Automation:

The word automation comes from the Greek word "automatos",meaning self-acting. The word automation was coined in the mid-1940s by the U.S. autombile industry to indicate the automatic handling of parts between production machi nes, together with their continuous processing at the machines. The advances in computers and control systems have extended the definition of automation.

Definition: Automation can generally be defined as the process of following a predetermined sequence of operations with little or no human labor, using especialized equipment and devices that perform and control manufacturing processes. Automation in its full sense, is achieved through the use of a variety of devices, sensors, actuators, techniques, and equipment that are capable of observing the manufacturing process, making decisions concerning the changes that need to be made in the operation, and controlling all aspects of it.

Figure 1 gives the general outline of course material covered in this textbook: automation of manufacturing processes.

Figure 1 Outline of Topics Covered in the Text.

2.1 HISTORY AND EVOLUTION OF AUTOMATION

Although metal working processes were developed as early as 4000 B.C., it was not until the beginning of the Industrial Revolution in the 1750s that automation began to be introduced in the production of goods. As can be seen in Table 1, machine

tools such as terret lathes, automatic screw machines, and automatic bottle-making equipment were developed in the late

1890s and early 1900s. Mass-production techniques and transfer machines were developed in the 1920s. These machines had fixed automatic mechanisms and were designed to produce specific products. These developments were best represented by the automob ile industry, which produced passenger cars at a high production rate and low cost.

The major breakthrough in automation began with the invention of numerical control (NC) of machine tools in the 1950s. Since this historic development, rapid progress has been made in automating aspects of manufacturing (See Table 1). These involve t he introduction of computers in the into automation, computerized numerical control (CNC), adaptive control (AC), industrial robots, and computer-integrated manufacturing (CIM) systems, including computer-aided design, computer-aided engineering and compu ter-aided manufacturing (CAD/CAE/CAM).

TABLE 1 DEVELOPMENT OF THE HISTORY OF AUTOMATION[kAL, 1995]

Date Development

1500-1600 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 calculators.

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 bottlemaking 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.

1948 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.

1960s Industrial robots.

1965 Large-scale integrated circuits.

1968 Programmable logic controllers.

1970 First integrated manufacturing system; spot welding of automobile bodies with robots.

1970s Microprocessors; minicomputer-controlled robot; flexible manufacturing systems; group technology.

1980s Artificial intelligence; intelligent robots; smart sensors; untended manufacturing cells.

1990s Integrated manufacturing systems; intelligent and sensor-based machines; telecommunications and global manufacturing networks; fuzzy logic devices; artificial neural networks.

TABLE 2

APPROXIMATE ANNUAL VOLUME OF PRODUCTION

Type of Production Number Produced Typical Products

Experimental or prototype 1-10 All

Piece or small batch 10-5000 Aircraft, special machinery, dies

Batch or high volume 5000-100,000 Trucks, agricultural machinery, jet engines, diesel engines

Mass production 100,000 and over Automobiles, appliances, fasteners

GOALS AND APPLICATIONS OF AUTOMATION

Goals of Automation

Automation has certain primary goals as listed below:

* Integrate various aspects of manufacturing operations so as to

improve the product quality and uniformity, minimize cycle

times and effort, and thus reduce labor costs.

* Improve productivity by reducing manufacturing

costs through better control of production. Parts

are loaded, fed, and unloaded on machines more efficiently. Machines are used more effectively and production

is organized more efficiently.

* Improve quality by employing more repeatable processes.

* Reduce human involvement, boredom, and possibility

of human error.

* Reduce workpiece damage caused by manual handling

of parts.

* Raise the level of safety for personnel, specially

under hazardous working conditions.

* Economize on floor space in the manufacturing

plant by arranging the machines, material movement, and related equipment more efficiently.

Areas of Automation Application

Automation is and will continue to be an evolutionary,at her than revolutionary, concept. Automation in mnufacturing plants has been implemented successfully in the following basic areas of activities:

* Manufacturing processes. Machining, forging, cold extrusion, and grinding operations are examples of processes that have been automated extensively.

* Materials handling. Materials and parts in various stages of completion (work in progress, WIP) are moved throughout a plant by computer-control equipment without human guidance.

* Inspection. Parts are automatically inspected for quality,

dimensional accuracy, and surface finish, either at the time of manufacturing (in-process inspection); or after they are made (post-process inspection).

* Assembly. Individually manufactured parts are

automatically assembled into subassemblies and finally

into a product.

* Packaging. Products are packaged automaically.

Industrial robots and computer numerical control machines are examples of automation equipment.

Other equipments used in automation to be covered in this course include:

* Programmable controllers

* Microprocessors

* Process control computers

* Industrial logic controllers

* Computer numerical control (CNC) systems

All these devices are considered members of the family of the flexible automation equipment. The focus of this course is on "how to apply", not on how to design, robots, CNC, and manufacturing automation. Automation can be applied to manufacturing all t ypes of goods, from raw materials to finished products, and in all types of production from job shops to large manufacturing facilities. The decision to automate a new or existing production facility require the following additional considerations:

* Type of product manufactured.

