SUNScholar - Browsing by Author "Van der Merwe, A. F."

Browsing by Author "Van der Merwe, A. F."

Now showing 1 - 14 of 14

Additive manufacturing for sustainable custom-designed implants
(Southern African Institute for Industrial Engineering, 2019) Booysen, G. J.; Van der Merwe, A. F.; De Beer, D. J.
ENGLISH ABSTRACT: Additive manufacturing (AM) has proven to be an attractive alternative manufacturing process compared with subtractive manufacturing (SM). Additive manufacturing has many advantages, such as mass customisation, less material wastage, and others listed in this article. However, the additive manufacturing of certified implants does not have the same degree of documentation and standardisation as the subtractive manufacturing process. As part of this research project, the problem statement is: “In offering additive manufacturing as an implant manufacturing solution, the complete process (design, manufacturing, and post-processing) had to be investigated in order to develop a certified manufacturing solution”.
Agent based job scheduling for a vehicle engine reconditioning machine shop
(Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Nyanga, L.; Van der Merwe, A. F.; Burawa, M.; Matope, S.; Dewa, M. T.
ENGLISH ABSTRACT: Job scheduling at a machine shop is a multi-decision criteria problem whose skills are acquired after some years of experience. For Small, Medium to Micro Enterprises (SMMEs) with limited machinery the objective when scheduling jobs should not only focus on machine utilization but also on the increase of job through put. The paper presents an agent based job scheduling system for a vehicle engine reconditioning machine shop to assist decision makers in job scheduling. The Analytic Hierarchy Process (AHP) method was used to compute the relative weights of each decision criteria used for job scheduling considering the job priority. The value of the job, the number of operations to be performed, the engine type, the frequency of the customer and the company to customer relationship rating are used to prioritize the jobs. A Multi Agent System (MAS) comprising of the provider, job allocator and machine agents is developed using the Java Agent development framework (JADE) methodology and modelled using Unified Modelling Language (UML 2). The provider agent schedules all the jobs based on job weight and earliest due dates. The job allocator agent is responsible for making sure that all the scheduled jobs are allocated to all the machines after which they are registered as complete jobs and can leave the system.
Design of a multi agent system for machine selection
(Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Nyanga, L.; Van der Merwe, A. F.; Tsakira, C.; Matope, S.; Dewa, M. T.
ENGLISH ABSTRACT: In a machine shop effective assignment of jobs to machines is a multi-criteria decision making problem which is usually done by professionals and experienced planners. The skill of job assignment becomes handy in machine shops which are in the Small, Medium to Micro Enterprises (SMMEs) category as they work on a variety of products with limited machinery. The paper presents a machine selection system for helping decision makers when selecting machines to be scheduled. Customer order parameters which include product weight, clamping force, mould dimensions, due date and lead time are used to select moulding machines suitable to manufacture the desired parts. The criteria for machine selection was developed using Analytical Hierarchy Process (AHP) were quality, time and cost were considered as the key parameters. The available machines which meet the requirements for moulding a desired part are then made to compete for the part using an English auction. A Multi Agent System consisting of a managing agent, administrator and bidding agents was developed to conduct the auction that takes place between machine agents viewed as potential contractors representing available machines in the production line. The multi agent system is developed using Java Agent Development framework (JADE). An injection moulding plant with 11 injection moulders was used as a case study for application of the system.
Development of a method of additive manufacturing by material extrusion along three-dimensional curves
(Southern African Institute for Industrial Engineering, 2019-11-15) Kirkman, D. M.; Van der Merwe, A. F.; Campbell, R. I.
ENGLISH ABSTRACT: A method of additive manufacturing (AM) for the extrusion of material along three-dimensional curves is proposed as an alternative to conventional methods of layer-based AM for the manufacture of components designed using topology optimisation. The objectives of the study are to formulate a toolpath-generation algorithm for the extrusion process, to design the testing apparatus and methods for the validation of the proposed extrusion process, and to generate feedback based on the results obtained during testing and validation for possible implementation in topology optimisation software. The outcome of the study is a process by which toolpaths can be generated for simple geometries, and implemented using a mounted extruder serving on to a serial robot-mounted build platform.
E-manufacturing - the roadmap for South African manufacturers
(Stellenbosch : Stellenbosch University, Department of Industrial Engineering, 2011-09) Nyanga, L.; Van der Merwe, A. F.
