Manufacturing Process - Modern Machining Processes

MANUFACTURING PROCESSMANUFACTURING PROCESS(BMFG 2323)(BMFG 2323)

LECTURE 9LECTURE 9

~ MODERN MACHINING PROCESSES ~

Prepared and presented by: Masjuri Bin Musa @ Othman

Faculty of Mechanical Engineering(Department of Innovation & Engineering Design)

Universiti Teknikal Malaysia Melaka

MODERN MACHINING PROCESSESMODERN MACHINING PROCESSES 1

@jurie 2007 – Lecture 9

Examples of Parts Made by Advanced Examples of Parts Made by Advanced Machining ProcessesMachining Processes

Figure Examples of parts made by advanced machining processes. These parts are made by advanced machining processes and would be difficult or uneconomical to manufacture by conventional processes. (a) Cutting sheet metal with a laser beam. (b) Microscopic gear with a diameter on the order of 100 m, made by a special etching process.



General Characteristics

of Advanced Machining Processes

TABLE 26. 1

Process Characteristics

Process parameters andtypical material removal

rate or cutting speed

Chemical machining (CM) Shallow removal (up to 12 mm) on large flat orcurved surfaces; blanking of thin sheets; low toolingand cost; suitable for low production runs.

0.0025–0.1 mm/min.

Electrochemical machining(ECM)

Complex shapes with deep cavities; highest rate ofmaterial removal among nontraditional processes;expensive tooling and equipment; high powerconsumption; medium to high production quantity.

V: 5–25 dc; A: 1.5–8 A/mm2

;2.5–12 mm/min, dependingon current density.

Electrochemical grinding(ECG)

Cutting off and sharpening hard materials, such astungsten-carbide tools; also used as a honing process;higher removal rate than grinding.

A: 1–3 A/mm2

; Typically 25

mm3

/s per 1000 A.

Electrical-dischargemachining (EDM)

Shaping and cutting complex parts made of hardmaterials; some surface damage may result; also usedas a grinding and cutting process; expensive toolingand equipment.

V: 50–380; A: 0.1–500;

Typically 300 mm3

/min.

Wire EDM Contour cutting of flat or curved surfaces; expensiveequipment.

Varies with material andthickness.

Laser-beam machining(LBM)

Cutting and holemaking on thin materials; heat-affected zone; does not require a vacuum; expensiveequipment; consumes much energy.

0.50–7.5 m/min.

Electron-beam machining(EBM)

Cutting and holemaking on thin materials; very smallholes and slots; heat-affected zone; requires a vacuum;expensive equipment.

1–2 mm3

/min.

Water-jet machining (WJM) Cutting all types of nonmetallic materials to 25 mmand greater in thickness; suitable for contour cuttingof flexible materials; no thermal damage; noisy.

Varies considerably withmaterial.

Abrasive water-jet machining(AWJM)

Single or multilayer cutting of metallic andnonmetallic materials.

Up to 7.5 m/min.

Abrasive-jet machining(AJM)

Cutting, slotting, deburring, deflashing, etching, andcleaning of metallic and nonmetallic materials;manually controlled; tends to round off sharp edges;hazardous.

Varies considerably withmaterial.



Chemical Milling (CHM)Chemical Milling (CHM)

Figure (a) Missile skin-panel section contoured by chemical milling to improve the stiffness-to-weight ratio of the part. (b) Weight reduction of space launch vehicles by chemical milling aluminum-alloy plates. These panels are chemically milled after the plates have first been formed into shape by processes such as roll forming or stretch forming. The design of the chemically machined rib patterns can be modified readily at minimal cost.



CHEMICAL MACHINING

- Was developed from the observation that chemical attack and etch most metals, stones, and some ceramics, thereby removing small amounts of material from the surface.-The CM process is carried out by chemical dissolution using reagents or etchants such as acids and alkaline solutions.

CHEMICAL MILLING

-In this particular process, shallow cavities are produced on plates, sheets, forgings, and extrusions, generally for the overall reduction of weight.- This process has been used on a wide variety of metals with depths of metal removal as large as 12 mm.- Selective attack by the chemical reagent on different areas of the workpiece surfaces is controlled by removable layers of material called masking.- Some surface damage may result from chemical milling because of preferential etching and intergranular attack, which adversely affect surface properties.

Chemical MachiningChemical MachiningFigure: (a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process. (b) Stages in producing a profiled cavity by chemical machining; note the undercut.





CHEMICAL BLANKING

-The process is similar to the blanking of sheet metals that is used to produce features which penetrate through the thickness of the material, with the exception that the material is removed by chemical dissolution rather than by shearing.- The application for chemical blanking are the burr-free etching of printed-circuit board, thin sheet metal stampings.

PHOTOCHEMICAL BLANKING (PHOTOETCHING)

-It is a modification of chemical milling process.- Material is removed (usually from a flat thin sheet) by photographic techniques.- Complex, burr free shapes can be blanked on metals as thin as 0.0025 mm.



Chemical Blanking and Electrochemical Machining (ECM)

Figure: Schematic illustration of the electrochemical-machining process.

Figure: Various parts made by chemical blanking. Note the fine detail.

Material removal by anodic dissolution, using electrode (tool) in close proximity to the work but separated by a rapidly flowing electrolyte.



ECM OperationECM Operation1. Material is deplated from anode workpiece (+ve pole) and

transported to a cathode tool (-ve pole) in an electrolyte bath.

