TechArchive

Original article date: October 1999

Hoerbiger-Origa has come up with a novel pneumatic valve that promises improved control and miniaturisation. Tommy Miller has been finding out

Following pioneering developments in piezo technology for pneumatic control, Hoerbiger-Origa (Interface) has made further advances in electro-pneumatic control. The new Megamic interface brings the benefits of silicon technology to the field of pneumatics and, in so doing, new levels of control and miniaturisation are now possible.

At the heart of the Megamic concept are Silicon electro-pneumatic micro-valves, which combine silicon technology with advanced actuation principles. With minute dimensions, low capacity electronic control and the highest degree of precision in a wide temperature range, the Megamic valves should be capable of fulfilling a variety of specialist applications.

Development of the actuation principle and construction of the Megamic silicon micro-valves were carried out in close co-operation with the Fraunhofer Institute and the Hahn-Schickard Institute for Micro and Information Technology.

The encapsulated silicon chip is actually a micro-valve, inside which a valve plate is moved by electrostatic attraction, and it is this that regulates the flow of gases. Various valve functions can be realised, such as 2/2 and 3/2-way valves, normally opened or closed. Electrostatic attraction allows the valve to be controlled with the smallest possible electrical current in a large temperature range.

Small amounts of air are regulated precisely, and this can be used for the full pressure range of pneumatic equipment, typically 0-16 bar. Additional components make this micro-valve more flexible for various flow rates and voltage ranges.

For automation technology, the micro-valve is combined with a pneumatic booster, resulting in a miniature valve only 10mm wide and with a nominal bore of 1.5mm. Given a suitable control circuit, the valve can be controlled with a TTL-peak signal. The miniature valve is ideally suited to miniature medical devices, analytical equipment, micro-assembly equipment and for piloting miniature conventional valves.

By utilising the silicon technology, further developments will enable the complete integration of sensors, control and communication electronics to facilitate the production of intelligent micro valves.

• Hoerbiger-Origa

October 1999

Original article date: October 1999

For securing tubes, cables and the like, Protex says that its Bandclamp is perhaps the only available method of rapidly clamping small diameters

Why does the Bandclamp score over the old-established and arduous worm-drive hose clip?

The answer, it seems, is because it can be opened and closed repeatedly over long service intervals, it may be released completely and it is fast to operate. For rapidly clamping small diameters in the range 110 to 25mm, it is arguably the only solution available. The simple platform type with spring claw, made in stainless or zinc-plated mild steel, offers custom band diameters from 110 down to 40mm. The maximum spring load is 65kg at a 1.5mm extension.

Technically described as an overcentre, lever-action fastener, there are many variants: Protex is one of only about 10 manufacturers worldwide and supplies around 500 individual catalogue items, plus variations, specials and alternative finishes. Variations include with or without a platform or saddle and mounted on a flexible, custom-made, stainless steel band. Some have an optional safety catch to prevent accidental opening. They can be released fully or made captive.

The variations in design are not to accommodate different diameters of substrate, but because of the pressure to be borne. For example, the 60-1750/PBC And 61-1750/PBC models are down to 25mm diameter. They are pressure tested up to the highest pressure that bandclamps can sustain – 6.5bar (100psi). To accommodate such an elevated pressure, these models have both a special strengthening saddle (a semi-circular shoe) and a triangular platform with a reinforcing ribbed plate underneath.

To make certain applications easier to accommodate, some models of the platform type are also designed with a captive catchplate and hinge built into the band.

Many bandclamps also actually incorporate a worm-drive hose clip – a device with which they normally compete – for extended adjustment (10 times the normal value). Others are in kit form for self-assembly, because users cannot always predict the required diameter in advance.

Uses exist in automotive engineering, chemical, pharmaceutical, food and water and waste treatment industries. Bandclamps are used to secure rubber hoses and tubes and other items, and to facilitate regular Health & Safety examination of exhaust ventilation plant.