* Quantity and rate of production.

* The particular phase of manufacturing operation

to be automated.

* Level of skill in the available workforce.

* Reliability and maintenance problems associated with

automated systems.

* Economics.

Because automation generally involves high initial cost of equipment, as well as a knowledge of the principles of operation and maintenance required, a decision on its implementation, must invlove a careful study with regard to the true needs of an organi zation. It is not unusual for a company to begin automation with great enthusiasm and with high cross-the-board goals, only to discover that its economic benefits were largely perceived rather than real, and that automation was, in the final assessment, not cost-effective. In many situations, selective automation, rather than total automation, of a facility would be desirable. Generally, the higher the level of skill available in the workforce, the less the need for automatio n, provided labor costs are justified and there is a sufficient number of workers available. Conversely, of course, if a manufacturing

facility is already automated, the skill level required is lower.

GETTING READY TO AUTOMATE

DESIGNING FOR AUTOMATION

Design for :

* Symmetry -- Figures 2 & 3

* Less parts tangling --Figure 4

* Feeding -- Figure 5 & 6

* Insertion -- Figure 7

* Fasteners -- Figure 8 & 9

STABILIZING THE PROCESS BEFORE AUTOMATING

* Product cycle time

* Reduction of inventory

* Reduction of set-up time

* Integration of quality control

* Achieving machine reliability

PRODUCTION VOLUME AND AUTOMATION (AUTOMATION AND PRODUCTION

QUANTITY)

Production volume is critical in determining the type of machinery and equipment --and the level of automation--required to produce parts economically. Before we proceed further, let us define some terms. Total production quantity is define d as the total number of parts to be made. This quantity can be produced in individual batches of various lot sizes. Lot size is greatly influences the economics of production. Production rate is defined as the number of parts produced per unit time, such as per day, month, or year. The approximate and generally accepted ranges of production volume are shown in Table 2 for some typical applications. As expected, experimental and prototype products represent the lowest olume. M ass production require large volumes of production.

TYPES OF AUTOMATION SYSTEMS

HARD AUTOMATION (FIXED POSITION AUTOMATION

Important Characteristics of Hard Automation:

* In hard (fixed position) automation, the production lines are designed to produce a standardized product, such as engine plocks, valves, gears, and spindle.

* Athough the product size and processing parameters such as speed, feed, and depth of cut) can be changed, these machines are specialized. They lack flexibility

and cannot be modified to any significant extent that have different shapes and dimensions.

* Because they expensive design and construct, their economic use requires mass production of parts in very large quantities.

* Machines used in hard-automation applications are usually built on the building-

block, or modular principle.

Machines used in hard-automation applications are usually built on the building-block, or modular principle. They are generally called transfer machines, and consist of the following two major components: powerhead productio n units and transfer mechanisms

Types of Hard Automation

Powerhead production units. Consisting of a frame or bed, electric driving motors, gearboxes, and tool spindles, powerhead production units are self-contained. They can easily be regrouped for producing a different part and thus have certain adap tability and flexibility. Transfer machines

consist of two or more powerhead units, which can be arranged on the shop floor in linear, circular, or U patterns. The weight and shape of parts influence the arrangement selected. The arrangement is also important for

continuity of operation in the event of tool failure or machines breakdown in one or more of the units. Buffer storage features are incorporated in these machines to permit continued operation.

Transfer mechanisms and transfer lines. Transfer mechanisms are used

to move the workpiece from one station to another in the machine- or from one machine to another- to enable various operations to be performed on the part. Workpieces are transferred by several methods; (1) rails along which the parts, usually place d on pallets, are pushed or pulled by

various mechanisms; (2) rotary indexing tables; and (3) overhead conveyors. Transfers of parts from station to station is usually controlled by sensors and other devices. Tools on transfer machines can be changed easily using toolholders with quick -change features. These machines may

be equipped with various automatic gaging and inspection systems. These systems are utilized between operations to ensure that the dimensions of a part produced in one station are within acceptable tolerances before that part is transferred to the nex t station. Transfer machines are also used extensively in automatic assembly.

The transfer lines or flow lines for a very large system for producing cylinder heads for engine blocks, consisting of a number of transfer machines, are shown in Fig. 5 This sytem is capable of producing 100 cylinder heads per hour. Note the various ma chining operations performed: milling, drilling, reading, boring, tapping, and honing, as well as washing and gaging.

SOFT AUTOMATION (FLEXIBLE AUTOMATION)

Characteristics of Soft Automation

It has been stated that hard automation generally involves mass-production machines that lack flexibility. In soft, flexible or programmable, automation, greater flexibility is achieved through computer control of the machinces and its various functions, using various programs that are described in detail for computer numerical systems. Soft automation is an important developement, because the machine can

be easily and readily reprogrammed to produce a part that has a different shape or dimension that the one just produced. Because of this capability, soft automation can produce parts with complex shapes.

