Workshop #4

Stennis Space Center January 7,2006

Introduction to Pneumatics

Overview

Methods of Power Transmission Pneumatics SystemsPneumatics Principles

PartsPneumatic Actuators

Force PrinciplesSolenoid Valves

Advantages

Methods of Power TransmissionMethods of Power Transmission

Electrical MotorsMechanical power transmission elementsFluid Power

Hydraulics Oil, Water, other liquids

Pneumatics Air, other gases

Electric Motors Motors convert electrical energy to mechanical

Electric motors used in First kit

Chipahua/CIM Motor Window Motor

Van Door MotorFisher-Price/Mabuchi

MotorGlobe Motor

Mechanical Power transmission elements

Gears

Belts

Chains

Bearings

Couplings

Mechanical Power transmission using gears

Pneumatics SystemsPneumatics Systems

Pneumatics DefinitionsPneumatics Definitions

Pneumatics is the general term used to describe the mechanics of gases

Pneumatics, derived from the Greek word pneumatikos, meaning coming from the windIt is the branch of science which treats the mechanical properties of air and other elastic fluids used to do work

Pneumatic Principlescompressor

reservoir tank

solenoid valve

cylinder

hose

PneumaticsPneumatics

Compressor

Accumulators

Actuators

Source of Air Flow –Driven by electric motor Provides the energy to perform the work

Reservoir tank - Energy Storage Devices

Cylinders convert energy in the compressed air pressure to linear power. Make things move

LinearRotary

PneumaticsPneumatics

Connectors tubing

Pressure regulators

Valves2-way3-way4-way

Plumbing- connectors -flexible tube

Pressure control -controls the force of the actuator

Control direction of flow

Compressor Thomas industries

12 volt systemGenerates pressure of 120 psiCompactVibration isolators

Relief Valveon Compressor

Protects compressor

Pressure SwitchSignals the controller to start or stop the compressor

Additional Compressor Components

Pressure In

NC NO

Common

Accumulators Pneumatic tank

Up to twoStore compressed air at 120 psiHelps keep the pressure constantSmooth out the pressure fluctuation

Cylinders

Rotary Actuator

Fittings and Plugs

Flow Controls

Regulate flow of air into and out of a cylinderUsed to control speed of a pneumatic cylinderIf used, attach directly to cylinder (only one end needed)

Exhaust Valve

Use to release pressure

FittingsFittingsConnection and DisconnectionConnection and Disconnection

RegulatorsRegulatorsRegulators Control Pressure

Relieving type in the FIRST kit – 2 are includedThe use of Regulators assures maximum efficiency

Allows air from reservoirs to flow to rest of pneumatic systemLimits pressure in valves, cylinders to 60 psi

Solenoid – Electric Valves

Pneumatic ActuatorsPneumatic Actuators – applies force or creates motion through the use of a pneumatic system

Pneumatic ActuatorsUse Pressurized Air to achieve motionProvide power and speed to any actuation system.Variety of Actuation mechanisms available

ArmsGrippersShifters

Arms

Grippers

Shifters

ActuatorsActuatorsConstruction & OperationConstruction & Operation

Basic Construction

Operation

Compressed Air is routed by the valve to extend or

retract the cylinder

ActuatorsActuators

Most Common types of Linear ActuatorsDouble Acting – Single Ended – Double Ended

Single Acting

Spring Return

All containCylinder Barrel Piston RodSealsSpring if used

Facts about PneumaticsFacts about Pneumatics

Pressure – Units of measureLbs per in2 or Force per unit area

Absolute Pressure – 14.7 psia at sea levelGauge Pressure – measured relative to ambient

Flow cfm cubic foot (feet) per minute Volume per unit time

Scfm Standard cubic foot (feet) per minute

Force Principles

Gauge Pressure works against each square inch of piston surface

The greater the square inch surface of the fluid, the less internal pressure will be developed.

