Manufacturing processes PART 1 PART 1 A.POURMIKAEIL A.POURMIKAEIL 1.

Manufacturing processes

PART 1

A.POURMIKAEIL

1

Manufacturing processes

PART 1

A.POURMIKAEIL

2

MATERIAL REMOVAL

PROCESSES

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INTRODUCTION OF METAL CUTTING

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MACHINING

TRADITIONAL MACHINING

TURNINGAND

RELATED

DRILLNG AND RELATED

MILLING

ABRASIVE MACHINING

GRINDING

OTHERABRASIVE

NONTRADITIONAL MACHINING

MECHANICAL ENERGY

ELECTROCHEMICAL

THERMALENERGY

CHEMICALMACHINING

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Figure 1:Classification of Material Removal Process

©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern

Manufacturing 3/e

Classification description 1

Conventional machining The most important branch Use sharp cutting tool Three principal

Turning Drilling Milling

Others machining operation

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Abrasive machining Removed material by hard & abrasive

particle Classified in two group:

Grinding Other abrasive

Honing Lapping Super finishing

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Nontraditional processes Use various energy forms other than

sharp cutting tools or abrasive particles to remove materials.

Classified into four group Mechanical Electrochemical Thermal chemical

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MachiningCutting action involves shear deformation of work material to form a chip As chip is removed, new surface is exposed


Manufacturing 3/e

Figure 2: (a) A cross‑sectional view of the machining process, (b) tool with negative rake angle; compare with positive rake angle in (a).

Advantages

Variety of work materials Metals Plastics Ceramics (in some technology) compsites

Variety of part shapes and geometry features. All regular geometry by combination several machining

operation in sequence, shapes of almost unlimited complexity and variety are produced.

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Advantages (continued)

Dimensional accuracy Some technology achieve 0.025 mm

tolerance . Good surface finishes

Very smooth surface Less than 0.4 microns Some abrasive processes better than

this

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Disadvantages

Waste of materials

Time consumption

Machining is generally performed after other processes.

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Machining in Manufacturing Sequence

Generally performed after other manufacturing processes, such as casting, forging, and bar drawing Other processes create the general shape of

the starting work part Machining provides the final shape,

dimensions, finish, and special geometric details that other processes cannot create

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Overview of machining technology

Most important machining operations: Turning Drilling Milling

Other machining operations: Shaping and planning Broaching Sawing

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Turning

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Single point cutting tool removes material from a

rotating work piece to form a cylindrical shape

Figure 3: Three most common machining processes: (a) turning,

©2007 John Wiley & Sons, Inc. M P

Groover, Fundamentals of

Modern Manufacturing 3/e

Drilling

Used to create a round hole, usually by means of a rotating tool (drill bit) with two cutting edges

Figure 4 (b) drilling,

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Manufacturing 3/e

MillingRotating multiple-cutting-edge tool is

moved across work to cut a plane or straight surface

Two forms: peripheral milling and face milling

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Figure 5: (c) peripheral milling, and (d) face milling ©2007 John Wiley & Sons, Inc. M P

Groover, Fundamentals of Modern Manufacturing 3/e

Cutting tool classification

1. Single-Point Tools One dominant cutting edge Point is usually rounded to form a nose radius Turning uses single point tools

2. Multiple Cutting Edge Tools More than one cutting edge Motion relative to work achieved by rotating Drilling and milling use rotating multiple

cutting edge tools

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Cutting tools

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Figure 6: (a) A single‑point tool showing rake face, flank, and tool point; and (b) a helical milling cutter, representative of tools with multiple cutting edges.




Cutting Conditions in Machining

Three dimensions of a machining process: Cutting speed v – primary motion Feed f – secondary motion Depth of cut d – penetration of tool below

original work surface

For certain operations, material removal rate can be computed as

RMR = v f d where v = cutting speed; f = feed; d = depth of cut 20

Cutting Conditions for Turning

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Figure 7: Speed, feed, and depth of cut in turning.




Roughing vs. Finishing

In production, several roughing cuts are usually taken on the part, followed by one or two finishing cuts

Roughing - removes large amounts of material from starting workpart Creates shape close to desired geometry, but

leaves some material for finish cutting High feeds and depths, low speeds

Finishing - completes part geometry Final dimensions, tolerances, and finish Low feeds and depths, high cutting speeds

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Machine Tools

A power‑driven machine that performs a machining operation, including grinding

Functions in machining: Holds workpart Positions tool relative to work Provides power at speed, feed, and depth that

have been set

The term is also applied to machines that perform metal forming operations 23

Chip Formation

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Figure 8: More realistic view of chip formation, showing shear zone rather than shear plane. Also shown is the secondary shear zone resulting from tool‑chip friction.

©2007 John Wiley & Sons, Inc. M P Groover,

Fundamentals of Modern Manufacturing 3/e

Four Basic Types of Chip in Machining

1. Discontinuous chip

2. Continuous chip

3. Continuous chip with Built-up Edge (BUE)

4. Serrated chip

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Discontinuous Chip

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Brittle work materialsLow cutting speedsLarge feed and depth of cut

High tool‑chip friction

Figure 9: Four types of chip formation in metal cutting: (a) discontinuous


Manufacturing 3/e

Continuous Chip

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Ductile work materials High cutting speeds Small feeds and depths Sharp cutting edge Low tool‑chip friction

Figure 10: (b) continuous©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern

Manufacturing 3/e

Continuous with BUE

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Ductile materialsLow‑to‑medium cutting speeds

Tool-chip friction causes portions of chip to adhere to rake face

BUE forms, then breaks off, cyclically

Figure 11: (c) continuous with built‑up edge


Manufacturing 3/e

Serrated Chip

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Semicontinuous - saw-tooth appearanceCyclical chip forms with alternating high shear strain then low shear strain Associated with difficult-to-machine metals at high cutting speeds Figure 12: (d) serrated


Manufacturing 3/e

Forces Acting on Chip

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Friction force F and Normal force to friction N Shear force Fs and Normal force to shear Fn

Figure13: Forces in metal cutting: (a) forces acting on the chip in orthogonal cutting


Manufacturing 3/e

Cutting Force and Thrust Force

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F, N, Fs, and Fn cannot be directly measuredForces acting on the tool that can be measured:

Cutting force Fc and Thrust force Ft

Figure14: Forces in metal cutting: (b) forces acting on the tool that can be measured


Manufacturing 3/e

Effect of Higher Shear Plane Angle

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Higher shear plane angle means smaller shear plane which means lower shear force, cutting forces, power, and temperature

Figure 15: Effect of shear plane angle : (a) higher with a resulting lower shear plane area; (b) smaller with a corresponding larger shear plane area. Note that the rake angle is larger in (a), which tends to increase shear angle according to the Merchant equation



Modern Manufacturing

3/e

Cutting Temperature

Approximately 98% of the energy in machining is converted into heat

This can cause temperatures to be very high at the tool‑chip

The remaining energy (about 2%) is retained as elastic energy in the chip

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Cutting Temperatures are Important

High cutting temperatures 1. Reduce tool life2. Produce hot chips that pose safety

hazards to the machine operator3. Can cause inaccuracies in part

dimensions due to thermal expansion of work material

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Manufacturing processes PART 1 PART 1 A.POURMIKAEIL A.POURMIKAEIL 1.

Documents

manufacturing processes

common machining processes

p groover

micronssome abrasive

exposed2007 john wiley

cutting edges figure

sharp cutting tools

b tool