Search results

Accuracy and building time are two important concerns in rapid prototyping (RP). Usually there exists a trade‐off between these two aspects pertaining to model building in RP. The use of variable thickness slicing can satisfy these two requirements to some extent. Introduces an adaptive variable thickness slicer implemented on a solid CAD modeller. The slicer employs a genetic algorithm to find the minimum layer thickness allowed at referenced height with a given cusp height tolerance. By introducing the variable thickness slicing technique, the optimal orientation for part building in RP systems is considered. Seeks to obtain the optimal orientation with adaptive slicing for part building in stereolithography (SLA) systems. Takes into consideration building time, accuracy and stability of the part when determining the optimal orientation. Results show that the proposed approach gives an effective and practical solution for building parts with curved surfaces.

The ability to evaluate and determine the best part building orientation for different rapid prototyping (RP) processes is important for building a satisfactory part/prototype within the limits of manufacturing time and building cost. It is also an essential step towards the identification of the most suitable RP process with a given RP application. This paper discusses the selection of building direction for four RP processes, namely stereolithography (SL), selective laser sintering (SLS), fusion deposition modelling (FDM) and laminated object manufacturing (LOM). Main differences in the four processes are first examined with emphasis on the effects of these differences with regard to the building inaccuracy, the surface finish, the manufacturing time and cost. An optimal orientation algorithm is demonstrated on a part considered for processing with one of the four RP processes. The influence of the process characteristics on the selection of appropriate orientation with different RP processes is illustrated in the example.

In rapid prototyping, such as SLA (stereolithography apparatus) and FDM (fused deposition modelling), the orientation of the part during fabrication is critical as it can affect part accuracy, reduce the production time, and minimize the requirement for supports and, thus, the cost of building the model. Presents a multi‐objective approach for determining the optimal part‐building orientation. Considers different objectives such as part accuracy and building time. Objective functions have been developed based on known sources of errors affecting part accuracy and the requirements of good orientations during the building of a model. The objective functions employ weights assigned to various surface types affecting part accuracy. The primary objective is to attain the specified accuracy achievable with the process. The secondary objective is to minimize the building time. Gives examples to illustrate the algorithm for deriving the optimal orientation which can assure better part quality and higher building efficiency.

A geometric benchmark part is proposed, designed and fabricated for the performance evaluation of rapid prototyping machines/processes. The benchmark part incorporates key shapes and features of better‐known benchmark parts. It also includes new geometric features, such as freeform surfaces, certain mechanical features and pass‐fail features that are increasingly required or expected of RP processes/systems. The part is suitable for fabrication on a typical RP machines. In this paper, the application of the benchmark part is demonstrated using relatively common RP processes. The ability of the benchmark part to determine achievable geometric features and accuracy by the aforementioned RP processes is presented and discussed.

Path generation is an important factor that affects the quality and efficiency of most laminated manufacturing processes such as SLS, SLA and FDM. This paper introduces an efficient path generation algorithm. The principle of the algorithm and its implementation are presented. A comparative study is used to analyze the effectiveness of this method. The results of comparison on both path length and processing time between the traditional method and the proposed method are discussed.

The feasibility of building copper‐based electrodes for electrical discharge machining (EDM) via laser cladding is investigated as an application of rapid prototyping (RP). Two material systems‐Cu/W (with and without nickel) and Cu/B₄C (with and without nickel) in certain compositions are selected for the experimental investigation. The laser claddings are realised via a 3000 W CO₂ laser with suitable parameters. The micro‐structures of the electrodes are analysed with a SEM. The performance of the EDM electrodes is examined in terms of machining rate and wear rate.

This study contributes to the extant literature on ICT firms by investigating the interrelationship between the health and safety (H&S) measures, market performance, and the coronavirus (COVID-19).

To conduct the confirmatory analysis by testing our hypotheses, data have been collected from Bloomberg of all ICT firms from five countries. The authors gathered from 2010 until 2020 as the research sample to examine the pandemic impact on market performance and H&S measures.

