Abstract
Milling is a widely employed material removal process for different materials. It is characterized by high material removal rate. Machining
leads to high friction between tool and workpiece, and can result in high temperatures, impairing the dimensional accuracy and the surface
quality of products. Application of conventional cutting fluid may not effectively control the heat generation in milling. Besides, cutting
fluids are a major source of pollution. Solid lubricant assisted machining is an environmental friendly clean technology for desirable control
of cutting temperature. The present work investigates the role of solid lubricant assisted machining with graphite and molybdenum
disulphide lubricants on surface quality, cutting forces and specific energy while machining AISI 1045 steel using cutting tools of different
tool geometry (radial rake angle and nose radius). The performance of solid lubricant assisted machining has been studied in comparison with
that of wet machining. The results indicate that there is a considerable improvement in the process performance with solid lubricant assisted
machining as compared to that of machining with cutting fluids.
q 2005 Elsevier Ltd. All rights reserved.
Keywords: Radial rake angle; Nose radius; Solid lubricant; Graphite; Molybdenum disulphide; End milling
1. Introduction
In any metal cutting operation, a lot of heat is generated
due to plastic deformation of work material, friction at the
tool–chip interface and friction between the clearance face
of the tool and workpiece. The heat generated in machining
adversely affects the quality of the products produced
(dimensional accuracy and surface finish). So, it is generally
considered that the heat produced during the machining
process is critical in terms of workpiece quality. Thus,
effective control of heat generated in the cutting zone is
essential to ensure good workpiece surface quality in
machining.
Cutting fluids have been the conventional choice to deal
with this problem. Cutting fluids are introduced in the
machining zone to improve the tribological characteristics
of machining processes and also to dissipate the heat
generated. But, the application of conventional cutting
fluids creates some techno-environmental problems like
environmental pollution, biological problems to operators,
water pollution, etc. [1]. Further, the cutting fluids also incur
a major portion of the total manufacturing cost [2]. All these
factors prompt investigations on the use of biodegradable
coolants and coolant free machining. But any attempt to
minimize or avoid the coolant can be dealt with only by
replacing the functions normally met by the coolants with
some other means. If friction at the tool and workpiece
interaction can be minimized, by providing effective
lubrication, the heat generated also can be reduced to
some extent. Advancement in modern tribology has
identified many solid lubricants, which can sustain and
provide lubricity over a wide range of temperatures.
In order to produce any product with desired quality by
machining, cutting parameters should be selected properly.
Cutting speed, feed rate, depth of cut are the process
parameters, which influence the machining process to great
extent. Apart from the process parameters, the geometry of
cutting tool has a significant effect on machining performance.
Among various parameters of tool geometry, radial
rake angle is one of the most important parameters, which
determines the tool and chip contact area and hence affects