Globalization and the internet have given customers a wide choice of products to choose from and they are now expecting a lot from products. Customers are demanding more value, less risk and better integration of products hence products now have a shorter product life cycle. E-manufacturing can help companies to optimize the use of production assets, reduce production cycle times and costs to meet these customer requirements. The paper shows factors that influenced an economy to successfully implement an emanufacturing model that transformed the economy from a struggling economy into an advanced economy. E-manufacturing models are discussed. Taiwan is used as a case study of how engineering chain can be utilized for SMEs to enjoy equally or even higher competitive advantage than their larger competitors by appropriately utilizing external networks. The situation in South Africa shows that the country can benefit from the growth of SMEs and e-manufacturing if networks and a culture of sharing information are built among SMEs and companies in the country.
A holonic approach to reactive scheduling when rush orders emerge
(Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Dewa, M. T.; Van der Merwe, A. F.; Matope, S.
ENGLISH ABSTRACT: Rush orders can complicate the life of project managers when they emerge especially if they are of a high priority. Initially prepared process plans and schedules become invalid while extra capacity may be needed to meet the new demands placed on the shop-floor. However, with the era of distributed manufacturing, skills and resources can be shared in an optimal manner. The paper presents an application for automated management of resources in response to varying demands experienced by an industrial cluster of tool and dies workshops. A set of holons are utilized to monitor progress of orders in process while responding in real time to new demands placed on the system. The system utilizes the Petri-net protocol for the bidding function and automatically organizes the manufacturing function in a cost effective and timely manner. The ARENA discrete event simulation platform was utilized to demonstrate system’s results in a virtual environment.
Holonic control system : a proposed solution for managing dynamic events in a distributed manufacturing environment
(South African Institute for Industrial Engineering, 2014) Dewa, M. T.; Matope, S.; Van der Merwe, A. F.; Nyanga, L.
ENGLISH ABSTRACT: Due to globalization, manufacturing of products is no longer a local activity done by a single company but rather a distributed venture as more firms are realizing the need to improve their flexibility and agility. The paradigm of e-manufacturing is gaining popularity among researchers and manufacturers who aim to improve their market share and shop floor visibility by belonging to larger collaborative networks. However, real-time events which lead to operational disturbances in a plant remain a challenge most manufacturers face since they result in deviation from initially prepared process plans and schedules, rendering them invalid before they can be launched on to the shop floor for implementation. The paper presents a Holonic Control System (HCS) as a proposed solution to managing this pandemic. The research focused on manufacturing firms in the Western Cape of South Africa which belong to the tooling industry. Cited in this paper are holonic architecture together with the success factors and barriers to implementing holonic control systems in South Africa. Results of the proposed system were generated by a simulation model and revealed that delivery time and resource utilization were improved by adopting the system.
'n Kritiese evaluering van die sosio-politieke dimensie in die relasionele groeimodel van Howard J. Clinebell
(Stellenbosch : Stellenbosch University, 1990-09) Van der Merwe, A. F.; Louw, D. J. (Daniel Johannes), 1944-; Stellenbosch University. Faculty of Theology. Dept. of Practical Theology and Missiology.
AFRIKAANSE OPSOMMING:
Micro-material handling employing e-beam generated topographies of copper and aluminium
(Southern African Institute of Industrial Engineering, 2011-11) Matope, S.; Van der Merwe, A. F.; Nemutudi, R.; Nkosi, M.; Maaza, M.
ENGLISH ABSTRACT: This paper focuses on the employment of copper and aluminium in a micro-material handling system actuated by Van der Waals forces. Electron beam (e-beam) evaporator deposited both materials on a silicon substrate at a rate of 0.6-1.2 Angstroms/second, vacuum pressure between 2x10-6 and 3x10-6mbar, and at a current less than 10mA. A Veeco NanoMan V Atomic Force Microscope with Nanoscope version 7.3 software was used to analyse the root mean square (rms) surface roughnesses of the generated topographies. Rumpf-Rabinovichs rms formula was used to determine the Van der Waals forces exerted by the surfaces. It was synthesised that an e-beam deposition of 7 minutes duration on both materials produced an optimum micro-material handling solution, with copper suitable for the pick-up position and aluminium for the placement position.
Micro-material handling, employing e-beam coatings of copper and silver
(Southern African Institute for Industrial Engineering, 2012-05) Matope, S.; Van der Merwe, A. F.; Rabinovich, Y. I.
ENGLISH ABSTRACT: Van der Waals forces and other adhesive forces impose great challenges on micro-material handling. Mechanical grippers fail to release micro-parts reliably because of them. This paper explores how the problematic Van der Waals forces may be used for micro-material handling purposes using surface roughnesses generated by e-beam coatings of copper and silver on silicon. An atomic force microscope, model Asylum MFP 3 D-Bio with version 6.22A software, was used to measure the forces exerted by the surfaces. A silver coating of 1.41 nm rms surface roughness value is found to exert the highest Van der Waals force, followed by a copper coating of 2.72 nm rms; a copper coating of 217 nm rms exerts the least force. This implies that, in a reliable micro-material handling system, these coatings are suitable for the interactive surfaces of the placement position, micro-gripper, and the pick-up position respectively.
