introduction to machine tools

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