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NEW DEVELOPMENTS IN PNEUMATICS

Dr Kurt Stoll Festo AG & Co., Ruiterstr 82, D-73734 Esslingen, Germany

ABSTRACT

This paper dealt with the new developments of

pneumatics in the following areas:

• Pneumatic components

• Industry segment specialized applications

• Best before-sales and after-sales services

KEYWORDS: Developments, Pneumatic drive,

Servo control, Field-bus, valve terminal, modular

systems, dynamic simulation, database

INTRODUCTION

Pneumatics were first utilised at the beginning of the

fifties Fig 1 shows a device built in 1955, which was

fitted with single-acting aluminium die cast cylinders A

typical pneumatic system of that time was used in this

device; it consisted of cylinders and manually operated

valves An operator played the roll of a “logic controller”

Fig 1 An early pneumatic system

Fig 2 A purely pneumatic sequence controller with 12

inputs and 12 outputs Over the past 50 years, with the rapid developments in science and technologies, especially in automation, mechanical, electronic and computer technologies, pneumatics has been experiencing a quick expansion and development Take automation sequence controllers as an example, the first pneumatic control systems functioned via valves that were actuated by driven camshafts In the seventies many purely pneumatically actuated sequence controllers such as the QUICKSTEPPER (Fig 2), which consisted of several pneumatic logic elements, were used

in applications

How is pneumatics applied in today’s modern world? I would like to focus on the new developments in pneumatics in the following areas:

• Pneumatic components

• Industry segment specialized applications

• Best before and after-sales services

NEW DEVELOPMENTS IN PNEUMATIC COMPONENTS

o The combination of different techniques The combining of pneumatics with electronics and of pneumatics with mechanics became an obvious trend over the last 10 years

Behind this trend is the fact that more and more pneumatic drives, sensors and valves are used in a modern automatic machine This means more inputs and outputs are required in the control system A purely pneumatic control system is no longer suitable to meet present

demands So in most machines today, PLCs or IPCs are

used as sequence controllers together with a large number

of electro-pneumatic converters, or solenoid valves

As a result, the pneumatic suppliers are faced with

demands to improve the performance and to expand the

functions of pneumatic components A pneumatic valve

should be easy to install and fast switching A pneumatic

drive should be able to move faster and more precisely

Sometimes an electro-pneumatic proportional valve is

required to convert a continuous electronic signal into

pneumatic signal

All this resulted in the combination of pneumatics,

electronics and mechanics

By combining pneumatics with mechanics, customers will

not only save engineering time with regard to designing

and testing, but also receive an optimised solution because

the product they receive is proven and tested by the

pneumatics manufacturer

Fig 3 shows a swivelling/linear unit, in which a linear

cylinder is combined with a rotary drive to get

independent linear and rotational movements

Fig 3 A swivelling/linear unit

Fig 4 shows pneumatic units used in an assembling

system This includes a linear and rotary cylinder

combined with a high precision guide unit Excellent

precision and rigidity can be achieved with this

combination of components

The “valve terminal” concept was introduced at the

beginning of the nineties In recent years valve terminals

have been widely used The origin of such a product is to

meet the demands of the larger scale control system In a

valve terminal, the valves and electronic I/Os are

integrated in accordance with specific user interfaces (Fig

5) Customers can order a valve terminal according to the

specification of their application They will get a complete

factory

Fig.4 Pneumatic units with several precision

mechanical parts pre-assembled and pre-tested unit They can link the valve terminal to a PLC or IPC via the desired interface, such as multipin or fieldbus They can even order a valve terminal with a PLC already integrated In this way, application engineers can easily divide their control systems into a couple of sub-systems They obtain the sub-systems from the suppliers with guaranteed functionalities That is to say, what the customers get are not only the components, but also the whole solution, a solution that suits their application

Fig 5 A valve terminal, the combination of pneumatics

and electronics

A valve terminal equipped with fieldbus connection makes it possible for the pneumatic system to be integrated as a part of a factory network

Another example of combination and integration is shown

as Fig 6, a pneumatic unit with the combination of a

cylinder, sensors, speed control valves and direction

control valve Where the interfaces to the sensor and

direction valve could be fieldbus or individual

connections

Fig 7 is a multi controlled positioning system, a

pneumatic servo-positioning axis is combined with an

electrically driven axis In this system, we can see that

both the guided pneumatic linear cylinder DGPL and the

guided electrical axis DGEL have the same mechanical

interfaces This makes it much easier for customers to

design their machines

Fig 6 Cylinder, solenoid valve, speed control valves

and sensors in an integrated unit

Fig.7 Pneumatic and electrical drives with the same

mechanical interface

o Compact performance

In many applications, a pneumatic control valve is to be

mounted together with some moving parts of the machine

In this case, the valve should be as light and as small as

possible On the other hand, in order to shorten machine

cycle time, the control valves should be installed as close

to the cylinder as possible

Fig 8 provides a direct comparison of a solenoid valve made in 1961 with one made in 1997, both valves have the same flow rate (400 l/min) but the new generation of solenoid valve is only 10 mm in width, while the old type

is 40 mm

Fig.8 In comparison, valves of 1961 and 1997, the same flow rate, but a quarter of the width

o More intelligence is integrated into products

Faster movement is often desired on a machine It is not difficult to get a cylinder to move faster But it is more difficult to stop a fast moving cylinder properly (without vibrations or shocks)

