Additive manufacturing of metal parts is gaining acceptance in industry due to its unique manufacturing capabilities. Higher surface roughness of printed parts is one of the major challenges of this advanced manufacturing technique, which requires a crucial post-processing stage before the components can be used in practice. This study investigates the influence of plasma electrolytic polishing (PeP) and the combination of PeP and particle blasting as a post processing technique for additively manufactured stainless steel samples. The results show a 70% improvement in surface roughness after 10 minutes of particle blasting and 3 minutes of PeP in sequence and presents the possibility of optimizing processing time to achieve better surface qualities with minimal post processing time.

Flexible ferroelectric PMN–35PT thick film structures with energy storage, piezoelectric and electrocaloric performance were prepared by the room-temperature aerosol deposition method.

Additive manufacturing (AM) of metallic parts is gaining momentum in production industries. In view of producing a metal microproduct using AM the issue of high surface roughness is prominent. Plasma electrolytic Polishing (PeP) is a post processing technology that greatly reduces surface roughness of metallic parts. In this paper the effects of PeP of microfluidic platform, printed with selective laser melting (SLM) technology, is presented. The results show that surface roughness of the specimens was severely reduced. Also, some geometrical defects inherent to SLM technology were partly removed. It is shown, that for smaller geometrical microfeatures (sizes of less than 0.5 mm) the effectiveness of PeP is reduced. Through this investigation it can be concluded that PeP is a promising post-processing technology for SLM printed microparts since it significantly improves the overall part quality. However, further improvements of the process chain need to be implemented in order to render the microfluidic platform functional.

This study focuses on influence of alloying content and type of manufacturing on the effectiveness of deep cryogenic treatment (DCT) on properties of selected high-alloyed ferrous alloys (HAFA): EN HS6-5-2, EN HS6-5-2-5, EN HS6-5-3 and EN HS12-1-4. In order to evaluate the dependency of DCT performance on chemical composition and manufacturing type, the microstructure, hardness, impact and fracture toughness and fatigue properties were analyzed. Additionally, the fatigue data was evaluated using an adapted strain-life model in order to understand the unique effects of DCT with selected factors and provide a model for estimating the fatigue limit of DCT HAFA. The study indicates that DCT affects carbide precipitation, size and morphology of nanocarbides, average distance between carbides and nanocarbides, as well as the base matrix (martensitic laths). The induced microstructural changes cause an overall positive change of mechanical properties in selected HAFA, which correlates well with individual alloying and manufacturing differences. Overall, DCT has greater effect on wrought HAFA than powder metallurgy manufactured HAFA, at which high content of W and Co generally degenerates the DCT induced microstructure modifications.

The Ice abrasive water jet technology uses cryogenically cooled ice particles instead of the mineral abrasive used in the Abrasive water jet technology. The aim is to avoid contamination of workpieces with mineral abrasives and to reduce the environmental impact of this technology. The ice particles are sucked into a high-speed water jet with speeds of up to 600 m.s(-1) using the Venturi effect. Direct observation of the process is very difficult due to the extreme operating conditions. We have clearly shown that at least some of the ice particles, which have cryogenic temperatures when entering the high-speed water jet, neither completely melt nor are completely crushed in contact with the jet. Further on, the erosion capability of ice particles was evaluated by blasting the aluminium and glass surfaces at two impinging angles and compared to garnet mineral abrasive, showing that ice particles have the potential to generate similar damage in the workpiece material as garnet. These findings pave the way for exploring the potential of abrasive waterjet technology in a wide range of new applications, such as food processing, medical implant and turbine blade manufacturing, and post-processing of parts manufactured with additive manufacturing technologies.

A custom-made stereolithographic printer using a digital light processing optical (DLP) system based on a digital micromirror device (DMD) was characterized. Several sizes of slanted grooved micromixers (SGM) were produced and typical dimensions were measured and compared to nominal values. The results show that the developed SLA printer is precise enough to be used for prototyping of larger microfluidic devices. The lateral geometries of the smallest printed micromixer designs deviated less than 20 mu m from the nominal values and related feature depths deviated for less than 15 mu m. However, further modifications are needed in order to improve the repeatability, accuracy, and printing resolution.

3D-printing technology is opening up new possibilities for the co-printing of sensory elements. While quasi-static research has shown promise, the dynamic performance has yet to be researched. This study researched smart 3D structures with embedded and printed sensory elements. The embedded strain sensor was based on the conductive PLA (Polylactic Acid) material. The research was focused on dynamic measurements of the strain and considered the theoretical background of the piezoresistivity of conductive PLA materials, the temperature effects, the nonlinearities, the dynamic range, the electromagnetic sensitivity and the frequency range. A quasi-static calibration used in the dynamic measurements was proposed. It was shown that the temperature effects were negligible, the sensory element was linear as long as the structure had a linear response, the dynamic range started at ∼ 30 μ ϵ and broadband performance was in the range of few kHz (depending on the size of the printed sensor). The promising results support future applications of smart 3D-printed systems with embedded sensory elements being used for dynamic measurements in areas where currently piezo-crystal-based sensors are used.

