shinmura et al. [19,20] studied the basic principles and grinding characteristics of the MAF process. It is found that under certain conditions, the material removal rate increases with the increase of the magnetic particle diameter. The final surface roughness value (Ra) increases as the diameter of abrasive particles increases. Increasing the magnetic flux density can improve the finishing efficiency and the final surface quality. It is verified that the MAF has the ability of plane finishing. Yin et al. [21] considerably improved deburring efficiency by using the vibration-assisted MAF process. Zou et al. [5,[22], [23], [24], [25], [26]] studied the polishing trajectory of the magnetic brush, and the precision and homogeneity of the plane magnetic abrasive finishing was improved by rationally planning the polishing trajectory of the magnetic brush, and proposed a new method that uses a magnetic machining fixture composed of rare-earth permanent magnets instead of traditional magnetic abrasives, which makes the internal finishing of non-ferromagnetic thick tubes possible. In addition, the finishing principle and finishing characteristics of MAF process using alternating magnetic field are also studied.

Previous studies have summarized the main parameters that affect the performance of the MAF process, and improved the efficiency of the MAF, which has made a great contribution to the development of the MAF process. However, the MAF process is still facing problems in actual production. The performance of the magnetic brush is a key factor in the finishing. In conventional MAF processing, the number of abrasive particles in the magnetic brush is limited, and the position of the abrasive particles is relatively fixed, which will cause the cutting edge of the abrasive particles to become dull gradually. The finishing efficiency decreases gradually as the finishing progresses. On the other hand, the original structure of the magnetic brush will be destroyed and deformed due to the interaction with the workpiece, which is also detrimental to the precision of MAF processing. The above problems make it impossible to continue the magnetic finishing process for a long time without replacing the magnetic brush. The QED company has successfully developed polishing equipment based on magnetorheological finishing (MRF) technology [14,15]. It can correct the shape or angle of optical components of different shapes. Make a great contribution to the precision machining of optical parts. However, it is difficult for ordinary laboratories to afford due to the high requirements for equipment and the magnetorheological fluid.

In order to overcome these problems, a new MAF process with renewable abrasive particles using the conveyor belt is proposed in this paper. Firstly, the slurry formed by the compound magnetic finishing fluid under the action of a magnetic field is used to finishing the workpiece. The compound magnetic finishing fluid consists of magnetic particles, abrasive particles and grinding fluid. It is flexible under the action of magnetic field and will not cause surface or subsurface damage to the workpiece. Secondly, we use the conveyor belt as the carrier of compound magnetic finishing fluid. The compound magnetic finishing fluid forms a strip-shaped slurry on the surface of the conveyor belt under the action of the magnetic field of the ring neodymium magnet. Driven by the conveyor belt, the strip-shaped slurry moves with it. While the compound magnetic finishing fluid is finishing the workpiece, it is also cycled and renewed. Thereby ensuring the stability of finishing. There is no need to interrupt processing during the finishing process, and the problems of blunt cutting edges of abrasive particles and deformation during finishing can be avoided. Compared with conventional MAF, this MAF process can improve the uniformity of the finishing surface and improve the finishing efficiency.

The purpose of this study is to understand the particularity of the process, study the magnetic field distribution in the processing area, and study the finishing force and the finishing behavior during processing. We made experimental device and conducted processing experiments. The influence of important process parameters, including abrasive particles, conveyor belt linear speed and working gap, on the surface roughness of the workpiece is studied.