Scielo RSS <![CDATA[South African Journal of Industrial Engineering]]> http://www.scielo.org.za/rss.php?pid=2224-789020120003&lang=pt vol. 23 num. 3 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Note from the editor</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300001&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>The Industrial Engineering publishing landscape</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300002&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Project management maturity and project management success in the engineering and construction industries in Southern Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300003&lng=pt&nrm=iso&tlng=pt Previous studies have attempted to determine how the success of South African IT projects related to the project management maturity of the organisations that executed the projects. The study reported in this article was conducted during 2010 in the engineering and construction sectors. This paper reports on a structured questionnaire distributed to 1,625 individuals mainly in the South African engineering and construction industries, from which 255 responses were received. 'Project success' was self-defined by the respondents, who identified 'project success' within their unique environments and contexts. The bulk of the projects (46%) were considered successful. The average perceived project management maturity level was 2.88.<hr/>Vorige studies het bepaal hoe die sukses van Suid-Afrikaanse IT projekte vergelyk met die projekbestuursvolwassenheid van die organisasies wat die projekte uitgevoer het. Hierdie studie is uitgevoer gedurende 2010 in die ingenieurs- en konstruksiebedrywe. 'n Gestruktu-reerde vraelys is versprei aan 1,625 mense wat meestal werksaam was in die Suid-Afrikaanse ingenieurswese-en konstruksiebedrywe, en 255 antwoorde is ontvang. 'Projeksukses' is selfgedefinieer deur die respondente op grond van hulle unieke omgewings en kontekste. Die grootste hoeveelheid van die projekte (46%) is as suksesvol gereken. Die gemiddelde waargeneemde vlak van projekbestuursvolwassenheid was 2.88. <![CDATA[<b>An analysis of maintenance performance systems in the South African mining industry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300004&lng=pt&nrm=iso&tlng=pt The measurement of performance is an essential part of the management process. The planning function usually defines the goals and objectives for the business enterprise or division of the enterprise. The control function should monitor the performance measures and establish corrective action if actual performance deviates significantly from planned performance. Maintenance performance measurement is therefore essential to ensure that maintenance objectives are achieved, and that maintenance adds value for the company. The objective of this paper is to discuss the findings of a project that investigated aspects of the maintenance performance system of a number of mining companies in South Africa. The findings of a survey indicated that maintenance performance management is not yet used to its full potential in the mining industry.<hr/>Die meting van prestasie is 'n noodsaaklike deel van die bestuursproses. Die beplannings-funksie defineer normaalweg die doelwitte vir die organisasie of divisie van die organisasie. Die beheerfunksie monitor die prestasie en bepaal of korrektiewe aksie nodig is wanneer die werklike prestasie noemenswaardig afwyk van die beplande prestasie. Prestasiemeting in instandhouding is dus noodsaaklik om te verseker dat die doelwitte vir die instand-houdingsafdeling bereik word en dat instandhouding waarde toevoeg vir die organisasie. Hierdie artikel bespreek die resultate van 'n projek wat verskeie aspekte van die prestasiestelsel van 'n aantal mynmaatskappye in Suid-Afrika ondersoek het. Die vernaamste bevinding van die projek is dat prestasiebestuur in instandhouding nog nie ten volle benut word deur verskeie mynmaatskappye in die mynbou-industrie nie. <![CDATA[<b>Approximations to performance measures in queuing systems</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300005&lng=pt&nrm=iso&tlng=pt Approximations to various performance measures in queuing systems have received considerable attention because these measures have wide applicability. In this paper we propose two methods to approximate the queuing characteristics of a GI/M/1 system. The first method is non-parametric in nature, using only the first three moments of the arrival distribution. The second method treads the known path of approximating the arrival distribution - by a mixture of two exponential distributions - by matching the first three moments. Numerical examples and optimal analysis of performance measures of GI/M/1 queues are provided to illustrate the efficacy of the methods, and are compared with benchmark approximations.