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Compliance with standard specifications in stairway design and construction, particularly the step geometry, is imperative for the safety and usability of stairs. The purpose of this study, was to assess the compliance of stair step geometry parameters with standard specifications in selected public buildings in Ghana. Specifically, the study investigated the prevalence of deviations in step geometry parameters from standard provisions; how significant these deviations are in comparison, and by theoretical association, the potential risk of accidents.

Field measurement of the geometric parameters of a total of 1954 steps in 204 flights of stairs within 28 university buildings was undertaken using a calibrated Multi Digit Pro + digital spirit level and a tape measure following the Nose-to-Nose Method. The results were analyzed using in Microsoft Excel 2016 and Minitab 18 and interpreted based on mean values, one-sample t-test and percentages.

Although some parameters generally complied with standard specifications, dimensional inconsistencies in risers and treads of adjacent steps were most prevalent, and significantly at margins far above standard specifications. The findings of the study show the unique limitation of the step geometry design requirements specified in the current Ghana National Building Code and the National Building Regulation, and by association, the potential risk of accidents and discomfort in the use of stairs in public buildings such as those on university campuses.

The observed deviations in the dimensions of risers and treads point to a lack of strict compliance with standard specifications in the design and construction of stairs. Apart from engaging skilled artisans, and intensifying supervision in stair construction, development control authorities in Ghana need to strengthen inspection of stairs during construction to ensure and enforce compliance.

Findings of the study provide insight into stairway design, as well as stair safety and usability in a developing world context, and allows for a more comprehensive study of stair-related accidents and discomfort associated with stairs in public buildings as a basis for the review of standards and codes in Ghana and other developing countries.

This study aims to examine the feasibility of feedforward actuation of the recoater blade position to alleviate the resin surface non-uniformity while moving over deep-to-shallow transitions of submerged (already cured) geometric features.

A two-dimensional computational fluid dynamics (CFD) model has been used to determine optimized blade actuation protocols to minimize the resin surface non-uniformity. An experimental setup has been designed to validate the feasibility of the proposed protocol in practice.

A developed protocol for the blade height actuation is applied to a rectangular stair-like configuration of the underlying part geometry. The evaluation of the actuation protocol revealed the importance of two physical length scales, the capillary length and the size of the flow recirculation cell below in the liquid resin layer below the blade. They determine, together with the length scales defining the topography (horizontal extent and depth), the optimal blade trajectory. This protocol has also shown its efficiency for application to more complicated shapes (and, potentially, for any arbitrary geometry).

This study shows that incorporation of a feedforward control scheme in the recoating system might significantly reduce (by up to 80%) the surface unevenness. Moreover, this improvement of performances does not require major modifications of the existing architecture.

The results presented in this work demonstrate the benefits of the integration of the feedforward control to minimize the leading edge bulges over underlying part geometries in stereolithography.

The purpose of this paper is to present the mechanical design and stability analysis of a new stair‐climbing robotic wheelchair.

A prototype stair‐climbing robotic wheelchair is constructed comprising a pair of rotational multi‐limbed structures pivotally mounted on opposite sides of a support base. The short arm, long arm, and triangular support structures within each rotational multi‐limbed structure rotate under the actuating effects of epicyclical gear trains.

The robotic wheelchair ascends and descends stairs in a statically stable manner and has an efficient planar navigation capability.

In its current state of development, the robotic wheelchair is controlled and powered remotely via umbilical cords rather than an onboard processor and power supply.

The robotic wheelchair provides an effective solution for enhancing the mobility of the elderly and disabled.

The rotational multi‐limbed mechanisms are developed to ensure the stability of the sitting base at all stages of the stair navigation maneuver without the need for additional servo‐mechanism. The proposed robotic wheelchair shows the simplification of the associated operation process.

This paper aims to present a new stair‐climbing wheelchair that tries to solve adaptability problems of previous prototypes.

A new prototype has been built using a new strategy. The climbing process is splint into two subproblems: climbing a single step and positioning the wheels on the staircase.

An optimized solution has been found for each subproblem, due to this the presented prototype is able to climb any staircase built according to standards, has a high capacity load and its stable equilibrium is always guaranteed.

The presented prototype is able to climb a parallel staircase; future works will try to solve the non parallel staircase climbing problem.

The practical application is to build an industrial new model of wheelchair that allows handicapped people to increase their mobility.

The principal value of the paper consists in using two independent mechanical solutions to solve the subproblems that appear when the stair‐climbing problem is split.

This research investigated the use of two relatively new technologies, abrasive flow machining (AFM) and stereolithography (SL), to minimize the time to develop a finished prototype. Statistical analysis was used to determine effects of media grit size, media pressure, build style, build orientation and resin type on flatness, material removal rate and surface roughness. Results indicated that media pressure, grit size, and build orientation were significant in at least one of the experiments performed. Scanning electron microscope (SEM) images showed the stair‐stepping effect of the SL process before AFM and the removal of the stair‐stepping after AFM. The SEM images showed a lack of typical AFM flowlines on the surface and suggested that the workpiece material is removed by brittle fracture. Data dependent systems analysis techniques were also used to study the surface roughness profiles.

Among the different methodologies used for performance control in precision manufacturing, the measurement of metrological test artefacts becomes very important for the characterization, optimization and performance evaluation of additive manufacturing (AM) systems. The purpose of this study is to design and manufacture several benchmark artefacts to evaluate the accuracy of the selective laser melting (SLM) manufacturing process.

