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This paper aims to study drop formation in piezoelectric industrial printheads during the inkjet printing processes. It presents how the piezoelectric printhead forms drops of nanoparticle ink and how the problems with different values of drop parameters may influence the printed pattern’ defects and quality.

A piezoelectric printhead with 128 nozzles was activated to operate in a controlled manner, and the droplets ejected from the nozzles were observed during falling and analysed in the printview system. The effect of varying the values of drop parameters on print quality and pattern defects has been analysed and discussed.

The obtained results allow the identification of the sources of the technological problems in obtaining repeatable performance drops with the desired properties, and indicate the importance of choosing the appropriate individually chosen strategy of controlling the printing for each individual application to get good-quality and free-from-defects patterns.

Because of the chosen research method (arbitrary selected printhead type and ink manufacturer), this study could have limited universality. Authors encourage the study of other kinds of piezoelectric heads or other conductive inks.

This study includes practically useful applications for users to improve the inkjet print quality.

This study presents results of original empirical research works on problems of the drops forming in the inkjet printing process, and finally, it identifies problems that must be resolved to disseminate this technology.

The purpose of this paper is to present a numerical approach for investigating different phenomena during multiple liquid drop impact on air‐water interface.

The authors have used the coupled level‐set and volume‐of‐fluid (CLSVOF) method to explore the different phenomena during multi‐drop impact on liquid‐liquid interface. Complete numerical simulation is performed for two‐dimensional incompressible flow, which is described in axisymmetric coordinates.

During drop pair impact at very low impact velocities, the process of partial coalescence is observed where the process of pinch off is different than single drop impact. At higher impact velocities, phenomena such as bubble entrapment are observed.

In this paper, a new approach has been developed to simulate consecutive drop impact on a liquid pool.

This paper aims to summarize the latest developments both in terms of theoretical understanding and experimental techniques related to inkjet fluids. The purpose is to provide practitioners a self-contained review of how the performance of inkjet and inkjet-based three-dimensional (3D) printing is fundamentally influenced by the properties of inkjet fluids.

This paper is written for practitioners who may not be familiar with the underlying physics of inkjet printing. The paper thus begins with a brief review of basic concepts in inkjet fluid characterization and the relevant dimensionless groups. Then, how drop impact and contact angle affect the footprint and resolution of inkjet printing is reviewed, especially onto powder and fabrics that are relevant to 3D printing and flexible electronics applications. A future outlook is given at the end of this review paper.

The jettability of Newtonian fluids is well-studied and has been generalized using a dimensionless Ohnesorge number. However, the inclusion of various functional materials may modify the ink fluid properties, leading to non-Newtonian behavior, such as shear thinning and elasticity. This paper discusses the current understanding of common inkjet fluids, such as particle suspensions, shear-thinning fluids and viscoelastic fluids.

A number of excellent review papers on the applications of inkjet and inkjet-based 3D printing already exist. This paper focuses on highlighting the current scientific understanding and possible future directions.

To review the concept of digital imaging for PCB manufacturing, with a specific focus on ink‐jet printing technologies.

This paper has been written to provide a review of digital imaging in the PCB industry. The application of ink‐jet printing in PCB manufacturing and the basic technology behind ink‐jet printing is described.

Ink‐jet printing in PCB manufacturing is a new technology, whose benefits and liabilities are still being determined. Although the concept of digital imaging fits a need in the industry for better control over registration, there are still many issues to be addressed for the technology to become widely adopted.

The value of the paper lies in educating the industry in the concepts of ink‐jet printing and the potential benefits it can deliver towards yield improvement and reduced costs in an ever‐more demanding and price sensitive market.

THE modern aeroplane is constructed largely from sheet metal. As such, the most important production problems are those of sheet metal forming, and assembling. Production is here considered as not only the act of forming and assembling the required number of parts, but also the making of forming tools, and all processing of parts such as heat‐treating. Only that phase of the above concept of production which deals with the tooling for production and the forming and heat‐treating will be considered here. The design of the aircraft parts will also be discussed somewhat, for it is obvious that the design of the part (designed shape and materials used) frequently determines whether the part can or cannot be readily made.

