manufacturing lecture
DESCRIPTION
manufacturing lectureTRANSCRIPT
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Manufacturing Technology – IME 307
Material Removal Processes
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
THEORY OF METAL MACHINING
1. Overview of Machining Technology
2. Theory of Chip Formation in Metal Machining
3. Force Relationships and the Merchant Equation
4. Power and Energy Relationships in Machining
5. Cutting Temperature
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
References:
Fundamentals of Modern Manufacturing: materials, processes, and systems, 3nd Ed., by Mikell P. Groover, JOHN WILEY & SONS, INC., 2007. (Chapter 21, pages 481-486)
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Material Removal Processes
A family of shaping operations, the common feature of which is removal of material from a starting workpart so the remaining part has the desired geometry
Machining – material removal by a sharp cutting tool, e.g., turning, milling, drilling
Abrasive processes – material removal by hard, abrasive particles, e.g., grinding
Nontraditional processes - various energy forms other than sharp cutting tool to remove material
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Fig 21.1 Classification of material removal processes
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Schematic illustration of the cutting processAfter K. Holmberg, A. Matthews. Coating Tribology: Properties, Techniques and
Applications in Surface Engineering, Elsevier, Amsterdam, 1994. (fig.7. 9)
Machining is a manufacturing process in which a sharp cutting tool is used to cut away material to leave the desired part shape.
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Cutting action involves shear deformation of work material to form a chip As chip is removed, new surface is exposed
Figure 21.2 (a) A cross‑sectional view of the machining process, (b) tool with negative rake angle; compare with positive rake angle in (a).
Machining
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Why Machining is Important
Variety of work materials can be machined Most frequently used to cut metals
Variety of part shapes and special geometric features possible, such as: Screw threads Accurate round holes Very straight edges and surfaces
Good dimensional accuracy (tolerances of ±0.025 mm are achievable)
Good surface finishes (Roughness values less than 0.4 microns achievable in conventional machining)
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Disadvantages with Machining
Wasteful of material Chips generated in machining are wasted
material, at least in the unit operation Time consuming
A machining operation generally takes more time to shape a given part than alternative shaping processes, such as casting, powder metallurgy, or forming
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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 workpart Machining provides the final shape,
dimensions, finish, and special geometric details that other processes cannot create
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Machining Operations
Most important machining operations: Turning Drilling Milling
Other machining operations: Shaping and planing Broaching Sawing
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Single point cutting tool removes material from a rotating workpiece to form a cylindrical shape rotating workpiece to generate a cylindrical shape,Tool feed is parallel to the axis of rotation of the workpiece.
Figure 21.3 Three most common machining processes: (a) turning,
Turning
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Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.
The Turning Operation
Figure 21.2 Schematic illustration of the turning operation showing various features.
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Basic principles of the turning operation
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Used to create a round hole, usually by means of a rotating tool (drill bit) with two cutting edges
Tool feed is parallel to its axis of rotation.
Figure 21.3 (b) drilling,
Drilling
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Drilling OperationAfter Ghosh, A. and Mallik, A.K. Manufacturing Science
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Rotating multiple-cutting-edge tool is moved across work to cut a plane or straight surface
Two forms: peripheral milling and face milling Tool feed is perpendicular to its axis of
rotation.
Figure 21.3 (c) peripheral milling, and (d) face milling.
Milling
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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Machining with multipoint toolsAfter Ghosh, A. and Mallik, A.K. Manufacturing Science
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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©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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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Figure 21.4 (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 Tools
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©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 (mm3/s)
where v = cutting speed m/s; f = feed mm (mm/rev for turning); d = depth of cut mm
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Cutting Conditions for Turning
Figure 21.5 Speed, feed, and depth of cut in turning.
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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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For Turning: Roughing cuts f = 0.4---1.25 mm/rev;
d = 2.5---20 mm Finishing cuts f = 0.125---0.4 mm/rev;
d = 0.75---2.0 mm
Cutting Fluid
is often applied to the machining operation to cool and lubricate the cutting tool.
Determining whether to use a cutting fluid
choosing the proper cutting fluid,
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
Characteristics of the typical operation of machining
Operation Sectional area of cut off layer, mm2
Energy for material removing10-3, J./cm3
Cutting speed, m/s
Productivity, sm3/sMRR
Turning 1,0 0,5…0,7 1,5…7,5 5∙10-2…5∙10
Broaching 0,5 2,5…3,7 0,01…0,1 4∙10-3…1∙10-1
Milling 0,3 5,0…7,5 2…6 2∙10-3…1,0
Reaming 0,1 12…30 0,15…1,6 5∙10-3…5∙10-1
Grinding 0,00005 55…70 25…50 5∙10-3…2∙10-2
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©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
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
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Conventional Machine Tools Used for the Three Common Machining Operations
Operation
Machine tool Definitions of speed, feed, and depth of cut
Turning Lathe Work rotates for speed motion.Tool is fed parallel to work axis.Depth of cut is tool penetration beneath original work surface.
Drilling Drill press Work is held stationary.Tool rotates and feeds in direction parallel to tool axis. Drill bit diameter determines hole diameter.Depth of cut is depth of hole.
Milling Milling machine
Tool rotates for speed motion.Work is fed in direction perpendicular to tool axis.Depth of cut is tool penetration beneath original surface.
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