Artefacts consist of different primitive features (planes, cylinders and hemispheres) on sloped planes (0°, 15°, 30°, 45°) and stair-shaped and sloped planes (from 0° to 90°, at 5° intervals), manufactured in 17-4PH stainless steel. The artefacts were measured optically by a structured light scanner to verify the geometric dimensioning and tolerancing of SLM manufacturing.

The results provide design recommendations for precision SLM manufacturing of 17-4PH parts. Regarding geometrical accuracy, it is recommended to avoid surfaces with 45° negative slopes or higher. On the other hand, the material shrinkage effect can be compensated by resizing features according to X and Y direction.

No previous work has been found that evaluates accuracy when printing inwards (pockets) and outwards (pads) geometries at different manufacturing angles using SLM. The proposed artefacts can be used to determine the manufacturing accuracy of different AM systems by resizing to fit the build envelope of the system to evaluate. Analysis of manufactured benchmark artefacts allows to determine rules for the most suitable design of the desired parts.

The purpose of this paper is to share with the solid freeform fabrication community a new procedure and benchmark geometries for evaluating SFF process capabilities. The procedure evaluates the range capability of various SFF and SFF‐based hybrid processes in producing rod and hole elements.

By following the procedure and using the appropriate combination of benchmark parts the user can determine the minimal rod and hole size capabilities of an SFF or SFF‐based process. Benchmark parts are designed to capture feature size limitations, build angle problems, and aspect ratio capabilities.

The geometries and procedure were found to work for evaluating simple rod and hole elements resulting from SFF‐based processes.

Future work could address slot and wall features using a similar procedure. Mechanical properties and performance of resulting parts are not within the scope of this procedure.

The procedure and benchmaking geometries could be employed for a range of scales down to the nano scale. The use of this procedure will lead to practical design inputs for the SFF‐based fabrication of components consisting of optimized lattice structures.

Limited published benchmarking procedures are available to the SFF community. This is the first systematic procedure proposed to evaluate SFF processes for “Rod” and “Hole” capabilities.

With the development of 3D printing or additive manufacturing (AM), curved layer fused deposition modeling (CLFDM) has been researched to cope with the flat layer AM inherited problems, such as stair-step error, anisotropy and the time-cost and material-cost problems from the supporting structures. As one type of CLFDM, cylindrical slicing has obtained some research attention. However, it can only deal with rotationally symmetrical parts with a circular slicing layer, limiting its application. This paper aims to propose a ray-based slicing method to increase the inter-layer strength of flat layer-based AM parts to deal with more general revolving parts.

Specifically, the detailed algorithm and implementation steps are given with several examples to enable readers to understand it better. The combination of ray-based slicing and helical path planning has been proposed to consider the nonuniform path spacing between the adjacent paths in the same curved layer. A brief introduction of the printing system is given, mainly including a 3D printer and the graphical user interface.

The preliminary experiments are successfully conducted to verify the feasibility and versatility of the proposed and improved slicing method for the revolving thin-wall parts based on a rotary 3D printer.

This research is early-stage work, and the authors are intended to explore the process and show the initial feasibility of ray-based slicing for revolving thin-wall parts using a rotary 3D printer. In general, this research provides a novel and feasible slicing method for multiaxis rotary 3D printers, making manufacturing revolving thin-wall and complex parts possible.

This paper aims to focus on the changes in thermal and surface characteristics of acrylonitrile butadiene styrene (ABS) material when exposed to chemical vapours for surface finishing. The poor surface finish and the dimensional accuracy of the fused deposition modelling parts (of ABS material) because of the stair-stepping hinder their use for rapid tooling applications, which can be improved by vapour finishing process. The differential scanning calorimetry (DSC) tests are performed to investigate the thermal behaviour of ABS thermoplastic after vapour finishing.

The hip prosthesis replica has been used to highlight the efficacy of chemical finishing process for intricate and complex geometries. The replicas are treated with chemical vapours for different durations. The DSC tests are performed along with surface roughness, surface hardness and dimensional measurements of exposed replicas and compared with unexposed replica.

The longer finishing time, i.e. 20 s, manifested higher melting peak temperature, higher melting enthalpy and higher heat capacity along with smoother and harder surface as compared with unexposed replica. The finishing process enhanced the bonding strength and the heat-bearing capacity of ABS material. The vapour finishing process enhanced the thermal stability of the material which may extend its sustainability at higher temperatures.

The improved thermal stability of ABS thermoplastic after chemical vapour finishing has been demonstrated. This advancement allows the use of ABS in functional tooling suitable for small production runs with higher flexibility and lead time savings.

The heat effects associated with phase transitions as a function of temperature are studied in case of replicas finished with chemical vapours. The relationship between melting enthalpy and surface characteristics has been ascertained.

Test the detail resolution of fused deposition modeling (FDM) in the direct manufacture of rapid prototypes with textured surfaces.

A benchmark part carrying regular surface patterns with different feature sizes and aspect ratios has been manufactured on a FDM system with different build orientations. Layered parts have been inspected to detect the occurrence of quality defects on textured surfaces.

The experiments reveal the ability of currently available FDM systems to enhance prototype surfaces with form details on a millimeter scale. Results assist in identifying conditions which need to be satisfied in order to successfully reproduce generic texture geometries.

Although the testing method can be applied to any layered manufacturing technique, results are limited to a specific process, and may be influenced by technical improvements of commercial fabrication systems.

A first contribution is given to a full feasibility assessment of direct texturing, which potentially appears as more responsive and cost‐effective solution than current post‐finishing practices.

The paper proposes a systematic approach to the manufacture of textured parts by rapid prototyping techniques. The analysis of surface appearance in the presence of small‐scale form details adds a novel aspect to current approaches to performance benchmarking, which typically focus on form errors and roughness of plain surfaces.