Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
PowerPoint to accompany
Krar • Gill • Smid
Technology of Machine Tools6th Edition
Introduction To Machine Tools
Section 1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
PowerPoint to accompany
Krar • Gill • Smid
Technology of Machine Tools6th Edition
History of MachinesUnit 1
1-3
Objectives
• The development of tools throughout history
• The standard types of machine tools used in shops
• The newly developed space-age machines and processes
1-4
History of Machine Tools
• Began during stone age (<50,000 years ago)– Hand tools of wood, animal bones, or stone
• Bronze age (4500 to 4000 b.c.)– Copper and bronze implements
– Power-operated (animal power)
• Iron age (1000 b.c.)– Iron replaced bronze
– Domesticated animals provided power
– Commodities handmade by skilled craftspeople
1-5
History of Machine Tools
• Machine age (~300 years ago)– Explored new sources of energy (water)
• Industrial age began when James Watt produced first steam engine (1776)– Steam engine provided power to other areas– Machines improved
• Steam/steel in ships, railroads, steam tractors• New power – electricity produced by generators• Diesel and gasoline engines
1-6
History of Machine Tools
• Progress continued slowly during first part of 20th century– Spurts during the two world wars
• Since 1950s, progress rapid• Now in space age
– Atom harnessed: nuclear power– Journey to moon and outer space– Calculators, computers, robots commonplace– Can mass produce parts to millionths of an inch
1-7
Improved Production
• Constant improvement made modern machine tools more accurate and efficient
• Improved production and accuracy– Hydraulics– Pneumatics– Fluidics– Electronic devices
1-8
Common Machine Tools
• Generally power-driven metal-cutting or -forming machines used to shape metals– The removal of chips– Pressing, drawing, or shearing– Controlled electrical machining processes
1-9
Machine Tool Capabilities
• Holding and supporting the workpiece
• Holding and supporting a cutting tool
• Imparting a suitable movement (rotating or reciprocating) to the cutting tool or the work
• Feeding the cutting tool or the work so that the desired cutting action and accuracy will be achieved
1-10
Machine Tool Categories
• Four broad categories– Chip-producing machines– Non-chip-producing machines– New-generation machines– Multi-tasking machines
1-11
Chip-producing Machine
• Form metal to size and shape by cutting away unwanted sections
• Generally alter shape of steel-produced products– Casting– Forging – Rolling
1-12
Non-chip-producing Machines
• Form metal to size and shape by pressing, drawing, punching, or shearing
• Produce parts by compressing granular or powdered metallic materials
1-13
New-Generation Machines
• Perform operations that cannot be done on
chip- or non-chip-producing machines
• Use either electrical or chemical energy
1-14
Multi-tasking Machines
• Combined machining and turning center
• Can produce virtually any shape part from rough to finish
• Consists of turning center with two independent spindles and vertical machining center with rotary tool spindle
• Combine Information Technology (IT) and Manufacturing Technology (MT)
1-15
Machine Tool Performance
• Metal-removal rate– Depends upon cutting speed, feed rate, and depth
of cut
• Accuracy– How precisely machine can position cutting tool
to given location once
• Repeatability– Ability of machine to position cutting tool
consistently to any given position
1-16
General Machine Shop Tools
• Tools basic to production of metal components
• Operations most commonly performed: turning, boring, threading, drilling, reaming, sawing, milling, filing, and grinding
• Basic Machine tools– Drill press, engine lathe, power saw, milling
machine and grinder
1-17
Drill Press
• First mechanical device developed
• Used primarily to produce round holes
• Function to grip and revolve cutting tool
• Common operations– Drilling, reaming, spot facing, countersinking,
counterboring, and tapping
1-18
Engine Lathe
• Used to produce round work
• Workpiece held and mounted on lathe spindle which is revolved against cutting tool
• Common operations– Straight turning, tapering, facing, drilling, boring,
reaming, and thread cutting
1-19
Two Types of Metal Saw
• Reciprocating cutoff saw– Used to cut work to length only
• Bandsaw– Horizontal
• Used to cut work to length
– Vertical• Used to cut work to length and shape
Material in vise and saw bladebrought into contact with work
Material on table and brought into contactwith continuous-cutting saw blade
1-20
Milling Machine
• Two types: horizontal and vertical milling
• Use one or more rotating milling cutters with single or multiple cutting edges
• Workpiece fed into revolving cutter
• Accessories allow wide variety of operations– Drilling, reaming, boring, counterboring and spot
facing
1-21
Grinder
• Use abrasive cutting tool on workpiece– Bring to accurate size
– Produce high surface finish
• Surface of work brought into contact with revolving grinding wheel
1-22
Common Types of Grinders
• Surface– Used to produce flat, angular, or contoured surfaces
• Cylindrical– Used to produce internal and external diameters
• Cutter and Tool– Used to sharpen milling machine cutters
• Bench or Pedestal– Used for offhand grinding and sharpening
1-23
Special Machine Tools
• Designed to perform all operations necessary to produce single component
• Include– Gear-generating machines– Centerless, cam and thread grinders– Turret lathes– Automatic screw machines
1-24
Computer Numerical Control Machines (CNC)
• Brought tremendous changes
• Computer control of machines has allowed speed of production and undreamed of accuracies– Operating commands executed with speed,
accuracy, efficiency and reliability
• Replacing conventional machine tools operated by hand
1-25
CNC Equivalent of Engine Lathe
• Capable of machining round parts in one sixth time of skilled machinist
• Two centers– Chucking
• Designed to machine parts in a chuck (holding and driving device)
– Turning • Designed mainly for shaft-type workpieces supported
by some type of tailstock center
1-26
Machining Centers
• CNC equivalent of milling machine– Can change cutting tools
• Two types of machining centers– Vertical
• Used for flat parts where three-axis machining required
– Horizontal• Spindle in horizontal position• Allows parts to be machined on any side in one setup
if equipped with indexing table
1-27
Electrical Discharge Machines
• Use controlled spark erosion process between cutting tool and workpiece to remove metal
• Two most common EDM machines– Wire-cut
• Uses traveling wire to cut internal and external shapes of workpiece
– Vertical ram (die sinking machine)• Feeds form tool down into workpiece
1-28
Machining New Space-age Materials
• Produce shapes which were difficult or impossible to produce by other methods
• Four new machine tools– Electro-discharge machining– Electochemical machining– Electrolytic grinding– Laser machining
1-29
Robotics
• One of fastest-growing areas of manufacturing industry
• Numerical control applied to robots
• Capable of handling materials and changing machine tool accessories easily and efficiently
1-30
Lasers
• Used increasingly for cutting and welding
• Used in sensing devices for extremely accurate measuring and surveying
• Used for many materials beyond metals
1-31
Past Half Century Developments
• Slow development until early 1930s
• After 1932 automation introduced
• Great Depression provided lull in production and time used to upgrade machines
• AMT (Association for Manufacturing Technology) list of important developments in metalworking in text