Spreading and absorption of small liquid drops on porous substrates is of interest in a number of fields ranging from additive manufacturing and composite processing to inkjet printing. In inkjet ...printing, spreading and absorption processes determine the final area of a printed dot, which is decisive for print quality in terms of coverage and resolution. However, it is not fully understood how substrate and liquid properties influence the involved physical processes and the resultant printed dot area. In this work, the printed dot area of overall 140 paper-liquid pairings representative for the operational window of an inkjet printer is evaluated. The results are explained by a simple model including spreading, absorption, and evaporation. The surface tension and viscosity of the liquids, as well as the pore size and polarity of the substrates were varied systematically to represent the range of uncoated paper-liquid pairings applicable for inkjet printing. Results show that the printed dot area mainly depends on the wettability of the liquid-substrate pairing followed by penetration speed. Evaporation and volume reduction due to roughness filling had little impact. The modeling results are in line with empirical observations showing that the dot area is closely related to the contact angle.
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•Evaluation of inkjet printed dots of 140 uncoated paper-liquid pairings.•Substrates and liquids were tailored to cover operation window of an inkjet printer.•Inkjet printed dot area is simulated from spreading, absorption and evaporation.•The printed dot area depends predominantly on the wetting interaction.
Maximizing the functionality of cationic polydiallyldimethylammonium chloride (poly-DADMAC) additive with minimal dosage in inkjet coatings can contribute to both an improvement in quality and a cost ...reduction. To do this, it is essential to understand how the cationic additive is distributed in the coating layer and how it affects the print quality. This study presents a three-step investigation to enhance the understanding of the distribution of poly-DADMAC, as well as its effect on inkjet print quality. First, the adsorption behavior of poly-DADMAC on silica pigments was investigated by measuring the surface charge of silica and the adsorption of the cationic additive. Second, the influence of poly-DADMAC on the printability of binder films was investigated. Finally, the effect of poly-DADMAC on the print quality of inkjet paper was examined. The addition of poly-DADMAC improved the print quality of the inkjet paper because of the improved holdout of the negatively charged colorants in the ink.
Embedded bioprinting overcomes the barriers associated with the conventional extrusion‐based bioprinting process as it enables the direct deposition of bioinks in 3D inside a support bath by ...providing in situ self‐support for deposited bioinks during bioprinting to prevent their collapse and deformation. Embedded bioprinting improves the shape quality of bioprinted constructs made up of soft materials and low‐viscosity bioinks, leading to a promising strategy for better anatomical mimicry of tissues or organs. Herein, the interplay mechanism among the printing process parameters toward improved shape quality is critically reviewed. The impact of material properties of the support bath and bioink, printing conditions, cross–linking mechanisms, and post‐printing treatment methods, on the printing fidelity, stability, and resolution of the structures is meticulously dissected and thoroughly discussed. Further, the potential scope and applications of this technology in the fields of bioprinting and regenerative medicine are presented. Finally, outstanding challenges and opportunities of embedded bioprinting as well as its promise for fabricating functional solid organs in the future are discussed.
Embedded bioprinting improves the shape quality of bioprinted constructs made up of soft materials and low‐viscosity bioinks. Herein, the interplay mechanism among the printing process parameters toward improved shape quality is critically reviewed. Outstanding applications, challenges, and opportunities of embedded bioprinting as well as its promise for fabricating functional solid organs in the future are also discussed.
Fused deposition modelling (FDM) 3D printing, as a supporting technology in social manufacturing and cloud manufacturing, is a rapidly growing technology in the era of industry 4.0. It produces ...objects with a layer-by-layer material accumulation technique. However, qualitative uncertainties are the common challenges yet. In order to assure print quality, studying the error causing parameters and minimizing their effects are important. This paper presents a feedback-based error compensation strategy, which integrates a fuzzy inference system and a grey wolf optimization algorithm. The objectives are twofold. First, the possible errors in FDM 3D printing are discussed in detail and optimal error causing parameters are obtained in percentage. This is used to understand the effects of the printing errors in every phase of the 3D printing process. From the nine optimization configuration trials used, Config-6 that has 100 number of iterations and 60 wolves is selected due to its higher convergence speed and best fitness value. The integral absolute error (IAE) is used as an objective function and the global minimum is achieved in the iteration interval
86
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100
. The outputs of this optimization problem are used to achieve the next objective. Second, a closed-loop quality monitoring approach comprising of inner-loops and an outer-loop is taken. The three inner-loops are used to monitor the errors during pre-printing, printing, and post-printing, respectively. The outer-loop, on the other hand, is responsible for monitoring the aggregated errors in all the three 3D printing phases. The error compensation system simulation in Matlab is run for 10 s, and the results show that the “normal” range deformation factors are reached within less than 2 s for the inner-loops, whereas the outer-loop deformation factor is achieved within 2 s. The responses are within the acceptable time range.