<hr/>Benaderings tot verskeie prestasiemaatstawwe in toustaanstelsels ontvang beduidende aandag weens die wye toepasbaarheid daarvan. In hierdie artikel word twee metodes voorgestel om die toustaaneienskappe van die GI/M/1-stelsel te benader. Die eerste metode is nie-parametries van aard en gebruik slegs die eerste drie momente van die aankomsverdeling. Die tweede metode volg die bekende roete om die aankomsverdeling te benader deur die eerste drie momente te pas, deur middel van 'n kombinasie van twee eksponensiële verdelings. Die doelteffendheid van die metodes word aan die hand van numeriese voorbeelde en optimale ontleding van die prestasiemaatstawwe van GI/M/1-stelsels bewys, en word vergelyk met benaderings. <![CDATA[<b>A study of the median run length (MRL) performance of the EWMA <i>t</i> chart for the mean</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300006&lng=pt&nrm=iso&tlng=pt The exponentially weighted moving average (EWMA) X chart is effective in detecting small shifts. However, the EWMA X chart is not robust enough to prevent errors in estimating the process standard deviation or a changing standard deviation. To overcome this problem, Zhang et al. suggested the EWMA t chart in 2009. The existing optimal design of the EWMA t chart is based on the average run length (ARL) criterion. This paper proposes that the optimal design of the EWMA t chart be based on the median run length (MRL). The MRL performances of the optimal EWMA X and optimal EWMA t charts are compared.<hr/>Die eksponensiaalgeweegde bewegende gemiddelde (EWMA) X -kaart is geskik om klein verskuiwings te bespeur. Die EWMA X -kaart is egter nie robuust genoeg om foute in die beraming van die proses standaardafwyking of 'n veranderende standaardafwyking te voorkom nie. Om die probleem te oorkom het Zhang et al. in 2009 die EWMA t-kaart voorgestel. Die bestaande, optimale ontwerp van die EWMA t-kaart is gebaseer op die gemiddelde lopielengte kriterium. Dié artikel stel voor dat die optimale ontwerp van die EWMA t-kaart eerder op die mediaanlopielengte gebaseer word. Die resultate van die gebruik van die mediaanlopielengte met die EWMA X - en die optimale EWMA t-kaarte word vergelyk. <![CDATA[<b>Tour construction heuristics for an order sequencing problem</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300007&lng=pt&nrm=iso&tlng=pt An order picking system that requires pickers to move in a clockwise direction around a picking line with fixed locations is considered. The problem is divided into three tiers. The tier in which orders must be sequenced is addressed. Eight tour construction heuristics are developed and implemented for an order picking system operating in unidirectional picking lines. Two classes of tour construction heuristics - the tour construction starting position (TCS) and the tour construction ending position (TCE) - are developed to sequence orders in a picking line. All algorithms are tested and compared using real life data sets. The best solution quality was obtained by a TCE heuristic with adaptations.