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The relationship between the major process variables (laser power, laser scan speed, scan length, beam overlap and Q‐switch pulse frequency) of direct metal laser re‐melting and their effect on the structure of single‐ and multi‐layer copper coupons has been investigated. The work successfully produced selectively fused copper powder layers and simple three‐dimensional copper structures with suitable laser parameters being identified for the production of parts, including thin‐walled cubic structures. It was shown that the specific energy density needed to melt thick powder beds was less than that to melt multi‐layer builds and that the type of substrate material used significantly affected the process parameters. Thus, the substrate and its thermal properties have a significant effect on the melt pool size and freezing rate.

The purpose of this paper is to report on a study of the movement of the powder bed material during selective laser sintering (SLS) of bisphenol‐A polycarbonate (PC) powder and its effect on the morphology of the sintered specimen.

Two sintering experiments, i.e. single‐spot laser sintering and raster‐scan laser sintering, were carried out and the material movement mechanisms were investigated in situ and subsequently by scanning electron microscopy.

During the raster‐scan laser sintering process, the movement of the powder was found to be primarily perpendicular to the scanning direction. When sintering at a high laser power, it significantly affected the surface morphology of the sintered specimens and parallel surface bands occurred along the scanning direction.

Experiments were carried out on a modified laser engraving machine rather than a commercial SLS machine.

A schematic model of the material movement mechanism for each of the sintering strategies is presented.

The results further the understanding of the sintering behaviour of the powder bed.

This paper aims to investigate the influence of nonuniform gas speed across the build area on the melt pool depth during laser powder bed fusion. This study focuses on whether a nonuniform gas speed is a source of process variation within an individual build.

Parts with many single-track laser scans were printed and characterized in different locations across the build area coupled with corresponding gas speed profile measurements. Cross-sectional melt pool depth, width and area are compared against build location/gas speed profiles, scan direction and laser scan speed.

This study shows that the melt pool depth of single-track laser scans produced on parts are highly variable. Despite this, trends were found showing a reduction in melt pool depth for slow laser scan speeds on the build platform near the inlet nozzle and when the laser scans are parallel to the gas flow direction.

A unique data set of single-track laser scan cross-sectional melt pool measurements and gas speed measurements was generated to assess process variation associated with nonuniform gas speed. Additionally, a novel sample design was used to increase the number of single-track tests per part, which is widely applicable to studying process variation across the build area.

The range of applications of the currently available biomass selective laser sintering (SLS) parts is limited and low-quality. This study aims to demonstrate the effects of the various processing parameters on the dimensional accuracy, bending strength, tensile strength, density and impact strength of the Prosopis chilensis/polyethersulfone (PES) composites (PCPCs) that were produced by SLS. The various processing parameters are laser power, scan speed, preheating temperature, scan spacing and layer thickness. In addition, the authors’ studied the effects of PCP particle size on the mechanical properties of the PCPCs.

The PCPC specimens were printed using an AFS SLS machine (additive manufacturing). The bending, tensile and impact strengths of the specimens were measured using a universal tensile tester. The dimensional accuracy of the bending specimens was determined by a Vernier caliper. The formability of the PCPC at various mixing ratios of the raw materials was earlier investigated by single-layer sintering experiments (Idriss et al., 2020b). The microstructure and particle distribution of the various PCPC specimens were analyzed by scanning electron microscopy (SEM).

The mechanical strengths (bending, tensile and impact strengths and density) and the dimensional accuracy of the PCPC SLS parts were directly and inversely proportional, respectively, to the laser power and preheating temperature. Furthermore, the mechanical strengths and dimensional accuracy of the PCPC SLS parts were inversely and directly proportional, respectively, to the scanning speed, scan spacing and layer thickness.

PCPC is an inexpensive, energy-efficient material that can address the drawbacks of the existing SLS parts. It is also eco-friendly because it lowers the pollution and CO₂ emissions that are associated with waste disposal and SLS, respectively. The optimization of the processing parameters of SLS in this study produced high-quality PCPC parts with high mechanical strengths and dimensional accuracy that could be used for the manufacture of the roof and wooden floors, construction components and furniture manufacturing.

To the best of the authors’ knowledge, this study is among the first to elucidate the impact of the various SLS processing parameters on the mechanical properties and dimensional accuracy of the sintered parts. Furthermore, novel PCPC parts were produced in this study by SLS.

Accurate build‐time prediction for making stereolithography parts not only benefits the service industry with information necessary for correct pricing and effective job scheduling, it also provides researchers with valuable information for various build parameter studies. Instead of the conventional methods of predicting build time based on the part’s volume and surface, the present predictor uses the detailed scan and recoat information from the actual build files by incorporating the algorithms derived from a detailed study of the laser scan mechanism of the stereolithography machine. Finds that the scan velocity generated from the stereolithography machine depends primarily on the system’s laser power, beam diameter, materials properties and the user’s specification of cure depth. Proves that this velocity is independent of the direction the laser travels, and does not depend on the total number of segments of the scan path. In addition, the time required for the laser to jump from one spot to another without scan is linearly proportional to the total jump distance, and can be calculated by a proposed constant velocity. Most profoundly, the present investigation concludes that the machine uses a velocity factor which is only 68.5 per cent of the theoretical calculation. This much slower velocity results in an undesired amount of additional cure and proves to be the main cause of the Z dimensional inaccuracy. The present build‐time predictor was developed by taking into account all the factors stated above, and its accuracy was further verified by comparing the actual build‐time observed for many jobs over a six month period.

Limited research has attempted to reveal the different modes of the melt pool formation in additive manufacturing. This paper aims to study the mechanisms of surface roughness formation, especially on the aspect of melt pool formation which determine the surface profile and consequently significantly influence the surface roughness.

