UNIT 1INTRODUCTION TO AUTOMATION

AUTOMATION: Automation is a technology by which a process or procedure is accomplished without human assistance. (or)The techniques of making a process or a system operate automatically.

Robotics: It is the branch of technology that deals with the design, construction, operation and application of Robots.

TYPES OF AUTOMATION:There are three broad classes of Automation,Automation

1.Fixed Automation 2. Programmable Automation 3. Flexible Automation

1. Fixed automation: It is a system in which the sequence of processing (or assembly) operations is fixed by

the equipment configuration. The operations in the sequence are usually simple. It is the integration and co-ordination of many such operations into one piece of equipment that makes the systems complex. The typical features of fixed automation are:

High initial investment for custom-engineered equipment High production rates Relatively inflexible in accommodating product changes.

The economic justification for fixed automation is found in products with very high demand rates and volumes. The high initial cost of the equipment can be spread over a very large number of units, thus making the unit cost attractive compared to alternative methods of production. Examples of fixed automation include mechanized assembly lines (starting around 1913-the product moved along mechanized conveyors, but the work stations along the line were manually operated) and machining transfer lines (beginning around 1924).

2. Programmable automation:

In this the production equipment is designed with capability to change the sequence of operations to accommodate different product configurations. The operations sequence is controlled by a program, which is a set of instructions coded so that the system can read and interpret them. New programs can be prepared and entered into the equipment to produce new products. Some of the features that characterize programmable automation include:

High investment in general-purpose equipment How production rates relative to fixed automation Flexible to deal with changes in product configuration Most suitable for batch production

Automated production systems that are programmable are used in low and medium-volume production. The parts or products are typically made in batches. To produce each new batch of different product, the system must be reprogrammed with the set of machine instructions that correspond to the new product. The physical setup of the machine must also be changed over: Tools must be loaded, fixtures must be attached to the machine table, and the required machine settings must be entered. This changeover procedure takes time. Consequently, the typical cycle for a given product includes a period during which the setup and reprogramming takes place, followed by a period in which the batch is produced. Examples of programmable automation include numerically controlled machine tools (first prototype demonstrated in 1952) and industrial robots (initial applications around 1961), although the technology has its roots in the Jacquard loom(1801).

3. Flexible automation: It is an automation is an extension of programmable automation. The concept of

flexible automation has developed only over the last 15 to 20 years, and the principles are still evolving. A flexible automated system is one that is capable of producing a variety of products (or parts) with virtually no time lost for changeovers from one product to the next. There is no production time lost while reprogramming the system and alternating the physical setup (tooling, fixtures, machine settings). Consequently, the system can produce various combinations and schedules of products, instead of requiring that they be made in separate batches. The features of flexible automation can be summarized as follows:

High investment for a custom-engineered system Continuous production of variable mixtures of products Medium production rates’ Flexibility to deal with product design variations

The essential features that distinguish flexible automation from programmable automation are;

(i). The capacity to change part programs with no lost production time, and

(ii). The capacity to change over the physical setup, again with no lost production time. These features allow the automated production system to continue production without

the downtime between batches that is characteristic of programmable automation. Changing the part programs is generally accomplished by preparing the programs off-line on a computer system and electronically transmitting the programs to the automated production system. Therefore, the time required to do the programming for the next job does not interrupt production on the current job. Advances in computer systems technology are largely responsible for this programming capability in flexible automation. Changing the physical setup between parts is accomplished by making the changeover the off-line and then moving it into place simultaneously as the next part comes into position for processing is one way of implementing this approach. For these approaches to be successful, the variety of parts that can be made on flexible automated production systems is usually more limited than a system controlled by programmable automation. Examples of flexible automation are the flexible manufacturing systems for performing machining operations that date back to the late 1960s.

