Search results

The purpose of this study is the 16-fold recycling process effect of VZH159 nickel alloy powder on its features and characteristics of the printed material obtained by selective laser melting (SLM). Chemical composition, content of gas impurities, powder grading, pore volume fraction and surface morphology of powder particles, structure and properties of SLM material, surface roughness and deviations from specified geometry of the test samples were investigated.

The experiment’s method procedure presumes the use of only recycled powder without adding any virgin powder at each build cycle. To avoid powder sloughing because of incomplete filling of the build space, a print area delimiter was used. For all manufactured samples, hot isostatic pressing was carried out in an ASEA Quintus-16 facility. Heat treatment was carried out in air furnaces. Structure investigations were carried out on a Leica DMIRM metallographic complex. Microstructure studies were carried out on a Verios 460 scanning electron microscope with X-ray microanalysis.

With the number of recycling stages, an increase in oxygen content is observed in the powder, which leads to an increment for oxides in the printed material. The 16-fold recycling does not have a significant effect on the features of the powder itself and the printed material if the build space is filled with manufacturing parts by no more than 20%.

The creep rupture strength of the SLM material, which appears to be a sensitive characteristic to the quality of the applied powder, does not change in the printed material after all stages of powder recycling as well.

The purpose of this paper is to investigate the polyamide 12 (PA12) powder properties deterioration in the laser sintering (LS) process and propose a methodology for more efficient powder recycling. The main goals are: to recommend a level of input PA2200 powder properties which could guarantee acceptable part quality in the LS process; and selection of the refresh rate in order to minimise the consumption of fresh material.

The paper analyses the LS processing conditions and current recycling practices in relation to the deterioration or ageing of the PA12‐based powders. Samples of new and recycled grades of PA2200 powder were artificially aged in a temperature‐controlled oven and then tested using melt flow rate (MFR) indexer. Also, un‐sintered powder samples collected from different locations within various builds, and different LS machines (EOSINT P700 and Sinterstation^® 2500 HiQ) were tested.

The powder exposed at higher temperature and longer time experiences a much higher deterioration rate. The temperature and the time at which the un‐sintered material was exposed are the most influential parameters for the powder aging. It was confirmed that the MFR index is a very sensitive indicator of the changes in the powder properties and provides a relatively fast and inexpensive method of measuring the rate of the powder degradation because of the LS process. The powder located in the periphery and the top of a build has a higher MFR and therefore is less deteriorated. In contrast, powder located in the centre, or in the bottom of a long build has much lower MFR and therefore is less usable.

Based on the findings, a methodology for powder recycling is proposed. It allows a better control of the input material properties, a consistent quality of the fabricated parts, and more efficient use of the LS material.

The paper provides some useful information for the properties deterioration of PA12‐based powders (PA2200) in relation to the temperature and time at which the material is exposed in the LS.

The purpose of this article is to determine if the level of recyclability of atomized Ti-6Al-4V powder, used as raw material in electron beam melting (EBM), is in compliance with aeronautical standards.

The adopted strategy for this study was to manufacture a series of builds in the EBM system recycling the same powder from build to build. Optimized EBM process parameters were used, as well as the common procedure of powder recycling for each build, to emulate real production conditions. The aim of the study is to confirm that the powder properties are kept within the range of chemical contents which complies with the aeronautical standards despite numerous reuses.

The conclusion of this study is that the EBM-processed Ti-6Al-4V powder properties are conserved in consecutive builds with recycled powder. This study shows that significant raw material can be saved by powder recycling since the powder quality is kept in range throughout consecutive builds, despite the working conditions of EBM.

The main two advantages of application of EBM in the aerospace sector are design freedom and reduction of buy-to-fly ratio. The design freedom enables the creation of lightweight structures, which can significantly reduce the fuel consumption, while the reduction of buy-to-fly ratio enables much material saving in manufacturing of aircraft parts.

The present study represents the first complete study on atomized Ti-6Al-4V powder processed in EBM which was made for the sake of aeronautical sector.

Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing the fabrication of gears without the aid of support structures and subsequent assembly. However, there are constraints in the process that negatively affect its adoption compared to other additive technologies such as material extrusion to produce gears. This study aims to demonstrate that it is possible to overcome the problems due to the physics of the process to produce accurate mechanism.

Technological aspects such as orientation, wheel-shaft thicknesses and degree of powder recycling were examined. Furthermore, the evolving tooth profile was considered as a design parameter to provide a manufacturability map of gear-based mechanisms.

