manufacturing automation

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian Schmid 2008, Pearson EducationISBN No. 0-13-227271-7

Automation in Manufacturing

FIGURE 14.1 Outline of topics described in this chapter.

Flexible fixturing

Assembly Robots Material handling

Design for assembly, disassembly, and service

Fixed sequence, variable sequence, playback, NC, intelligent

Manipulators, automated guided vehicles

AC optimization

AC constraint

Computer NC

Adaptive control

Numerical control

Programming

Direct NC

Computer aided

Manual

Soft automation

Hard automation

Transfer machines

Automation of manufacturing processes Sensors


History of AutomationDate Development1500-1600 Water power for metalworking; rolling mills for coinage strips.1600-1700 Hand lathe for wood; mechanical calculator.1700-1800 Boring, turning, and screw cutting lathe, drill press.1800-1900 Copying lathe, turret lathe, universal milling machine; advanced mechanical calcu-

lators.1808 Sheet-metal cards with punched holes for automatic control of weaving patterns in

looms.1863 Automatic piano player (Pianola).1900-1920 Geared lathe; automatic screw machine; automatic bottle-making machine.1920 First use of the word robot.1920-1940 Transfer machines; mass production.1940 First electronic computing machine.1943 First digital electronic computer.1945 First use of the word automation.1947 Invention of the transistor.1952 First prototype numerical control machine tool.1954 Development of the symbolic language APT (Automatically Programmed Tool);

adaptive control.1957 Commercially available NC machine tools.1959 Integrated circuits; first use of the term group technology.1960 Industrial robots.1965 Large-scale integrated circuits.1968 Programmable logic controllers.1970s First integrated manufacturing system; spot welding of automobile bodies with

robots; microprocessors; minicomputer-controlled robot; flexible manufacturing sys-tem; group technology.

1980s Artificial intelligence; intelligent robots; smart sensors; untended manufacturingcells.

1990-2000s Integrated manufacturing systems; intelligent and sensor-based machines; telecom-munications and global manufacturing networks; fuzzy-logic devices; artificial neuralnetworks; Internet tools; virtual environments; high-speed information systems.

TABLE 14.1 Developments in the history of automation and control of manufacturing processes. (See also Table 1.1.)


Flexibility and Productivity

FIGURE 14.2 Flexibility and productivity of various manufacturing systems. Note the overlap between the systems, which is due to the various levels of automation and computer control that are applicable in each group. See also Chapter 15 for more details.

Transfer line

Conventional flowline

Flexible manufacturing

line

Conventional job shop

Flexible manufacturing

system

Increasing productivity

Incre

asin

g f

lexib

ility

Soft automation Hard automation

Manufacturing cell

Stand-alone NC production

Type of production Number produced Typical productsExperimental or prototype 1-10 All typesPiece or small batch < 5000 Aircraft, machine tools, diesBatch or high quantity 5000-100,000 Trucks, agricultural machinery, jet engines, diesel

engines, orthopedic devicesMass production 100,000+ Automobiles, appliances, fasteners, bottles, food

and beverage containers

TABLE 14.2 Approximate a n n u a l q u a n t i t y o f production.


Characteristics of Production

FIGURE 14.3 General characteristics of three types of production methods: job shop, batch production, and mass production.

Production rate

Production quantity

Plant layoutProcess Flow line

Labor skill

Part variety

General purpose Equipment Special

Mass production

Type of production

Batch productionJob shop


Transfer Mechanisms

FIGURE 14.4 Two types of transfer mechanisms: (a) straight, and (b) circular patterns.

(a) (b)

Powerheads

Workpiece

Rotaryindexing table

Workpiece

Power heads

Pallet


Transfer Line

FIGURE 14.5 A traditional transfer line for producing engine blocks and cylinder heads. Source: Ford Motor Company.

Machine 2:

Mill, drill,ream, plunge

mill

Start

Machine 1:

Mill

Machine 3:

Drill, ream,plunge mill

Machine 4:

Drill, bore

Machine 5:

Drill, bore

Machine 6:

Drill, ream,bore, mill

Machine 10:

Bore

Machine 8:

Mill

Machine 7:

Drill, ream, bore

Machine 9:

Mill, drill, ream

Machine 12:

Bore

Machine 11:

Drill, ream,bore

Wash

Wash

Machine 13:

Finish hollow mill,finish gun ream,finish generate

Machine 14:

Ream, tap

Machine 15:

hone, wash, gage,bore, mill

Air test

AssembleAssembleAssemble

End


Dimensioning Example

FIGURE 14.6 Positions of drilled holes in a workpiece. Three methods of measurements are shown: (a) absolute dimensioning, referenced from one point at the lower left of the part; (b) incremental dimensioning, made sequentially from one hole to another; and (c) mixed dimensioning, a combination of both methods.