The nomenclature of parts used in the production of car wiring systems for BMW, MERCEDES, SKODA and other cars at the Ukrainian-German joint venture Kromberg & Schubert has up to 10,000 names. They ...are structurally diverse, ranging from simple parts such as rods and levers to body parts with internal holes, voluminous pockets and so on. Until recently, these parts were made from different compositions of metal. In use, they lost their effectiveness over time - wear of the working surfaces or destruction. Before the pandemic, used parts were replaced by ordering them from other companies. This practice proved to be inefficient: high costs of developing prototypes, transportation and testing under production conditions. One of the most promising directions in the development of modern engineering is the development of new technologies for rapid manufacturing. The essence of such technologies is the layer-by-layer construction of products from polymer materials on the basis of CAD models - models whose three-dimensional geometry is described in digital form using solid modelling programmes (SolidWorks, CATIA, ProE, AutoCAD, etc.). Trial batches of brackets produced at the company using such technologies showed the promise of adaptive technologies.
Aperiodic, clustered-dot, halftone patterns have recently become popular for commercial printing of continuous-tone images with laser, electrophotographic presses, because of their inherent stability ...and resistance to moiré artifacts. Halftone screens designed using the multistage, multipass, clustered direct binary search (MS-MP-CLU-DBS) algorithm can yield halftone patterns with very high visual quality. But the characteristics of these halftone patterns depend on three input parameters for which there are no known formulas to choose their values to yield halftone patterns of a certain quality level and scale. Using machine learning methods, two predictors are developed that take as input these three parameters. One predicts the quality level of the halftone pattern. The other one predicts the scale of the halftone pattern. To provide ground truth information for training these predictors, human subjects viewed a large number of halftone patches generated from MS-MP-CLU-DBS-designed screens and assigned each patch to one of four quality levels. For each patch, the location of the peak in the radially averaged power spectrum (RAPS) is calculated as a measure of the scale or effective line frequency of the pattern. Experimental results demonstrate the accuracy of the two predictors and the effectiveness of screen design procedures based on these predictors to generate both monochrome and color high quality halftone images.
3D printing technologies of construction materials are gaining ground in the building industry. As well documented in the literature, these advanced manufacturing methodologies aim to reduce ...work-related injuries and materials waste, enhancing architectural flexibility which would enable more sophisticated designs for engineering and aesthetic purposes. In this framework, the development of functional and eco-sustainable printable materials represents an extremely attractive challenge for research, promoting digital fabrication to reach its maximum cost-effective and technological potentials. The use of recycled tire rubber particles in 3D printable Portland-based compounds is an exclusive contribution in this field. This line of research aims to integrate the well-known engineering performances of rubber-cement materials with the advanced peculiarities of additive manufacturing methodologies. As an innovative contribution, the authors propose here a detailed study on the possible relationship between rubber particle size and technological properties of the 3D printable mix. Specifically, two groups of continuous size grading polymer aggregates (0-1 mm rubber powder and 1-3 mm rubber granules as fine and coarse fractions, respectively) were analyzed in terms of impact on rheology, print quality, microstructure, mechanical properties, and acoustic insulation performance. Concerning the print quality, rubber aggregates altered the fluidity of the fresh mix, improving the adhesion between the printed layers and therefore enhancing the mechanical isotropy in the post-hardening sample. A remarkable influence of the rubber gradation on the compounds’ behaviour was found in hardened properties. By comparing the rubberized compounds, the fine polymer fraction shows greater interfacial cohesion with the cement paste. However, more significant mechanical strength loss was found due to a greater reduction in density and increased porosity degree. On the other hand, mortars doped with larger rubber particles tend to have a higher unit weight, finest pore distribution, minor mechanical strength drop, and higher ductility but worse interface binding with the matrix. Regarding the acoustic insulation properties, a proper balance between rubber powder and granules in the mixes allows to obtain comparable/superior performance compared to plain mortar but the effect of the aggregate size is strongly dependent on the sound frequency range investigated. Future findings revolve around applicability studies of these formulations in civil and architectural fields, benefiting from the design flexibility of 3D printing. Doi: 10.28991/cej-2021-03091701 Full Text: PDF
Purpose
The wide application of metal material extrusion (MEX) has been hampered by the practicalities associated with the resulting shrinkage of the final parts when commercial three-dimensional ...(3D) printing equipment is used. The shrinkage behaviour of MEX metal parts is a very important aspect of the MEX metal production process, as the parts must be accurately oversized to compensate for shrinkage. This paper aims to investigate the influence of primary 3D printing parameters, namely, print speed, layer height and print angle, on the shrinkage behaviour of MEX Steel 316L parts.
Design/methodology/approach
Two groups of dog-bone and rectangular-shape specimens were produced with the BASF Ultrafuse Steel 316L metal filament. The length, width and thickness of the specimens were measured pre- and post-debinding and sintering to calculate the percentile shrinkage rates. Analysis of variance (ANOVA) was used to evaluate and rank the significance of each manufacturing parameter on shrinkage. Typical main print quality issues experienced in this analysis are also reported.
Findings
The shrinkage rates of the tested specimens ranged from 15.5 to 20.4% along the length and width axis and 18.5% to 23.1% along the thickness axis of the specimens. Layer height and raster angle were the most statistically significant parameters influencing shrinkage, while print speed had very little influence. Three types of defects were observed, including surface roughness, surface deformation (warping and distortion) and balling defects.
Originality/value
This paper bridges an existing gap in MEX Steel 316L literature, with a focus on the relationship between MEX manufacturing parameters and subsequent shrinkage behaviour. This study provides an in-depth analysis of the relationship between manufacturing parameters – layer height, raster angle and print speed and subsequent shrinkage behaviour, thereby providing further information on the relationship between the former and the latter.
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