Nico Treurnicht

QUANTIFYING SYSTEM RELIABILITY IN RAIL TRANSPORTATION IN AN AGEING FLEET ENVIRONMENT

Die bestuur van fisiese bates het in die afgelope tyd al meer belangrik geword, veral in bate intensiewe organisasies. Hierdie artikel stel ’n metode voor wat die betroubaarheid van rollende materiaal bates in die spoor bedryf kwantifiseer deur gebruik te maak van falingstatistiek. Falingverspreidings en interafhanklikheid van stelsels word gebruik om te bepaal wat die invloed is van komponent falings op die betroubaarheid van die totale stelsel. Hierdie benadering word dan gebruik om die betroubaarheid van individuele treinstelle te bepaal. Aanbevelings word ook gemaak hoe om betroubaarheid te gebruik om die beplanning van instandhouding te doen.

INVESTIGATING OF ECO- AND ENERGY-EFFICIENT LUBRICATION STRATEGIES FOR THE DRILLING OF LIGHT METAL ALLOYS

Energy use will be one of the main drivers for the achievement of more eco-efficient drilling processes in the automotive industry. Industry awareness of the environmental impact of used cutting emulsions, and the negative effect on worker health, has increased sharply. This has led to innovative lubrication methods such as through-spindle minimal quantity lubrication (MQL) for drilling aluminium-silicon alloys. In this work the performance of MQL at different cutting speeds and feed rates has been investigated using infrared temperature measurements. The results indicate that MQL is a feasible ecoefficient alternative to conventional flood cooling when drilling aluminium-silicon alloys. OPSOMMING Energiebenutting maak een van die hoofdryfvere uit om eko-doeltreffendheid te behaal in boorprosesse in die motornywerheid. Nywerheidsbewustheid van die omgewingsimpak van gebruikte sny-vloeistowwe, en die negatiewe effek daarvan op werkergesondheid, het skerp toegeneem. Hierdie bewustheid het aanleiding gegee tot die ontwikkeling van smeringsmetodes soos deur-spil minimale hoeveelheid smering (Engels: Minimal Quantity Lubrication, MQL) vir die boor van aluminium-silikon legerings. In hierdie werk word die prestasie van MQL ondersoek teen verskillende snyspoed- en voertempo-kondisies deur middel van infra-rooi temperatuurmeting. Die resultate dui daarop dat MQL ’n lewensvatbare eko-vriendelike alternatief tot konvensionele vloedverkoeling is, wanneer aluminium-silikon legerings geboor word.

Using Poka-yoke methods to improve employment potential of intellectually disabled workers

In this project an electronic manufacturing process, namely ribbon cable assembly, was adapted for execution by intellectually disabled individuals. To make the work accessible to them, human error was controlled by a Poka-yoke approach. The design of the work process used industry standard tooling. Mistake-proofing design identified possible errors, and introduced mechanisms and tests that enabled the worker to avoid them. Test results were analysed using learning theory. It is concluded that intellectually disabled individuals can be enabled to perform the task within normal variation compared with a minimum task time, by using the Poka-yoke approach. Selection, however, is desirable. OPSOMMING ’n Elektroniese vervaardigingsproses, naamlik platkabelsamestelling, word aangepas vir uitvoering deur intellektueel gestremde persone. Vir toeganklikheid deur hierdie groep, word menslike foute beheer deur die Poka-yoke-benadering. Die ontwerp van die werkproses maak gebruik van standaard nywerheidgereedskap. Die ontwerp fokus daarop om die moontlikheid van foute te identifiseer en kenmerke, meganismes, en toetsapparaat te inkorporeer om die voorkoms daarvan onmoontlik te maak. Toetsresultate word ontleed met leerteorie. Die slotsom is dat intellektueel gestremde persone bemagtig kan word, met die Poka-yoke-benadering, om hierdie taak uit te voer binne normale variasie vergeleke met die minimum taaktyd. Keuring is wel wenslik.

A QUANTITATIVE ANALYSIS OF SUPPLY RESPONSE IN THE NAMIBIAN MUTTON INDUSTRY

Agricultural activities in Namibia contribute 5.5% of Namibia’s GDP, while 70% of the population relies on agriculture for employment and day-to-day living. The purpose of this study is to investigate the relationships between the various price and non-price factors contributing to the supply dynamics within the mutton industry in Namibia. The autoregressive distributed lag approach to co-integration was used to determine the longrun and short-run supply response elasticities between economic and climatology factors on time-series data. Supply shifters showed significant short-run and long-run elasticities with regard to the mutton produced. Results also revealed that the system takes nearly two months to recover to the long-run supply equilibrium, should any disturbances occur within the supply system.

Table grape punnet packaging : the influence of check-weighing

Most of South Africa’s table grapes are exported to the EU and the UK. In recent years, prepackaged table grapes are now preferred in many European supermarkets. This increased demand has resulted in stringent quality standards, including the specification of punnet mass. Locally, table grapes are packed manually using seasonal labour, who often have limited formal education. Punnets must conform to upper and lower mass limits, but many deviations occur due to human and machine error. Check-weighing proved effective in reducing out-of-specification punnets, but human and machine errors were still problem factors. OPSOMMING Die meeste Suid-Afrikaanse tafeldruiwe word uitgevoer na die Europese Unie en die Verenigde Koninkryk. Die voor-verpakking van tafeldruiwe in ‘punnets’ begin al meer voorkeur geniet by Europese supermarkte. Hierdie verhoging in aanvraag het gelei tot strenger gehaltestandaarde, insluitend ‘punnet’ massa. In Suid-Afrika word meestal gebruik gemaak van seisoenale werkers met beperkte formele onderrig om tafeldruiwe te verpak. ‘Punnets’ moet voldoen aan boonste en onderste massagrense, maar baie deviasies kom voor as gevolg van menslike- en masjienfoute. Geoutomatiseerde eksterne toetsweging lewer positiewe resultate ten opsigte van vermindering van oor- en ondergewig ‘punnets’, maar menslike- en masjienfoute bly steeds probleemfaktore. a a a a a a a a a a a a a a a a a

Using palletised work-holding to emulate 5-axis machining of aerospace components in the developing world

This paper proposes the application of precision pallet technology, together with common 3-axis milling, to machine certain complex aerospace components that are normally 5-axis machined. In this approach a set of different customised precision pallets are used to present each complex plane to the 3-axis machine as a series of horizontal planes for machining. After machining one surface, the pallet is exchanged for another that has been pre-setup in machining time. Trials confirm the viability of the approach, with capital recovery in less than a year. OPSOMMING Hierdie artikel stel die aanwending van presisiepallettegnologie, saam met gewone 3-as frees, voor om komplekse lug- en ruimtevaartkomponente te vervaardig. Die gebruiklike metode om hierdie komponente te vervaardig vereis 5-as masjinering. In die voorgestelde benadering word ’n stel verskillende pasgemaakte presisiepalette gebruik om elke komplekse vlak as ’n reeks horisontale vlakke te posisioneer vir masjinering. Die gevolg is dat eenvoudige en vinnige vlakfrees voldoende is. Nadat een vlak gemasjineer is, word die pallet vervang met ’n ander wat vooraf opgestel is gedurende masjineringstyd. Toetse bevestig die lewensvatbaarheid, met kapitaaldelging in minder as ’n jaar.