1. Factors Affecting Tool Life In Machining Processes

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

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

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

5. INTRODUCTION
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.
Factors Affecting Tool Life In Machining Processes

6. Tool Life and Machinability
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.
Factors Affecting Tool Life In Machining Processes

7. Tool Damage
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.
Factors Affecting Tool Life In Machining Processes

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

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

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

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

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

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

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

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

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

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

18. Geometry of cutting tool varies with
Cutting Tool Geometry
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

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

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

21. Rake angle Rake angles are three types, positive, zero and negative.
Cutting Tool Geometry
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.
Factors Affecting Tool Life In Machining Processes

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

23. Nose Radius Nose radius is very critical part of the cutting edge.
Cutting Tool Geometry
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.
Factors Affecting Tool Life In Machining Processes

24. Factors affecting selection cutting tool material
The cutting operation involved
Workpiece material
Production requirements
Surface finish and accuracy requirements.
Machine to be used
Factors Affecting Tool Life In Machining Processes

25. 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
Factors Affecting Tool Life In Machining Processes

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

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

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

29. Cutting Tool Characteristics
To stand against high stress
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.
Factors Affecting Tool Life In Machining Processes

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

31. Cutting speed has the greatest influence on tool wear and tool life.
Depth of cut
Feed rate
Cutting Speed
Cutting Conditions
Cutting speed has the greatest influence on tool wear and tool life.
Most materials can be machined over a wide range of speeds.
When a shorter tool life is allowable the speed can be increased
Relationship between tool life and cutting speed is expressed by Taylor equation for tool life
𝑉 𝑇 𝑛 =𝐶
Factors Affecting Tool Life In Machining Processes

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

33. Limitations to maximizing feed rate
Depth of cut
Feed rate
Cutting Speed
Cutting Conditions
Feed rate changes have a less effect on tool life than cutting speed does.
Relationship between tool life and cutting conditions is expressed by modified Taylor equation
𝑉 𝑇 𝑛 𝑓 𝑎 𝑑 𝑏 = 𝑘 𝑡
Limitations to maximizing feed rate
Horsepower available on the machine tool.
Chip groove geometry.
Surface finish required.
Part configuration.
Factors Affecting Tool Life In Machining Processes

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

35. Depth of cut is limited by
Feed rate
Cutting Speed
Cutting Conditions
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
Factors Affecting Tool Life In Machining Processes

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

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

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

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

40. Other functions of cutting fluids
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
Factors Affecting Tool Life In Machining Processes

41. Cutting fluids properties
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.
Factors Affecting Tool Life In Machining Processes

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

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

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

45. Factors Affecting Tool Life In Machining Processes

46. Thank you
Factors Affecting Tool Life In Machining Processes

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