<hr/>'n Stelsel vir die opmaak van bestellings word ondersoek. Die stelsel vereis dat die werkers in 'n kloksgewyse rigting om 'n uitsoeklyn beweeg. Die probleem is verdeel in drie vlakke van besluite. Die besluit wat handel oor die volgorde waarin bestellings opgemaak word, word ondersoek. Agt toer-konstruksie-heuristieke is ontwikkel en geïmplementeer waarin die bestellings in 'n eenrigting uitsoeklyn opgemaak word. Twee klasse toer-konstruksie-heuristieke - die toer-konstruksie-beginposisie (TCS) en die toer-konstruksie-eindposisie (TCE) - is ontwikkel om die volgorde van bestellings in 'n uitsoeklyn te bepaal. Al die algoritmes word getoets en vergelyk vir werklike datastelle. Die beste oplossingskwaliteit is verkry deur 'n TCE-heuristiek met aanpassings. <![CDATA[<b>A differential evolution algorithm developed for a nurse scheduling problem</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300008&lng=pt&nrm=iso&tlng=pt Nurse scheduling is a type of manpower allocation problem that tries to satisfy hospital managers' objectives and nurses' preferences as much as possible by generating fair shift schedules. This paper presents a nurse scheduling problem based on a real case study, and proposes two meta-heuristics - a differential evolution algorithm (DE) and a greedy randomised adaptive search procedure (GRASP) - to solve it. To investigate the efficiency of the proposed algorithms, two problems are solved. Furthermore, some comparison metrics are applied to examine the reliability of the proposed algorithms. The computational results in this paper show that the proposed DE outperforms the GRASP.<hr/>Verpleegsterskedulering is 'n mannekragtoedelingsprobleem wat deur regverdige skof-skedules beide hospitaalbestuurders se teikens en verpleegpersoneel se voorkeure bevredig. Dié artikel handel oor 'n verpleegsterskeduleringprobleem wat gebaseer is op 'n werklike gevallestudie en stel twee metaheuristieke voor om die probleem op te los - 'n differensiaal evolusionêre metode en 'n gulsige, ewekansige, aanpasbare soekprosedure. Om die doel-treffendheid van die voorgestelde algoritmes te ondersoek word twee probleme opgelos. Verder word vergelykende maatstawwe gebruik om die betroubaarheid van die voorgestelde algoritmes te ondersoek. Die berekende resultate in die artikel toon dat die differensiaal evolusionêre algoritme beter vaar as die gulsige, ewekansige, aanpasbare soekprosedure. <![CDATA[<b>A new ranking approach and its application to solving fuzzy critical path problems</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300009&lng=pt&nrm=iso&tlng=pt There are several methods for solving fuzzy critical path problems in which ranking approaches are used to compare fuzzy numbers. In this paper, some fuzzy critical path problems are chosen to show that the results obtained with fuzzy critical path methods that use existing ranking approaches are not appropriate according to real life situations. To obtain appropriate results, a new ranking approach the Mehar ranking approach, is proposed for comparing LR flat fuzzy numbers. To show the advantages of the Mehar ranking approach over existing approaches, selected fuzzy critical path problems are solved by using the existing methods together with the Mehar ranking approach. It is shown that the obtained results are appropriate.<hr/>Daar bestaan verskeie metodes om wasige kritieke padprobleme op te los wat rangordening toepassings gebruik om wasige getalle te vergelyk. In dié artikel word 'n paar wasige kritieke padprobleme gekies om te bewys dat die resulte verkry met die wasige kritieke padmetode, wat bestaande rangordening benaderings gebruik, nie voldoende is volgens lewenswerklike voorbeelde nie. Om gepaste resultate te kry word 'n nuwe rangordening benadering, die 'Mehar rangordening benadering', voorgestel om LR plat, wasige getalle te vergelyk. Om die voordele van die Mehar benadering te wys word geselekteerde probleme opgelos met beide bestaande metodes en die Mehar rangordening benadering. Die resultate bewys dat die verkreë resultate gepas is. <![CDATA[<b>Modular research equipment for on-line inspection in advanced manufacturing systems</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300010&lng=pt&nrm=iso&tlng=pt The significance of inspection processes increases when producing parts with high levels of customer input. These processes must adapt to variations in significant product characteristics. Mass customisation and reconfigurable manufacturing are currently being researched as ways to respond to high levels of customer input. This paper presents the research and development of modular inspection equipment that was designed to meet the on-line quality requirements of mass customisation and reconfigurable manufacturing environments. Simulated results were analysed for application in an industrial environment. The implementation of the equipment in South Africa is briefly discussed. The research indicates that manufacturers need only invest in the required equipment configurations when they are needed for on-line inspection.