Cutting surface finish of the product. The cutting temperature

Cutting temperature

The cutting temperature is vital, particularly when
its high, it effects both the tool and the work being output. A large section
of heat is taken away by the chips. This is not a major concern as the chips
are not used. The possible effects of high cutting temperatures are that the
tool will be likely to wear out much faster. 
There will be some sort of flaking and on the cutting edge because of
the thermal shocks. The elevated temperatures will also cause build up
formation. The cutting tool during the procedure of machining is a great concern
since cutting metals are related with elevated temperatures in the cutting zone.
Having a high temperature of the
cutting tool causes hardness change, metallurgical transformation, or even
chemical composition change due to work done in deforming and in overcoming sliding
friction between tool, workpiece, and chip. Henceforth, they have reflective
consequences on the tool life, dimensional and form accuracy, and surface finish
of the product. The cutting temperature on the tool is particularly crucial since
a lot of heat is being produced. The rise of the heat temperature and cooling
of the tool at work are linked with considerable temperature differences in
cutting edges. Moreover, the heat generated during chip formation does not flow
effortlessly through the workpiece and chip.

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Tool materials

Tool
materials play a huge role in material cutting and tool wear. The progression
of high speed steels to carbide and moving further onto ceramics and other
durable material. From the 1960’s the
development of the use of coatings, particularly titanium nitride, allows
high-speed steel tools to cut faster and last longer. titanium nitride provides
a high surface hardness, resists corrosion, and it minimizes friction.
In the industries, carbide tools have substituted high-speed steels in most
applications. These tools cut around 3/5 times quicker than high-speed steels.
A great percentage of cobalt binder increases the tool strength, on the other
hand it lowers the wear resistance. Carbide
is used in solid round tools or in the form of replaceable inserts. Many
manufacturers of carbide tools create a variety for certain applications. The correct
choice of the tool can increase the life or improve the cutting speed of the
same tool. The tools that are Shockproof those types are used for interrupted
cutting. The stronger tools are chemically-stable types which are essential for
high speed finishing a material like steel. The heat-resistant tools are required
for machining the alloys, like Inconel and Hastelloy.

 

 

 

 

Work
material

When the material reaches its maximum the followings
occurs, if the work material is brittle, a crack will appear in from of the cutting
edge, later it results in fracture. If the work material is ductile, a visible
crack will not be observed because of healing. The tool materials must be firmer
than the material which is to be cut, and the tool must be able to resist the
heat produced in the metal-cutting process. Moreover, the tool must have a precise
geometry, with clearance angles designed so that the cutting edge can co-operate
with the workpiece without the rest of the tool holding on the workpiece
surface. The workpiece is a piece of pre-shaped material that is secured to the
fixture, which itself is attached to a platform inside the milling machine. The
cutter is a cutting tool with sharp teeth that is also secured in the milling
machine and rotates at high speeds. By feeding the workpiece into the rotating
cutter, material is cut away from this workpiece in the form of small chips to
create the desired shape.

 

Contact stresses

 

The contact stresses involve physical processes on the
surfaces and the contact of the cutting tool when the chip has been removed so
it can be investigated.  The contact
layers depend on the length of elastic, parts of this layer are on the normal
and shear stresses contact zone. A natural white layer is produced in the cutting
process which plays a protective role and results in the reduction rate of tool
wear. As the metal is cut the cutting force acts through a small section of the
rake face, which Is in contact with the chip and is further known as the tool
chip interface. The contact of the tool chip interface the correct procedures
should be analysed such as, the contact pressures between the stresses
(normal/shear), the temperature distribution between the tool and the material,
and finally the parameters of relative motion. Experimental techniques have
been done to understand the stresses which include split tool, dynamometer and photo
elastic tools. The transparent tool is used to gain a direct observation of the
tool chip interface. The stress increases with the cutting speed for a wide
range of metallic work materials decrease with the rake angle. The mean contact
stress is found to be a function and a characteristic of the state of stress in
the contact zone. Moreover, the shear contact stress determines to a
significant extent temperature at the tool chip contact, it can be stated that
this temperature is solely a function of the cutting speed and the work
material.

Cutting
conditions

 

When the cutting conditions are correct the work can
be done swiftly. Various decisions must be made regarding the cutting tool and
the cutting conditions. These include surface finish, geometry, speed of the
machine, the depth of the cut and the cutting fluid that needs to be applied
for the correct material.  The cutting
tool wear must be monitored to prevent the tool from breakage also a rough
finish to the workpiece. The tool
cutting edge angle significantly affects the cutting process because, for a
given feed and cutting depth, it defines the uncut chip thickness, width of
cut, and thus tool life. The physical background of this phenomenon can be
explained as follows: when or decreases, the chip width increases
correspondingly because the active part of the cutting-edge increases. This
results in improved heat removal from the tool and hence tool life increases.
For example, if the tool life of a high-speed steel (HSS) face milling tool
having or = 60° is taken to be 100% then when or = 30° its tool life is 190%,
and when or = 10° its tool life is 650%. An even more profound effect of or is
observed in the machining with single-point cutting tools. For example, in
rough turning of carbon steels, the change of or from 45° to 30° sometimes
leads to a fivefold increase in tool life

Fluids

 

The cutting fluids in the machining process and used
for several reasons which have a significant impact on the tool. The fluids
help by improving the tool life by cooling down the temperature, the fluid also
reduces the thermal deformation on the work piece, it also helps by giving a
smooth finish and flushes away the excess chip from the cutting zone. The
fluids also help as applies a corrosion protection over the machined surface. There
are generally three types of liquids: mineral, semi-synthetic, and synthetic.
Semi-synthetic and synthetic cutting fluids represent attempts to combine the
best properties of oil with the best properties of water by suspending
emulsified oil in a water base. These properties include: rust inhibition,
tolerance of a wide range of water hardness (maintaining pH stability around 9
to 10), ability to work with many metals, resist thermal breakdown, and
environmental safety. Besides cooling, cutting fluids also aid the cutting
process by lubricating the interface between the tool’s cutting edge and the
chip. By preventing friction at this interface, some of the heat generation is
prevented. This lubrication also helps prevent the chips from being welded onto
the tool, which would interfere with subsequent cutting.

 

 

 

 

Cutting tool shape

 

Types of tools

Facing

This
is usually the first step of any lathe operation on the lathe machine. The
metal is cut from the end to make it fit in the right angle of the axis and
remove the marks.

Tapering

Tapering
is to cut the metal to nearly a cone shape with the help of the compound slide.
This is something in between the parallel turning and facing off. If one is
willing to change the angle, then they can adjust the compound slide as they
like.

Parallel Turning

This
operation is adopted to cut the metal parallel to the axis. Parallel turning is
done to decrease the diameter of the metal.

Parting

The
part is removed so that it faces the ends. For this the parting tool is
involved in slowly to make perform the operation. For to make the cut deeper
the parting tool is pulled out and transferred to the side for the cut and to
prevent the tool from breaking

Cutting
tools for metal cutting have many shapes, each of which are described by their
angles or geometries. Every one of these tool shapes have a specific purpose in
metal cutting. The primary machining goal is to achieve the most efficient
separation of chips from the workpiece. For this reason, the selection of the
right cutting tool geometry is critical. Other chip formation influences
include:


the workpiece material


the cutting tool material


the power and speed of the machine


various process conditions, such as heat and vibration