Results show that there are some differences in the functioning of the gear depending on the type of powder used, 100% virgin or 50% virgin and 50% recycled for five cycles. The application of a groove on a gear produced with 100% virgin powder allows the mechanism to be easily unlocked regardless of the orientation and wheel-shaft thicknesses. The application of a specific evolutionary profile independent of the diameter of the reference circle on vertically oriented gears guarantees rotation continuity while preserving the functionality of the assembled mechanism.

In the literature, there are various studies on material aging and reuse in the PBF-LB/P process, mainly focused on the powder deterioration mechanism, powder fluidity, microstructure and mechanical properties of the parts and process parameters. This study, instead, was focused on the functioning of gears, which represent one of the applications in which this technology can have great success, by analyzing the two main effects that can compromise it: recycled powder and vertical orientation during construction.

This study aims to report the preparation, selective laser sintering (SLS) processing and properties of a new nylon elastomer powder. The effects of solvent, dissolution temperature and time and cooling method and speed on the particle size and morphologies of the prepared nylon elastomer powder are investigated.

The prepared nylon elastomer power possesses the particle size of around 50 mm and is spherical in shape, indicating that this study provides the feasible dissolution-precipitation process, a distillation cooling method and a suitable solvent to prepare nylon elastomer powders.

Compared to pure nylon 12, the nylon elastomer has a lower part bed temperature and a wider sintering window for the SLS process. The wider sintering window indicates the better SLS processibility. The lower part bed temperature is beneficial to the recycling of material and the decrease in the requirement of SLS equipment.

The nylon elastomer in this study has a lower part bed temperature and a wider sintering window for the SLS process. The wider sintering window indicates better SLS processibility. The lower part bed temperature is beneficial to the recycling of material and the decrease in the requirement of SLS equipment.

This study aims to demonstrate for the first time that the cheap, commodity polymer, poly(propylene), can be successfully processed using high speed sintering, and that it can be recycled several times through the process, with little to no detriment to either the polymer itself or the parts obtained. This is significant as a step towards the realisation of high speed sintering as a technology for high-volume manufacturing.

A poly(propylene) powder designed for laser sintering was used to build parts on a high speed sintering machine. The unsintered powder was then collected and reused. Repeating this process allowed creation of seven generations of aged powder. A variety of characterisation techniques were then used to measure polymer, powder and part properties for each generation to discern any effects arising from ageing in the machine.

It was found that poly(propylene) could be used successfully in high speed sintering, albeit with a low build success rate. Increased powder age was found to correlate to an increase in the build success rate, changes in microscopic and bulk powder properties and improvement to the dimensional accuracy of the parts obtained. By contrast, no discernible correlations were seen between powder age and polymer molecular weight, or between powder age and the tensile properties of parts.

This is the first report of the use of poly(propylene) in high speed sintering. It is also first study regarding powder recyclability in high speed sintering, both in general and using poly(propylene) specifically.

Owing to the operating principle of powder bed fusion processes, selective laser sintering (SLS) requires effective management of the mixture ratio of processed material previously exposed to the high temperatures of processing with new virgin material. Therefore, this paper aims to fully understand the effect that the successive reprocessing has in the powder material and to evaluate its influence on the properties of SLS parts produced at different building orientations.

Polyamide 12 material with 0%, 30% and 50% of virgin powder and parts produced from them were studied through five consecutive building cycles and their mass, mechanical, thermal and microstructural properties were evaluated. Then, the experimental data was used to validate a theoretical algorithm of prediction capable to define the minimum amount of virgin powder to be added on the processed material to produce parts without significant loss of properties.

Material degradation during SLS influences the mass and mechanical properties of the parts, exhibiting an exponential decay property loss until 50% of the initial values. The theoretical algorithms of reprocessing proved the appropriateness to use a mixture of 30% of virgin with 70% of processed material for the most common purposes.

This paper validates a methodology to define the minimum amount of virgin material capable to fulfil the operational specifications of SLS parts as a function of the number of building cycles, depending on the requirements of the final application.

The use of theoretical models of prediction allows to describe the degradation effects of SLS materials during the sintering, ensuring the sustainable management of the processed powder and the economic viability of the process.

This purpose of this paper is to provide an overview of the steps and processes behind successfully adapting novel materials, namely virgin glass and recycled glass, to three‐dimensional printing (3DP).