Silver, copper and aluminium coatings for micro-material handling operations
(Southern African Institute for Industrial Engineering, 2013-08) Matope, S.; Van der Merwe, A. F.; Rabinovich, Y. I.
ENGLISH ABSTRACT: Micro-material handling has challenges accompanying it because of adhesive forces, which make the picking and placing of micro-parts difficult. The adhesive forces hinder the picking of a micro-part, and once picked, they pose even a greater challenge when attempts to release a micro-part are made. Van der Waals forces are part of the adhesive forces and are always present between interacting surfaces in a micro-material handling operation. However, Van der Waals forces can profitably be manipulated in a micro-material handling operation. The paper reveals how the Van der Waals forces can be advantageously used in micro-material handling operations involving silver, copper and aluminium coatings of rms surface roughness values ranging from 0.5 nm to 2.72 nm, which are produced by the electron beam evaporation (e-beam) method. These were found to exert Van der Waals forces ranging from 17 nN to 314 nN, which can be used for reliable micro-material handling operations.
Study on applicability of adhesive forces for micro-material handling in production technology
(Stellenbosch : Stellenbosch University, Department of Industrial Engineering, 2011-09) Neugebauer, R.; Koriath, H-J.; Van der Merwe, A. F.; Muller, M.; Matope, S.
Micro-material handling and micro-assembly becomes increasingly important in largevolume manufacturing of products like sensors in automotive applications. Smaller dimensions of the micro-objects lead to problems with regard to the reliability of the manufacturing process because adhesive forces become predominant over gravity for objects whose dimensions are in the micro-range. In contrast to the common approach of minimizing those adhesive forces, this paper focuses on the use of the three main adhesive forces, van-der-Waals, electrostatic and surface tension forces, as gripping principles. These forces are compared to conventional vacuum grippers with regard to gripping forces and complexity of application. Modelling of the forces is executed for separation distances in the range of 1x10-12 m - 1x10-3 m. Even though vacuum forces dominate in magnitude over others within the whole range, there are several disadvantages of using them. On the other hand adhesive forces are advantageous in that they require little amount of energy and they do not mechanically strain the micro-parts being handled.
Viability of telemedical remote robotic systems
(Industrial Engineering, Stellenbosch University, 2011-09) Smit, A.; Van der Merwe, A. F.
Worldwide, the demand for telemedicine devices and systems has risen steadily in recent years. The design of remote robotic systems has always been a complex undertaking. Technological limitations affecting bandwidth and access to communications infrastructure have impeded the advancement of a long distance remote robotic telemedicine system training purposes. Assessing the commercial viability and acceptability will be achieved by evaluating responses from expert user groups. This plays a crucial role in the development of future systems as well as providing expert-user data on user perception of such systems and data on the current viability of long distance patient care. An assessment of the information that is required to be presented to the medical professional in both training and diagnostic situations would have to be completed by making use of questionnaires and interviews. The system will be developed using low cost technologies with support structures in place as to facilitate financial feasibility and minimization of complexity along with intuitive control inputs. The results of the study will provide valuable information for the future development of commercially viable robotic telemedicine systems in South Africa.
XAP - an open source protocol for eHealth
(Industrial Engineering, Stellenbosch University, 2011-09) Van der Merwe, A. F.
In a recent SAIIE conference paper it was suggested to use xAP protocol in the telemedicine environment. Telemedicine has since been described to evolve into eHealth where the focus is not only on the remote control of health systems, but now also includes local control. This wider scope is necessary to allow seamless communication amongst systems, irrespective to whether they are in the same room or in a remote location. Local communication is via intranet with a higher data transport rate than internet. Larger data packages can be transported than economical on the internet. This research proposes a framework using a xAP datagram instead of sending the complete data package. It will only broadcast the availability of a data package to both local and remote systems. The bulk content can then be requested for download to local and remote systems either in compressed or uncompressed format. The xAP datagram carries information on the formats that the bulk data can be downloaded in. Intelligence at the retriever would decide which format to download. The compression format can be negotiated at download time. Protocols utilized are UDP for xAP broadcasting and TCP for bulk data retrieval. Scope: It is important to note that this research is on the efficacy of a datagram to broadcast data availability announcements and not on the design of a database. Also that data retrieval via TCP is not considered as it is used for bulk content retrieval after the announcement and only when an internet link is available. Lastly the bulk content download format negotiation is already available by others, usually “APP” developers of smart devices or similar.

Browsing by Author "Van der Merwe, A. F."

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