This paper discusses interplay between the design of a Staggered Herringbone Micromixer (SHM) and micro Electrical Discharge Machining (EDM) milling technology. SHM consists of a main channel and many herringbone lookalike grooves at the bottom, which enhance mixing. Firstly, a brief overview on how the technological model of micro EDM milling was constructed is presented. Anticorrosive stainless steel was used as a workpiece material on the basis of which the database for the technological model was established. In the second part the technological model was used for micromixer design optimization. Different SHM designs that can be machined in the same amount of time, were compered via their mixing efficiency. Mixing efficiency was estimated by performing Computational Fluid Dynamics (CFD) simulations. The results show, that smaller and shallower grooves are not efficient in the terms of mixing. An important design parameter is also the orientation of the grooves. In the end, a favorable SHM design is presented.

Microproduction-based lab-on-a-chip technologies have recently been substantially advanced and have become widely used in various multidisciplinary research fields, including biological, (bio-) chemical, and biomedical fields. A key factor in microproduction is micro tooling. For mass production it is of paramount importance to produce tools from materials with excellent mechanical properties, thus the machining processes need to be able to produce geometrical features smaller than 1 mm in such materials. In this paper, an indirect process chain for production of micromixer and comprising of waterjet (WJ) and abrasive waterjet (AWJ) machining, die-sinking electrical discharge machining (EDM) and casting of polydimethylsiloxane (PDMS) is presented. The main source of dimension deviations is WJ machining. AWJ machining performs much better for the given application the precision is satisfactory, but the kerf width is too large.

Flow boiling of degassed double-distilled water in a single 50 × 50 μm and 100 × 50 μm microchannel was investigated on the basis of experimental measurements and high-speed visualization. The visualized events during boiling were analyzed in terms of the bubble frequencies and boiling front oscillations in microchannels. A digital image sequence analysis algorithm was composed to determine the time dependence of bubble and meniscus locations. The results show (i) the dynamic characteristics of boiling in microchannels, (ii) the increase of fundamental oscillation frequencies with increasing heat flux and temperature of the microchannel bottom, (iii) the amplitudes of the flow boiling oscillations are inversely proportional to the fundamental frequencies. The outcomes of the study are important as the oscillations during boiling in single microchannels are experimentally confirmed to be predictable in terms of oscillation frequencies and amplitudes trends and dependencies. This knowledge is especially significant at constructing efficient two-phase micro heat exchangers, micro mixers or micro reactors, as the cross section and the length of the channel become exceedingly important design parameters in micro devices with boiling.

Ice jet technology also known as ice abrasive water jet (IAWJ) is a prototype technology currently under development. In IAWJ technology ice particles made from water are used instead of mineral abrasive. The aim is to increase the productivity of pure water jet (WJ) while keeping its advantages, producing no other waste product but water. Technology has great potential to be used in food and medical industries as well as other areas where cleanliness of the process and no additional waste product is of high priority. In order to use ice as an abrasive it has to be used at extremely low temperatures where its mechanical properties such as hardness become usable for machining applications. The paper presents the latest findings and achievements of IAWJ technology as well as the approaches and methodology used during its development. Two approaches to obtain ice particles in the water are studied, namely generation of ice particles in the cutting head during the machining process and generation of ice particles outside of the cutting head which are added to the jet similarly as in injection AWJ technology. The main challenge is to provide very cold and thus hard ice particles in the cutting zone where they are used as an abrasive and maintaining the system stability. It is therefore essential to monitor and control the temperatures occurring in the system. The presence of ice particles inside the jet could not be directly identified due to instrument limitations. Positive effect of ice on cutting efficiency was observed but could not be sufficiently studied due to instabilities present in the current state of the prototype.

A general research direction of stereolithography based on digital light processing (DLP) is to reduce the production time and to increase manufacturing accuracy. Compared to fused deposition modelling (FDM) machines, machines for DLP stereolithography are expensive and thus not available to a broad range of users as it is the case with FDM 3D printers. Comparing technologies, DLP stereolithography offers quicker and more accurate production. In this paper, performances of a low cost DLP stereolithographic printer is presented. Three main challenges are treated: an uneven illumination of commercial DLP projectors, a direction of illumination and a selection of optimal 3D printing parameters. Uneven illumination of DLP projector results in smaller usable working area and poor printing quality. The problem is solved by implementing an appropriate software mask, thus the product quality is not influenced by its position on a working table. The direction of illumination has a key role in DLP stereolithography. It is shown that constrained surface (illumination through a transparent bottom of the vat) gives better 3D printing accuracy compared to free surface (illumination of the photopolymer surface) stereolithography. To further improve the product quality, the optimal process parameters are determined. Using the Taguchi based surface response methodology optimal process parameters are defined and by using them, the deviation of the actual dimensions from the specified dimensions is less than 80 mu m.

