Pneumatic ElectroPnuematic Jan2008

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PNEUMATICS AND ELECTRO-PNEUMATICS TECHNOLOGY

UNIVERSITY KUALA LUMPURMALAYSIA FRANCE INSTITUTE

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Principles of pneumatics

Pnuematics defined • Pnuema – Air (wind or breath in ancient Greek)

• Matic – movement

• It means control movement of air• In industries, it is referred as the used of compressed air to transmit power or/and motion

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MOST ENERGY SOURCE

• Electricity• Hydraulics• Pneumatic• Etc

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Why Pnuematic? The advantages:• Cheap – Air is available in unlimited

supply• Air is non-explosive and non-toxic• Compressed air can be transmitted over

long distance• Compressed air can be stored• Fast• Easily control the speed and movement• Clean• Overload proof

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Disadvantages:• Air absorbs moisture and drying may

have to be considered• The exhaust air causes noise. Sound

absorbers may be required• Pressure limit which can be used in a

compressed air system• Smooth and even movement not

possible

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Pneumatics is used in carrying out machining and working operations.For example:• Drilling• Turning• Milling• Sawing• Finishing• Forming• Quality control

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Principles of pneumaticsApplication example: Conveyor line diverter

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Application example: Pneumatic cutter

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Unit for pressure• PSI• Pa• Bar (normally used in industries)• N/m2 (SI unit)

- Gauge pressure vs absolute pressure

- Vacum

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ELEMENTS OF PNUEMATICS SYSTEM• Energy supply, source• Input elements, input signal• Processing elements, processor

signal• Final control element, control signal• Actuating devices, output

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Electro-pneumatic System• Combination of electrical control and

pneumatic technologies

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Electro-pneumatic System

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Electro-pneumatic SystemAdvantages of electro-pneumatic:• Higher reliability (fewer moving parts

subject to wear)• Lower planning and commissioning

effort particularly for complex controls• Lower installation effort, particularly

when modern components such as valve terminal are used

• Simpler exchange of information between several controllers

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Pnuematic System and Air Generation

ENERGY SUPPLY UNIT (AIR GENERATION)

• Air compressor• Air receiver/reservoir• Air cooler• Air dryer• Service unit – Filter, Regulator &

Lubricator (FRL unit)

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Pnuematic System and Air GenerationCompressed air distribution system:

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SYMBOL FOR ENERGY SUPPLY UNIT

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SYMBOL FOR ENERGY SUPPLY UNIT

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Energy Supply Unit

TYPE OF COMPRESSOR• Reciprocating

- piston- diaphragm

• Rotary- vane- screw

• Flow compressor- axial flow- radial flow

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Energy Supply UnitType of compressor

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ENERGY SUPPLY UNIT

Type of compressor

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Type Of Compressor

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Type Of Compressor

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Air Drying

Refrigeration Drying

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Refrigeration Drying

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AIR DRYING

Absorption and Adsorption drying

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ABSORPTION DRYING

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ADSORPTION DRYING

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ENERGY SUPPLY UNITSURVICE UNIT• Compressed air filter

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COMPRESSED AIR FILTER

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SERVICE UNIT

Pressure regulating valve

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PRESSURE REGULATING VALVE

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SERVICE UNITCompressed air lubricator

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COMPRESSED AIR LUBRICATOR

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Pneumatic Symbols and Standard

Flow path

Switching position

Flow path blocked

Connection ports

Directional Control Valves

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- Way valve

Number of ports

Number of switching positions

2 2

- Way valve32


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Directional control valves

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Port designation

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Port designation

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Input Elements ValveTypes of actuation

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Input Elements ValveTypes of actuation

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Pneumatic Symbols and StandardNon-return, flow control and pressure control valves

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Pneumatic Symbols and StandardNon-return, flow control and pressure control valves

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Pneumatic Working Elements

Linear:• Single acting cylinder• Double acting cylinder• Rodless cylinder

Rotary:• Rotary actuator• Swivel drive/cylinder

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Pneumatic Working Element

Single acting cylinder

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Single Acting Cylinder

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Single Acting Cylinder

Bellow / membrane cylinder

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Pneumatic Working ElementDouble acting cylinder

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Double Acting Cylinder

• With out cushioning

• With cushion

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Cylinder Construction

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Type Of Mounting

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Type Of Mounting

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Type Of Mounting

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Type Of Mounting

Rod end mountings

F

UF

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Rodless Cylinder

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Rodless Cylinder

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Rotary Cylinder & Swivel Drive

Swivel Drive

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Rotary Cylinder & Swivel Drive

Rotary cylinder

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Force CalculationPascal’s Law:pressure exists when a force F is imposed on an enclosed fluid with a surface A, The pressure exerts an equal effect on all points of the surfaces.

FP

A

P =FA

N/m2

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Force CalculationTheoretical Force: Fth

Fth is the calculated force based on Pascal’s Law without consideration of all the resistance forces.

Frictional Resistance: Ff

To be considered during extend and retract strokes. Estimated at about 10 to 12% of Fth.

Spring Resistance: Fsp

To be considered when using spring loaded single acting cylinders. Estimated at about 15% of Fth.

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Force Calculation

Example 1:A double acting cylinder is used to transfer work-pieces in a production machine. Determine the extend and retract forces if the piston diameter of the cylinder is 80mm, rod diameter 15mm and the pressure used is 6bar. Assume frictional force is 10% of theoretical force.

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Force Calculation

Example 2:A clamping vice uses a single acting cylinder to clamp the work-pieces. Determine the extend force if the piston diameter of the cylinder is 80mm, rod diameter 15mm and the pressure used is 6bar. Assume frictional and spring forces are 10% and 15% of theoretical force respectively.

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Design and construction of pneumatic control circuits

Exercise 1.