•  Protex

October 1999

Original article date: November 1999

We all know that ergonomics in the workplace is important. And you can leave the technicalities to the suppliers, as Bott tells David Norris

There may be companies which are concerned only with avoiding prosecution by the Health and Safety Executive, with little regard for the well-being of their workforce. But more and more British workplaces are seeing the benefits of an ergonomically efficient working environment, according to storage and workshop hardware specialist Bott. And as one of the company’s customers, Blue Circle, says: “If your workforce knows that a system has been designed around them rather than being imposed on them, they are far more willing to give their best and be loyal to the company.”

Injury potential can be minimised in several ways. Make production and finding equipment easier, minimising risk of strain or direct injury. Provide a clear, visual map of the workplace for ease of equipment and tool location and re-location (and define work and storage areas). Make sure potential hazards are more than obvious. And make certain that, by use of intelligent, expedient storage and work areas, the space around machinery is left clear and uncluttered.

Even flooring is a potential hazard: it must be carefully designed for minimum operator fatigue and maximum accident prevention.

Bott equipment can be colour-coded if required, not only enhancing the quality of the visual map in the workplace but also making sure that certain colours denote certain types of hazard. The silhouetting of toolboards can, like colour-coding, make tool and equipment location and re-location easy, highlighting any that are missing or left lying around to provide potential hazards.

Mobile, adjustable storage facilities of varying shapes and sizes enable a workshop which is safe and highly organised to be taken to the task, rather than the worker having to continually waste down-time by fetching equipment from a static source.

Look at security as well. Mechanisms such as safety triggers make certain that drawers do not suddenly open whilst static or in transit. And of course the old favourite of ergonomists, seating: ensure that where machine fitters and mechanics have to stoop or work at low heights or where operators have to stand for long periods by a machine or workbench, the design makes for maximum comfort and maximum adjustment.

• Bott

November 1999

This article was originally written in the period 1995-2000

Mayr Transmissions argues that electronic overload protection still can’t react quickly enough.

Electronic devices for overload protection used to be extremely slow, compared to mechanical torque limiting systems, such as the Mayr EAS-NC. With substantial improvements in servomotors and intelligent controls, this gap has been reduced and servomotors today can react much faster than ever before. Lighter and more powerful motors with responsive electronic controls make motors extremely dynamic.

Some manufacturers argue therefore that, with lower inertia of the servomotor, it is no longer necessary to use mechanical torque limiters to protect a machine against the costly damage and downtime caused by jams or collisions. In order to evaluate this situation, Mayr Transmissions has undertaken research, including all the ranges of low inertia motors from the leading manufacturers. Technical data, including inertia and acceleration, has been considered.

The minimum stopping times of motors have been calculated at different inertias on the driven side of the motor. In order to avoid any controversy about the electronic reaction times in the system, zero delay was assumed, which in practice never happens Ð a more realistic value would be 5ms.

The stopping times of the fastest motors on the market have been applied to an actual collision test of a machine.. The maximum torque would occur in this machine after 15-20ms, whereas the fastest motor would take approximately 30ms to come to a complete stop. A mechanical torque limiter reacts in this realistic example in 3ms. This means that when using electronic protection, the maximum collision force that occurs in 10-20ms still applies before the feed drive can be stopped. The damage still occurs.

This of course is only example using a specific machine, but, considering the fact that the more commonly used motors would take 50-60ms to stop the drive, it is not possible for an electronic system to beat an instantaneous mechanical system. Only if there is very slowly increasing torque will an overcurrent relay be adequate.

Any future limitation to reduce motor inertia to a value that would allow faster stopping times relies on the ratio of motor inertia to ballscrew and turret inertia not exceeding 1:2.5.