The transition from 3DP ceramic systems to glass systems will be examined in detail, including the necessary modifications to binder systems and printing parameters. The authors present preliminary engineering data on shrinkage, porosity, and density as functions of peak firing temperature, and provide a brief introduction to the complexities faced in realizing an adequate and repeatable firing method for 3D printed glass.

Shrinkage behavior for the 3D printed recycled glass showed significant anisotropy, especially beyond peak firing temperatures of 730°C. The average shrinkage ratios for the slow‐ and fast‐axes to the Z‐axis were 1:1.37 and 1:2.74, respectively. These extreme differences can be attributed to the layer‐by‐layer production method and binder burn‐off. At 760°C, the apparent porosity reached a minimum of 0.36 percent, indicative of asymptotic behavior that approaches a fully dense 3DP glass specimen. At low firing temperatures, the bulk density was similar to water, but increased to a maximum of 2.41 g/cm³. This indicates that 3DP recycled glass can behave similarly to common glass with accepted published bulk densities ranging from 2.4‐2.8 g/cm³.

Heating schedule analysis and optimization may reduce geometric variations, therefore, the firing method should be investigated in greater depth.

This paper provides a guide to successfully adopting glass to commercially available 3DP hardware. This research has also enabled rapid prototyping of recycled glass, a monumental step towards a sustainable future for 3DP.

The purpose of this paper is to give an insight into relevant aspects of 3D printing of clay paste enhanced with scrap polymer powder which have not been investigated by previous studies. Specifically, the geometrical features of the deposited lines, dimensional accuracy of benchmarks and mechanical properties of printed parts are investigated.

Firstly, the 3D printer is used to deposit lines of the paste under various combinations of material composition and process parameters. 3D scanning is used to measure their dimensional and geometrical errors. The results are elaborated through statistics to highlight the role of material and processing conditions. Then, four benchmark parts are printed using materials with different percentages of polymer powder. The parts are scanned after each step of the post-processing to quantify the effects of printing, drying and melting on dimensional accuracy. Finally, drop weight tests are carried out to investigate the impact resistance of specimens with different powder contents.

It is found that the quality of deposition varies with the printing speed, nozzle acceleration and material composition. Also, significant differences are observed at the ends of the lines. Materials with 10 Wt.% and 40 Wt.% of powder exhibit relevant shape variations due to the separation of phases. Accuracy analyses show significant deformations of parts at the green state due to material weight. This effect is more pronounced for higher powder contents. On the other hand, the polymer reduces shrinkage during drying. Furthermore, the impact test results showed that the polymer caused a large increase in impact resistance as compared to pure clay. Nonetheless, a decrease is observed for 40 Wt.% due to the higher amount of porosities.

The results of this study advance the knowledge on the 3D printing of clay paste reinforced with a scrap polymer powder. This offers a new opportunity to reuse leftover powders from powder bed fusion processes. The findings presented here are expected to foster the adoption of this technique reducing the amount of waste powder disposed of by additive manufacturing companies.

This study offers some important insights into the relations between process conditions and the geometry of the deposited lines. This is of practical relevance to toolpath planning. The dimensional analyses allow for understanding the role of each post-processing step on the dimensional error. Also, the comparison with previous findings highlights the role of part dimensions. The present research explores, for the first time, the impact resistance of parts produced by this technology. The observed enhancement of this property with respect to pure clay may open new opportunities for the application of this manufacturing process.

This paper aims to present parametric models to estimate the environmental footprint of the selective laser sintering (SLS)’ production phase, covering energy and resource consumption as well as process emissions. Additive manufacturing processes such as (SLS) are often considered to be more sustainable then conventional manufacturing methods. However, quantitative analyses of the environmental impact of these processes are still limited and mainly focus on energy consumption.

The required Life Cycle Inventory data are collected using the CO2PE! – Methodology, including time, power, consumables and emission studies. Multiple linear regression analyses have been applied to investigate the interrelationships between product design features on the one hand and production time (energy and resource consumption) on the other hand.

The proposed parametric process models provide accurate estimations of the environmental footprint of SLS processes based on two design features, build height and volume, and help to identify and quantify measures for significant impact reduction of both involved products and the supporting machine tools.

The gained environmental insight can be used as input for ecodesign activities, as well as environmental comparison of alternative manufacturing process plans.

This article aims to overcome the current lack of environmental impact models, covering energy and resource consumption as well as process emissions for SLS processes.