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Manufacturing processes
PART 1
A.POURMIKAEIL
1
Manufacturing processes
PART 1
A.POURMIKAEIL
2
MATERIAL REMOVAL
PROCESSES
3
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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Classification description 2
Abrasive machining Removed material by hard & abrasive
particle Classified in two group:
Grinding Other abrasive
Honing Lapping Super finishing
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Classification description 3
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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.
©2007 John Wiley & Sons, Inc. M P
Groover, Fundamentals of
Modern Manufacturing 3/e
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.
©2007 John Wiley & Sons, Inc. M P
Groover, Fundamentals of
Modern Manufacturing 3/e
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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
©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern
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
©2007 John Wiley & Sons, Inc. M P
Groover, Fundamentals of
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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