Abrasive water jet (AWJ) cutting is a versatile technology, but it is limited by relative poor accuracy. The main problem is the unknown diameter of the jet, as there is no device or instrument on the market that would enable a quick and easy measurement of it. With such an instrument the diameter could be regularly measured, nozzle wear monitored and noted offset adjusted. This would greatly improve the quality control of the process and the accuracy of the cut. This paper investigates the usage of a through-beam laser sensor for monitoring jet diameter and nozzle wear. Experiments were performed with five differently worn nozzles, with two different water pressures, with and without abrasive, at different standoff distances and with varying measuring times. Results show that the instrument is capable of monitoring the jet diameter and nozzle wear with an accuracy of +/- 0.03 mm, but it is very susceptible to the jet's spray and abrasive sticking to the sensor's screens. Jet diameter correlated better with the diameter of the focusing nozzle when taking measurements without the abrasive, at high water pressures and at a standoff distance of 1 mm.

Purpose: Abrasive water jet (AWJ) cutting uses mineral abrasive to cut practically all materials. In ice abrasive water jet (IAWJ) cutting, the ice particles are used as abrasive. IAWJ is under development with the aim to bridge the gap in productivity between the abrasive water jet (AWJ) and water jet (WJ) cutting. It is clean and environmentally friendlier in comparison with AWJ, while its cutting efficiency could be better than WJ. Design/methodology/approach: The main challenge is to provide very cold and thus hard ice particles in the cutting zone, thus cooling the water under high pressure is utilized. Further on, two approaches to obtain ice particles in the water are studied, namely generation of ice particles in the cutting head and generation of ice particles outside of the cutting head and adding them to the jet similar as in AWJ technology. In this process it is essential to monitor and control the temperature occurring in the system. Findings: To have ice particles with suitable mechanical properties in the cutting process, the water have to be precooled, ice particles generated outside the cutting head and later added to the jet. The results show that, contrary to the common believe, the water temperature is not significantly changed when passing through the water nozzle. Research limitations/implications: The presence of ice particles was only indirectly identified. In the future, a special high speed camera will be used to study the influence of process parameters on ice particle distribution. Practical implications: IAWJ technology produces much less sludge (waste abrasive and removed workpiece material mixed with water) than AWJ technology which is beneficial in e.g. disintegration of nuclear power plants. IAWJ technology has also great potential in the food and medical industries for applications, where bacteria growth is not desired. Originality/value: The paper presents the latest achievements of IAWJ technology.

Abrasive Waterjet technology is a machining process using high speed water with the addition of mineral abrasive grains to remove the workpiece material. Due to the intrinsic properties of the process, the interface zone where the material removal occurs is hidden in the workpiece. One of the possibilities to observe propagation of the cutting front is to visualise it by means of a thermal camera or in the case of transparent materials by an optical camera also. The resulting images can be analysed by using the methods of digital image processing to extract the parameters of the cutting front, which can be used to control the process.

Ice abrasive water jet (IAWJ) technology is a technology under development with the aim to breach the gap in productivity between the abrasive water jet (AWJ) and water jet (WJ) cutting by using ice particles instead of mineral abrasive. Such technology would be clean and environmentally friendlier in comparison with AWJ, while its cutting efficiency would be better than that of WJ. Due to heavy temperature dependence of the mechanical properties of ice used as an abrasive, it is essential that the temperatures occurring in the system are monitored and controlled. This paper presents the results from temperature measurements of water taken from different parts of the IAWJ prototype, both before and after the orifice, at different temperature and pressure conditions, using different orifice sizes.

During the last few years, different research groups have been developing systems for the transition of abrasive water jet into ice abrasive water jet. The aim of this new technology is to make the technology cleaner from both practical and ecological points of view. Mineral abrasive is replaced with ice grains that melt away after the machining process, leaving the workpiece uncontaminated. Several different approaches to this technology were studied. Thermal aspects of integrating the ice abrasive water jet technology into commercially available machines were considered. The results and analyses of water temperature measurements on the ice abrasive water jet machine are presented in this article.

Sustainability has become a major concern in many countries and is leading to strict regulations regarding the impact of products and services during their manufacturing, use, and disposal. Power consumption monitoring in manufacturing companies can lead to a reduction of machine tools energy wastes and consequently to lower expenses. To this end, a complete transparency of energy usage among the entire manufacturing facilities is required. Despite the small volume of material processed, micro manufacturing processes are energy intensive and the optimization of energy usage becomes critical for manufacturing sustainability. Electrical discharge machining (EDM) is considered an attractive solution for the manufacturing of microcomponents. In this paper, a low cost and modular data acquisition system, based on open-hardware and open-source software, for online energy consumption monitoring, is presented. The system described is applied for energy efficiency analysis of the micro EDM milling process by using a state of the art commercial machine tool. A number of sensors is connected to the data acquisition system to measure the energy consumption of the main sub-systems of the machine tool, data is recorded through a microcontroller, and sent to the main computer via Wi-Fi for data storage and analysis. Results show that the process efficiency depends on machine parameters but it is always far below 0.01 %. Solutions are suggested to improve the energy efficiency of the machine tool considered in this work.