First, our results reveal a significant and positive relationship between market performance (proxied by Tobin’s Q) and the H&S measures of information technology (IT) firms. Second, the authors find that the IT firms have significantly increased the H&S measures during the COVID-19 period and were dynamic in linking employees’ adaptive capabilities to positive attributes. This has contributed to business success, resiliency, and sustainability.

The authors used a quantitative method of testing our hypotheses. Future studies may consider checking the robustness using qualitative methods such as structural or semi-structural interviews.

The study offers valuable insights to academics, practitioners, stakeholders, policymakers, and international entities by fostering knowledge about responses to crises, integrating digital solutions, and disseminating digital information. The study also has implications on the health, social, business, and economic levels. This study is a call for international and local humanitarian organisations such as United Nations High Commission, Care international and many more to understand the gravity of safety of the workers in the workplace during the pandemic period and introduce a firm-level policy accordingly.

This paper is novel considering that the paper is unique in evaluating ICT firms’ market performance and H&S from a global perspective, considering the context of this historical pandemic.

Under this heading are given each month the principal articles of aeronautical interest appearing in the current issues of the Journals of the leading Professional Societies and Institutions.

Leading developers and providers in the modern space launch market note a splash in the development of ultralight launch vehicle (LV), driven by the growing demand for small satellites for large constellations in low Earth orbits. One of the promising ways to solve the problem of the quick launch of such satellites is to use a new type of ultralight launch vehicle with a plastic body. The project of such a launch vehicle was proposed by Oles Honchar Dnipro National University (Ukraine). Along with that, there is a need for appropriate research studies on the thermal resistance of the plastic shell, as the physical, mechanical and thermophysical characteristics of polymers significantly differ from traditional aerospace materials. The purpose of this study is to validate the design and ballistic parameters of such a launch vehicle in terms of providing an acceptable thermal environment at the atmospheric phase of the trajectory.

The workability of a new type of propulsion system is being investigated experimentally in bench conditions. To study the process of aerodynamic heating of a plastic shell, numerical modeling based on the integration of the flight dynamics and heat transfer equations is used.

Brief information about the design of a new type of ultra-light autophage launch vehicle with a plastic body is presented. A mathematical model for the movement of the launch vehicle at the atmospheric phase of the trajectory, and for the heating of the polyethylene body of the launch vehicle, taking into account the dynamic change in the atmospheric parameters is proposed. The influence of the motion trajectory on the thermal environment of the rocket body is investigated, rational motion trajectories and corresponding permissible g-loads are determined.

The fundamental possibility of using plastic (polyethylene) as a structural material and fuel for bodies of a new type of ultralight launch vehicles has been substantiated. It is shown that to ensure acceptable thermal conditions of a plastic body, it is necessary to use thermal insulation. It is proposed to use a polymeric Teflon coating as such thermal insulation. The results are important for the development of technologies for launching small satellites into orbit, as the use of plastic as the main structural material of the rocket body will significantly reduce the launch cost.

The covenant strength of flexible workspace (FW) providers as tenants is debatable. There is the argument that providers are risky mainly due to the very nature of their business which consists of volatile revenue streams obtained from subletting the space in membership format, paying little attention to covenants. On the other hand, there is also the argument that the presence of a provider can add vibrancy and diversity to a building whilst also offering an additional amenity to existing tenants through overflow space, making FW providers desirable. This paper aims to explore this ambiguity by comparing rents paid by FW providers and other tenants within the same building in London over the period 2011 to 2021.

Using a dataset of 1,042 leases in London over the period of 2011–2021 which was extracted from CoStar, the rent conditions of FW providers and their peers within the same building were analysed employing a hedonic pricing model.

The results of the analysis suggest that FW providers have a negative and statistically significant effect on the effective rent in comparison to other tenants within the same building over the analysed period.

This analysis has the potential to identify how FW providers are perceived in the market and offers both academics and practitioners valuable insights.

The relationship between landlords and FW providers as tenants does not have a major coverage in the literature.