(a)

+ + + + +

++

+

+

+

+

(b) (c)


Numerical Control

FIGURE 14.8 Schematic illustration of the components of (a) an open-loop, and (b) a closed-loop control system for a numerical control machine. (DAC is digital-to-analog converter.)

Computer:

Input commands, processing,output commands

Spindle

Work table

Machine tool

Lim

it s

witches

Positio

n feedback

Drive s

ignals

FIGURE 14.7 Schematic illustration of the major components of a numerical control machine tool.

(a)

Steppingmotor

Pulse train

Work table

Leadscrew

Gear

(b)

Feedback signal

DC

servomotor Gear

Input 1

2

Work table

Leadscrew

Comparator DAC

Positionsensor


Displacement Measurement

FIGURE 14.9 (a) Direct measurement of the linear displacement of a machine-tool worktable. (b) and (c) Indirect measurement methods.

(a)

(b) (c)

Rack and pinion

Rotary encoderor resolver Linear motion

Worktable

Rotary encoderor resolver

Ball screw

Machine column

Worktable

Scale

Sensor

Machine bed


Tool Movement & Interpolation

FIGURE 14.11 Types of interpolation in numerical control: (a) linear; (b) continuous path approximated by incremental straight lines; and (c) circular.

(a) (b)

Holes

1

2

3

4

Workpiece

Cutter

Workpiece

Cutterpath

Cutterradius

Machinedsurface

FIGURE 14.10 Movement of tools in numerical control machining. (a) Point-to-point system: The drill bit drills a hole at position 1, is then retracted and moved to position 2, and so on. (b) Continuous path by a milling cutter; note that the cutter path is compensated for by the cutter radius. This path can also compensate for cutter wear.

(a)

y

x

(b) (c)

1

2

34

5

y

y

x

x

Quadrant

Segment

Full circle


CNC Operations

FIGURE 14.12 (a) Schematic illustration of drilling, boring, and milling operations with various cutter paths. (b) Machining a sculptured surface on a five-axis numerical control machine. Source: The Ingersoll Milling Machine Co.

(a) (b)

Point-to-point

Workpiece

Milling

3-axis contourmilling

2-axis contourmilling

Point-to-point andstraight line

2-axis contouring withswitchable plane

3-axis contouring continuous path

Drilling andboring


Adaptive Control

FIGURE 14.13 Schematic illustration of the application of adaptive control (AC) for a turning operation. The system monitors such parameters as cutting force, torque, and vibrations; if they are excessive, AC modifies process variables, such as feed and depth of cut, to bring them back to acceptable levels.

Spindlemotor

Tachometer

Servodrives

Machinetool

Position

CNC Commands

% Spindle load

Spindle speed

Torque

VibrationAC

Part manufacturing

data

Velocity

Parameterlimits

Readout

Resolver

FIGURE 14.14 An example of adaptive control in slab milling. As the depth of cut or the width of cut increases, the cutting forces and the torque increase; the system senses this increase and automatically reduces the feed to avoid excessive forces or tool breakage. Source: After Y. Koren.

Conventional

Cutter travel

Adaptive control

Fe

ed

pe

r to

oth

(a)

WorkpieceCutter

Variable width of cut

(b) (c)

Variable depth of cut


In-Process Inspection

Cutting tool

Final worksize control

Gaginghead

Controlunit

Machinetool

Workpiece

FIGURE 14.15 In-process inspection of workpiece diameter in a turning operation. The system automatically adjusts the radial position of the cutting tool in order to machine the correct diameter.


Self-Guided Vehicle

FIGURE 14.16 (a) A self-guided vehicle (Tugger type). This vehicle can be arranged in a variety of configurations to pull caster-mounted cars; it has a laser sensor to ensure that the vehicle operates safely around people and various obstructions. (b) A self-guided vehicle configured with forks for use in a warehouse. Source: Courtesy of Egemin, Inc.

(a) (b)


Industrial Robots

FIGURE 14.18 Various devices and tools that can be attached to end effectors to perform a variety of operations.

2500 mm 3000 mm

2025 mm1075 mm

1200 mm

(a) (b)

2

3

1

4

5

6

FIGURE 14.17 (a) Schematic of a six-axis KR-30 KUKA robot; the payload at the wrist is 30 kg and repeatability is 0.15 mm (0.006 in.). The robot has mechanical brakes on all of its axes. (b) The work envelope of the KUKA robot, as viewed from the side. Source: Courtesy of KUKA Robotics.

