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Selective laser sintering (SLS) is an essential technology in the field of additive manufacturing. However, SLS technology is limited by the traditional point-laser sintering method and has reached the bottleneck of efficiency improvement. This study aims to develop an image-shaped laser sintering (ISLS) system based on a digital micromirror device (DMD) to address this problem. The ISLS system uses an image-shaped laser light source with a size of 16 mm × 25.6 mm instead of the traditional SLS point-laser light source.

The ISLS system achieves large-area image-shaped sintering of polymer powder materials by moving the laser light source continuously in the x-direction and updating the sintering pattern synchronously, as well as by overlapping the splicing of adjacent sintering areas in the y-direction. A low-cost composite powder suitable for the ISLS system was prepared using polyether sulfone (PES), pinewood and carbon black (CB) powders as raw materials. Large-sized samples were fabricated using composite powder, and the microstructure, dimensional accuracy, geometric deviation, density, mechanical properties and feasible feature sizes were evaluated.

The experimental results demonstrate that the ISLS system is feasible and can print large-sized parts with good dimensional accuracy, acceptable geometric deviations, specific small-scale features and certain density and mechanical properties.

This study has achieved the transition from traditional point sintering mode to image-shaped surface sintering mode. It has provided a new approach to enhance the system performance of traditional SLS.

This study aims to investigate the effect of MoS2 powder on tribological properties of sliding interfaces.

Loose MoS2 powder was introduced in the gap of point-contact friction pairs, and sliding friction test was conducted using a testing machine. Friction noise, wear mark appearance, microstructure and wear debris were characterized with a noise tester, white-light interferometer, scanning electron microscope and ferrograph, respectively. Numerical simulation was also performed to analyze the influence of MoS2 powder on tribological properties of the sliding interface.

MoS2 powder remarkably improved the lubrication performance of the sliding interface, whose friction coefficient and wear rate were reduced by one-fifth of the interface values without powder. The addition of MoS2 powder also reduced stress, plastic deformation and friction temperature in the wear mark. The sliding interface with MoS2 powder demonstrated lower friction noise and roughness compared with the interface without powder lubrication. The adherence of MoS2 powder onto the friction interface formed a friction film, which induced the wear mechanism of the sliding interface to change from serious cutting and adhesive wear to delamination and slight cutting wear under the action of normal and shear forces.

Tribological characteristics of the interface with MoS2 powder lubrication were clarified. This work provides a theoretical basis for solid-powder lubrication and reference for its application in engineering.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0150/

Modern powder coatings were introduced in 1952. They created great interest and much was written about them and much predicted for them. They did indeed find a niche, but they did not deliver quite as had been anticipated and by the early 1960's their star was waning. But one must never discount the impact of advancing technology — particularly when economy, convenience and performance are involved. Novel methods of application, primarily electrostatic spraying to complement the original fluidised bed approach, new formulations, faster curing epoxies and a better understanding of both the virtues and the defects of this method for industrial coating, has brought powder coatings back into their own.

Two new technologies are described for manufacturing circuitry commonly used in printed circuit boards (PCBs), multi‐chip modules (MCMs), hybrid circuits and other applications. Both processes involve the additive use of dry conductive powders which are in the micron and sub‐micron size range. Various conductive powders, such as copper, can be used. In addition, custom powder formulations to create resistive circuit elements can now be used during the same fabrication operations. The two new processes offer significant advantages over current methods. The laser in combination with sub‐micron powders allows extremely fine circuit lines and spaces to be written. Line widths of 1 mil (25 microns) can be produced. Three‐dimensional surfaces can have circuitry fabricated on them using both process methods. Lasers allow for a higher degree of accuracy, repeatability and product yield than currently experienced within the industry. Line widths and thicknesses can be software controlled and in real time. The processes do not use resists, etching or wet chemicals, thus providing substantial savings due to fewer process steps and the elimination of wet chemical handling and disposal, which is of mounting environmental concern. Use of clean process water is not required, which is an issue of cost and supply, especially in drought‐ridden areas. Very little waste is generated with the new processes as they are additive and unused powder can be reused. The first process utilises a laser to write the circuit lines on the substrate directly from a CAD/CAM database. No artwork is required for production purposes. All existing software can be used for inputting and driving the process equipment. In the process, a film of heat‐activated adhesive is laid on a substrate on top of which a layer of conductive powder is placed. The low‐power laser defines the circuitry by activating the powder and adhesive. Powder which is not activated is removed and reused. Applications include prototype production for the rapid turnaround of product to design engineers. The second process uses technology similar to that used in desktop laser printers. Instead of using toner and paper, conductive powder particles are deposited directly onto a substrate to create circuitry. The transfer and deposition of the powder are performed electrostatically and employ the same principles used in a photocopier. This allows for high volume production, with manufacturing times measured in seconds and minutes. CAD/CAM systems can be used directly; the equipment can be desk‐sized and is capable of operating in an office or laboratory environment. This yields savings on expensive custom facilities. Desktop manufacturing of circuitry using these new patented processes is within sight.

This study aims to investigate the microtopography transformation at a low-speed heavy-load interface with the lubrication of powder particles and its nonlinear friction effect on the sliding pair in contact.

Based on the universal mechanical tester (UMT) tribometer and VK shape-measuring laser microscope, comparative friction experiments were conducted with graphite powder lubrication. The friction coefficient with nonlinear fluctuations and the three-dimensional morphology of the boundary layer at the interface were observed and analyzed under different operating conditions. The effects on lubrication mechanisms and frictional nonlinearity at the sliding pair were focused on under different surface roughness and powder layer thickness conditions.

