1. Factors Affecting Tool Life In Machining
Processes

2. Factors Affecting Tool Life In Machining Processes
What are these??

3. Factors Affecting Tool Life
In Machining Processes
ME 572
Analysis of Manufacturing Processes
Mohammad AlJuhani

4. Factors Affecting Tool Life In Machining Processes
Introduction
Tool Life and Machinability
Tool Damage
Causes of tool damage
Factors Affecting Tool Life in Machining Processes

5. Factors Affecting Tool Life In Machining Processes
• Cutting tool life is important consideration in metal cutting
processes.
• In machining operations, cutting conditions such as tool angles,
cutting speeds and feed rates are usually selected to give an
economical tool life.
• Conditions giving a short tool life are uneconomical because
tool grinding and tool replacement costs are high.
• Factors affecting tool life should be carefully monitored to
minimize their consequences.

6. Factors Affecting Tool Life In Machining Processes
• A tool that doesn’t perform the desired function can be declared as
failed, or reached the end of its useful life.
• At this point of time, the tool is not necessarily unable to cut the
workpiece but is merely unsatisfactory (may not give the desired
surface finish or dimensional tolerances) for the purpose required
• The tool life is defined as the length of cutting time that the tool
can be used.
Tool Life and Machinability

7. Factors Affecting Tool Life In Machining Processes
• Tool damage can be classified into two groups, wear and fracture by means of its scale
and how it progresses.
• Wear is loss of material on an asperity or micro-contact, or smaller scale, down to
molecular or atomic removal mechanisms. It usually progresses continuously.
• There are two main types of tool wear
• Flank wear
• Crater wear
• Fracture, on the other hand, is damage at a larger scale than wear and it occurs
suddenly.
Tool Damage

8. Factors Affecting Tool Life In Machining Processes
Tool damage. Flank wear vs. cutting time

9. Factors Affecting Tool Life In Machining Processes
Mechanical Damage
Thermal Damage
Adhesion
Causes of tool damage

10. Factors Affecting Tool Life In Machining Processes
Mechanical Damage
Mechanical
Damage
FractureChippingAbrasion Fatigue
It is independent of temperature.
Causes of tool damage

11. Factors Affecting Tool Life In Machining Processes
Causes of tool damage
Mechanical Damage

12. Factors Affecting Tool Life In Machining Processes
Thermal
Damage
Plastic
deformation
DiffusionChemical
reaction
It increases drastically with increasing
temperature
Causes of tool damage

13. Factors Affecting Tool Life In Machining Processes
Causes of tool damage

14. Factors Affecting Tool Life In Machining Processes
Causes of tool damage

15. Factors Affecting Tool Life In Machining Processes
Occurs when work or chip material welds to
the tool surface.
Adhesion Damage
Causes of tool damage

16. Factors Affecting Tool Life In Machining Processes
Causes of tool damage

17. Factors Affecting Tool Life In Machining Processes
Factors
Affecting
Tool Life
Cutting Tool
Geometry
Cutting Tool
Material
Cutting Tool
Characteristic
s
Cutting
Conditions
Workpiece
Material.
Cutting Fluid

18. Geometry of
cutting tool
varies with
Type of
operation being
performed,
Surface finish
requirements.
Power and
speed of
machine
Workpiece
material,
Factors Affecting Tool Life In Machining Processes
Cutting Tool
Geometry

19. Cutting
tool
geometry
is directly
affects
Machined
surface
quality.
Productivity
of
machining.
Chip
control.
Magnitude and
direction of the
cutting forces
Tool life.
Distribution of
the thermal
energy
Temperature
distribution in
the cutting
wedge
Factors Affecting Tool Life In Machining Processes
Cutting Tool
Geometry

20. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Geometry

21. Factors Affecting Tool Life In Machining Processes
Rake angle
Rake angles are three types, positive, zero and negative.
For ductile materials, the rake inclination is a positive angle
Since their shearing is low.
For brittle materials, the rake inclination is a negative angle.
The advantages of increasing rake angle
• Reduces the horsepower consumption.
• The cutting force and tool-chip contact temperature change in
approximately the same way.
The disadvantages of increasing rake angle
• The strength of the cutting wedge decreases when the rake angle
increases.
• The region of the maximum contact temperature at the tool-chip
interface shifts toward the cutting edge.
Cutting Tool
Geometry

22. Factors Affecting Tool Life In Machining Processes
Flank angle
The flank angle affects the performance of the cutting tool
mainly by decreasing the rubbing between the tool
surface and workpiece surface.
With increasing the flank angle the following advantages
are obtained:
• Cutting edge radius decreases which leads to decrease in
the frictional and deformation components of the flank
force.
• The strength of the region adjacent to the cutting edge
decreases.
• Heat dissipates through the tool decreases.
Cutting Tool
Geometry

23. Factors Affecting Tool Life In Machining Processes
Nose Radius
Nose radius is very critical part of the cutting edge.
If the radius is made of sharp angle, the produced finished surface will
be rough and tool life will be short.
A large nose radius benefits
• Better surface finish.
• Faster feed rate.
• Stronger tool.
• Allow faster cutting speed
However, large radii have negative sequences such as tool chatter.
Cutting Tool
Geometry

24. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Material
Factorsaffectingselection
cuttingtoolmaterial
The cutting operation
involved
Workpiece material
Production
requirements
Surface finish and
accuracy requirements.
Machine to be used

25. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Material
Major qualities required
in a cutting tool
Resistance to heat
(hot hardness)
Resistance to
mechanical impact
thermal shock.
Resistance to wear
(hardness)
Resistance to fracture
(toughness)
Chemical stability to the
workpiece material

26. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Material

27. Factors Affecting Tool Life In Machining Processes
Today, 50% of HSS, 85% of carbide and 40% of super-hard tools
used in industry are coated
Cutting Tool
Material
Cutting
Tool
Coating
Improve
wear
resistance
Reduce
thermal
conductivity.
Reduce
frictional
contact.

28. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Material
Uncoated cutting tool Coated cutting tool

29. Factors Affecting Tool Life In Machining
Processes
CuttingToolCharacteristics
Tostandagainsthighstress
Pressure resistance.
Bending strength.
Edge strength.
Inner bonding strength.
High temperature strength.
Small propensity to diffusion and
adhesion (Chemically stable).
Abrasion resistance.
Reproducible wear behavior.
Cutting Tool
Characteristics

30. Factors Affecting Tool Life In Machining Processes
Depth of cut
Feed rate
Cutting Speed
Cutting
Conditions

31. Factors Affecting Tool Life In Machining Processes
Cutting
Conditions
Depth of cut
Feed rate
Cutting Speed

32. Factors Affecting Tool Life In Machining Processes
Cutting
Conditions
Depth of cut
Feed rate
Cutting Speed

33. Factors Affecting Tool Life In Machining Processes
Depth of cut
Feed rate
Cutting Speed
Cutting
Conditions

34. Factors Affecting Tool Life In Machining Processes
Cutting
Conditions
Depth of cut
Feed rate
Cutting Speed

35. Factors Affecting Tool Life In Machining Processes
Depth of cut has least effect upon tool life, so the heaviest (10 times the
feed rate) possible depth of cut should always be used.
Depth of cut is limited by
• Amount of metal to be machined from the workpiece,
• Power available on machine tool,
• Rigidity of the work piece and cutting tool
• Rigidity of the setup.
• Workpiece configuration
• Insert size & thickness
Cutting
Conditions
Depth of cut
Feed rate
Cutting Speed

36. Factors Affecting Tool Life In Machining Processes
Cutting
Conditions
Depth of cut
Feed rate
Cutting Speed

37. Factors Affecting Tool Life In Machining Processes
Machinability
of workpiece
criteria
Tool life
Surface
roughness
Surface
integrity
Magnitude of
cutting
forces
Energy
(power)
consumption
Workpiece
Material.

38. Factors Affecting Tool Life In Machining Processes
Factors
determine
conditions of
the work
material
Microstructure.
Grain size.
Heat
treatment.
Chemical
composition.
Fabrication
Yield and
tensile
strength.
Hardness
Workpiece
Material.

39. Factors Affecting Tool Life In Machining Processes
Main Cutting
Fluid Functions
Lubrication effect Cooling effect
Removing chips
away from the
cutting zone
Cutting
Fluid

40. Factors Affecting Tool Life In Machining Processes
Otherfunctionsofcuttingfluids
Reduction of cutting forces/
energy consumptions.
Improvement of surface finish
and dimensional accuracy.
Extend tool life.
Facilitate chip removal.
Corrosion prevention on
workpiece and machines.
Lowering workpiece
temperature.
Lubrication of machine tool
sliding guides
Cutting
Fluid

41. Factors Affecting Tool Life In Machining Processes
Cuttingfluidsproperties
Good lubricating
properties
High cooling capacity
Low viscosity to provide
free flow of cutting fluid.
Chemically stable.
Non-corrosive.
High flash point to reduce
fire risks.
Allergy free.
Less evaporative.
Low cost.
Cutting
Fluid

42. Cutting Fluids
Selection
Type of machining
processes.
Type of
machined
workpiece
material.
Type of cutting
tool material.
Factors Affecting Tool Life In Machining Processes
Cutting
Fluid

43. Factors Affecting Tool Life In Machining Processes
Cutting
Fluid
CuttingFluidEffects
Environmental
Biodegradability
Life cycle
assessment
Bioaccumulability
and
biomagnifications
Energy saving and
fuel economy
Renewability
Health
Respiratory
problems.
Dermatological
problems

44. Factors Affecting Tool Life In Machining Processes
Environmental
machining
Dry cutting
Minimum
quantity
lubricant
Vegetable
based cutting
fluids
Cutting
Fluid

45. Factors Affecting Tool Life In Machining Processes

46. Factors Affecting Tool Life In Machining
Processes

47. Factors Affecting Tool Life In Machining Processes
Cutting Tool
Geometry