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.

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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

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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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Climb milling

Conventional milling

Dimensions in face milling

Modern Machining Processes

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Electro Discharge Machine (EDM)

Wire-EDM

Electro Chemical Machining (ECM)

Laser Beam Machining (LBM)

Electron Beam Machining (EBM)

Water Jet Machining

Abrasive Jet Machining

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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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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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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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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

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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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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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Mitsubishi 2D/3D Laser Processing

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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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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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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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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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