Cutting Tool Materials
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High-speed steel are the most common cutting tool material used
Cemented Carbide
− are composed primarily of carbon mixed with tungsten, tantalum and titanium powders and bonded by cobalt in a sintering process. − have excellent red hardness capabilities. − can remove large amounts of materials in a short period of time. − are capable of CS 3−4 times greater than HSS cutting tools.
− are inexpensive when compared to other materials. − capable of withstanding heavy shocks or interrupted cuts. − are easier to grind.
Introduction / machinning of metal 26
Cemented carbide tools are used on a lathe in 2 ways :- Brazed
Throwaway inserts Brazed inserts
Throwaway inserts
Oxides
− latest developments in cutting tool materials made from Aluminum oxide with nickel binder. − have very low heat conductivity, high strength but brittle
− are not generally used where interrupted cuts are required. − can withstand CS 2−3 times faster than carbide tool
Generally referred to as ceramic cutting tool
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Cutting Tool Materials
must have certain characteristic
• Hardness particularly at elevated temperature (hot hardness) • Toughness so that impact force do not chip or fracture the tool • Wear resistance
• Chemical stability or inertness
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Cutting Tool Materials
Machining Parameters
Introduction / machinning of metal 29
ft/min .)(
)(12 )(
inD
CSedcuttingsperpmN
(mm) D
(mm/min) CS
rpmFor metric system
Cutting Speed
D = The diameter of the workpiece / tool N = Rotational Speed (rpm) of the workpiece / tool
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Power = Torque x Rotational speed (radians/second)
Power = Specific energy x MRR
Operating Drilling Machine
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Material Removal Rate MRR is the volume of material removed by the drill per unit time.
min/mm 4/D 32 NfMRR
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Operating Turning Machine
min/mm 3NfdDMRR avg
d = Depth of cut
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Operating Turning Machine
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Operating Milling Machine
SLAB MILLING FACE MILLING END MILLING
Up milling
Down milling
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Operating Milling Machine
FEED FEED
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Operating Milling Machine
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Introduction / machinning of metal 38
Climb milling
Conventional milling
Dimensions in face milling
Modern Machining Processes
Introduction / machinning of metal 39
Electro Discharge Machine (EDM)
Wire-EDM
Electro Chemical Machining (ECM)
Laser Beam Machining (LBM)
Electron Beam Machining (EBM)
Water Jet Machining
Abrasive Jet Machining
Introduction / machinning of metal 40
EDM - Electrical Discharge Machining
Remove metal by the eroding action of small electrical spark.
(electrically non-conductivity)
(Negative polarity)
(Positive polarity)
(to reduce the gap as the w.p. is eroded)
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Introduction / machinning of metal 41
EDM - Electrical Discharge Machining
Electrode tool materials
- Graphite and Copper - Alloy of zinc and tin - Cu-tungsten, Silver-tungsten
(Spark 8,300 – 16,600 oC)
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Introduction / machinning of metal 42
Application
- Hard, difficult to machine metals - Able to machine burr-free, intricate configuration, narrow slots and blind cavities or holes.
EDM - Electrical Discharge Machining
Milling
EDM
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Introduction / machinning of metal 43
Wire EDM
Uses a slender wire as an electrode. Extremely useful for narrow slots and detailed internal features in the workpiece.
(can cut plate as thick as 300 mm)
Wire made of brass, copper, tungsten App. 0.25 mm diameter
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Wire EDM
Introduction / machinning of metal 44
Parts produced by wire EDM
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Introduction / machinning of metal 45
ECM - Electrochemical Machining
Is the process of removing metal from a workpiece by a reverse plating action.
- produce burr-free finish - no danger of any metallurgical damage
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Introduction / machinning of metal 46
LBM - Laser Beam Machining
A laser is a device to produce a beam of light.
The highly focused, high density energy melts and evaporates portion of w.p.
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Good for low reflectivity and low thermal conductivity material.
Laser Beam Machining
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Parts produced by laser cutting
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Laser Beam Machining
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Laser Beam Machining
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Introduction / machinning of metal 50
Mitsubishi 2D/3D Laser Processing
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Introduction / machinning of metal 51
EBM - Electron Beam Machining
The source of energy is high velocity electrons, which strike the surface of the workpiece and generate heat.
The applications are similar to those of LBM, except that EBM requires a vacuum.
¾ of light speed
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Introduction / machinning of metal 52
Water Jet Machining
A pressure of about 400 Mpa is generally use for efficient operation.
Jet nozzle diameters usually range between 0.05 mm and 1 mm.
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Introduction / machinning of metal 53
Materials can be cut with this technique - plastics, fabric, rubber, wood, paper, leather, brick, and composite materials
Advantages
- cut can be start at any location. - no heat is produced, no deflection - environment safe manufacturing process.
Water Jet Machining
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Introduction / machinning of metal 54
Abrasive-Jet Machining
A high-velocity jet of dry air, nitrogen, or carbon dioxide containing abrasive particles is aimed at the workpiece surface under controlled condition.
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Introduction / machinning of metal 55
The impact of particles develops sufficient concentrated force to perform :
- cutting small holes, slots, or intricate patterns - deburring or removing small flash from parts - trimming and beveling - general cleaning of components
Abrasive-Jet Machining
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