ActuatorsActuatorsDifferential AreasDifferential Areas

Force Consideration• Consider the effective area on which the pressure acts• On single ended cylinders there is a differential• Don’t forget friction

CylindersForce = Pressure Area

2” diameter pistonArea = 3.14 12 = 3.14 in2

Pressure = 60 psi3.14 in2 60 psi = 188 lbsForce while extending greater than while retracting

Main decisions: Length and diameterDiameter based on required forceLarger diameter: more force, but more air

Cylinder maximum force

¾” Dia Cylinder½” - 10” Throw 26 lb max force

1-1/2” Dia Cylinder½”-24” Throw 106 lb max force

2” Dia Cylinder½”-24” Throw 188 lb max force

Cylinder ForcesForce Applied = Pressure * Cross Sectional Area

Pressure applied on a flat plate, causes a force! The bigger the plate, or the higher the pressure, the greater the force.

Less force “in” than “out”.This is due to a reduced cross section (caused by the rod being in the way!)

1.5” Bore Cylinder

Retracted Length = 4.38 + Stroke + .25 + 1.31 = 5.94 + Stroke

Base Dimension = 4.38 + Stroke Length = ? +Locking Nut = .25 +Clevis Dimension = 1.31

Extended Length = 5.94 + (2 x Stroke Length)

Single Solenoid Valve

When energized, cylinder goes to one stateWhen de-energized, cylinder always returns to rest state

When power is cut at the end of the match, cylinder will return to rest state

Each valve powered by one relay module (only in forward)

Double Solenoid Valves

One solenoid pulsed to move cylinder one way, other solenoid pulsed to move cylinder the other wayResults unpredictable if both pulsed Valve will stay in either state when neither solenoid energizedCan use one relay for each solenoid or one relay and two diodes

4-way Valves in your kit4-way Valves in your kit

Double Solenoid (detented)SMC

Single Solenoid (spring offset)SMC

4-way Valves in your kit4-way Valves in your kit

Single Solenoid (spring offset)Festo

4-way Valves in your kit4-way Valves in your kit

Single SolenoidPoppet (Spring Offset)

4-way 5-port Valves4-way 5-port ValvesDirectional ControlDirectional Control

Passage A Passage B

Spool

Valve Body

PressurePassage

ExhaustPassage

SolenoidSpring

Why use Pneumatics in 2006? Why use Pneumatics in 2006? The AdvantagesThe Advantages

Complete kit:All the parts required to build an operating systemWeight:equal or lighter than comparable alternatives

Adjustable Force: Different bore cylinders change the available force

and

By adjusting the applied pressure you can instantly adjust the force

Durableno burned up motors – stall with no damage

Strongfrom 9 lbs to 180 lbs – easily adjustable

Custom cylinders in just a few days by UPS

Last minute additionsadd a valve or a cylinder quickly

Why use Pneumatics in 2006? Why use Pneumatics in 2006? The AdvantagesThe Advantages

Why use Pneumatics in 2006? Why use Pneumatics in 2006? The AdvantagesThe Advantages

Multiple cylinders use same compressor

Strongfrom 9 lbs to 180 lbs – easily adjustable

Custom cylinders in just a few days by UPS

Last minute additionsadd a valve or a cylinder quickly

Why do we design with pneumatics?Simple… Pneumatic Cylinders are force vectors.Each cylinder represents a force, which will be applied over a certain distance.Most pneumatic design involves arms or linkages of some type.Know principles of leverage and torque!

Safety Safety always be considered

Relieve the pressure before working on the systemBe aware of pinch pointsAvoid side-loading – increases friction and wearAvoid getting grit or metal shavings on the rod or in

the cylinderUse flow controls for safety

Compressed Air is like a coiled spring

Safety MUST

Interesting LinksFluid Power Educational

Foundationwww.fpef.org

Nason Corporationwww.nasonptc.com

Bosch Rexroth www. bosch-rexroth.com

www.boschrexroth.com

Bimba Manufacturingwww.bimba.com

Lord Corp www.lordmpd.com

Fluid Power Dist. Ass’n www.fpda.org

Clippard Instrument Lab.www.clippard.com

Monnier, Inc. www.monnier.com

Fluid Power Society www.ifps.org

Wikawww.ewika.com/

WikaSite/GlobalSites.aspx

Norgren www.norgren.com

Nat’l Fluid Power Ass’n www.nfpa.com

Festowww.festo.com

Parker www.parker.com

SMC Pneumatics www.smcusa.com

Q/A

Any Questions?About this lecture?About Pneumatics?About Design?About FIRST?About the Game?