18MEPK0 – METAL CUTTING
ENGINEERING
Course Outcomes
By the end of the course, student will be able to:
1. Explain the types and characteristics of tool materials,
cutting tools nomenclature and various tool angle
specification
2. Explain the Mechanics of the machining process
3. Examine the thermal aspects and cutting fluids
4.
Examine the tool wear, tool life, machinability.
5.
Determine the tool life and surface roughness of machined
surfaces
6.
Optimize the machining cost by varying the cutting
parameters
18MEPK0 – METAL CUTTING
ENGINEERING
Chapter-6
Economics of machining
process
Prof. M.Karthic, M.E
E-mail: mkmect@tce.edu
2
Chapter-6
Economics of machining process
6.1 Introduction – Cost of single pass turning operations - 2
6.2 Optimal cutting speed for minimum cost in turning -1
Optimal cutting speed for maximum rate of production in
6.3
turning – 1
6.4 Restrictions on optimum cutting conditions - 1
6.4 Restrictions on optimum cutting conditions
Often the cutting velocity and feed determined through
optimization have to be modified because only a finite number of speed and
food steps are available on the machine tool Factors, which influence the
choice of speed and feed as follows:
1. Requirement of surface finish
2.
Requirement of dimensional accuracy or tolerances
3. Available horsepower on the machine tool
4. Available speed and food steps on the machine tool.
6.4 Restrictions on optimum cutting conditions
The requirement of surface finish would place a limit on the
maximum feed with which the desired surface finish can be obtained
(Dependence d surface finish on food is discussed in the chapter on surface
integrity).
The requirement of dimensional accuracy would limit the
permissible deflection of work piece and tool and hence the maximum
cutting force during the machining Power requirement in turning depends
on cutting force and cutting speed
6.4 Restrictions on optimum cutting conditions
However, the cutting force depends on feed and depth of cut.
Therefore, the cutting power involves all the three process parameters, i.e.
cutting speed, f and depth of cut. Also, the tool life depends on the above
three parameters, Le V and & Consequently, power would place severe
restrictions on the choice of food and cutting speeds, particularly for
roughing operations in which the tendency is to use the maximum speed.
The cutting speed calculated from optimizing equations may not be
available on the machine tool because speeds are provided in a limited
number of speed. In case of a stepped drive, the nearest available machine
speed has to be used Only of the machine is provided with a stepless drive,
the calculate optimum speed can be used
6.4 Restrictions on optimum cutting conditions
The effect of all these restrictions is shown in figure 10.4. The
permissible may give us the cutting speed corresponding to point A
(Figure104) However the available power on the machine may shift it to
point B.
Points And B may control the process in case of roughing
operations, where surface fin and dimensional accuracy are not very
important. For finishing operations
6.4 Restrictions on optimum cutting conditions