<hr/>Die belangrikheid van inspeksieprosesse verhoog wannneer onderdele met hoë vlakke van kliëntinsette vervaardig word. Hierdie prosesse moet aanpas by variasies in belangrike produkeienskappe. Massadoelmaking en herkonfigureerbare vervaardinging word tans nagevors as 'n moontlike manier om hoë vlakke van kliëntinsette te hanteer. Hierdie artikel hou die navorsing en ontwikkeling van modulêre inspeksietoerusting voor wat ontwikkel is om aan die "op-die-lyn"-gehaltevereistes van massadoelmaking en herkonfigureerbarre vervaardigingsomgewings te voldoen. Gesimuleerde resultate is geanaliseer vir toepassing in 'n industriële omgewing. Die implementering van die toerusting in Suid-Afrika word kortliks bespreek. Die navorsing toon dat vervaardigers slegs hoef te belê in die nodige toerusting-konfigurasies wanneer dit benodig word vir "op-die-lyn"-inspeksie. <![CDATA[<b>Residual stress measurements and structural integrity implications for selective laser melted TI-6al-4v<a href="#back"><sup>#</sup></a></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300011&lng=pt&nrm=iso&tlng=pt Selective laser melting (SLM) of Ti-6Al-4V has significant potential in the aerospace and biotechnology industries. SLM employs a focused laser beam to melt successive layers of metallic powder into complex components. This process can result in the generation of high thermally-induced residual stresses. These residual stresses, together with micro-flaws/ pores from the inherent fabrication process, may lead to premature fatigue crack initiation and propagation at relatively low cyclic stresses. The hole-drilling strain gauge method was used to evaluate residual stresses within SLM Ti-6Al-4V specimens, with the intention of understanding the associated mechanisms for the successful application of SLM Ti-6Al-4V in industry.<hr/>'Selective laser melting' (SLM) van Ti-6Al-4V het aansienlike potentiaal in die lugvaart en biotegnologiese bedrywe. SLM maak gebruik van 'n gekonsentreerde laser straal om agtereenvolgende lae metaal poeier te smelt en sodoende intrieke metal komponente te vorm. Gedurende SLM kan hoë resterende spanning veroorsaak word as gevolg van hoë temperature. Hierdie spanning, asook mikrodefekte wat gedurende die vormingsproses ontstaan, mag lei tot voortydige materiaalverswakking deur spleet vorming en verspreiding gedurende betreklik lae sikliese spannings. Resterende spanning in Ti-6Al-4V eksemplare is bereken deur 'n boor-versonke rekstrokie metode om sodoende die meganismes verantwoordelik vir die suksessvolle toepassing van SLM in die Ti-6Al-4V bedryf te bepaal. <![CDATA[<b>Assessment of surface finish and dimensional accuracy of tools manufactured by metal casting in rapid prototyping sand moulds</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300012&lng=pt&nrm=iso&tlng=pt In this paper, an initial assessment of the quality parameters of the surface finish and dimensional accuracy of tools made by metal casting in rapid prototyping (RP) sand moulds is undertaken. A case study from a local tool room, dealing with the manufacturing of an aluminium die for the lost wax process, is employed. Modern techniques, including surface roughness analysis and three dimensional scanning, are used to determine and understand how each manufacturing step influences the final quality of the cast tool. The best surface finish obtained for the cast die had arithmetic average roughness (Ra) and mean average roughness (Rz) respectively equal to 3.23µΓη and 11.38µΓη. In terms of dimensional accuracy, 82% of cast-die points coincided with the Computer Aided Design (CAD) data, which is within the typical tolerances of sand cast products. The investigation shows that mould coating contributes slightly to the improvement of the cast tool surface finish. The study also found that the additive manufacturing of the sand mould was the chief factor responsible for the loss of dimensional accuracy. These findings indicate that machining will always be required to improve the surface finish and the dimensional accuracy of cast tools in RP sand moulds.