Enhancing Droplet Quality of Edible Ink in Single and Multi-Drop Methods by Optimization the Waveform Design of DoD Inkjet Printer

The multi-drop method with a good droplet quality is a big challenge in inkjet technology. In this study, optimization of Drop on Demand (DoD) inkjet printer waveform design was conducted. The effectiveness of the waveform design, so-called W waveform, from previous study as a preliminary vibration for the multi-drop ejection method was investigated. The unmodified W waveform was proven not to be an effective waveform for lower viscosity of liquid, especially when compared by the standard waveform obtained from a print-head manufacturer. Edible ink with a viscosity below the optimum range for print-head specifications was employed as the operating liquid. The preliminary vibration W waveform was modified to improve the droplet quality of the edible ink. It was proven that a 40% adjusted voltage of the rear wave of the W waveform was effective as the optimum waveform design for edible ink. The droplet quality of the multi-drop ejection method for grey-scale technology was improved by optimizing the W waveform design.

Feasibility of Acoustic Print Head Monitoring for Binder Jetting Processes with Artificial Neural Networks

The clogging of piezoelectric nozzles is a typical problem in various additive binder jetting processes, such as the manufacturing of casting molds. This work aims at print head monitoring in these binder jetting processes. The structure-born noise of piezoelectric print modules is analyzed with an Artificial Neural Network to classify whether the nozzles are functional or clogged. The acoustic data are studied in the frequency domain and utilized as input for an Artificial Neural Network. We found that it is possible to successfully classify individual nozzles well enough to implement a print head monitoring, which automatically determines whether the print head needs maintenance.

Multi-material integrated 3D printing of cylindrical Li-ion battery

A simple, low cost and highly efficient method of fabrication has always been the goal of manufacturing technology. In order to improve the speed of fabrication and simplify the preparation steps, this work proposes a multi-material integrated 3D printing method, aiming to obtain the desired structure from the print head in one step. As a typical example, a cylindrical Li-ion battery (LIB) with core-shell structure was integrally fabricated using this method. A multi-material print head is designed based on the structure to be printed. Special inks with the characteristics of non-Newtonian fluid for the LIB were developed. Anode, cathode, separator layer, and packaging layer were easily printed simultaneously, and the printing parameters were studied. Electrochemical performance of the printed battery was tested with the charge and discharge capacities of the printed battery up to 147 and 99 mAh g−1 at 0.1 C rate, respectively. The proposed multi-material integrated printing method greatly reduces the printing process and improves the fabrication efficiency. This system can be directly extended to fabricate other integrated devices such as supercapacitors. Based on this idea, it should also be possible to design different print heads to print other periodic structure in one step.

Establishment of a Rotary Print Head to Effect Residual Stresses and Interlayer Bonding in an FLM-Process

In fused layer modeling (FLM) manufacturing technology, there is an increased demand for semi-crystalline materials due to their favorable mechanical properties, such as high strength and toughness. The reasons for their limited use are process-related residual stresses and reduced interlayer bonding, resulting in component distortion, warping and poor strength. Addressing these problems, this paper presents the development and implementation of a rotary print head that enables local laser pre-deposition heating and forced air cooling in the 2.5-dimensional FLM process. Samples of polypropylene are fabricated to investigate the effects of the modified process on residual stresses and interlayer bonding. The investigations show that local laser pre-deposition heating can positively influence the interlayer bonding. In combination with a reduction of the extrusion temperature and additional cooling, it is possible to considerably reduce the residual stresses. The results of this research show that pre-deposition heating and forced air cooling significantly improve the processability of semi-crystalline thermoplastics in the FLM process.

Designing an Interchangeable Multi-Material Nozzle System for 3D Bioprinting Process

Three-dimensional bioprinting is a rapidly growing field attempting to recreate functional tissues for medical and pharmaceutical purposes. Development of functional tissue requires deposition of multiple biomaterials encapsulating multiple cell types i.e. bio-ink necessitating switching ability between bio-inks. Existing systems use more than one print head to achieve this complex interchangeable deposition, which decreases efficiency, structural integrity, and accuracy. In this research, we developed a nozzle system capable of switching between multiple bio-inks with continuous deposition ensuring the minimum transition distance so that precise deposition transitioning can be achieved. Finally, the effect of rheological properties of different bio-material compositions on the transition distance is investigated by fabricating the sample scaffolds.

Experimental studies for the additive manufacturing of continuous fiber reinforced composites using UV-curing thermosets

The economical production of lightweight structures with tailor-made properties and load-adapted geometry is limited using conventional technologies. Additive manufacturing processes offer a high potential to meet these requirements, where the established solutions are based primarily on thermoplastics matrix systems. From a process-technological point of view, thermoplastics enable simplified processing, but only a limited range of applications for high-performance components. These limitations are due to their comparatively low heat resistance, low melting temperatures and limited adhesion to embedded reinforcing fibers. In contrast, thermosets show high potential for realization of high- performance lightweight structures with adaptable properties. The present work employs a UV-curing thermoset resin for the impregnation of a continuous filament strand for 3D printing. The main challenge is to reconcile the crosslinking reaction of the thermoset and the process velocity during impregnation and cure. The liquid polymer must provide low initial viscosity to impregnate the filaments and a sufficiently high cure rate and dimensional stability after discharge from the print head to ensure sufficient bonding strength to the substrate. To demonstrate feasibility, a prototypic print head with UV-LED activation was designed and implemented. With a robot-guided printing platform, the 3D-deposition of continuous fiber-reinforcements without additional supporting structures can be realized. To derive initial process parameters, reaction and thermos-mechanical properties are determined by rheometer measurements. Impregnation and cure behavior of the glass fiber reinforced resin is investigated. The presented results provide a reliable process window and a straightforward process monitoring method for further enhancement of the conceived 3D printing process.

Research on Intelligent Control System of Thermal Print Head Based on FPGA

Thermal print head heating realtime temperature fluctuations are too large, often causing damage to the print head heating point, resulting in poor print quality and unsatisfactory print results. Therefore, in order to improve the stability of the thermal print head during printing, and at the same time solve the inefficiency of the traditional single chip microcomputer control of the thermal print head heating method, a field programmable gate array (FPGA) based thermal print head heating control method is proposed. In order to control the core, the intelligent fuzzy PID control algorithm is used to ensure that the temperature of the print head can be stabilized quickly. Through simulation and experimental verification, it is shown that the intelligent fuzzy PID control algorithm greatly improves the temperature stabilization effect, and the time required to reach stability short, not only improve the printing accuracy, but also extend the life of the print head.