Nut driver

(a) (b) (c)

(d) (e) (f)

Small power tool

Deburring tool

Dial indicator

Sheet metal

Electromagnet

Gripper

Object

Vacuum line

Suction cup

Robot arm

Workpiece


Robot Types & Workspaces

FIGURE 14.19 Four types of industrial robots: (a) Cartesian (rectilinear); (b) cylindrical; (c) spherical (polar); and (d) articulated, (revolute, jointed, or anthropomorphic). Some modern robots are anthropomorphic, meaning that they resemble humans in shape and in movement. These complex mechanisms are made possible by powerful computer processors and fast motors that can maintain a robot's balance and accurate movement control.

(d)(a) (b) (c)

FIGURE 14.20 Work envelopes for three types of robots. The selection depends on the particular application (See also Fig. 14.17b.)

Rectangular

(a)

Cylindrical Spherical

Workenvelope

Workenvelopes

(b) (c)


Robot Applications

FIGURE 14.21 Spot welding automobile bodies with industrial robots. Source: Courtesy of Ford Motor Co.

FIGURE 14.22 Sealing joints of an automobile body with an industrial robot. Source: Cincinnati Milacron, Inc.


Robots and Transfer Lines

FIGURE 14.23 An example of automated assembly operations using industrial robots and circular and linear transfer lines.

Circulartransfer line

Robots

Remote center compliance

Torque sensor

Visual sensing

Linear transfer line

Programmablepart feeder


Advanced End Effectors

FIGURE 14.24 A toolholder equipped with thrust-force and torque sensors (\it smart tool holder), capable of continuously monitoring the machining operation. (See Section 14.5). Source: Cincinnati Milacron, Inc.

Toolholder

Chuck

On-board electronicsto process signals

Drill

Straingages

Inductive transmitter

FIGURE 14.25 A robot gripper with tactile sensors. In spite of their capabilities, tactile sensors are now being used less frequently, because of their high cost and low durability (lack of robustness) in industrial applications. Source: Courtesy of Lord Corporation.


Applications of Machine Vision

FIGURE 14.26 Examples of machine vision applications. (a) In-line inspection of parts. (b) Identifying parts with various shapes, and inspection and rejection of defective parts. (c) Use of cameras to provide positional input to a robot relative to the workpiece. (d) Painting of parts with different shapes by means of input from a camera; the system's memory allows the robot to identify the particular shape to be painted and to proceed with the correct movements of a paint spray attached to the end effector.

(c)

(b)

(d)

(a)

Robotcontroller

Cameraview 1

Cameraview 2

Visioncontroller

Work-piece

Controller Camera 2Camera 1

Camera

Controller

Good Good Good

RejectRejectRejectReject

Robot

Camera

Workpieces

Visioncontrollerwith memory

Paintspray


Fixturing

FIGURE 14.27 Components of a modular workholding system. Source: Carr Lane Manufacturing Co.

FIGURE 14.28 Schematic illustration of an adjustable-force clamping system. The clamping force is sensed by the strain gage, and the system automatically adjusts this force. Source: After P.K. Wright and D.A. Bourne.

Clamp

Amp ADC

Relay Microcomputer

Solenoidvalve

Work table

Workpiece

Hydraulicline

Hydraulic cylinder

Strain gage


Design for Assembly

FIGURE 14.29 Stages in the design-for-assembly analysis. Source: After G. Boothroyd and P. Dewhurst.

Analyzefor manualassembly

Analyze forhigh-speedautomaticassembly

Analyzefor robotassembly

Select theassembly method

Improve the designand re-analyze


Indexing Machines

FIGURE 14.30 Transfer systems for automated assembly: (a) rotary indexing machine, and (b) in-line indexing machine. Source: After G. Boothroyd.

(a)(b)

Stationaryworkhead

Completedassembly

Work carriersindexed

Parts feeder

Indexing table

Work carriers

Stationaryworkhead

Parts feeder


Vibratory Feeder Guides

FIGURE 14.31 Examples of guides to ensure that parts are properly oriented for automated assembly. Source: After G. Boothroyd.

(a)

(c) (d)

(b)

Cutout rejectscup-shaped partsstanding on their tops

Parts rejectedif laying on side

Bowl wall Scallop Wiper blade

To deliverychute

Bowlwall

Slottedtrack

To deliverychute Slot in track

to orient screws

Screws rejected unlessin single file, end-to-end,or if delivery chute is full

Screws rejectedunless lying on side

Wiperblade

Pressurebreak

Bowl wallNarrowed track

Widthwise parts rejectedwhile only one row oflengthwise parts passTo delivery

chute

Bowl wallV cutout

To deliverychute

Part rejected ifresting on its top


Robotics Example: Toboggan Deburring

FIGURE 14.32 Robotic deburring of a blow-molded toboggan. Source: Courtesy of Kuka Robotics, Inc. and Roboter Technologie, GmbH.

Toboggan

Robot

Deburring toolFixture

Cutouts

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manufacturing automation