Relationship of Fixed Automation, Programmable Automation & Flexible Automation,

Fixed Automation

Programmable Automation

Flexible Automation

1 Sequence of operations are fixed

Capability to change the sequence of operations

2 Volume of production is very high

Volume of production is relatively low

Mid-volume production range (i.e.n Medium)

3 Product life cycle should be long

4 Low unit cost High unit cost High unit cost relative to fixed or programmable automation

5 Mass production Batch production Mass / Batch

6 Product variety is Low Product variety is High Medium product variety

NEED OF AUTOMATION:Companies undertake projects in manufacturing automation and computer-integrated

manufacturing for a variety of good reasons. Some of the reasons used to justify automation are the following,

(1). Increased productivity: Automation of manufacturing operations holds the promise of increasing the

productivity of labor. This means greater output per hour of labor input. Higher production rates (output per hour) are achieved with automation than with the corresponding manual operations.(2). High cost of labor:

The trend in the industrialized societies of the world has been toward ever-increasing labor cost. As a result, higher investment in automated equipment has become economically justifiable to replace manual operations. The high cost of labor is forcing business leaders to substitute machines for human labor. Because machines can produce higher rates of output, the use of automation results in a lower cost per unit of product.

(3). Labor shortages: In many advanced nations there has been a general storage of labor. West Germany, for

example, has been forced to import labor to augment its own labor supply. Labor shortages also stimulate the development of automation as a substitute for labor.(4). Trend of labor toward the service sector:

The trend has been especially prevalent in United States. At this writing(1986), the proportion of the work force employed in manufacturing stands at about 20%. In 1947, this percentage was 30%. By the year 2000, some estimates put the figure as low as 2%. Certainly, automation of production jobs has caused some of this shift. However, there are also social and institutional forces that are responsible for the trend. The growth of government employment at the federal, state, and local levels has consumed a certain share of the labor market which might otherwise have gone into manufacturing. Also, there has been a tendency for people to view factory work as tedious, demeaning, and dirty. This view has caused them to seek employment in the service sector of the economy (government, insurance, personal services, legal, sales, etc.).(5). Safety:

By automating the operation and transferring the operator from an active participa -tion to a supervisory role, work is made safer. The safety and physical well-being of the worker has become a national objective with the enactment of the Occupational Safety and Health Act of 1970 (OSHA). It has also provided an impetus for automation.(6). High cost of raw materials:

The high cost of raw materials in manufacturing results in the need for greater efficiency in using these materials. The reduction of scrap is one of the benefits of automation.(7). Improved productive quality:

Automated operations not only produce parts at faster rates than do their manual counterparts, but they produce parts with greater consistency and conformity to quality specifications.(8). Reduced manufacturing lead time:

For reasons that we shall examine in subsequent chapters, automation allows the manufacturer to reduce the time between costumer order and product delivery. This gives the manufacturer a competitive advantage in promotion good customer service.(9). Reduced in-process inventory:

Holding large inventories of work-in-process represents a significant cost to the manufacturer because it ties up capital. In-process inventory is of no value. It serves none of the purposes of raw materials stock or finished product inventory. Accordingly, it is to the manufacturer’s advantage to reduce work-in-progress to a minimum. Automation tends to accomplish this goal by reducing the time a work part spends in the factory.(10). High cost of not automating:

A significant competitive advantage is gained by automating a manufacturing plan. The advantage can’t easily be demonstrated on a company’s project authorization form. The benefits of automation often show up in intangible and unexpected ways, such as improved quality, higher sales, better labor relations, and better company image. Companies that do

not automate are likely to find themselves at a competitive disadvantage with their customers, their employees, and the general public.

AUTOMATION STRATEGIES: There are certain fundamental strategies that can be employed to improve productivity in manufacturing operations. Since these strategies are often implemented by means of automation technology, we refer to them as automation strategies. Each strategy is discussed in the following list 1. Specialization of operations:- The first strategy involves the use special purpose

equipment designed to perform one operation with the greatest possible efficiency. This is analogous to the concept of labor specialization, which has been employed to improve labor productivity

2. Combined operations:- Production occurs as a sequence of operations. Complex parts may require dozens, or even hundreds, of processing steps. The strategy of combined operations involves reducing the number of distinct production machines or workstations through which the part must be routed. This is accomplished by performing more than one operation at a given machine, thereby reducing the number of separate machines needed. Since each machine typically involves a setup, setup time can usually be saved as a consequence of this strategy. Material handling effort and nonoperation time are also reduced.

3. Simultaneous operations:- A logical extension of the combined operation strategy is to perform at the same time the operations that are combined at one work station. In effect, two or more processing (or assembly) operations are being performed simultaneously on the same work part, thus reducing total processing time.

