2. 1.11.1 INTRODUCTIONINTRODUCTION
• The technology by which a process or procedure isThe technology by which a process or procedure is
accomplished without human assistance.accomplished without human assistance.
• A technique that can be used to reduce costs and/or toA technique that can be used to reduce costs and/or to
improve quality.improve quality.
• Can increase manufacturing speed, while reducing cost.Can increase manufacturing speed, while reducing cost.
• Can lead to products having consistent quality, perhapsCan lead to products having consistent quality, perhaps
even consistently good qualityeven consistently good quality
• It is implemented using a program of instructionsIt is implemented using a program of instructions
combined with a control system that executes thecombined with a control system that executes the
instructions.instructions.
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3. • To automate a process, power is required, both toTo automate a process, power is required, both to
drive the process itself and to operate the programdrive the process itself and to operate the program
and control system.and control system.
• Automated processes can be controlled by humanAutomated processes can be controlled by human
operators, by computers, or by a combination of theoperators, by computers, or by a combination of the
two.two.
• If a human operator is available to monitor and controlIf a human operator is available to monitor and control
a manufacturing process,a manufacturing process, open loop controlopen loop control maymay
be acceptable.be acceptable.
• If a manufacturing process is automated, then itIf a manufacturing process is automated, then it
requiresrequires closed loop controlclosed loop control, also known as, also known as
feedback controlfeedback control..
• Figure 1.1 shows example of open loop control andFigure 1.1 shows example of open loop control and
closed loop control.closed loop control.
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4. BASIC ELEMENT OF ANBASIC ELEMENT OF AN
AUTOMATED SYSTEMAUTOMATED SYSTEM
• Consists of 3 basic elements:Consists of 3 basic elements:
1)1) The actuator (which does the work)The actuator (which does the work)
• Controlled by the controller.Controlled by the controller.
• The actuator in an automated process may in fact be severalThe actuator in an automated process may in fact be several
actuators, each of which provides an output that drivesactuators, each of which provides an output that drives
another in the series of actuator.another in the series of actuator.
• Some actuators can only be on and off. Other actuatorsSome actuators can only be on and off. Other actuators
respond proportionally with the signal they receive from arespond proportionally with the signal they receive from a
controllercontroller
• Actuators can be selected for the types of inputs they require,Actuators can be selected for the types of inputs they require,
either DC or AC.either DC or AC.
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5. 2)2) The controller (which ‘tells’ the actuator to doThe controller (which ‘tells’ the actuator to do
work)work)
• A controlled system either may be a simple digital system orA controlled system either may be a simple digital system or
an analog system.an analog system.
• Digital and analog controllers are available ‘off the shelf’ soDigital and analog controllers are available ‘off the shelf’ so
that systems can be constructed inexpensive and with littlethat systems can be constructed inexpensive and with little
specialized knowledge required.specialized knowledge required.
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6. 3)3) The sensor (which provides feedback to theThe sensor (which provides feedback to the
controller so that it knows the actuator is doingcontroller so that it knows the actuator is doing
work)work)
• Obviously, controlled automation requires devices to senseObviously, controlled automation requires devices to sense
system output.system output.
• Sensors also can be used so that a controller can detect andSensors also can be used so that a controller can detect and
respond to changing conditions in its working environment.respond to changing conditions in its working environment.
• Switches and transducers are another name for sensors.Switches and transducers are another name for sensors.
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7. • Switches can detect when a measured condition exceeds aSwitches can detect when a measured condition exceeds a
pre-set level. Examples, closes when a workpiece is closepre-set level. Examples, closes when a workpiece is close
enough to work on.enough to work on.
• Transducers can describe a measured condition. Examples,Transducers can describe a measured condition. Examples,
output increased voltage as a workpiece approaches theoutput increased voltage as a workpiece approaches the
working zone.working zone.
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8. 1.21.2 TYPE OFTYPE OF
AUTOMATIONAUTOMATION
• Hard AutomationHard Automation
• Controllers were built for specific purposes and couldControllers were built for specific purposes and could
not be altered easily.not be altered easily.
• Early analog process controllers had to be rewired toEarly analog process controllers had to be rewired to
be reprogrammed.be reprogrammed.
