What are The Factors Affecting Tool Life? (Metal Cutting and Cutting Tool)
What is Tool Life?
Tool life can be defined as the time interval for which the tool works satisfactorily between two successive grindings.
Tool Life is affected mainly with the following factor :
1.Cutting Speed:
Tool Life decrease as the cutting speed increases as the temparature rises with increase the cutting speed. heat is concentrated on the tool and then on the work and the hardness of tool my changes also wear occur on flank.
2. Ratio of Feed to a Depth of Cut(f/d)
The ratio of feed to the depth of the cut affect the tool life. A fine feed area of cutting tool face over which chip passing is greater than that of a coarse feed for a given volume of swart removal but offset this will be greater.
3.Area of Cut
4.Shape and Angle of Tool
The tool life is affected by the shape. The nose radius tends to improve tool life. A tool with a large rake angle becomes weak as a large rake angle reduces the tool cross-section and the amount of metal to absorb the heat. The effect of end cutting edge angle is to improve surface finish, rigidity, and equivalent speed.
5.Nature and Quality of Coolants(Cutting Fluid)
Cutting fluid reduces the coefficient of friction at the chip tool interface and increases tool life.
6.Tool Material and its Heat Treatment
It is found that at high temperatures the characteristics like hardness, wear resistance, strength, heat conductivity, impact resistance, abrasion resistance may change. The cutting speed has a large effect on tool life also feed and depth of cut.
7.Rigidity of Tool, Work, and Machine Tool
In the machining operation, both the workpiece and machine should remain rigid. If not vibration will occur and the cutting tool will be subjected to intermittent cutting so it cause decrease tool life.
8.Physical Property of Work Piece
The physical property of workpiece material effect tool life by affecting from stability and rate of wear of a cutting tool.
Tool life measured:
Tool life is the time interval for which the tool works satisfactorily between two successive grindings. tool life may be calculated in the following way:
The number of pieces machined.
Total time of operation.
The volume of material removed.
Time of actual operation, viz. , the time, the tool is in contact with the job.
Equivalent cutting speed.
The volume of metal removed from the workpiece between tool sharpening for a definite depth of cut, feed, and cutting speed can be determined as follows :
notation:
t = Depth of cut in mm
s = Feed-in mm per rev
d = Diameter of the workpiece in mm
T = Time to tool failure in min
n = Revolution per min of the workpiece
L = Tool life in term of metal removed until tool fails in mm3
V = Cutting speed in m per min
Length of a chip in one revolution = πd mm
Cross-section area of chip = t*s mm2
Volume of metal removed/rev = πd*t*s mm3
Volume of metal removed /min =Ï€ d t s n mm3 /min
Volume of metal removed until tool fails =Ï€ d t s n T mm3
L =Ï€dtsnT
V=(Ï€dn/1000 ) m/min
Tool-life L= 1000 ts VT mm3/min