4. Integration of operations:- Another strategy is to link several workstations into a single integrated mechanism using automated work handling devices to transfer parts between stations. In effect, this reduces the number of separate machines through which the product must be scheduled. With more than one workstation, several parts can be processed simultaneously, thereby increasing the overall output of the system.

5. Increased flexibility:- This strategy attempts to achieve maximum utilization of equipment for job shop and medium-volume situations by using the sa\me equipment for a variety of products. It involves the use of flexible automation concepts explained in chapter1. Prime

objectives are to reduce setup time and programming timr for the production machine. This normally translates into lower manufacturing lead time and lower work-in-process.

6. Improved material handling and storage:- A great opportunity for reducing nonproductive time exists in the use of automated material handling and storage systems. Typical benefits included work-in-progress and shorter manufacturing lead times.

7. On-line inspection:- Inspection for quality of work is traditionally performed after the process. This means that any poor-quality product has already been produced by the time it is inspected. Incorporating inspection into the manufacturing process permits corrections to the process as product is being made. This reduces scrap and brings the overall quality of the product closer to the nominal specifications intended by the designer.

8. Process control and optimization:- This includes a wide range of control schemes intended to operate the individual processes and associated equipment more efficiently. By this strategy, the individual process times can be reduced and product quality improved.

9. Plant operations control:- whereas the previous strategy was concerned with the control of the individual manufacturing process, this strategy is concerned with control at the plant level. it attempts to manage and coordinate the aggregate operations in the plant more efficiently. Its implementation usually involves a high level of computer networking within the factory.

10. Computer integrated manufacturing(CIM):- Taking the previous strategy one step further, we have the integration of factory operations with engineering design and many of the other business functions of the firm.CIM involves extensive use of computer applications, computer data bases, and computer networking in the company.

BAISC ELEMENTS OF AN AUTOMATED SYSTEM:1. Power source to accomplish the process and to operate the system.2. Program of instructions to direct the process.3. Control system to actuate the instructions.

(1)

POWER

(2) (3)

Figure: Elements of an Automated System1) Power, 2) Program of Instruction, and 3) Control System

1. Power Source: Power is required to drive the process as well as the controls. The term process refers to the manufacturing operation that is performed on a work unit (casting, forging, molding, machining, and welding). There are many sources of power available, but the principal source of power used in automated system is electricity (electric power is widely available at moderate cost).

Power is required for the following functions,1. To drive the process.2. Loading and unloading the work unit.3. Material transport between operations.4. To actuate the control signals.5. Data acquisition and information processing.

2. Program of Instructions: The actions performed by an automated process are defined by a program of instructions. Whether the manufacturing operation involves low, medium or high production, each part or product made in the operation requires one or more processing steps, the particular processing steps for the work cycle are specified in a work cycle program. Work cycle programs are called part program in numerical control.

Following points has to be considered while setting a work cycle program,1. Number of steps in work cycle.2. Manual participation in work cycle.3. Process parameters.4. Operator instructions.5. Variations in part or product styles.6. Variations in starting work units.

3. Control System: The control element of the automated system executes the program of instructions. The controls in an automats system can be either closed loop or open loop.

PROGRAM OF INSTRUCTIONS

CONTROL SYSTEM

PROCESS

Closed loop control system ( or feedback control system) is one in which the output variable is compared with an input parameter.

Open loop control system operates without the feedback system. It is generally simpler and less expensive than a closed loop system.

LEVELS OF AUTOMATION:We can identify five possible levels of automation, in the production plant.

rateLevel 5Enterprise Level

Level 4Plant Level

Cell or system LevelLevel 3

Corporateinformation system

Productionsystem

Manufacturing System( group of machines)

1. Device level: This is the lowest level in automation hierarchy. It includes the actuators, sensors and other hardware components that comprise the machine level. The device are combined into the individual control loops of the machine, for example the feedback control loop for one axis of a CNC machine or one joint of an industrial robot.

2. Machine level: Hardware at the device level is assembled into individual machines. Examples include CNC machine tools and similar production equipment, industrial robots, powered conveyors and automated guided vehicles. Control functions at this level include performing the sequence of steps in the program of instructions in the correct order and making sure that each step is properly executed.