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Exercise 2.

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Components designation

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Components designation: Example

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Direct and indirect actuation

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DIRECT ACTUATION

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INDIRECT ACTUATION

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Pneumatic Control DevicesDirectional Control Valves

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Pneumatic Control DevicesShuttle Valve (OR)

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Shuttle Valve (OR)

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Pneumatic Control DevicesDual Pressure Valve (AND)

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Dual Pressure Valve (AND)

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EXERCISE 3.

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SHUTTLE VALVE (OR FUNCTION)

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EXERCISE 4.

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DUAL PRESSURE VALVE (AND FUNCTION)

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Pneumatic Control DevicesOne-way Flow Control Valve

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One-way Flow Control Valve

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One-way Flow Control Valve

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EXERCISE 5.

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5/2 WAY DOUBLE PILOT VALVE (SPEED CONTROL)

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Exercise 6. A container of washers is to be dipped in and out of the cleaning bath by using a double acting cylinder. The start and stop for this continuous movement is to be achieved by actuating the ‘START’ and ‘STOP’ pushbuttons each.On actuating the ‘STOP’ pushbutton, the container should stop at the top. The speed for forward and retract strokes are controllable.

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ELECTRO PNEUMATIC

Pneumatic Vs electro-pneumatic Electro-pneumatic component Electrical component Electro-pneumatic controller Design and construction of electro-

pneumatic control circuits

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Electro-pneumatic components

Function of solenoid A magnetic field is

induced when a current passed through an electrical conductor

A soft iron core (amature) is drawn into a coil through which the current is flowing

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Electro-pneumatic componentsSolenoid Valves

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Solenoid Valves

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Solenoid Valves

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Solenoid Valves

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Solenoid Valves

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Solenoid Valves

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Solenoid Valves

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Electrical components

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Design and construction of elctro-pneumatic control circuits

Using a sorting device, parts are to be transferred from conveyor belt. By pressing the pushbutton switch, the piston rod of a single-acting cylinder pushes the part off the conveyor belt. When the pushbutton is released, the piston rod returns to the retracted end position.

Exercise 7:

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Design and construction of electro-pneumatic control circuits

Using a special device, the valve in a pipe line is to be opened and closed. The valve is opened by pressing the pushbutton switch. When the pushbutton is released the valve is closed.

Exercise 8:

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Wooden planks are to be pushed along from a gravity feed magazine to a clamping device. By pressing a pushbutton switch one plank is pushed by the slide out of the gravity feed magazine. After the slide has reached the forward end position it is returned to its start position.

Exercise 9:

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Design and construction of electro-pneumatic control circuits Exercise 10:

Using a conveyor belt, parts are to be transported in linear timed sequence to work stations which are arranged in line after one another. When the latching pushbutton (or selector) switch is activated the main wheel is indexed by the oscillating piston rod of a cylinder via a pawl. When the pushbutton (or selector) switch is activated again the drive is switched off.

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Coil

Coil connections

Contacts

Contact connections

Return spring

Cover

Symbol

A1

A2 11

12

14

21

22

24

Armature

Relay

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Relay

Symbol

A1

A2 11

1214

21

2224

A1 A2 4 2 1

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Relay

Symbol

A1

A2

11

1214

21

2224

A1 A2 4 2 1

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Repeat the exercise 10 but the conveyor is controlled by using ‘Start’ and ‘Stop’ pushbuttons.

Exercise 11:

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Electro-pneumatic controller

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Electro-pneumatic componentsPressure Switch

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Exercise 12:

Parts are to be stamped with a stamping device. By pressing two pushbutton switches the die is pushed down and the part is stamped. When the stamping pressure has been achieved the dieis returned to its start position.

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Electrical componentsTime relay (Timer)

Two types:•Pull-in (on) delay and •Drop-out (off) delay

Pull-in (on) delay

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Pull-in (on) delay Timer

Signal behavior:

Time relay (Timer)

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Drop-out (off) delay

Time relay (Timer)

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Time relay (Timer)Drop-out (off) delay

Signal behavior:

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Using a hot pressing die, packing material is to be sealed by application of heat. By pressing a pushbutton switch the heating rail is advanced and the packaging material is heated along the adhesive strip. After the adhesion time of 10 seconds has reached, the heating rail is returned to its start position.

Exercise 13:

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Using a transfer station blocks are to be transferred from a magazine to a processing station.The blocks are pushed out of the magazine by cylinder 1A and transferred to the processing station by cylinder 2A. The piston rod of cylinder 2A may only return when the piston rod of cylinder 1A has reached the retracted end position. The magazine is monitored by means of a limit switch. If there are no more blocks in the magazine, it is not possible to start the cycle. This is indicated by means of an audible signal. The control is to be operated in single cycle.

Exercise 14:

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Control of Multiple Cylinders

Chronological sequence is simplified by using:• Displacement step diagram (pictorial)• Vector diagram

Example: 1A→ 2A→ 2A← 1A←• Abbreviation notation

Example: 1A+ 2A+ 2A- 1A-

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Workpieces are inserted into the clamping device by hand. Clamping cylinder 1A is to extend when the start button is pressed. When the workpiece is clamped, it is to be drilled via feed unit 2A and the drill retracted once again. Then, the clamping cylinder 1A is to release the workpiece.

Exercise 15:

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Control of Multiple CylindersMethods for construction a circuit diagramTwo primary methods:

• Intuitive method - conventional or trial and error methods.

• Methodical design I accordance with prescribed rules and instructions.

Signal overlapsOvercome by signal cut-out through:1) Components

• Idle roller limit switch• Timer

2) Circuit• Electrical Cascading Circuit• Electrical Shift register

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THE ENDTHANK YOU

Pneumatic ElectroPnuematic Jan2008

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