INVESTIGATIONS ON THE EFFECT OF
PROCESS PARAMETERS ON THE QUALITY OF
MACHINED SURFACE IN LASER BEAM
MACHINING OF MILD STEEL
Pratik, 2Mohammad Arshad Emran, 3Deepak D, 4Anjaiah
DEPARTMENT OF MECHANICAL AND MANUFACTURING
ENGINEERING, MANIPAL INSTITUTE OF TECHNOLOGY, MANIPAL
UNIVERSITY, MANIPAL - 576104,INDIA
Abstract— Laser Beam Machining is widely used manufacturing technique utilized to perform cutting, engraving and welding operations on a wide variety of materials ranging from metals to plastics. In the present work an attempt has been made to study the effect of pr ocess parameters such as feed rate, input power and standoff distance on the quality of the machined surface using Carbon dioxide (CO2) laser beam on 3 mm thick mild steel sheets. The quality of cut is assessed in terms of response parameters such as upper kerf width, lower kerf width, taper of the cut surface and surface roughness. Design of experiments was implemented by using a full factorial design. The effect of the process parameters on response have been shown by means of main effect plots developed using statistical software. It was found that upper kerf width decreased with increase in feed rate and increased with increase in laser power. Surface roughness of the cut decreases with increase in feed rate and power.
Keywords - Laser beam machining, Upper kerf width, Lower kerf width, Surface roughness, design of experiments
Laser beam machining (LBM) is widely used in aircraft and automotive industries. It is used to perform various operations such as cutting, drilling, welding and engravi ng on a wide range of materials. Earlier laser technology had a limited scope and was used only in high technology industries. With many advances in the laser technology over the years it is now being used for mass production in many industries. The benefi ts of using laser technology are high precision, improved cut quality and cost effectiveness due to high production rate . In laser machining workpiece material is melted due to localized heating using a highly coherent beam of monochromatic light. The beam is focused to a very small spot using a suitable lens. The molten material is blown away using an assist gas such as oxygen and nitrogen. The process parameters of LBM affect the quality of the cut produced. In the present study an attempt has been m ade to determine the effect of feed rate, power and standoff distance on the quality of cut. The quality of cut is assessed in terms of upper kerf width, lower kerf width, taper angle and surface roughness. A. K. Dubey et al.  had optimized two kerf qualities namely kerf deviation and kerf width and found that assist gas pressure and pulse frequency significantly affects the kerf quality. B.S. Yilbas  studied the effects of cutting speed, laser power on quality of cut in laser cutting of 12mm thick m ild steel sheets. The author found that cutting speed and laser power intensity significantly affect the striation formation around the cut edges. B.S. Yilbas determined the relationship between parameters and cut quality and found that at the critical gas pressure (giving the maximum useful jet velocity), cutting speed is almost independent of workpiece thickness at high power intensities. N. Rajaram et al.  investigated the effect of cutting speed and power on surface roughness, striation frequency and size of heat affected zone (HAZ) in CO2 laser cutting of 4130 steel and found that an increase in cutting speed decreases the kerf width and an increase in power increases the kerf width. Feed rate has a major effect on surface roughness. Increase in feed rate results in an increase in surface roughness. An optimum feed rate for which surface roughness...