• Mayr Transmissions
• Tel: 01535 663900
• Fax: 01535 663261
• Contact: G A Harrison (Technical Director)

Original article date: February 2000

Are you considering using robotics for the first time, but don’t know where to start? Tommy Miller suggests one possibility: Edubot

Taking the first steps towards using robotics can be a very daunting prospect for many people. The fear of the unknown, along with the possibility of spending thousands of pounds on equipment that no-one can operate, let alone understand, often discourages companies from investing in technology that could lead to long-term time and cost savings.

To address this problem, Robotica has designed a programmable robotic arm for use in the teaching of robotics technology. The Edubot is a six-axis open kinematic robotic arm that can be supplied pre-assembled or in kit form, and is controlled through a PC via Robotica’s control software. At under (UK pounds)500, Edubot allows the building, programming and operation of a robot to be learned in an entertaining, cost-effective way.

As well as performing simple pick-and-place tasks, the robotic arm can be interfaced with other devices to complete a sophisticated robotic system. Analogue and digital inputs allow limit switches, pressure sensors, infrared sensors and ultrasonic distance sensors to be connected, and digital outputs enable relays, motors, conveyors, solenoids and LEDs to be controlled from the computer. The software and electronics are suitable for radio-modem communication, so Edubot may be used in wireless mobile robotics applications.

Servo controller

At the heart of Edubot is the Robotica R/C servo controller II, with two analogue inputs, four digital inputs and three digital outputs, connected via an RS232 connector to the computer serial port. Up to four robots can be controlled from one serial port.

The control software supplied with the Edubot includes the following:

• Mouse and/or joystick control.
• R/C servomotors can be controlled either manually or through a program sequence.
• All input and output states can be observed constantly, and they can also be controlled through a mouse click on the screen.
• Different configuration settings can be created for immediate recall, such as servo limits, park position, labels and operational mode.

Programming the unit to perform various tasks is simple thanks to easy-to-use, efficient single character commands, and a comprehensive ‘Help’ menu that is incorporated within the software.

• Robotica

February 2000

Original article date: October 1999

The Government’s Environmental Technology Best Practice Programme says that tagging saves money. Tommy Miller reports on how it can

Essentially, the tagging of products can reduce waste for companies through automation, distribution, production/product quality, recycling/ disposal, security and warehousing. It is hardly surprising, therefore, that tagging is now becoming more generally accepted as an integral part of the manufacturing process

The type of tagging that is used will depend on many things, but there are three main categories of tag to choose from. Whilst optical tags (such as barcodes and two-dimensional codes) are low cost, they are limited in the amount of data that they can hold. Magnetic and electromagnetic devices are slightly more expensive, but they are read-write devices and do not need a clear line of sight. Another disadvantage of this category of device is that they are not especially robust: they are vulnerable to temperature and magnetic fields and they need to be kept away from metal objects.

If the budget will allow it, radio frequency identification is often the best option. These devices can store large amounts of data, they are read-write, reasonably robust and multiple tags can be read simultaneously.

Once a tagging system is operational, it becomes far easier to identify individual items or packages containing many items. Tagging can also be used to identify the location of objects, and relevant information about those objects can also be retrieved or stored. Information about objects is particularly valuable. This might relate to the process conditions prevalent when the object was manufactured, or a batch reference can be used as they key to a vast database of information.

Cost savings can accrue from staff no longer having to enter data manually, or from not having to search for products. Higher quality data can cut the amount of rework and can save production time. Furthermore, the availability of up-to-date, accurate data can reduce the need to hold stocks of parts, sub-assemblies or finished goods. Another important point is that tagging can also leads to benefits for the environment.