At a certain external load and sliding speed, the initial specimen surface with an appropriate initial roughness and powder thickness can store and bond the powder lubricant to form a boundary film readily. The relatively flat and firm boundary layer of powder at the microscopic interface can reduce the coefficient of friction and suppress its nonlinear fluctuation effectively. Therefore, proper surface roughness and powder layer thickness are beneficial to the graphite lubrication and stability maintenance of a friction pair.

This research is conducive to developing a deep understanding of the microtopography transformation with frictional nonlinearity at a low-speed heavy-load interface with graphite powder lubrication.

Selective metal powder sintering is a layer‐by‐layer manufacturing system producing metallic parts with good mechanical properties. Describes why an Fe‐Cu powder mixture has been selected as the basic material for the process. Deals with the powder deposition issue and proposes a mechanism which can deposit thin powder layers on top of a recipient. Shows that the powder deposition mainly depends on the powder properties. States that the required powder properties are partially compatible with the specifications set by the technology of selective sintering but that some properties are in conflict with one another. Discusses the resulting compromises needed in the powder mixtures and the required modifications to the deposition mechanism.

Many of you may already be familiar with the term ‘powder coating’. For those of you who are not, I would like to describe the term briefly. Powder coating is a relatively new process by which dry plastic powders are applied to a clean metal surface. After application, the coated object is heated, fusing the powder to form a smooth, tough coating. Available today are many plastic powders offering a wide range of properties and colours. These powders are fully formulated and are free‐flowing ready for application to metal. Previous coatings for such items have been applied from solution. The dry plastic powders are normally higher molecular weight polymers than those used in solution: because of this, the coatings produced have greatly increased durability, toughness and abrasion resistance.

This article aims to focus on the food value of the mushroom. Because of its low calorific value and very high content of proteins, vitamins and minerals, mushrooms may contribute significantly in overcoming protein deficiency in developing countries like India.

Oyster (Pleurotus sajor caju) mushroom cultivated on two substrates i.e. wheat straw and brassica straw were procured. Freshly harvested and washed mushrooms were cut into small pieces. Sliced mushrooms were divided into four portions. Two portions were left untreated and dried using sun and oven drying methods. The third portion was blanched in boiling water at 100 °C for two mins, cooled immediately and drained. The blanched samples were divided into two portions. One portion was sun dried and another was oven dried. The fourth portion was soaked in solution of citric acid (0.25 percent) for 30 mins and drained. The steeped samples were divided into two portions. One portion was sun dried and another was oven dried. Each sample was dried from initial moisture content of 91 percent on fresh weight basis of the final moisture content 10 percent on dry weight basis. All the samples were ground to make fine powder. The untreated and treated samples were analysed for physico‐chemical properties and sensory evaluation by using standard methods.

Treated and untreated powders prepared from oyster (Pleurotus sajor caju) mushrooms grown on two substrates i.e. wheat and brassica straw were analysed for physical and chemical characteristics. Among the powders, T₆ (steeped in 0.25 percent citric acid and oven dried) powder exhibited highest yield followed by untreated and blanched powders. On the other hand, untreated samples T₁ (sun dried) and T₄ (oven dried) showed higher browning index as compared to pretreated powders. Steeped samples (T₃ and T₆) from both type of mushrooms, irrespective of drying methods exhibited higher values of water retention capacity and swelling index as well as sensory attributes (colour, aroma and texture) In terms of chemical analysis, steeped samples from both types of mushrooms, irrespective of drying methods, exhibited higher contents crude protein, crude fibre and ash as compared to blanched powders. Blanching in hot water may cause leaching out of nutrients.

With regard to healthy benefits and medicinal value of mushroom, its production and consumption should be increased. However, mushroom production does not demand land, but helps in the bioconversion of potential pollutants like agro‐wastes to useful and nutritive food for human consumption, which is essential to a developing country like India.

The findings of this article may contribute significantly in overcoming protein deficiency in developing countries like India. Mushrooms have a low carbohydrate content, no cholesterol and are almost fat free. Therefore, they form an important constituent of a diet for a population suffering from atherosclerosis.

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.

The purpose of this paper is to report on a study of the effect of glass microsphere (GMS) and potassium bromide (KBr) powder as an additive on the reflectance and transmittance of TrueForm^TM acrylic‐styrene co‐polymer (TF) powder to CO₂ laser during selective laser sintering (SLS).

GMSs and KBr powder were chosen because glass is opaque to CO₂ laser while KBr is transparent. The GMSs were treated with silane coupling agent and hydrofluoric acid to study the surface effect on the optical properties of TF/GMS blends. KBr powder was blend with TF powder in an attempt to modify the penetration depth of the laser in the powder bed. An integrating sphere was used to measure the reflectance of the powder bed. In the measurement of transmittance, a power meter was placed below the powder layer, which was supported by a KCl disc, to register the transmitted laser energy through the powder layer.

For the TF/GMS blends, smaller GMSs gave a higher reflectance while the surface treatments had little effect. The transmittance of both the polymer and the blends were very low. Although bulk KBr is highly transparent to CO₂ laser, adding 30 vol% of KBr powder to TF hardly increased the transmittance of the powder bed.

Experiments were carried out on a modified laser engraving machine rather than a commercial SLS machine. The laser energy density used was lower than that for normal SLS processes and no significant changes of physical condition of the powder bed were inflicted. The results only indicate the optical properties in the initial state.

The effects of transparent and non‐transparent fillers on the optical properties of the powder bed are presented.

This work furthers the understanding of heat absorption behavior of the powder bed during SLS.