------------------------Monitor------------------------- The Newsletter for PC-Based Data Acquisition and Control Issue 37 www.windmill.co.uk August 2001 --------------------ISSN 1472-0221---------------------- Welcome to the August Edition of Monitor. We hope you enjoy it, but should you wish to cancel your free subscription please visit http://www.windmill.co.uk/newsletter.html This month, everything you ever wanted to know about electroforming and computerisation. A story illustrating how an automated control system increases safety, provides comprehensive records and improves the quality of the finished product. CONTENTS ======== * Windmill News: Current monitoring device now available from our Data Acquisition Catalogue * Automating Electroforming Processes -- What is electroforming? -- The electroforming process -- Computerised control - Controlling the current density - Monitoring voltage to prevent overheating - Monitoring temperature and level - Controlling dosing - Laboratory control: ventilation for cyanide and acid fumes - Equipment checking - Calculating the thickness of deposited metal on complex shapes - Displaying and logging data - Future developments: web-based distance learning * Data acquisition and control exhibitions ________________________________________________________ Windmill News: Current monitoring device now available over the Internet ________________________________________________________ Our on-line catalogue is now stocking a current measurement device for use with USB and ISA-bus units. This boxed unit sits outside the PC and accepts 8 current and 8 voltage inputs. For more details see https://www.windmillsoft.com/daqshop/data-acquisition.html ________________________________________________________ Automating Electroforming Processes ________________________________________________________ Contents ======== -- What is Electroforming? -- The Electroforming Process -- Computerised Control - Controlling the Current Density - Monitoring Voltage to Prevent Overheating - Monitoring Temperature and Level - Controlling Dosing - Laboratory Control: Ventilation for Cyanide Fumes - Equipment Checking - Calculating the Thickness of Deposited Metal on Complex Shapes - Displaying and Logging Data - Future Developments: Web-Based Distance Learning What is Electroforming? ======================= In electroforming a thick layer of metal is deposited either into a mould, or over a mandrel or model, which is usually later removed. This leaves a metallic object that is light, strong and an accurate replica. Electroforming is used in many industries, including in manufacturing precision components for the automotive and aerospace industries, in making fine jewellery and in exact reproduction of museum pieces. The Electroforming Process ========================== The mould or mandrel is placed in a tank of electroforming solution containing, for example, salts of nickel, silver or gold. The positive current from a power supply is connected to a pure metal plate at one end of the tank (the anode) and, at the other end of the tank, the negative current is connected to the piece of work to be electroformed (the cathode). The positive metallic ions are attracted to the negatively charged piece of work, where they are deposited. The metal in solution is replenished from the anode. Computerised Control ==================== At its simplest, electroforming equipment can comprise just a small bath, a battery and manual calculations. However, for larger installations with several tanks and where precision is required, computer control comes into its own. The successful metal deposition depends on many factors, most of which can be monitored and controlled by a computer. A computerised system can also control the laboratory or workplace environment. It's perhaps easiest to illustrate by using a real example. The University of Central England's School of Jewellery run eleven electrodeposition tanks. They control these tanks and log environmental data using a system provided by Biodata Ltd (www.microlink.co.uk), who employed the software expertise of Windmill Software. * CONTROLLING THE CURRENT DENSITY Every electroforming solution has a range of upper and lower electrical power limits, between which a good result may be obtained. This is called the Current Density. Too little power and no metal will be deposited. Too much and the grains might brush off as a powder. The current density, measured in amps per square decimetre or amps per square foot, has therefore to be accurately measured and controlled. To calculate the current density required, we need to know the surface area of the object - a large object consumes more energy and has a higher resistance than a smaller one. The computer ensures that the optimum current density is applied throughout the process. * MONITORING VOLTAGE TO PREVENT OVERHEATING The power supply's voltage drives the target current through the electroforming solution. The software monitors this voltage. Should it start to rise during the process it means that the resistance in the path of the current is increasing. This increase in resistance may be due to degradation of a contact point with the anode or cathode, which with quite high current passing through can lead to overheating. The software alerts operators and can automatically shut down the tank if necessary. * MONITORING TEMPERATURE AND LEVEL The tank takes time to reach its operating temperature. The computer therefore starts heating the tanks before the start of the working day, so that it is ready when people arrive. The software monitors the tank for high or low temperatures, which indicate a failure of the heating controller. It also monitors the level of liquid in the tank - automatically turning the heating off if the liquid level falls. * CONTROLLING DOSING Dosing pumps are used to replace chemicals that are consumed in the electrodeposition process. The gold alloy tank in the School of Jewellery, for example, has 3 dosing pumps - each independently controlled. Chemicals are consumed on a current/time basis. The computer monitors the current through the tank and automatically doses the tank at regular ampere-minute intervals. However, the system also allows people to manually request a dose be