• This controllers do what they are designed and built toThis controllers do what they are designed and built to
do, quickly and precisely perhaps, but with littledo, quickly and precisely perhaps, but with little
adaptability for change (beyond minor adjustments).adaptability for change (beyond minor adjustments).
• Modification of hard automation is time-consumingModification of hard automation is time-consuming
and expensive, since modifications can only beand expensive, since modifications can only be
performed while the equipment sits idle.performed while the equipment sits idle.
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9. • Soft AutomationSoft Automation
• Modern digital computers are re-programmable.Modern digital computers are re-programmable.
• It is even possible to reprogram them and test theIt is even possible to reprogram them and test the
changes while they work.changes while they work.
• Even if hardware changes are required to a softEven if hardware changes are required to a soft
automation system, the lost time duringautomation system, the lost time during
changeover is less than for hard automationchangeover is less than for hard automation
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10. • In other books/references, automation can beIn other books/references, automation can be
classified into three basic types:classified into three basic types:
• Fixed AutomationFixed Automation
• A system which the sequence of processing (orA system which the sequence of processing (or
assembly) operations is fixed by the equipmentassembly) operations is fixed by the equipment
configurations.configurations.
• Each operations in the sequence is usually simple.Each operations in the sequence is usually simple.
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11. • The features of fixed automation;The features of fixed automation;
• High initial investment for custom-engineered equipmentHigh initial investment for custom-engineered equipment
• High production ratesHigh production rates
• Relatively inflexible in accommodating product variety.Relatively inflexible in accommodating product variety.
• Examples, machining transfer lines and automated assemblyExamples, machining transfer lines and automated assembly
machines.machines.
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12. • Programmable AutomationProgrammable Automation
• The production equipment is designed with theThe production equipment is designed with the
capability to change the sequence of operations tocapability to change the sequence of operations to
accommodate different product configurations.accommodate different product configurations.
• The operation sequence is controlled by aThe operation sequence is controlled by a
program, which is a set of instruction coded soprogram, which is a set of instruction coded so
that they can be read and interpreted by thethat they can be read and interpreted by the
system.system.
• New programs can be prepared and entered intoNew programs can be prepared and entered into
the equipment to produce new products.the equipment to produce new products.
• The physical setup of the machine must beThe physical setup of the machine must be
changed for each new products.changed for each new products.
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13. • This changeover procedures takes time.This changeover procedures takes time.
• Examples: numerical control (NC) machine tools,Examples: numerical control (NC) machine tools,
industrial robots and PLC.industrial robots and PLC.
• The features of programmable automation;The features of programmable automation;
• High investment in general purpose equipment.High investment in general purpose equipment.
• Lower production rates than fixed automation.Lower production rates than fixed automation.
• Flexibility to deal with variations and changes in productFlexibility to deal with variations and changes in product
configuration.configuration.
• Most suitable for batch production.Most suitable for batch production.
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14. • Flexible AutomationFlexible Automation
• An extension of programmable automation.An extension of programmable automation.
• Capable of producing a variety of parts/productsCapable of producing a variety of parts/products
with virtually no time lost for changeovers from onewith virtually no time lost for changeovers from one
part style to the next.part style to the next.
• The features of flexible automation;The features of flexible automation;
• High investment for custom-engineered system.High investment for custom-engineered system.
• Continuous production of variable mixtures of products.Continuous production of variable mixtures of products.
• Medium production rates.Medium production rates.
• Flexibility to deal with product design variations.Flexibility to deal with product design variations.
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15. • Examples, flexible manufacturing systems forExamples, flexible manufacturing systems for
performing machining operations.performing machining operations.
The relative positions of the three types ofThe relative positions of the three types of
automation for different production volume andautomation for different production volume and
product varieties are shown in Figure 1.2.product varieties are shown in Figure 1.2.
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16. 1.31.3 REASON FORREASON FOR
AUTOMATINGAUTOMATING
• To increase labor productivityTo increase labor productivity
• To reduce labor costTo reduce labor cost
• To improve worker safetyTo improve worker safety
• To improve product qualityTo improve product quality
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17. AUTOMATION CONTROLAUTOMATION CONTROL
• Usually implies a sequence of mechanical steps.Usually implies a sequence of mechanical steps.
