Levels of Automation (2024)

Chapter: Automation, Production Systems, and Computer Integrated Manufacturing : Automotion and Control Technologies

LEVELSOF AUTOMATION

Theconcept of automated systems can be applied to various levels of factoryoperations. One normally associates automation with the individual productionmachines. However, the production machine itself 1~made up of subsystems thatmay themselves be automated. For example. one of tile important automationtechnologies we discuss in this pari of the book isnumcrical control(Chapter6).A modern numerical control (NC) machine tool is an automated system.However, the NC machine itself is composed of multiple control systems. Any NC machine has at least two axes ofmotion, and some machines have up to five axes. Each of these axes operates asa positioning system, as described in Section 3.1.3, and is, in effect, itselfan automated system. Similarly, a NC machine is often part of a largermanufacturing system, and the larger system may itself be automated. Forexample, two or three machine tools may be connected by an automated pacthandling system operating under computer control. The machine tools alsoreceive instructions (e.g., part programs) from the computer. Thus we havethree levels of automation and control included here (the positioning systemlevel, the machine toollevel, and the manufacturing system level). For our purposesin this text, we can identify five possible levels of automation in aproduction plant. They are defined next, and their hierarchy is depicted inFigure 3.6.

Device level. This is the lowest level in ourautomation hierarchy. It includes the actuators, sensors, and other hardwarecomponents that comprise the machine level. The devices are combined into theindividual control loops of the machine; for ex· ample, the feedback controlloop for one axis of a CNC machine or one joint of an industrial robot.

Machine [ewl. Hardwareat the device level is assembled into individual machines. Examples include CNCmachine tools and similar production equipment, industrial roo bOIS, poweredconveyors, and automated guided vehicles. Control functions at this

levelinclude performing the sequence of steps in the program of instructions in thecorrect order and making sure that each step is properly executed.

Cell or system level. This isthe manufacturing cell or system level, which operates under instructions from the plant level. A manufacturing cell or system isa group of machines or workstations connected and supported by a materialhandling system, computer. and other equipment appropriate to the manufacturingprocess. Production lines arc included in this level. functions include partdispatching and machine loading. coordination among machines and materialhandling system, and collecting and cvaluatinginspection data.

Plum level. This is the factory or productionsystems level. It receives instructions from(hecorporate iuforrnation system and translates them into operational plans forproduction. Likely functions include: order processing, process planning,inven. tory control, purchasing, material requirements planning, shop floorcontrol, and qualiry control.

Enterprise level. This isthe highest level.consisting of the corporate information systern.It isconcerned with all of the functions necessary to manage the company: marketingand sales, accounting, design, research, aggregate planning, and masterproduction scheduling.

Most ofthe technologies discussed in this part of the book are at level 2 (the machinelevel), although we discuss level! automation technologies (the devices thatmake up a control system) in Chapter 5. The level 2 technologies include theindividual controllers (e.g .. programmable logic controllers and digitalcomputer controllersj.numerical controt machines. and industrial robots. Thematerial handling equipment discussed in Part 11 abo represent technologies atlevel 2. although some of the handling equipment are themselves sophisticatedautomated systems. The automation and control issues at Jevel2 aTCconcerned with the basic operation of the equipment and the physical processes they

perform

Controllers.machines, and material handling equipment are combined into manufacturingcells. or production lines. or similar systems, which make up level 3,considered in Part III. A manufacturingsystem is defined in this book as a collection of integrated equipmentdesigned for some special mission, such as machining a defined part family orassembly of a certain product. Manufacturing systems also include people.Certain highly automated manufacturing systems can operate for extended periodsof time without humans present to attend to their needs. But most manufacturingsystems include workers as important elements of the system: for example,assembly workers on a eooveyorized production line or part loaders/unloadcrs ina machining cell. Thus, manufacturing systems are designed with varying degreesof automation; some are highly automated, others are completely manual, andthere is a wide range between.

Themanufacturing systems in a factory arc components of a larger system, which werefer to as a production system. We define a production system as the people, equipment, and procedures that areorganiz.ed for the combination of materials and processes that comprise acompany's manufacturing operations. Production systems are at level 4, theplant level, while manufacturing systems are at level 3 in our automationhierarchy. Production systems include not only the groups of machines andworkstations in the factory but also the support procedures that make themwork. These procedures include productioncontrol, inventory control, material requirements planning. shop floor control.and quality control. These systems are discussed in Parts IV and V. They areoften implemented not only at the plant level but also ar the corporate level(level S).

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Automation, Production Systems, and Computer Integrated Manufacturing : Automotion and Control Technologies : Levels of Automation |