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Article
Publication date: 12 April 2022

Weijie Zhou, Yi Zhang, Bin Yang, Xing Lei, Zhaowen Hu and Wei Wang

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

Industrial Lubrication and Tribology, vol. 74 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 23 September 2021

Ryuichi Kobayashi, Takashi Kigure and Ming Yang

This paper aims to describe a new process for suppressing the formation of orange peel, which is a polymer laser sintering (LS) process error.

Abstract

Purpose

This paper aims to describe a new process for suppressing the formation of orange peel, which is a polymer laser sintering (LS) process error.

Design/methodology/approach

The target for controlling the suppression of orange peel is securing the contact between the molten polymer and the surrounding powder. The authors set the powder bed temperature closer to the melting temperature than that for a typical LS. Alternatively, the authors use a low-power laser to irradiate the powder bed surrounding the parts being built. The surface finish of the built parts was evaluated using a three-dimensional scanner.

Findings

Both approaches were effective in suppressing orange peel. From the viewpoint of reusability of the used powder, the process that includes low-power laser irradiation is practical. The presence or absence of contact between the surrounding powder and the molten polymer determines whether the orange peel is formed.

Research limitations/implications

The authors have not tested orange peel suppression for complex shapes.

Originality/value

The authors have demonstrated a concrete process that can suppress orange peel formation even for powders with low melt-flow rates. Furthermore, a mechanism for the formation/suppression of orange peel based on the experimental results was proposed.

Details

Rapid Prototyping Journal, vol. 28 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 27 July 2021

Cong Liu, Yanguo Yin, Baohong Tong and Guotao Zhang

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

Abstract

Purpose

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

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Peer review

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

Details

Industrial Lubrication and Tribology, vol. 73 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 27 September 2022

Taylor Davis, Tracy W. Nelson and Nathan B. Crane

dding dopants to a powder bed could be a cost-effective method for spatially varying the material properties in laser powder bed fusion (LPBF) or for evaluating new…

Abstract

Purpose

dding dopants to a powder bed could be a cost-effective method for spatially varying the material properties in laser powder bed fusion (LPBF) or for evaluating new materials and processing relationships. However, these additions may impact the selection of processing parameters. Furthermore, these impacts may be different when depositing nanoparticles into the powder bed than when the same composition is incorporated into the powder particles as by ball milling of powders or mixing similarly sized powders. This study aims to measure the changes in the single bead characteristics with laser power, laser scan speed, laser spot size and quantity of zirconia nanoparticle dopant added to SS 316 L powder.

Design/methodology/approach

A zirconia slurry was inkjet-printed into a single layer of 316 SS powder and dried. Single bead experiments were conducted on the composite powder. The line type (continuous vs balling) and the melt pool geometry were compared at various levels of zirconia doping.

Findings

The balling regime expands dramatically with the zirconia dopant to both higher and lower energy density values indicating the presence of multiple physical mechanisms that influence the resulting melt track morphology. However, the energy density required for continuous tracks was not impacted as significantly by zirconia addition. These results suggest that the addition of dopants may alter the process parameter ranges suitable for the fabrication of high-quality parts.

Originality/value

This work provides new insight into the potential impact of material doping on the ranges of energy density values that form continuous lines in single bead tests. It also illustrates a potential method for spatially varying material composition for process development or even part optimization in powder bed fusion without producing a mixed powder that cannot be recycled.

Details

Rapid Prototyping Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 November 1972

Americus

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…

Abstract

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.

Details

Pigment & Resin Technology, vol. 1 no. 11
Type: Research Article
ISSN: 0369-9420

Article
Publication date: 1 March 1993

P. Soszek

Two new technologies are described for manufacturing circuitry commonly used in printed circuit boards (PCBs), multi‐chip modules (MCMs), hybrid circuits and other…

Abstract

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.

Details

Circuit World, vol. 19 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 September 1995

B. Van der Schueren and J.P. Kruth

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…

2480

Abstract

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.

Details

Rapid Prototyping Journal, vol. 1 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 August 1973

G.E. Bond and J.N. Ralston

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…

Abstract

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.

Details

Pigment & Resin Technology, vol. 2 no. 8
Type: Research Article
ISSN: 0369-9420

Article
Publication date: 11 September 2007

V. Dunkwal, S. Jood and S. Singh

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…

1003

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Practical implications

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.

Originality/value

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.

Details

British Food Journal, vol. 109 no. 9
Type: Research Article
ISSN: 0007-070X

Keywords

Article
Publication date: 1 September 2005

K.M. Fan, W.L. Cheung and I. Gibson

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

1750

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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

Practical implications

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

Originality/value

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

Details

Rapid Prototyping Journal, vol. 11 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

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