<hr/>In dié artikel word 'n aanvanklike beoordeling van kwaliteitsparameters in terme van oppervlak-afwerking en dimensionele akuraatheid van gietstukke vervaardig deur metaal gieting in snel-prototipering sand gietvorms gedoen. 'n Gevallestudie aangaande die vervaardiging van 'n aluminium gietstuk vir die verlore wasproses word gebruik. Moderne tegnieke, soos oppervlak-grofheidsanalise en drie-dimensionele skandering, word gebruik om te bepaal hoe elke vervaardigingstap die finale kwaliteit van die gietstuk beïnvloed. Die beste oppervlak afwerking verkry vir die gietstuk het Ra en Rz waardes van 3.23 µπι en 11.38 µΓη onderskeidelik gehad. In terme van dimensionele akkuraatheid, het 82% van die gietvormpunte ooreengestem met die rekenaarnumeriesbeheerde data wat binne tipiese toleransies is vir sandgegote produkte. Die ondersoek wys dat gietvorm oppervakbedekking effens bydra tot die verbetering van die gietstukafwerking. Ook is gevind dat die snel-prototiperingvervaardigingsproses van die sandgietvorm die hooffoorsaak is vir die verlies aan dimensionele akkuraatheid. Dié bevindings dui aan dat masjinering altyd nodig sal wees om die oppervlak-afwerking en dimensionele akkuraatheid te verbeter. <![CDATA[<b>High-speed 5-axis machining for tooling applications</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300013&lng=pt&nrm=iso&tlng=pt In the modern metalworking industry, production moulds often have complex geometry, with undercut regions, small corner radii, sharp edges, deep cavities, or large cores. Conventional manufacturing process chains to machine these complex features are often lengthy and inefficient due to multiple steps. This article presents current results obtained through industry projects and experimental work using 5-axis high-speed machining with high-end CAD/CAM systems to improve process efficiency. Cost optimisation and lead time shortening can be clearly shown. This is of particular importance for South African manufacturing companies, where multi-axis HSC technology - although not totally unknown - is significantly under-used.<hr/>OPSOMMING In die moderne metaalnywerheid word produksiegietvorms dikwels gekenmerk deur komplekse geometrië, bv. ondersny areas, klein hoek radiusse, skerp rante, diep holtes, en groot kerne. Konvensionele vervaardigingsproseskettings om hierdie komplekse kenmerke te masjieneer is dikwels langdurig en ondoeltreffend weens veelvuldige stappe. Hierdie artikel dui op resultate verkry vanaf industrie-verwante projekte, sowel as eksperimentele werk, waar 'n 5-as hoë spoed freesmasjien gebruik was tesame met top reeks CAD/CAM stelsels om prosesdoeltreffendheid te verbeter. Koste optimisering en verkorting van lei tye kan duidelik getoon word, wat van besondere belang is vir Suid-Afrikaanse vervaar-digingsmaatskappye wat van multi-as hoë spoed masjieneringstegnologië gebruik maak. <![CDATA[<b>Forecasting modeling and simulation analysis of a power system in China, based on a class of semi-parametric regression approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300014&lng=pt&nrm=iso&tlng=pt Forecasting electricity consumption is one of the most important challenges in electricity system planning. This paper presents an improved semi-parametric regression model using the Student distribution function of residual to replace the nonparametric component of the traditional semi-parametric model, thus eliminating the effects of the residual disturbance term. Compared with general linear models, the models make statistical inferences and can automatically regulate the boundary effect, which gives the forecast result a higher accuracy. A case study using data from China is presented to demonstrate the effectiveness of the approach.<hr/>OPSOMMING Die vooruitskatting van elektrisiteitverbruik is een van die belangrikste uitdagings in elektrisiteitstelselbeplanning. Dié artikel bevat 'n verbeterde, semi-parametriese regressie-model, wat gebruik maak van die Studentverdelingsfunksie van residuee om die nie-para-metriese komponent van die tradisionele semi-parametriese model te vervang, en sodoende die effekte van die residuversteuringsterm uit te skakel. In vergelyking met algemene lineêre modelle, kan die model statistiese afleidings maak en outomaties die grenseffek reguleer, wat lei tot groter akuraatheid van die vooruitskatting. 