3. Cell or system level: This is the manufacturing cell or system level, which operates under instructions from the plant level. A manufacturing cell or system is a group of machines or work-stations connected and supported by a materisl handling system, computer and other equipment appropriate to the manufacturing process. Production lines are included in this level. Functions include part dispatching and machine loading, coordination among machines and material handling system and collecting & evaluating inspection data.

4. Plant level: This is the factory or production system level. It recieves instructions from the corporate information system and translate them into operational plans for production. Likely functions include order processing, process planning, inventory control, purchasing, material requirements planning, shop floor control and quality control.

5. Enterprise level: This is the highest level of automation, consisting of the corporate information system. It is concerned with all of the functions necessary to manage the company, i.e., marketing & sales, accounting, design, research, aggregate planning and master production schedule.

HARDWARE COMPONENTS FOR AUTOMATION AND PROCESS CONTROL

1. Sensors for measuring continuous and discrete process variables.2. Actuators that drive continuous and discrete process variables.3. Devices that convert continuous analog signals to digital data.4. Devices that convert digital data into analog signal.5. Input and output devices for discrete data.

Above figure shows the overall configuration of the process control system and how these five components categories are used to interface the process with the computer. This model represents the general arrangement of most of the material handling systems and manufacturing systems.Sensors: A sensor is device that converts a physical variable of one form into another form that is more useful for the given application.

A continuous variable or parameter is generally considered to be analog, which means it can take on any value within a certain range. Examples include force, temperature, pressure, flow rate and velocity.

A discrete variable or parameter is one that can take on only certain values within a given range, it can take on either of two possible values ON or OFF, open or closed. Examples include limit switch open or closed, motor ON or OFF and workpart present or not present in the fixture.

Common measuring devices used in automation,Measuring device DescriptionAccelerometer Analog device used to measure vibrations

Ammeter Analog device that measures the strength of an electrical current

Dynamometer Analog device used to measure force, power or torque

Actuators: An actuator is a hardware device that converts a controller command signal into a change i a physical parameter. The change in the physical parameter is usually mechanical, such as a position or velocity change.Most actuators can be classified into three categories,

1. Electrical actuators2. Hydraulic actuators3. Pneumatic actuators

1. Electrical actuators: These are most common, they include electric motors of various kinds, stepper motors, and solenoids. Electrical actuators can be either linear (output is linear displacement) or rotational (output is angular displacement).The other type of Electrical actuators in addition to motors include, solenoids and relays, which are electromagnetic devices like electric motors, but they operate differently.

2. Hydraulic actuators: These actuators use hydraulic fluid to amplify the controller command signal. The available devices provide either linear or rotational motion. Hydraulic actuators are often specified when large forces are required.

3. Pneumatic actuators: These actuators use compressed air (typically “shop air” in the factory) as the driving power. Again both linear and rotatioanal pneumatic actuators are available. Because of the relatively low air pressures involved, these actuators are usually limited to relatively low force applications.

Analog to Digital Converters (ADC) / Digital to Analog Converters (DAC)ADC converts the nalog signals from the process into the digital values to be used by the

computer. The process performed by a DAC is reverse to the ADC process. The DAC transfers the digital output of the computer into a continuos signal to drive an analog actuator or other analog device.

The procedure for converting an analog signal from the process into digital form typically consists of the following steps,

1. Sensor and Transducer: This is the measuring device that generates the analog signal.2. Signal Conditioning: The contiuos analog signal from the transducer may require

conditioning to render it into more suitable form.3. Multiplexer: The multiplexer is a switching device connected in series with each input

channel from the process.4. Amplifier: these are used to scale the incoming signal up or down to be compatible with

the range of the analog-to-digital converter.5. Analog-to-digical converter: As its name indicates, the function of the ADC is to convert

the incoming analog signal into its digital counterpart.Input and Output Devices:

1. Contact Input/output Interface: A contact i/p interface is a device by which binary data are read into the computer from some external source. The contact o/p interface is the device that communicates on/off signals from the computer to the process.

2. Pulse Counters & Generators: A pulse counter is a device used to convert a series of pulses into a digital value. The value is then entered in to the computer through its i/p channel. A pulge generator is a device that produces a siries of electrical pulses whose total number & frequency are specified by the control computer. The total number of pulses might be used to drive the axes of a positioning system.

