PurposeThe research was undertaken to characterise the three dimensional printing (3DP) process in term of the achievable dimensional and geometric accuracy.Design/methodology/approachNew benchmark models were developed that represent characteristics needing to be investigated. The parts were fabricated in different materials. A program was written to measure the features on a numerically controlled coordinate measurement machine. Finally, a statistical analysis was done. The results are reported in terms of statistical parameters and international tolerance (IT) grades.FindingsThe paper provides general IT grades of the 3DP process for parts printed using different materials (powders).Research limitations/implicationsThe research is limited to specific materials and equipment.Practical implicationsThe data is very useful for designing products to be manufactured on 3DP machines applying either direct or indirect methods.Originality/value3DP is more and more used for rapid prototyping with great potential towards rapid manufacturing. Designers need to know the capability profile of the process they are going to use. There is a significant lack of published data on the 3DP process characteristics. This research was conducted to fill this gap and provide much needed accuracy information.
This paper discusses the results obtained from studies on different rapid tooling process chains for improved design and manufacture of foundry equipment for sand casting of prototypes in final material for functional and pre-production tests of vehicles, using the three-dimensional printing process as core technology. Subsequently, while considering aspects such as time, cost, quality (accuracy and surface roughness), and tool life, a framework for evaluation and selection of the most suitable process chain in accordance to specific requirements is presented. Apart from only using these process chains for prototype manufacturing, initial results from a study to apply one of these process chains in automated sand casting full production is also presented. This research builds on an in-depth characterization of the accuracy and repeatability of a three-dimensional printing process.
Quality assurance within local educational institutions has been under the spotlight in recent years. In particular these institutions are increasingly subjected to minimum standards specified by controlling bodies such as the Higher Education Quality Committee and others. The moderation of examination papers is an important quality assurance activity to ensure that an examination paper's standard, content, span and marking are fair and reasonable. This paper describes a sampling plan to determine the number of answer books to be checked to confirm that individual marks were awarded correctly. The sampling procedure relates the confidence that marks awarded in a set of examination books meets a specified minimum standard to the number of books moderated. OPSOMMINGGehalteversekering binne plaaslike opvoedkundige instellings word toenemend onderwerp aan minimum standaarde soos neergelê deur die Kwaliteitskomitee vir Hoër Onderwys en ander. Die moderering van eksamenantwoordstelle is 'n belangrike gehalteversekeringsaktiwiteit wat verseker dat 'n eksamen se standaard, inhoud, bestek en nasien regverdig en redelik is. Die artikel beskryf 'n steekproefplan vir die proses om individueel toegekende punte vir korrektheid na te gaan. Die voorgestelde prosedure gee die verband tussen die sekerheid dat die punte toegeken deur die eksaminator voldoen aan 'n gespesifieerde minimum standaard en die aantal boeke wat gemodereer moet word (steekproefgrootte).
ABSTRACT:This paper describes a formula for scheduling the day-to-day operation of a lift club. The formula is remarkably simple, and can easily be implemented on a spreadsheet. It is also extremely flexible and can cater for almost any peculiarity that may arise. Much like a business, the lift club is viewed as an entity in its own right, rather than as a collection of individuals. The scheme can be used to generate interesting statistics such as percentage utilization of each member, average percentage utilization of all members, effective size of the lift club, etc. In addition, a graph, depicting each member's liability towards the club against time, can be generated. Finally, every member can obtain a record of his/her trip data over any specific period, which may be handy for income tax purposes. OPSOMMING:Hierdie artikel beskryf 'n fonnule vir die dag-tot-dag skedulering van 'n saamryklub. Die fonnule is merkwaardig eenvoudig en kan maklik op 'n sigblad geimplementeer word. Dit is ook besonder buigsaam deurdat dit vir bykans enige gebeurlikheid voorsienning maak. Die voorgestelde skeduleringsmetode beskou die saamryklub as 'n entiteit in eie reg, en skeduleing word vanuit die saamryklub se oogpunt gedoen. Die skema kan gebruik word om interesante statistieke soos byvoorbeeld die persentasie benutting deur enige lid, die gemiddelde persentasie benutting deur aIle lede, die effektiewe grootte van die klub, ens., te genereer. Voorts kan 'n grafiek gegenereer word wat elke lid se aanspreeklikheid teenoor die klub as 'n funksie van tyd grafies vertoon. Laastens kan enige lid op enige stadium 'n rekord trek van die aantal saamrygeleenthede wat hy oor 'n bepaalde periode voorsien en ontvang het. Dit mag handig wees vir belasting doeleindes.http://sajie.journals.ac.za
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