Effect Of Cutting Parameters On Surface Roughness Of Mild Carbon Steel During Turning Operations

INTRODUCTION

Machining is the process in which a tool removes material from the surface of a less resistant body, through relative movement and application of force. The material removed, called chip, slides on the face of tool, known as tool rake face, submitting it to high normal and shear stresses and, moreover, to a high coefficient of friction during chip formation. Most of the mechanical energy used to form the chip becomes heat, which generates high temperatures in the cutting region. Due to the fact that the higher the tool temperature, the faster it wears, the use of cutting fluids in machining processes has, as its main goal, the reduction of the cutting region temperature, either through lubrication reducing friction wear, or through cooling by conduction, or through a combination of these functions.

In recent time, many machining industries try to achieve high quality, dimensional accuracy, surface finish, high production rate and cost saving product. Using turning process, large amount of cutting fluids is required and that caused the total cost of productions increased. When inappropriately handled, cutting fluids may damage soil and water resources, causing serious loss to the environment. Therefore, the handling and disposal of cutting fluids must obey rigid rules of environmental protection. On the shop floor, the machine operators may be affected by the bad effects of cutting fluids, such as by skin and breathing problems. Due to the technological innovations, machining without cutting fluid, such as dry machining, machining with MQL and cryogenic machining, is already possible, in some situations. However, it is important to remove cutting fluids from the process without harming productivity, tool life and work piece quality.

Technological evolution has provided some options for the use of cutting fluids in machining processes. Tool material properties have been improved and new tool materials have been developed in order to avoid or minimize the use of cutting fluids. Therefore, properties such as resistance against abrasion and diffusion, hot hardness and ductility have been greatly improved with the new tool materials. Tool coatings have provided high hardness, low friction coefficient and chemical and thermal stability to the tool. Tool geometries have been optimized to better break chips and also to produce lower surface roughness values in the workpiece. New concepts of machine tool design have allowed machining speeds to become faster, and increased rigidity enables more severe cutting operations to be used.

In dry cutting operations, the friction and adhesion between chip and tool tend to be higher, which causes higher temperatures, higher wear rates and, consequently, shorter tool lives. Therefore, completely dry operation is not suitable for all processes and all materials especially hard materials. So, in this experiment, the optimum parameters have to be found out in order to achieve the desired surface roughness. In turning operation, there are a lot of parameters those could affect the surface roughness of the work piece, such as depth of cut, feed rate, cutting speed, operating temperature, material used, and so on.

Surface finish of the machined parts is one of the important criteria by which the success of a machining operation is judged. In addition, surface finish is also an important characteristic that may dominate the functional requirements of many component parts. A good surface finish component part has a lot of advantages compared to a bad surface finish component part. For example, in prevention of premature fatigue failure, the good surface finish is one of the necessary criteria. Besides that, good surface finish can improve corrosion resistance; reduce friction, wear and noise. Thus, the life of product or component part can be improved with good surface finish. In economy, a better and long-life product is always the choice of consumers.

1.2       Problem Statement

The challenge of modern machining industries is mainly focused on the achievement of high quality, in terms of work part dimensional accuracy and surface finish, high production rate and cost saving, with a reduced environmental impact. In machining process, it is necessary to attain the desired surface quality in order to produce parts providing the required functions.

The surface quality can affect some mechanical properties of the product, such as wear resistance, corrosion resistance, friction and so on. By the way, surface finish quality is influenced by various parameters. It will be costly and time consuming to acquire the knowledge of appropriate cutting parameters. At this point, surface roughness prediction will be helpful, which is mostly based on cutting parameters and sometimes some other parameters on dry machining. The concept of dry machining which is no any lubrication and cutting fluid applied during the operation, has been suggested since a decade ago, as a means of addressing the issues of environmental intrusiveness and occupational hazards, associated with the airborne cutting fluid particles on factory shop floors.

The absence of cutting fluid also leads to economic benefits by way of saving lubricant costs and work piece, tool machine cleaning cycle time. Health problem is caused by the long-term exposure to cutting fluids and the environment problem is caused by inappropriate way to handle the cutting fluids. In order to eliminate the effect of cutting fluids, dry machining has become a reliable choice in machining of some materials. However, some engineering materials still require cutting fluid in their machining operations and this is because of the needed surface quality, tool life, and machining dimensional accuracy. Hence the implementation of machining without coolant will bring down the manufacturing cost but can cause tool wear problems and low surfaces finish. Minimum quantity of lubricant can cut of manufacturing cost and produce better surface finish than dry cutting.

1.3.      Objectives of the Study

The objective of this study is to test the effect of cutting parameters on surface roughness of mild carbon steel during turning operations.

1.4.      Significance of the Study

This study will help machine operator in increasing the work surface smoothness and decreasing the machining time