FEEDERS, HOPPERS, ORIENTERS:SELECTOR AND ORIENTOR: The purpose of the selector and/or is to establish the proper orientation of the components for the assembly work head. A selector is a device that acts as a

filter, which allows only those parts to pass through which are in correct orientation. Improperly oriented components are rejected back into the hopper. An orientor is a device that allows properly oriented parts to pass through but provides a re-orientation of components that are not properly oriented initially.

Feeders are commonly vibratory bowl feeders, where parts in a bowl are vibrated using a rotary motion, so that they climb a helical track. As they climb, a sequence of baffles and cutouts in the track create a mechanical ‘filter’ that causes parts in all but one orientation to fall back into the bowl for another attempt at running the gauntlet. Other common devices use centrifugal forces, reciprocating forks, or belts to push parts through filters. These devices all have the disadvantage that design and setup for new parts requires manual trial and error, which is slow and error-prone. Vibration frequencies have been studied to optimize throughput and sensors have been proposed to make feeders more efficient and effective. Parts feeders provide a cast-effective alternative to manual labor, saving manufacturers valuable time and labor costs. One operator can oversee a number of automated machines, as opposed to one worker hand loading one machine.

Types of Feeders Apron Feeders Belt Feeders Vibratory Feeders Rotary Feeders Reciprocating Feeders Disc Feeders Screw Feeders Centrifugal Feeders Flexible Feeders

Some of the commonly used feeders are described below:Apron Feeders: Apron feeders are useful for feeding large tonnages of bulk solids being particularly relevant to heavy abrasive ore type bulk solids and materials requiring feeding at elevated temperatures. They are also able to sustain extreme impact loading. Apron feeders

use overlapping. Reinforced pans attached to chains or joined by links. An endless conveyor travelling over rollers is created. The products are made by a number of manufacturers and come in multiple shapes and widths.

Some feeders are made of extra heavy structural steel and are particularly suited to handling coarse, abrasive material. For service applications such as feeding the primary crusher, producers should make sure the feeder is up to the job. As with any product, it is best to shop around not just for price, but to make certain the feeder matches the application.

Reciprocating feeders (Plate feeders): Plate Feeders also known as reciprocating feeders as shown in below figure, are in widespread use, usually at the tail end of a conveyor or elevator to relieve pressure and drag. Designed for feeding at a fixed rate, a plate is driven reciprocally under a head of bulk material. Size varies and the feed rate can be controlled easily. These feeders use rollers to support the product ranging from sand and gravel to crushed stone that pass over belt feeders.

Advantages Low cost Ability to handle a wide range of miscellaneous materials.

Disadvantages

Not self - cleaning Not recommended for highly abrasive materials.

Reciprocating-Tube Hopper Feeder: Reciprocating – tube hopper feeder consists of a conical hopper with a hole in the center through which the delivery tube passes. Relative vertical motion between the hopper and the tube is achieved by reciprocating either the tube or the hopper. During the period when the top of the tube is below the level of parts, some parts will fall into the delivery tube.

Vibratory Bowl Feeder: Vibratory parts feeding is a technology used to orient (proper position), singulate (proper quality) and differentiate (separate/sort) and move parts to a desired location. Vibratory bowl feeders are used for feeding in oriented form a wide range of components such as steel balls, nuts, belts, washers, rivets, nails, caps, plugs, spoons, droppers, rings and various other components having very odd shapes. The vibratory bowl feeder is the oldest and still most common approach to the automated feeding (orienting) of industrial parts. These feeders are very useful for automatic feeding of such components to various machines, etc., and on automatic assembly lines. The size of the feeders varies from 200mm – 1000 mm diameters depending upon size, shape and weight of components. There are no moving parts in the equipment and thus no wear and tear and need no maintenance. The reason for the success of vibratory bowl feeders is the underlying principle of sensor less manipulation that allows parts positioning and orienting without sensor feedback. This principle is even more important at small scales, because sensor data will be accurate and more difficult to obtain.Vibratory feeder terminologyHopper (or storage hopper). The storage hopper is the storage area provided to backlog bulk parts prior to entering the feeder bowl. This hopper eliminates overloading or in sufficient

loads of parts, causing the bowl not to function as required. Feed rate from the hopper to a bowl is mattered by a level control switch.Basic bowl. The band, bottom and track assembly prior to any tooling for a specific part. Basic bowls are not off – the – shelf standard items. They are individually designed and can be supplied for any profile of part up to approximately 5” long.

