Improvement of Machinability Responses of Mild Steel During Electromagnet Assisted Turning Process

Abstract

This project aims to investigate the effects of magnetic field applied in different orientation on the machinability responses of mild steel during turning operation. The machinability responses include tool wear, surface roughness, cutting force, temperature, chip morphology. A control experiment was also done where no magnetic field is applied at all. The result showed significant reduction in the tool wear of the inserts with the application of magnetic fields. Not only non magnetic cutting shows the trend of increasing tool wear with the increase in cutting speed or depth of cut, trends can also be seen in case of magnetic cutting. It was also observed that the trends in the change in tool wear due to the application of magnetic field changes with different designs of electromagnets used to change the orientation of magnetic field lines. And explanation for this phenomenon is that there are several factors responsible for the tool wear during machining operation and these can be affected by different orientation of magnetic field lines. These include cutting force reduction due to e.m.f. induced as a result of magnetic flux lines intersecting with the work piece, reduction of vibration of the tool, high temperature resulting in softening of the work piece, building up a lubricating layer on the cutting edge of the tool insert. All the electromagnets do not result in the improvement of machinability responses in the similar way. They vary with the change in cutting parameters. The project is successful in establishing an improvement in tool life with the application of magnetic field on the tool insert during turning. The quality of the finished product along with the productivity play a significant role in today‟s manufacturing market. From customers‟ viewpoint quality is very important because the extent of quality of the produced item influences the degree of satisfaction of the consumers during usage of the product. Every manufacturing industry aims at producing a large number of products within relatively lesser time. But it is felt that reduction in manufacturing time may cause severe quality loss. However application of magnetic field can result in the surface 6 quality of the product conditioned by the cutting parameter. The surface quality during magnetic cutting is significantly improved than that obtained from non magnetic cutting. The orientation of field lines also has some impact on the surface quality which is mainly because of the chip adhering to the tool during cutting operation. Behavior of chips indicate the vibration nature of the machine and the tool. Chips produced during cutting operation have some teeth in its cross section which have been viewed with microscope to find out the effect of these electromagnets on the serration behavior. Here also it is clearly shown that the teeth produced during magnetic cutting are smaller in size whereas they are much bigger for non magnetic cutting. This phenomenon indicates that application of external electromagnetic force reduces the vibration of the machine tool. Temperature and cutting force are related with each other. Reduction of cutting force during magnetic cutting occurs due to the induced emf by the magnetic field lines intersecting with the work piece. Since an emf is induced there will be an eddy current over the surface of the work piece. This increases the temperature of the work piece and the tool insert. Having difficulties in measuring the temperature of the work piece, we have measured the temperature of the insert near the cutting junction with the aid of a thermocouple. When the emf is induced, according to Lenz‟s law there will be a back emf which will oppose the change in the flux that produces it. This has the result of inducing a force on the work piece that has a damping effect, as can be seen from the reduction of cutting forces.