In this study, the conditions under which different modes of melt pool formation (conduction mode and keyhole mode) occur for the case of as-fabricated Hastelloy X using direct metal laser solidification (DMLS) are derived and validated experimentally. Top surfaces of uni-directionally built samples under various processing conditions are cut, grinded, polished and etched to reveal their individual melt pool morphologies. Similarly, up-skin (slope angle < 90°) and down-skin (slope angle > 90°) melt pool morphologies are also investigated to compare the differences. Surface tension gradients and resultant Marangoni flow, which dominate the melt flow in the melt pool, is also calculated to help better evaluate the melt pool shape forming.

Two types of melt pool formation modes are dominating in DMLS: conduction mode and keyhole mode. Melt pool formed by conduction mode generally has an aspect ratio of 1:2 (depth vs width) and is in elliptical shape. Appropriate selection of scanning laser power and speed are required to maintain a low characteristic length and width ratio to prevent ballings. Melt pool formed by keyhole mode has an aspect ratio of 1:1 or less. High-energy contour promotes formation of key-hole-shaped melt pool which fills the gaps between layers and smoothens the up-skin surface roughness. Low-energy contour scan is necessary for down-skin surface to form small melt pool profiles and achieve low Ra.

This paper provides valuable insight into the origins of surface quality problem of DMLS, which is a very critical issue for upgrading the process for manufacturing real components. This paper helps promote the understanding of the attributes and capabilities of this rapidly evolving three-dimensional printing technology and allow appropriate control of processing parameters for successful fabrication of components with sound surface quality.

The purpose of this paper is to present a literature review of laser scanning and 3D modelling devices, modes of delivery and applications within the architecture, engineering, construction and owner-operated sector. Such devices are inextricably linked to modern digital built environment practices, particularly when used in conjunction with as-built building information modelling (BIM) development. The research also reports upon innovative technological advancements (such as machine vision) that coalesce with 3D scanning solutions.

A synthesis of literature is used to develop: a hierarchy of the modes of delivery for laser scan devices; a thematic analysis of 3D terrestrial laser scan technology applications; and a componential cross-comparative tabulation of laser scan technology and specifications.

Findings reveal that the costly and labour intensive attributes of laser scanning devices have stimulated the development of hybrid automated and intelligent technologies to improve performance. Such developments are set to satisfy the increasing demand for digitisation of both existing and new buildings into BIM. Future work proposed will seek to: review what coalescence of digital technologies will provide an optimal and cost-effective solution to accurately re-constructing the digital built environment; conduct case studies that implement hybrid digital solutions in pragmatic facilities management scenarios to measure their performance and user satisfaction; and eliminate manual remodelling tasks (such as point cloud reconstruction) via the use of computational intelligence algorithms integral within cloud-based BIM platforms.

Although laser scanning and 3D modelling have been widely covered en passant within the literature, scant research has conducted a holistic review of the technology, its applications and future developments. This review presents concise and lucid reference guidance that will intellectually challenge, and better inform, both practitioners and researchers.

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation.

After each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing.

It is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure.

There has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.

In this paper, an experimental apparatus was designed and subsequent theoretical analysis and simulations were conducted on the effectiveness and advantages of a novel laser beam scan localization (BLS) system.

The system used a moving location assistant (LA) with a laser beam, through which the deployed area was scanned. The laser beam sent identity documents (IDs) to unknown nodes to obtain the sensor locations.

The results showed that the system yielded significant benefits compared with other localization methods, and a high localization accuracy could be achieved without the aid of expensive hardware on the sensor nodes. Furthermore, four positioning mode features in this localization system were realized and compared.

In this paper, an experimental apparatus was designed and subsequent theoretical analysis and simulations were conducted on the effectiveness and advantages of a novel laser BLS system. The system used a moving LA with a laser beam, through which the deployed area was scanned. The laser beam sent IDs to unknown nodes to obtain the sensor locations.

The purpose of this paper is to investigate the influence of surface topology on the performance of laser line scanning probe and to suggest methodology for 3D digitization of specular surfaces.

Two different molds, one having milled surface and the other with polished surface, were used to identify effect of surface characteristics on the performance of laser line scanning probe mounted on bridge-type coordinate measuring machine. The point cloud data acquisition of two surfaces was carried out using different combinations of laser scanning parameters. The point cloud sets thus obtained were analyzed in terms of completeness, noise and accuracy. The polished mold which exhibited specular reflection was digitized at different scanning angles of laser line scanning probe using the best combination of scanning parameters.

Results confirmed that surface characteristics play important role to determine quality of the reverse engineering (RE) process. The results in terms of completeness, accuracy and noise for point cloud sets have successfully been obtained for milled and polished surfaces. Three-dimensional (3D) comparison analysis suggested larger deviation in cases of polished surface as compared to milled surface. The point cloud set acquired with proposed approach was better in terms of both completeness and noise reduction.

There has been an increased demand for measurement of metallic, polished and shiny surfaces in automotive, aerospace and medical industries. These surfaces are very difficult to scan because they exhibit specular reflection instead of diffuse reflection. Laser line scanning probe which is a non-contact method is in great demand for RE. This is due to the fact that it possesses very high data acquisition speed. However, laser scanning is hugely affected by surface characteristics which in turn govern specular reflection.In this paper, it has been shown that a surface that exhibits various degrees of specular reflection can be digitized efficiently if appropriate combination of scanning parameters and positions of laser line scanning probe are used. Also, this paper has attempted to offer a procedure to overcome incompleteness and noise in 3D data as obtained by the laser line scanning probe.