Factor Affecting on Tool Life- taylor’s Equation For tool Life Calculation
Definition Of Tool Life:
Tool life may be defined as the period of time that the cutting tool performs efficiently.
Many variables such as material to be machined, cutting tool material, cutting tool geometry, machine condition, cutting tool clamping, cutting speed, feed, and depth of cut, make cutting tool life determination very difficult.
taylor’s tool life equation
The first comprehensive tool life data were reported by EW. Taylor in 1907 and his work has been the basis for later studies. Taylor showed that the relationship between cutting speed and tool life can be expressed empirically by:
VT = C
V= cutting speed, in feet per minute
T = tool life, in minutes
C= a constant depending on work material, and other machine variables. Numerically it is the cutting speed which would give 1 minute of tool life.
n = a constant depending on work and tool material.
C: constant that depends on tool-work material combination and tool geometry (>100)N, n1, n2: Constants depending upon tool material (=0.1 to 0.4).
This equation predicts that when plotted on log-log scales, there is a linear relationship between tool life and cutting speed. The exponent n has values ranging from 0.125 for high-speed steel (HSS) tools, to 0.70 for ceramic tools.
Tool Forces and Power Consumption:
The use of tool forces or power consumption as a criterion of machinability of the workpiece material comes about for two reasons.
First,the concept of machinability as the ease with which a metal is cut implies that a metal through which a tool is easily pushed should have a good machinability rating.
Second,the more practical concept of machinability in terms of minimum cost per part machined, relates to forces and power consumption, and the overhead cost of a machine of proper capacity.
When using tool forces as a machinability rating, either the cutting force or the thrust force (feeding force) may be used. The cutting force is the more popular of the two since it is the force that pushes the tool through the workpiece and determines the power consumed.
Although machinability ratings could be listed according to the cutting forces under a set of standard machining conditions, the data are usually presented in terms of specific energy. Workpiece materials having a high specific energy of metal removal are said to be less machinable than those with a lower specific energy.
The use of net power consumption during machining as an index of the machinability of the workpiece is similar to the use of cutting force.