'n Gevallestudie wat gebruik maak van data van China demonstreer die effektiwiteit van die benadering. <![CDATA[<b>The application of a computerised decision support system for generator maintenance scheduling</b>: <b>a South African case study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300015&lng=pt&nrm=iso&tlng=pt In the generator maintenance scheduling (GMS) problem, a schedule is sought for the planned maintenance outages of generating units in a power system. The GMS model considered in this paper is formulated as a mixed-integer quadratic program assuming a reliability objective, subject to certain constraints. A generic GMS solution methodology is derived, capable of solving general GMS problem instances that conform to this model structure, and implemented in a computerised decision support system. The decision support system is then used to solve a real-life case study in the South African national power system.<hr/>OPSOMMING In die generator-instandhoudingskeduleringsprobleem (GISP) word daar gesoek na 'n skedule vir die beplande instandhouding van kragopwekkingseenhede binne 'n kragstelsel. Die GISP-model wat in hierdie artikel beskou word, is 'n gemengde, heeltallige, kwadratiese program, en bevat 'n betroubaarheidsdoel, onderhewig aan sekere beperkings. 'n Generiese GISP-oplossingsmetodiek is ontwikkel om enige GISP van die vorm soos in hierdie model te kan oplos. Die oplossingsmetodiek word in 'n gerekenariseerde besluitsteunstelsel geïmplementeer, waarna 'n realistiese gevallestudie, binne die konteks van die Suid-Afrikaanse nasionale kragstelsel, daarmee opgelos word. <![CDATA[<b>The strategic relevance of technology-related variables to the competitiveness of small- to medium-sized furniture manufacturers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300016&lng=pt&nrm=iso&tlng=pt SMMEs can make a critical and positive economic contribution to South Africa, and small- to medium-sized furniture manufacturers (SM/FMs) have the potential to contribute to economic growth, job creation, and GDP. However, the furniture industry has not stayed abreast of technological advances. To survive in an environment of increasing competition and imports, competitive strategies must be devised. One such strategy is for technology adoption and implementation that can provide solutions for the furniture industry to improve speed, quality, variety, flexibility, and productivity, resulting in improved competitiveness. However, the adoption of technology means that its acquisition and application must be managed strategically, as the use of technology involves far more than simply taking it into account during the business-planning process. This paper investigates the impact of business strategy and selected technology-related variables on the competitiveness of SM/FM.<hr/>OPSOMMING SMMEs het die potensiaal om 'n kritiese en positiewe bydrae te maak tot Suid-Afrika se ekonomiese groei en SM/FMs, tot die skepping van werksgeleenthede, en tot die BNP. SM/FMs het egter nie op die hoogte gebly met tegnologiese ontwikkelings en die aanwen-ding daarvan nie. Om in 'n omgewing van toenemende mededingendheid en invoere te wedywer moet effektiewe strategieë ontwikkel word. Een strategie wat moontlik sal lei tot verhoogde mededingendheid is die aanwending van tegnologie wat oplossings kan bied in terme van spoed, kwaliteit, verskeidenheid, aanpasbaarheid, en produktiwiteit. Die aanwending van tegnologie moet egter op 'n strategiese manier bestuur word, want dit behels veel meer as bloot om tegnologie in ag te neem gedurende die strategiese beplanningsproses. Hierdie artikel ondersoek die invloed van besigheidstrategieë en sekere tegnologie-verwante veranderlikes op die mededingendheid van SM/FMs. <![CDATA[<b>Table grape punnet packaging</b>: <b>the influence of check-weighing</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2224-78902012000300017&lng=pt&nrm=iso&tlng=pt 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.<hr/>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.