Fig 9 shows a soft-stop cylinder, in which a displacement sensor, a 5/3 dynamic proportional valve and a smart controller are included With such a system, the time taken for the cylinder to travel from one end position to the other can be reduced by 30% In addition, 2 freely selectable intermediate position settings are possible

Fig.9 Fast speed and soft stop

Fig 10 shows a pneumatic servo positioning system A

digital smart controller is employed in such a system

Fig.10 Smart pneumatic positioning axes

The controller is robust and suitable for industrial

applications Built-in intelligence enables it to find the

optimised control parameters The user needs only to

input the essential application data, such as the load,

stroke, diameter and so on Or even more simply, in the

case of the SPC11 controller, just to push a “teach-in”

button

o Cutting costs with the modular product concept

In a modern highly automated machine, the control

system often has many functions One solution is to make

such products, in which all the necessary functions are

integrated, but this may incur high manufacturing costs

Fig 11 A modular valve terminal with 26 solenoid

valves and various electronic interfaces

A very elegant way is to use a modular product concept The benefit of a modular product for customers is that they can order the products in modules which exactly meet their requirements They only pay for the functions they need

A modular valve terminal is shown in Fig 11 Customers can configure or select the number and the size of the valves, the quantity of the electronic I/Os and so on Fig 12 and Fig 13 show modular vacuum components and modular air service unit respectively

Fig.12 A modular vacuum system with freely

combinable suction cup holder, angle compensator, filter and suction cup

o Innovation, the new driving principle

A new single-acting pneumatic drive - fluidic muscle - is shown in Fig 14 It can output 10 times more force than a standard cylinder of equivalent diameter Fig 14 shows some applications of such a drive

Fig 13 A modular air service unit with manual on-off

valve, compressed air filter and regulator,

lubricator, soft-start valve, distributor and

pressure switch

Fig 14 Fluidic muscle and some typical applications

It is well known that with a pneumatic cylinder it is very

difficult to achieve slow movement without the stick-slip

effect To overcome this disadvantage electrically driven

cylinders of the same size and with the same installation

interfaces as standard pneumatic cylinders have been

developed and applied in applications Customers don’t need to make mechanical modifications to their machines

TRENDS REGARDING APPLICATIONS

With regard to pneumatic applications, one of the most important tasks today is to develop more and more specialized products for the various industry segments

Fig 15 Pneumatic components for the food and packing

industry Fig 15 shows cylinders and valves that have been specially developed for the food and packaging industry, where high corrosion resistance and ease of cleaning are essential

The electronics and handling and assembly industry also need pneumatic products that can meet special requirements Fig 4 shows some precisely guided pneumatic drives with very high rigidity that are suitable for use in the handling and assembling industry Fig 16 shows some miniature precisely guided pneumatic actuators that suit the applications in the electronics industry

Fig 16 Components for the electronics industry

OPTIMUM SERVICES ARE DESIRED

It is not enough nowadays just to offer customers a good

pneumatic product Customers need more and more help

with their everyday tasks This is because they get less

and less time for designing, establishing and maintaining

their machines

A very efficient way is to help the customer by providing

new software tools

An electronic catalogue using the database principle

makes it possible to access product information and

drawings quickly and easily, via function searching,

image searching and other searching methods (Fig 17)

Fig 18 shows a software tool ProPneu, which differs

from a normal dynamic simulation software tool ProPneu

can not only check an existing pneumatic system via

dynamic simulation but also automatically select the

components according to the performances required by

the customer The customer needs only provide Propneu

with a limited amount of information concerning an

application

The settings and parameters of the components, such as

the setting of the pneumatic cushioning and the flow

control valves, can be automatically optimised by

Propneu, according to the criteria the user has selected

Propneu can also recommend the appropriate pneumatic

components for a given task, e.g to move a defined load

in a required time and a certain distance vertically,

horizontally or any inclined installation

Fig 19 shows the software FluidDraw that assists

customers in creating pneumatic circuits on a CAD

system If customers need to know whether their circuit

sequences are correct, then FluidSim is the right

simulation tool

Fig 17 Fast product accessing via the electronic catalogue

Fig 18 ProPneu, an intelligent software for the selecting,

simulating and optimising of a pneumatic system

Fig 19 Software for designing and simulating circuits

for pneumatic sequences

Fig 20 3D CAD drawings on a Website

More and more engineers use a CAD system for

machine design, so, it is very helpful for them to get 2D

or 3D CAD drawings of the pneumatic components they

have selected As shown in Fig 20, they can now easily

import a 2D or 3D CAD drawing via the Internet

REFERENCES

[1] Arnold, G., Pneumatics and Hydraulics in the History

of Energy Technology O+P Vol, 18, 1969 [2] Stoll, Kurt, What is Pneumatics? Thesis, University

of Stuttgart, 1958 [3] Pneumatic Tips, No 51/1994, Festo Pneumatic, Esslingen

[4] Pneumatic World, 2000, No 1, 2 [5] Werner Deppert, Kurt Stoll, Cutting Costs with Pneumatics, 1988, ISBN 7-111-07456-4, in 14 Languages (including Chinese)

[6] Stefan Hesse, 99 Examples of Pneumatic Applications, 2000

[7] Hong Zhou, A Smart Pneumatic Servo Positioning Axis and Its Applications, 3rd JHPS, Proceedings of the Third JHPS International Symposium on Fluid Power, Yokohama, 1996