• The Environmental Technology Best Practice Programme is a joint DTI and DETR programme.
• For more details on tagging from the Environmental Technology Best Practice Programme call the Environment and Energy Helpline on 0800 585794 (UK only)

October 1999

This article was originally written in the period 1995-2000

How much torque should be put into a joint? This value is often not defined, so a design engineer often has to base the value on experience and values which the fastener manufacturer may recommend. It is also possible to establish the approximate optimum torque by a trial and error method:

• 1 Take a small number (say, 10-20) of new screws and make sure they are free of any lubricant. Using the screwdriver, tighten the fasteners to within 10% of the estimated torque.
• 2 The assemblies should then be subject to normal service loadings, including vibrations, temperature changes, etc. Note any loosening or relaxation in the joint. Adjust the screwdriver torque level and repeat the test with new screws and components until total joint integrity in service is achieved.
• 3 The establish the ultimate over-torque level by applying a low friction lubricant to the screw threads and hand tightening them to specified torque +10%. Observe the degrees of rotation in the screw in case they suddenly increase, indicating “necking” or fatigue in the screw. Then continue to apply torque until either the thread strips or the screw head breaks off.
• 4 The established safe torque should then be inserted on the production drawings.

Fastener torque values

Clamping force is what actually keeps a joint together and applying torque to a threaded fastener achieves this clamping force by using the thread pitch to pull the screw head down onto the surface of the work place. The table shows recommended torque values for metric fasteners of different tensile strengths or grades. The values shown are for lightly oiled, plain steel screws, having a coefficient of 0.125. The most common grade is 8.8, but 10.9 and 12.9 are also used. It is not recommended that grades below 8.8 are used for machine screws which will be assembled by power tools.

Screwdrivers and Screwdriving is a handy, 24 page, A5 guide to component jointing using threaded fasteners from Desoutter. Its five main sections cover: Threaded Fasteners (illustrating the different types of self-tapping screws and screwheads); Types of Joint; Torque, Screwdriving Tools; and Problem Solving. Single copies are available free of charge by circling the enquiry number immediately below. Also, to assist manufacturers in building up training programmes, the company tells us that the material is available in 8.5 x 11in format for copying onto overhead transparencies.

• Desoutter
• Tel: 0181 205 7050
• Fax: 0181 205 5167

Original article date: June 2000

Keeping the weight down has long been a recipe for success for Lotus. On two new models the company is taking advantage of bonded aluminium space frames

Lotus, the legendary sports car manufacturer, is building on the successful Elise model. Three new models incorporating a bonded aluminium space frame chassis are headed for road and track.

This summer, Lotus is to begin building a new sports car for GM subsidiaries Vauxhall and Opel called the VX 220 and the Speedster. Both take advantage of space frames made by Hydro Automotive Structures that weigh in at just 68kg.

In fact, the VX 220/Speedster tips the scales at only 850kg, paired up with a 2.2 litre mid-mounted engine. The bonded aluminium chassis offers not only light weight, but also high torsional rigidity, absolutely necessary for precise control at high speeds.

The bonded frame allows an even lighter chassis than with other methods. Adhesive bonding allows thinner extrusions because the aluminium is not subjected to the strength-sapping welding process, according to Lotus.

In all, there are more than 60 parts in the Elise space frame. The individual extrusions come from Hydro Aluminium Extrusion in Tonder, Denmark. Machining is performed at Hydro Automotive Structures in Bromyard, England, anodising at Hydro Aluminium Extrusion in Bedwas, Wales and assembly is at Hydro Automotive Structures’ plant in Worcester, close to Lotus.

The bonding adhesive is precisely applied by robotic equipment. The assembled chassis is placed in an oven and heated to 185degC to cure the adhesive.

Lotus and Hydro developed the space frame for the Elise – a first for a production road car. The high strength-to-weight ratio and the light components meant that Lotus could use a smaller engine – a 1.8 litre in the original Elise – saving money and even more weight. The Elise weighs just 699kg and even the beefed-up 143hp Elise 111S tips the scales at just 714kg.

Also in production now with space frames from Hydro is the 340R, an exclusive sports car based on the Elise. The stripped-down 340R will be limited to a production of just 340, the company says. The concept car was originally designed with no doors, no side windows, no roof and minimal bodywork.

