Characterization of silver nanoparticle inks toward stable roll-to-roll gravure printing

The rheological properties of silver inks are analyzed, and the printing results are presented based on the inks and roll-to-roll printing speed. The shear viscosity, shear modulus, and extensional viscosity of the inks are measured using rotational and extensional rheometers. The inks exhibit the shear thinning power law fluids because the concentration of dispersed nanoparticles in the solvent is sufficiently low, which minimizes elasticity. After the inks are printed on a flexible substrate through gravure printing, the optical images, surface profiles, and electric resistances of the printed pattern are obtained. The width and height of the printed pattern change depending on the ink viscosity, whereas the printing speed does not significantly affect the widening. The drag-out tail is reduced at high ink viscosities and fast printing speeds, thereby improving the printed pattern quality in the roll-to-roll process. Based on the results obtained, we suggest ink and printing conditions that result in high printing quality for complicated printings, such as overlay printing registration accuracy, which imposes pattern widening and drag-out tails in printed patterns.

Recycling Polymer Blend made from Post-used Styrofoam and Polypropylene for Fuse Deposition Modelling

Fuse deposition modelling (FDM) has become a revolutionary manufacturing technology as it offers numerous advantages, including freedom of fabrication, mass customisation, fast prototyping, and cost-effectiveness. Thermoplastic material is commonly used as feedstock for FDM process. The current state of material development, the recycled plastic material also can be used as printing material for FDM machine. Expanded polystyrene (EPS) has been extensively used as packaging materials for many industries but rarely be recycled, as its relatively large volume with minimal weight is unconducive for transportation. This research aimed to utilize EPS waste and turn it into FDM feedstock. This research also aims to enhance the properties of recycled polystyrene (rPS) made from EPS waste by blending it with polypropylene (PP). Different ratios of rPS/PP blends were prepared and extruded into FDM filament using filament extruder. The formulated filaments were printed into specimen using FDM machine. This research found the filament made from rPS/PP blends can be printed into specimen with good printing quality if the nozzle temperature controlled at 240° C with 120 % extrusion rate. With this printing parameter, the specimen printed with rPS/PP blend filament exhibit the greatest adhesion between the deposited layers without any visible voids or gaps. Besides, the printed specimen with rPS/PP blends possess lower tensile strength, but higher tensile modulus as compared to the printed specimen with neat rPS. The addition of more PP decreased both tensile strength and modulus of rPS/PP blends. On the other hand, the rPS/PP blends have higher thermal stability as the PP content increased. Overall, the rPS/PP blends filament shows a great potential as a feedstock material for FDM fabrication.

A Multi(two)-Nozzle Cable-Driven Parallel Robot For 3D Printing Building Construction: Path Optimization and Vibration Analysis

This paper proposes a multi-nozzle cable-driven parallel robot for 3D printing building construction. This system has two independently moving nozzles mounted on the existing printing head. The printing time can be reduced dramatically with this system as the travel path of the printing head can be reduced to almost half thanks to those two nozzles that print almost half of the printing contour. To fully take advantage of two nozzle structures effectively, the path of the printing head is optimized to secure the minimum travel length of both the printing head and two nozzles. The smoothness of the optimal path is secured by applying the non-uniform rational B-splines (NURBS). In addition, free vibration of the proposed CDPR printer’s structure is analyzed to improve the printing quality and help the control of the proposed CDPR plain by using a finite element formulation of cables of the proposed robot.

Pad-Printing as a Fabrication Process for Flexible and Compact Multilayer Circuits

The purpose of this paper is to present a newly developed process for the fabrication of multilayer circuits based on the pad-printing technique. Even though the maturity level, in terms of accuracy, substrate type and print size of several printing industrial processes is relatively high, the fabrication complexity of multilayer printed electronics remains relatively high. Due to its versatility, the pad-printing technique allows the superposition of printed conductive and insulating layers. Compared to other printing processes, its main advantage is the ability to print on various substrates even on flexible, curved or irregular surfaces. Silver-based inks were used for the formulation of conductive layers while UV inks were employed to fulfil the functionality of the insulating layers. To demonstrate the functionality of the pad-printing results, a multilayer test pattern has been designed and printed on Kapton®. Furthermore, to demonstrate the efficacy of this approach, a multilayer circuit composed of three stacked layers has been designed and printed on various substrates including Kapton®, paper and wood. This electronic circuit controls an array of LEDs through the manipulation of a two-key capacitive touch sensor. This study, allowed us to define recommendations for the different parameters leading to high printing quality. We expect a long-term beneficial impact of this study towards a low-cost, fast, and environmental-friendly production of printed electronics.

Research on the printing error of tilted vertical beams in delta-robot 3D printers

Purpose A three-dimensional (3D) printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. The purpose of this study is to analyze the influence of such errors on printing accuracy and printing quality for delta-robot 3D printer. Design/methodology/approach First, the kinematic model of a delta-robot 3D printer with an ideal geometric structure is proposed by using vector analysis. Then, the normal kinematic model of a nonideal delta-robot 3D robot with tilted vertical beams is derived based on the above ideal kinematic model. Finally, a 3D printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. Findings The results show that tilted vertical beams can indeed cause 3D printing errors and further influence the 3D printing quality of the final products and that the 3D printing errors of tilted vertical beams are related to the rotation angles of the tilted vertical beams. The larger the rotation angles of the tilted vertical beams are, the greater the geometric deformations of the printed structures. Originality/value Three vertical beams and six horizontal beams constitute the supporting parts of the frame of a delta-robot 3D printer. In this paper, the orientations of tilted vertical beams are shown to have a significant influence on 3D printing accuracy. However, the effect of tilted vertical beams on 3D printing accuracy is difficult to capture by instruments. To reveal the 3D printing error mechanisms under the condition of tilted vertical beams, the error generation mechanism and the quantitative influence of tilted vertical beams on 3D printing accuracy are studied by simulating the parallel motion mechanism of a delta-robot 3D printer with tilted vertical beams.

On the in situ elimination of pores during laser powder bed fusion of a titanium alloy

The printing quality of the laser powder bed fusion (LPBF) components largely depends on the presence of various defects such as massive porosity. Thus, the efficient elimination of pores is an important factor to the production of a sound LPBF product. In this work, the efficacy of two in situ laser remelting approaches on the elimination of pores during LPBF of a titanium alloy Ti-6.5Al-3.5Mo-l.5Zr-0.3Si (TC11) were assessed using both experimental and computational methods. These two remelting methods are the surface remelting, and the layer-by-layer printing and remelting. A multi-track and multi-layer phenomenological model was established to compute the evolution of pores with the temperature and velocity fields. The results showed that surface remelting with a high laser power such as 180 W laser can effectively eliminate pores within three deposited layers. However, such a remelting cannot reach defects in deeper regions. Alternatively, the layer-by-layer remelting with a laser power of 180 W can effectively eliminate the pores formed in the previous layer in real time. The results obtained from this work can provide useful guidance for the in situ control of printing defects supported by the real time monitoring, feedback and operation systems of the intelligent LPBF equipment.