Browsing by Author "De Beer, Neal"

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    Development of a process chain for digital design and manufacture of patient-specific intervertebral disc implants with matching endplate geometries
    (Stellenbosch : University of Stellenbosch, 2011-03) De Beer, Neal; Van der Merwe, A. F.; Scheffer, C.; Dimitrov, D. M.; University of Stellenbosch. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Back pain is a common concern amongst a growing population of people across the world today, where in most cases the pain can become unbearable resulting in major lifestyle adjustments. Seventy to eighty percent of the population of the Western world experiences low-back pain at one time or another. Pain can be produced as a worn disc becomes thin, narrowing the space between the vertebrae. Pieces of the damaged disc may also break off and cause irritation to the nerves signalling back pain. Depending on the severity of a patient’s condition, and after conservative treatment options have been exhausted, a disc replacement surgery (arthroplasty) procedure may be prescribed to restore spacing between vertebrae and relieve the pinched nerve, while still maintaining normal biomechanical movement. Typical complications that are however still observed in some cases of disc implants include: anterior migration of the disc, subsidence (sinking of disc) and lateral subluxation (partial dislocation of a joint). Issues such as function, correct placement and orientation, as well as secure fixation of such a disc implant to the adjacent vertebrae are highly important in order to replicate natural biomechanical behaviour and minimise the occurrence of the complications mentioned. As various imaging and manufacturing technologies have developed, the option for individual, patientspecific implants is becoming more of a practical reality than it has been in the past. The combination of CT images and Rapid Manufacturing for example is already being used successfully in producing custom implants for maxilla/facial and cranial reconstructive surgeries. There exists a need to formalise a process chain for the design and manufacture of custom-made intervertebral disc implants and to address the issues involved during each step. Therefore this study has investigated the steps involved for such a process chain and the sensible flow of information as well as the use of state-of-the-art manufacturing technologies. Strong emphasis was placed on automation of some of the processes as well as the user-friendliness of software where engineers and surgeons often need to work together during this multi-disciplinary environment. One of the main benefits for customization was also investigated, namely a reduction in the risk and potential for implant subsidence. Stiffness values from pressure tests on vertebrae were compared between customized implants and implants with flat endplate designs. Results indicated a statistically significant improvement of customized, endplate matching implants as opposed to flat implant endplates. Therefore it may be concluded that the use of customized intervertebral disc implants with patient specific endplate geometry may decrease the risk and potential for the occurrence of subsidence.
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    Improvements in the capability profile of 3-D printing : an update
    (Southern African Institute for Industrial Engineering, 2014-08) Dimitrov, Dimitar Marinov; De Beer, Neal
    Knowledge about the capabilities of a production system is an important issue. The three-dimensional (3-D) printing (drop-on-bed) process has become a well-established Additive Manufacturing (AM) technology. Initially intended for use mainly as a concept modeller, its scope of application has expanded to include, among others, fit and functional models, pattern-making for casting and moulding processes, rapid tooling, and medical and architectural models. This growth in applications has stimulated a reciprocal improvement in available materials and the technological capabilities of 3-D printing, such as accuracy, strength and elongation, surface finish, build time, and cost. These factors are of significance to users who want to control their processes better and to designers who want to define their expectations and determine their requirements. Thus this paper aims to provide a technical update, highlighting the influence level of different factors on a system’s capabilities. This paper uses the example of the ZPrinter 310 system from the Z Corporation, applies appropriate statistical techniques, and takes into consideration the latest material and machine developments, in order to report on the current improvements of the capability profile of this important process.
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    An investigation towards developing capability profiles of rapid prototyping technologies with a focus on 3D-printing
    (Stellenbosch : Stellenbosch University, 2004-03) De Beer, Neal; Dimitrov, D. M.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Rapid prototyping (RP) technologies have expanded vastly over recent years. With the advent of new materials along with new processes, each technology has been contributing to the diversities in different fields of application for the growing technologies. In the course of improvement, it is however critical to understand exactly what the capability of each individual technology is in order to compare future improvements, or even to compare current processes and technologies. The objective of this research has been to develop capability profiles of prominent RP technologies: 3D-Printing (3DP), Selective Laser Sintering (SLS), and Laminated Object Manufacturing (LOM) - in which different characteristics of each technology are measured and quantified. A capability profile may be regarded as a set of building blocks that give a representation of the RP technology's ability and is defined by quantifying the following characteristics: Accuracy (both dimensional- and geometrical accuracy) Surface finish measures Strength and elongation Build time, and Cost The significance behind developing capability profiles lies in the need to more accurately describe and compare each of the different processes - especially Z Corporation's 3DP, since although this process is regarded as very capable in many areas, little has been published to substantiate this opinion. When users of these technologies are pushing the limits of their machines, it becomes critical to know exactly what these boundaries are in order to know with some measure of certainty that they will be able to fulfil a certain customer demand or expectation. For South Africa in particular, the industry's growing interest in rapid prototyping is triggering inevitable questions as to whether a certain RP technology can produce the desired solutions to their problems. The South African industry's growing awareness about rapid prototyping is opening new doors for better solutions to new and existing problems - but ultimately, before investing money, customers want to know if RP is going to meet the standards needed to solve their solutions. On a more general level, this study can also be seen to bear significance in contributing to research in what has become known as rapid manufacturing (RM). This term is defined as the manufacture of end-use products using additive manufacturing techniques. RM must guarantee long-term consistent component use for the entire product life cycle or for a defined minimal period for wearing parts [1]. However, before it is possible to guarantee long-term consistency of components, one must first ensure consistency of the process. Once a process is consistent, the next question becomes: What is it capable of doing consistently? This study aims to answer this question for the three processes (3DP, SLS and LOM) mentioned earlier. In doing so, this study and its development of capability profiles, seeks to contribute and be of value in both academic circles as well as for industry partners and system manufacturers.