Next in line is the M250 coupe. Light weight, combined with a powerful V6 mid-placed engine, mean that the M250 will perform well on acceleration. It is expected to go into production in 2002.

• Hydro Aluminium Structures
• Hydro Aluminium Extrusions

June 2000

Original article date: January 1998

Today, for the first time, anyone with an Internet connection can access details of over three million patents. Derwent Information, the international provider of patent information has launched Patent Explorer. This innovative new product, developed in co-operation with Microsoft, is the first Internet service to provide both full text searching and facsimile images of documents from the US and European Patent Offices.

Patent Explorer offers users a unique point and click research tool. Even without specialist training, patents can be searched using over 40 different criteria, including company name, date, technology area, patent number and inventor name. Once the search is finished, the patents can be reviewed online, either as text or an exact image including diagrams, or downloaded to a file for local viewing and printing. Complete documents can be ordered online for delivery by fax or post.

Patents can provide a wealth of data for companies including technical and business information. With Patent Explorer, users can monitor the research activities of competitors, alert themselves to developing new technologies that may have an impact on business and also ensure that their own intellectual property rights are not being infringed. Within a week of publication by the relevant Patent Office, Derwent customers can search all European and US text and image data. As well as the latest patents, Patent Explorer can be used to trace the development of a particular technology as it holds all US patents dating back to 1974 and European patents from 1978 onwards.

For advanced users, Patent Explorer is packed with additional features. Customised search and display templates can be created and sophisticated Boolean operators can be used to tailor the search further. Individually tailored search profiles can be created and saved and set up to run on a weekly or monthly basis as a technology alerting service, with users prompted by e-mail when matching documents are loaded onto the database.

The first commercial release of Patent Explorer is aimed at the corporate user. Companies with large usage requirements can opt for an attractive discounted pre-payment arrangement. Alternatively, organisations with a lesser requirement can make use of a pay as you go option.

The service is open to visitors atwww.patentexplorer.com

©In Press PR Ltd1997

January 1998

Original article date: September 1998

MTE Turck has introduced the R55 colour mark sensor for print verification label detection and web cutoff registration.

The Banner R55 colour mark sensor operating at extraordinary speeds of up to 10 000 operations per second is designed for printing presses and all types of labelling and sensing registration marks on packaging material. However its versatility opens up a much wider range of industrial applications.

The electronic design includes a solid-state emitter and receiver that allows the sort of colour mark resolution once only possible with incandescent systems. The R55 solid state light source can detect all colours found in contemporary print jobs even on extremely low contrast mark such as 20% yellow ink on newsprint.

The R55 has a response time of only 50us and can therefore fulfil the fastest requirements for users with high-speed production lines and web offset presses. The speed allows smaller colour marks to achieve the required throughput. In some cases colour marks can be eliminated using an “eye spot” on the package instead. It also includes a built-in 50ms delay and one-shot logic to allow an interface with slower input devices such as PLCs.

An advanced LED moving bar graph display indicates the contrast level between the colour mark and the background. It also indicates the sensor switch point making setup fast and easy. The sensitivity can be adjusted using a 15-turn knob. It works for all applications without the need to switch between multi-coloured LEDs. But when scanning difficult colour combinations new high power green LEDs are used which give a greater range of sensing contrast compared with red or blue.

The R55 has high tolerance to web flutter or other situations where there is a slight variation in the target distance. This is achieved by a focal point of 10mm and a depth of field of +/-3mm. The built-in analogue output enables the R55 to become a sensitive instrument that can measure surface brightness and texture consistency and perform colour recognition and surface mapping.

The R55 is designed to withstand impact and severe environmental conditions. It is also leak-proof and meets IP67 and NEMA6 standards. Rugged input and output circuitry prevents damage from high voltage transients or reverse polarity and provides noise interference immunity. Outputs are protected against stray pulses at switch-on as well as continuous overload at short circuits.

• MTE Turck
• George Perkins
• 01702 525186

September 1998