Further advances in flexible automation, with extensive use of modern computers, has led to the developement of flexible manufacturing systems, with high levels of efficiency and productivity.

PROGRAMMABLE CONTROLLERS

The control of manufacturing processes in a proper sequence, involving groups of machines and various material-handling equipment and accessories, has traditionally been done by timers, switches, relays, counters, and similar hardwired devices based on me chanical, electro-mechanical, and pneumatic principles. Beginning in 1968, programmable logic controllers (PLC; also called PC, but not to be confused with personal computers) were introduced to replace these devices. A programmable logic controll er has been defined by the National Electrical Manufaturers Association (NEMA) as "a digitally operating electronic apparatus which uses a programmable memory for the internal storage of instructions for implementing specific functions such as log ic, sequencing, timing, counting, and arithmetic to control, through digital or analog input/output modules, various types of machines or processes." The digital computer, which is used to control the functions of a programmab le controller, is considered to be within this scope.

Because relay control panels can now be eliminated and PLCs can be reprogrammed and take less space, programmable controllers have become widely adopted in manufacturing systems and operations. Their basic functions are on-off, motion, sequential operati ons, and feedback control. In addition to their use in manufacturing process control, they are also used in system control with high-speed digital processing and communication capabilities. These controllers perform reliabl in industrial environments and improve the overall efficiency of the operations, PLCs are becoming less popular in new installations due to advances in numerical control machines, but they still represent a very large installation base.

STABILIZING MANUFACTURING PROCESS

Prerequisites to process automation are:

* Process stability

* Product stability

* Market demand for the product must be

stable or growing.

When the above three variables are stabilzed and properly controlled, there will be less variability in the product quality resulting from assignable causes, except from chance causes.

Statistical process control (SPC) techniques have been used effectively to control and monitor process variable, such as product quality. It has also been used to assess process stabilty. The assumption underlying the SPC is that the summation of all factory variables follow a normal (Gaussian) distribution. This is called the central limit theorem. The normal distribution curve is bell-shaped shown in Figure 12, where the vertical axis represents the probability density, f(x), for an y value of the variable along the horizontal axis.

The central limit theorem permits us to approximate the sampling distribution for X-bar by an appropriate normal curve, regardless of the form of the population frequency distribution (in which the sample, n, is 30 or mor e data points).

Causes of Variability in Manufacturing Processes

1. Assignable Causes

* Causes for defects that can be detected and corrected

* Causes due to human and machine errors.

Examples: errors due to unskilled labor and/or obsolescence or dullness of machines.

2. Chance Causes

* Causes due to statistical (probabilistic) error

* Inherent causes which cannot be detected and corrected.

* Use of statistical process to control manufacturing system.

Figure 12(a) shows a bell-shaped curve generated from normal distribution or Gaussian distribution). This curve approximates the frequency distribution plot of large samples (n 30 sample data) of data points for normally distributed variables. Thi s curve when turned at 90 degrees becomes statistical process control chart with upper control limit (x + 3o ), lower control limit (x + 3o ), and center line (x) as seen in Figure 12(b).

The sample standard deviation is computed the formula:

s = / [ (xi - x)2/ (n-1)],

where,

x = xi /n

xi = Sample observations

n = sample size

s = o and x = u (approximation).

Key to Statiscal Process Control Technique:

If an observation occurs outside the range of x _ 3 sigma, then it is typically presumed to represent a change in the process (mfg. process) variable, not a random variable.

NOTE:

The relationship between "part tolerance" ( + )and "process standard deviation" (o ) is important for product for both product quality and the automation potential of manufacturing process (mfg.). Figure 13 shows several possible relationships betwee n part tolerance and normal process variation. Only the relationship shown in Figure 13(d) demonstrates sufficient control of the mfg. process variable for factory automation. Even the process that fits Figure 13(d) might quite nicely fit Figure 13(c) wh en tighter tolerances are applied to satisfy the requirements of an industrial robot or other automated mfg. equipment. Certainly, this is a possibility that the automation engineer should evaluate before plunging into a robotics or automation pro ject.

Product Cycle Time Verses Manufacturing Cycle Time

Product cycle time is the time required to lunch a new product from concept, market analysis, product design, and process development. An additional benefit of designing for automation is the gains that can be made in reducing product design cycle.

Manufacturing cycle time refers to production time required to manufacture an individual part or item of a product. The manufacturing cycle time is significantly affected by automation.

Note: Go over equation (1) page 14 and sample problem 1.3 page 16.

HOME WORK: PROBLEMS #1.4, 1.6, 1.7 & 1.8

DUE DATE: Jan. 21, 1997.