applied, recording this event. There is also a push-button on the tank panel to disable automatic dosing. This interfaces with the computer through a digital input. The computer checks this digital input before proceeding with dosing - raising an alarm if the dosing is thus disabled. The software requires operators to acknowledge the alarm to confirm that dosing is suspended. * LABORATORY CONTROL: VENTILATION FOR CYANIDE FUMES Because of the use of cyanide and acid based electroforming solutions, the workplace has to have adequate ventilation. In the School of Jewellery, the acid and cyanide lines are provided with fans to extract the air above each tank. These fans have a scheduled on- off cycle, typically on for 5 minutes in every 20. They can also be switched on and off manually when required. The computer monitors pressure switches in the ventilation ducts to ensure that the fans are operating correctly. Any failure and it sounds an emergency alarm. * EQUIPMENT CHECKING At the beginning of an electroforming process, the computer checks all the necessary equipment is in place. For example - it makes sure that the correct tank filter is connected. Should the filter be missing, or of the wrong type, the computer alerts operators, switches off the power to the filter and refuses to start the electroforming process. The computer controls each tank's equipment, such as filters, agitators and aerators, through digital outputs. Should any of the equipment fail during the process, the computer sounds an alarm and if necessary shuts down the process for that tank. A corner of the University's new Electroforming Laboratory * CALCULATING THE THICKNESS OF DEPOSITED METAL ON COMPLEX SHAPES It can be difficult to calculate the surface area of some complex shapes. This is important as the thickness of metal deposited is proportional to the current passing through a unit of surface area multiplied by time. However, if we have a test piece of work with a known surface area, the computer can measure the percentage of current going through the test piece. It can then calculate the amount of metal deposited on the test piece and therefore calculate the thickness of the plating material. This, providing the test piece is not located in a preferentially good position in the tank, will be less than or equal to the thickness of metal deposited on the work itself. * DISPLAYING AND LOGGING DATA Each tank has its own display page with buttons for Running and Pausing. Alarm messages are displayed and tanks are shown in different colours for different alarm states. More detailed display pages are available, for example for heater and filter information. History graphs are also displayed. All data, including alarms and manual events, are logged to disk. * FUTURE DEVELOPMENTS: WEB-BASED DISTANCE LEARNING Future developments for the School of Jewellery's system include a distance learning facility. Students will be able to view activity within the laboratory through a web browser and see the status of the various electrodeposition tanks. Using the web system, the lecturer will be able to remotely interact with the student. * This article has highlighted some of the advantages and uses of a computerised system. It increases safety - shutting down tanks should conditions not be right, not starting processes if the necessary equipment is not in place, sounding emergency alarms if cyanide extractor fans are not working correctly, and so on. It provides comprehensive records of the processes, logging all data to disk including information about tasks performed manually, any alarm conditions that occurred and the steps taken to remedy the situation. It also improves quality by ensuring optimum conditions. For more information on a computerised electrodeposition system contact Windmill Software at [email protected] Our thanks to Les Curtis, The School of Jewellery, University of Central England, for his help with this article. ________________________________________________________ Exhibitions and Conferences ________________________________________________________ Upcoming data acquisition and control exhibitions include: Automation 2001 4-6 September Helsinki Fair Centre Finland Comprises an extensive exhibition and seminar program. http://www.finnexpo.fi/exhibition.asp?Id=600&code_language=en ISA 2001 11-13 September Houston Texas USA The premier instrumentation, systems and automation conference in North America. This year features 700 exhibitors, over 25 training courses and nearly 100 seminars. https://www.isa.org/events/1,1313,0,00.html Automation Europe 18-20 September Paris France Billed as "the automated installation industrial performance event", companies will be exhibiting their automation, instrumentation, communication, monitoring, test and measurement equipment. 13000 visitors are expected to attend. http://www.automationeurope.com/ Interkama 2001 24-28 September Dusseldorf Germany A biennial event showcasing industrial communication, automation and measurement. http://www.interkama.de/ ISA 2001 UK 10-11 October 2001 Buton-Upon-Trent UK ISA's first European instrumentation conference and exhibition comprises four conference sessions running parallel each day, plus a two-day exhibition. https://www.isa.org/ Manufacturing Week 2001 30 October - 1 November NEC Birmingham UK Includes 4 exhibitions: Drivers, Motors and Controls; Porduction; Automation and The Design Engineering Show. http://www.manweek.co.uk/ ________________________________________________________ * Copyright Windmill Software Ltd * Reprinting permitted with this notice included * For more articles see http://www.windmill.co.uk We are happy for you to copy and distribute this newsletter, and use extracts from it on your own web site or publication, providing the above notice is included and a link back to our website is in place. An archive of previous issues is at http://www.windmill.co.uk/newsletter.html and an index of articles at http://www.windmill.co.uk/newsletter.html Windmill Software Ltd, PO Box 58, North District Office, Manchester, M8 8QR, UK Telephone: +44 (0)161 833 2782 Facsimile: +44 (0)161 833 2190 E-mail: [email protected] http://www.windmill.co.uk/ https://www.windmillsoft.com/
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