Screw Feeder:

Centrifugal Hopper Feeder: A centrifugal feed device is a hopper feeder system as shown in figure with a central flat or conical turntable, which drives the working materials on this via a rotary action. The resulting centrifugal force causes work pieces to separate out of the heap and move towards the edge of the drum. Here they meet the delivery ring and slide onto ramp. The speeds of the turntable and the delivery ring can be adjusted separately. Separated out work pieces can be aligned by orienting devices and thus proceed to the hopper. Complex work pieces can be fed by means of a conveyor belt. Any excess conveyed work pieces fall back into the heap in the hopper.

Belt Feeders: Belt feeders are used to provide a controlled volumetric flow of bulk solids from storage bins and bunkers. Like screw feeders, belt feeders can be an excellent choice when there is a need to feed material from an elongated hopper outlet. Belt feeders generally can handle a higher flow rate than screw feeders. These types of feeders have more moving parts and therefore generally require more attention and maintenance than a well-designed screw or vibrating pan feeder. They generally consist of a flat belt supported by closely spaced idlers and driven by end pulleys.

Some particular Features of belt feeders include: Suitable for withdrawal of material along slotted hopper outlet when correctly designed. Can sustain high impact loads from large particles.

Centreboard Hopper Feeder: In this feeder, a blade made of hardened steel, with a shaped top is oscillated up and down (by a crank mechanism) through a mass of parts. Properly oriented parts are picked by the blade and discharged by gravity into the track. This type of feeder is suitable for parts having simple shape like balls, cylinders, nuts and bolts, rivets, etc. These are very robust and have long working life. The capacity of centerboard hopper is large. The disadvantage of these is that they cannot be used for fragile components and the degree to which they can orient is rather limited.

Flexible Feeders: A Crucial component of any assembly system is parts feeder. Unfortunately, parts feeders are also one of the most specialized components of such systems.

While a modular approach could be employed which would allow specialized feeders to be quickly brought into the work cell, there are several difficulties, which present themselves using this approach. First, a feeding system tends to be large and bulky in comparison to other specialized components, such as a robot’s gripper. Size alone could make storingall the specialized feeders difficult. Second, a feeding system is generally more expensive than other specialized components. It might be difficult to economically justify building several new feeders for each new product being assembled. Third, the lead – time to build and adjust most current feeding systems is rather along. This diminishes the ability of the work cell to be rapidly adapted to new products. Therefore. Simple placing current feeding technology behind a generic, modular interface is not a feasible solution.

A typical robotic mechanical assembly work cell may have several feeders that are tooled specifically for particular parts. Any change to the design of a part requires that the feeder be either re – tooled or completely replaced. With today’s product life cycle as short as a few months for many consumer products, this is no longer acceptable. The need for a greater flexibility, lower cost of automation and faster product change over time has brought about a new approach to pars feeding, termed ‘flexible feeding”. Flexible feeding is a emerging alternative to traditional part feeding methods. This alternative greatly enhances the versatility of a manufacturing work cell by using a robot manipulator and sophisticated sensing devices such as machine vision; thereby significantly reducing both cost and set up time.

Just as robots are considered “flexible” devices with certain designs better suited to certain tasks, the same is true for flexible feeders. A single flexible is not capable of feeding all parts types. Part size, part geometry, mass and material will all affect the choice of the feeder used. Similarly, the choice of vision system will depend on requirements for image resolution, the vision algorithms and tool sets needed, and the vision processing performance required.

Advantages of flexible feeding:Some of the advantages of the flexible concept of automation are:

Tooling is soft. The tooling is the vision and robot software. No long lead times to fabricate tooling.

Tooling is flexible. Simultaneous product and tooling development can occur with flexible feeding. Flexible feeding easily accommodates design changes that occur in product development.

The ability to quickly produce new products at production volumes is a competitive advantage.

Avoids the expense of building prototype and manual assembly tooling. Can automate with lower production volumes through combining of product on same flex

feeding cell.

Simultaneous quality vision inspection using the vision system that guides robot. Majority of tooling capital expense is reusable if new product is not successful in the

marketplace.