https://www.um.edu.mt/library/oar/handle/123456789/76130 2026-04-20T22:52:11Z 2026-04-20T22:52:11Z https://www.um.edu.mt/library/oar/handle/123456789/102096 2022-09-28T11:04:42Z 2011-01-01T00:00:00Z

Title: Pro-active guidance for interdisciplinary artefact design : a 'feasible solution space' filtering approach framework from 'life-oriented product structure specifications' Abstract: In artefact design, as discussed by Restrepo et al (2010), complexity is characterized by: critical decision-making; low tolerance for errors; team collaboration - individuals with a wide variety of backgrounds who may be physically and geographically apart from one another; highly specialised knowledge; highly specialised skills; and possible unforeseeable events can have catastrophic consequences. Tomiyama (2006) claims that complexity of artefacts is increasing due to: a) technological advances - that reflect customers' ever increasing needs to produce, smaller, cheaper artefacts that are capable of performing multiple functions; and b) combination of different disciplines. Minimally invasive surgical (MIS) instruments are an example of complex artefacts since they comply with the above definitions (Restrepo et al 2010). This is confirmed by Pederson and Nielsen (2008), who describe the development of medical devices as a 'complex process'. MIS instruments are different to open surgery instruments due to their miniature size since tiny end-effectors are passed through typically 5mm and 10mm trocars so that very small incisions are performed to result in benefits to the patient including less bleeding, less chance of infections, smaller scars and less chance of post-operative complications. Apart from the fact that MIS instruments have micro-scaled features, which makes them much more complex to design and manufacture since it is not just a matter of downscaling, they are also a type of interdisciplinary artefact (Grech 2010a) since they combine knowledge from more than one discipline - in this case the 'engineering related' micro manufacturing discipline and the 'non-engineering related' biomedical discipline. As stated by Tomiyama and Meijer (2006): 'Next generation product development should target more on knowledge-centered integration due to increasing importance of knowledge intensive products and product service systems that require a wide variety of product life cycle knowledge.' To be able to design such interdisciplinary artefacts from a multi-X point of view, knowledge needs to be captured from different stakeholders involved in the different life phases of the artefact (e.g. from surgeons and nurses in the use phase in the case of surgical instruments, sterilization officers in the cleaning phase, technicians in the servicing phase). However, these stakeholders are too busy to be present while the designer is designing and thus the designer needs to have access to this knowledge by some other means. [...] Description: PH.D

2011-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/101766 2022-09-26T11:17:52Z 2008-01-01T00:00:00Z

Title: Paper-based computer-aided form sketching : a prescribed sketching language-based approach Abstract: Due to its efficacy in rapidly externalizing form concepts, paper-based sketching is still extensively used by practising designers. It is a common practice that form concepts are sketched on paper prior to being translated into three-dimensional (3D) virtual models for further development. A critical literature review reveals that presently designers do not have adequate support in this translation process. In view of the above, this thesis proposes and develops a framework for a computer based tool aimed at integrating paper-based form sketching with Computer-Aided Design (CAD). The core of this framework is a prescribed sketching language (PSL), required to create a dialogue between the designer and the computer. PSL is based upon modelling principles commonly employed in CAD systems. It is composed of user- and pre- defined graphical elements and a set of pre-defined rules for drawing them on paper. Computer-related frames making up the framework have been implemented in a prototype tool, mX-Sketch. An evaluation of the framework from the user's and computer's perspectives has been carried out. Evaluation results revealed a positive feedback by practising designers towards the notion of using PSL to integrate traditional sketching with CAD. The evaluation also showed that PSL contributes towards the automatic translation of paper-based form sketches into 3D virtual models. At the same time, the results obtained collectively suggest that further work is required before PSL and the supporting tool can be used in design practice. Description: PH.D

2008-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/78551 2021-07-27T08:33:27Z 2013-01-01T00:00:00Z

Title: Investigating the bond strength in micro insert moulding Abstract: Micro insert moulding (µinsert moulding) is a cost efficient manufacturing process capable of fabricating multi material micro parts. It is a combination of micro replication (µreplication moulding) and micro assembly (µassembly) and involves moulding a polymer over a micro 'insert'. Three out of four works reviewed on µinsert moulding considered the bond strength as a quality criterion. A critical appraisal of works relevant to the bond strength in µinsert moulding reflected that the effects of all the relevant design considerations on the bond strength were not known. Amongst these was the aspect ratio of the insert embedded in the polymer as well as the shrinkage of the polymer. These were to be investigated experimentally along with a new 'bond enhancing' treatment for the insert as well a new polymer material. A discussion on the theoretical effects of the physical mechanisms relevant to the bond strength in µinsert moulding helped derive the relevant experimental factors. A sand blasting treatment was selected as the new surface treatment. This was applied to carbon steel wire and the effects of this treatment on the roughness of the insert were characterized using image metrology software. A mould was successfully designed and fabricated in order to carry out experiments. Simulations of cavity filling were done subject to the used process parameters. The new material tested was ethylene-vinyl-acetate (EVA). Acrylonitrile-butadiene styrene (ABS) and POM (polyoxymethylene) were also investigated. The sand blasting treatment indicated statistically to increase the bond strength for all materials. Cross sections of the polymer/insert interface were taken in order to observe the interlocking. It was visually evident that the interlocking for sand blasted inserts was superior to that achieved by untreated inserts. A high embedded insert aspect ratio indicated statistically to result in poor bond strength. This was noted from the effects of the embedded insert length. This was attributed to the possibility of polymer hesitation and was observed under a microscope. The effects of the shrinkage of the polymer on the bond strength were discussed analytically. Description: M.SC.ENG.

2013-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/78549 2021-07-27T08:19:46Z 2013-01-01T00:00:00Z

Title: Combining additive and subtractive manufacturing Abstract: Electron Beam Melting (EBM) is a state of the art technology that is poised to revolutionize the way products are manufactured. High customization combined with superior material properties have given a wide range of applications to the parts produced by means of this technology. The layer by layer building technique employed by this Additive Manufacturing (AM) technology permits high geometry flexibility and short lead times. Additionally, EBM uses as its energy source an electron beam which is able to produce full dense parts made of metals such as titanium alloys, a material that is difficult to machine using other conventional methods. Description: M.SC.ENG.

2013-01-01T00:00:00Z