Influence of Process Parameters and Initial Surface on Magnetic Abrasive Finishing of Flat Surfaces on CNC Machine Tools

Andrii Zelinko,Viktor Maiboroda,Florian Welzel,Dirk Biermann

doi:10.3390/jmmp5040108

Abstract

Magnetic abrasive finishing (MAF) shows a high potential for use on computerized numerical control (CNC) machine tools as a standard tool to polish workpieces directly after the milling process. This paper presents a new MAF tool with a single, large permanent magnet and a novel top cover structure for finishing the plain ferromagnetic workpieces. The top cover structure of the MAF tool, combined with an optimized working gap, ensures the effect of mechanical powder compaction, which leads to a significant increase in process capability and surface roughness reduction. The influence of the process parameters such as feed rate, equivalent cutting speed, working gap (including for three grain sizes) and the gap to the magnet was investigated. In addition, the influence of the initial surface after face milling, end milling, ball end milling and grinding on the surface quality after MAF was investigated. Furthermore, three typical surfaces after milling and MAF were analyzed. By magnetic abrasive finishing, a significant surface quality improvement of the initial milled surfaces to roughness values up to Ra = 0.02 µm and Rz = 0.12 µm in one processing step could be achieved.

Highlights

Various studies investigate the process parameters [1,2,3,4,5,6,7] and describe for example the influence of the working gap, the abrasive weight percentage and rotational speed on the normal finishing force and torque, while Magnetic abrasive finishing (MAF) of the paramagnetic disk workpiece that was clamped between two MAF tools [1]
Further work describes the influence of abrasive grain size as well as feed rate in addition to abovementioned process parameters on the percentage change in surface roughness Ra, during the equal MAF process of paramagnetic stainless steel and copper alloy [2]
Further work indicates that process parameters such as voltage supplied to the electromagnet and working gap have a major influence on the material removal [5]

Summary

Introduction

Magnetic abrasive finishing (MAF) is characterized by a high complexity of the process, powder motion kinematic, mechanical and magnetic interaction of forces and numerous influencing factors To these factors belong process kinematics (finishing of flat or freeform surface, wave or tube, etc.), process parameters (cutting speed, feed rate, working gap and magnetic flux density), workpiece properties (mechanical and magnetic properties, initial surface), MAF tool (quantity, dimension, arrangement of permanent- or electromagnets), magnetic abrasive powder (type, manufacturing method, grain size, ferromagnetic and abrasive percentage) and cooling lubricant (type, chemical reactions). Various studies investigate the process parameters [1,2,3,4,5,6,7] and describe for example the influence of the working gap, the abrasive weight percentage and rotational speed on the normal finishing force and torque, while MAF of the paramagnetic disk workpiece that was clamped between two MAF tools [1]. Simulation of the magnetic flux density distribution on a paramagnetic workpiece between the MAF tool and optional permanent magnet below the workpiece show that an additional NdFeB magnet improves by an increase of 1.5 times the magnetic flux density in the working gap [7]

Methods

Results

Conclusion