• A camshaft is an automation controller because itA camshaft is an automation controller because it
mechanically sequences the steps in the operationmechanically sequences the steps in the operation
of an internal combustion engine.of an internal combustion engine.
• Manufacturing processes are often sequenced byManufacturing processes are often sequenced by
special digital computers, known as programmablespecial digital computers, known as programmable
logic controller (PLC).logic controller (PLC).
• PLC can detect and can switch electrical signalsPLC can detect and can switch electrical signals
on and off.on and off.
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18. PROCESS CONTROLPROCESS CONTROL
• Usually implies that the product is produced in aUsually implies that the product is produced in a
continuous stream.continuous stream.
• Often, it is a liquid that is being processed.Often, it is a liquid that is being processed.
• Early process control system consisted of specially-Early process control system consisted of specially-
designed analog circuitry that measured a system’sdesigned analog circuitry that measured a system’s
output ( e.g., the temperature of liquid leaving a tank),output ( e.g., the temperature of liquid leaving a tank),
and changed that input ( e.g., changing the amount ofand changed that input ( e.g., changing the amount of
cool liquid mixed in) to force the output to stay at a presetcool liquid mixed in) to force the output to stay at a preset
value.value.
• Now, process control is accomplished using digitalNow, process control is accomplished using digital
computers.computers.
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19. Production Quantity and ProductProduction Quantity and Product
VarietyVariety
• First, letFirst, let
• Q= production quantityQ= production quantity
• P=product varietyP=product variety
• Q refers to the number of units of a given part orQ refers to the number of units of a given part or
product that are produced annually by a plant.product that are produced annually by a plant.
• Let us identify each part or product style by using theLet us identify each part or product style by using the
subscript j, so that Qsubscript j, so that Qjj =annual quantity of product style j=annual quantity of product style j
(products/yr).(products/yr).
• Then let QThen let Qff =total quantity of all parts or products made=total quantity of all parts or products made
in the factory.in the factory.
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20. where P = total number of different part or product styles, and jwhere P = total number of different part or product styles, and j
is a subscript to identify products, j=1,2,…,Pis a subscript to identify products, j=1,2,…,P
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∑
=
=
P
j
jf QQ
1
QQjj and Qand Qff are related as follows :are related as follows :
21. • P refers to the different product designs or types that areP refers to the different product designs or types that are
produced in a plant. It is a parameter that can be counted, and yetproduced in a plant. It is a parameter that can be counted, and yet
we recognize that the difference between products can be greatwe recognize that the difference between products can be great
or small.or small.
• Hard product variety is when the products differ substantially.Hard product variety is when the products differ substantially.
Refers to the number of distinct product lines produced by theRefers to the number of distinct product lines produced by the
factory.factory.
• Soft product variety is when there are only small differencesSoft product variety is when there are only small differences
between products. Refers to the number of models in a productbetween products. Refers to the number of models in a product
line.line.
• Let us divide P into two levels, P1 represents hard product varietyLet us divide P into two levels, P1 represents hard product variety
and P2 is for soft varietyand P2 is for soft variety
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22. Product and Part ComplexityProduct and Part Complexity
• Let nLet npp = the number of parts per product.= the number of parts per product.
• Let nLet n00 = the number of operations or processing steps to make a= the number of operations or processing steps to make a
partpart
• Assuming that the number of product designs P are produced inAssuming that the number of product designs P are produced in
equal quantities Q, all products have the same number ofequal quantities Q, all products have the same number of
component ncomponent npp, and all components require an equal number of, and all components require an equal number of
processing step nprocessing step n00. In this case, the total number of product units. In this case, the total number of product units
produced by the factory given by :produced by the factory given by :
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PQQf =
23. • The total number of parts produced by the factory is given by :The total number of parts produced by the factory is given by :
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ppf PQnn =
And the total number of manufacturing operation cyclesAnd the total number of manufacturing operation cycles
performed by the factory is given by :performed by the factory is given by :
opof nPQnn =