The PCB industry is quickly gearing up for the digital printing age. While photo imaging and screen‐printing have been commonly used as recognized and established techniques in the PCB industry, their high tooling costs and time‐consuming procedures are willingly exchanged by digital printing, following the establishment of this technology both in everyday office uses and in a variety of industrial applications. In the PCB industry, a number of companies have recently begun to offer various digital printing system configurations. This paper discusses the basic requirements of PCB ink‐jet printing systems. Possible solutions and basic system engineering considerations are presented, to show the optimal system configuration.

This paper aims to study the packing density of printed paths on different substrate materials. It presents problems which appear when the necessity of printing one or more narrow paths occurs.

A piezoelectric printhead containing nozzles with a diameter of 35 µm was used for printing nanoparticle silver ink on different polymer substrates which were treated by plasma or not treated at all. The shape, defects, resistance and printing parameters for the printed paths were analysed.

The obtained results allow the identification of the sources of the technological problems in obtaining a high packing density of the paths in a small area of substrate and the repeatable prints.

The study could have limited universality because of the chosen research method; printhead, ink, substrate materials and process parameters were arbitrarily selected. The authors encourage the study of other kinds of conductive inks, treatment methods and printing process parameters.

The study includes practically useful information about widths, shapes, defects and the resistance of the paths printed using different technological parameters.

The study presents the results of original empirical research on problems of the packing density of inkjet printed paths on a small area of substrate and identifies problems that must be resolved to obtain effective interconnections in the inkjet technology.

The review glances upon the colorants used for printing on ceramic substrates by ink jet technology and techniques, chemistry involved during the selection of the colorants.

The ink jet technology is an easy and a convenient technique, specially designed colorants are used for such applications with tailor made properties and features.

New developments in technology and chemistry of colorants to achieve successes in application studies of ceramic substrates.

N/A.

This review glances upon the history, development and practical approach of the current techniques with available dyes and pigments and the techniques involved during the synthesis and application.

The review paper provides information about the development of the inkjet technique on ceramics and available colorants with methods.

Entrepreneurship and small business formation.

BA (Entrepreneurship); BA (Small Business Formation); BA (Management).

Owing to youth unemployment in sub-Saharan economies, youth entrepreneurship is now a major policy alternative across the subcontinent. It is also an immediate alternative for unemployed school drop-outs. Botswana is encouraging youth entrepreneurship through funding youth projects as an intervention. This case study presents decision alternatives considered by young adults when thinking about the future – to proceed with school or to start their own business. The other set of decision alternatives is which business idea to pursue – turning a hobby into a business opportunity or pursuing a new opportunity altogether. Mr Supang, owner of Swanscapes (Pty) Ltd, has to debate these decision alternatives with himself. Swanscape has to contend with a growing market but is unsure of where to get expansion finance. With expansion finance having been availed, managerial skills limitations will have to be dealt with. The company should focus on three other very important decisions: how to compete with large contractors currently dominant in the market and other small businesses that have recently entered the market in flower pot production; how to develop own skills and those of employees; and finally how to grow the business. Swanscapes remains hamstrung with the decision of which mode of growth strategy to adopt.

The goal of this case study is to illustrate the tough decision alternatives unemployed youth starting their own small businesses have to juggle with. The case also illustrates the hurdles novice entrepreneurs have to contend with in order to establish a brand for their product or service. It also illustrates the impact of inadequate managerial and technical skills on growth strategies an owner may have.

Teaching notes are available. Please consult your librarian for access.

The purpose of this paper is to find optimal sintering conditions of silver-based nano-inks for achieving the high electrical conductivity of the deposited layers applied on polyimide foils as well as the influence of ageing on the electrical conductivity. Therefore, the investigation in the field of silver layers deposited by inkjet printing technology is presented in this paper.

The four-point resistance measurements were realized for a detailed and precise analysis of the resistance of two different silver layers under different sintering conditions depending on the type of nano-ink varied about the recommended values. Highly accelerated stress tests (HASTs) were also applied as an ageing method for confirmation of the high electrical stability of the silver layers.

The results prove the strong influence of the temperature and the time of the sintering process on the sheet resistance of the investigated silver-based layers deposited by inkjet printing technology on polyimide foils. The HASTs caused significant changes in the electrical conductivity for both nano-inks presented in this paper. The existence of noticeable dependence among the resistivity, thermal treatment and ageing was proved.

The main benefit lays in the optimization of sintering conditions to improve the electrical conductivity of the silver layers. The paper also presents a new approach for a stability analysis of the silver layers by HASTs.