2. Electrolyte flows rapidly between the two poles to carry off deplated material, so it does not plate onto tool.

3. Electrode materials: Cu, brass, or stainless steel

4. Tool has inverse shape of part i.e. tool size and shape must allow for the gap.

5. Based on Faraday’s 1st Law: amount of chemical change (amount of metal dissolved) is proportional to the qty of electricity passed (current x time); V = Citwhere V = volume of metal removed; C = specific removal rate which work material; I = current; and t = time



ECM ApplicationsECM Applications

1. Die sinking – irregular shapes and contours for forging dies, plastic molds, and other tools.

2. Multiple hole drilling – many holes can be drilled simultaneously with ECM

3. Holes that are not round, since rotating drill is not used in ECM

4. Deburring



Examples of Parts Made by ECMExamples of Parts Made by ECM

Figure: Typical parts made by electrochemical machining. (a) Turbine blade made of a nickel alloy, 360 HB; note the shape of the electrode on the right. (b) Thin slots on a 4340-steel roller-bearing cage. (c) Integral airfoils on a compressor disk.



Electrochemical Grinding (ECG)Electrochemical Grinding (ECG)

Figure: (a) Schematic illustration of the electrochemical-grinding process. (b) Thin slot produced on a round nickel-alloy tube by this process.

Special form of ECM in which a grinding wheel with conducive bond material is used to augment anodic dissolution of metal part surface.



ECG ApplicationsECG Applications

1. Sharpening of cemented carbide tools

2. Grinding of surgical needless, other thin wall tubes, and fragile parts.

3. Deplating responsible for 95% of metal removal, and abrasive action removes remaining 5%.

4. Because machining is mostly by electrochemical action, grinding wheel lasts much longer (less frequent dressing)



Electrical-Discharge Machining (EDM)Electrical-Discharge Machining (EDM)(a)

(b)

Figure: (a) Schematic illustration of the electrical-discharge machining process. This is one of the most widely used machining processes, particularly for die-sinking operations. (b) Examples of cavities produced by the electrical-discharge machining process, using shaped electrodes. Two round parts (rear) are the set of dies for extruding the aluminum piece shown in front.



EDM OperationsEDM Operations1. Only electrically conducting work materials.

2. Hardness and strenght of the work material are not factors in EDM.

3. Material removal rate is related to melting point of work material.

4. Shape of finished work surface produced by a formed electrode tool.

5. Sparks occur across a small gap between tool and work.

6. Requires dielectric fluid, which creates a path for each discharge as fluid becommes ionized in the gap.



Examples of EDMExamples of EDMFigure shows stepped cavities produced with a square electrode by the EDM process. The workpiece moves in the two principal horizontal directions (x-y), and its motion is synchronized with the downward movement of the electrode to produce these cavities. Also shown is a round electrode capable of producing round or elliptical cavities

Figure shows schematic illustration of producing an inner cavity by EDM, using a specially designed electrode with a hinged tip, which is slowly opened and rotated to produce the large cavity



Wire EDMWire EDM

Figure: (a) Schematic illustration of the wire EDM process. As much as 50 hours of machining can be performed with one reel of wire, which is then discarded. (b) Cutting a thick plate with wire EDM. (c) A computer-controlled wire EDM machine.

Special form of EDM that uses small diameter wire as electrode to cut a narrow kerf in work



Laser-Beam Machining (LBM)

Figure (a) Schematic illustration of the laser-beam machining process. (b) and (c) Examples of holes produced in nonmetallic parts by LBM.

Uses the light energy from a laser to remove material by vaporization and ablation.



LBM Operation

Laser - Light amplification by stimulated emission of radiation.

• A laser converts electrical energy into a highly coherent light beam with the following properties:- monochromatic (theoretically, single wave length)- highly colimated (light rays are almost perfectly parallel)

2. These properties allow laser light to be focused, using optical lenses, onto a very small spot with resulting high power densities.



LBM Applications

1. Drilling, slitting, slotting, scribing, and marking operations

2. Drilling small diameter holes down to 0.025 mm (0.001 in)

3. Generally used on thin stock

4. Work materials: metals with high hardness and strength, soft metals, ceramics, glass and glass epoxy, plastics, rubber, cloth, and wood.



Water-Jet Machining (WJC)

Figure (a) Schematic illustration of water-jet machining. (b) A computer-controlled, water-jet cutting machine cutting a granite plate. (c) Examples of various nonmetallic parts produced by the water-jet cutting process.

(c)

Uses a fine, high pressure, high velocity stream of water directed at work surface for cutting.



WJC Applications

1. Usually automated by CNC or industrial robots to manipulate nozzle along desired trajectory.

2. Used to cut narrow slits in flat stock e.g. plastic, textiles, composites, floor tile, carpet, leather, and cardboard.

3. Jet nozzle diameters range 0.05 to 1 mm. The smaller the narrow groove in the material.

4. Not suitable for brittle materials e.g. glass.

5. No crushing or burning of work surface, minimum material loss, no environmental pollution, and ease of automation.



Abrasive Water Jet Machining (AWJC)

• Similar to WJC but abrasive particles is added into the water jet stream.

• Used on metals.

• Additional process parameters: abrasive type, grit size, and flow rate.- abrasives: aluminum oxide, silicon dioxide, and garnet (a silicon mineral)- grit size range between 60 and 120

4. Abrasive type, grit size, and flow rate determine the material removal rate of the material.

5. Uses rubies, sapphires, and carbide based composite materials to improved nozzle life.



Abrasive Jet Machining (AJM)

Figure Schematic illustration of the abrasive-jet machining process.

High velocity of gas containing small abrasive particles.



AJM Applications

1. Usually performed manually by operator who directs nozzle.

2. Normally used as a finishing process rather than cutting process.

3. Use for deburring, trimming and deflashing, cleaning, and polishing.

4. Work materials e.g. thin flat stock of hard, brittle materials such as glass, silicon, mica, ceramics.

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Manufacturing Process - Modern Machining Processes