Development of a Acrylonitrile Butadiene Styrene toner for an electrophotography based additive manufacturing process

Research in to utilising electrophotography for Additive Manufacturing has been under investigation for over a decade. However, the research has been primarily focused on resolving the height limitations caused by charge accumulation and also the development of toners from tough engineering polymers. The aim of this study is to develop a suitable negatively charging engineering polymer for the Selective Laser Printing process and a more efficient method of generating toners with a suitable particle range and to assess the mechanical properties of parts produced using the toner developed through this route. The study is comprised for two parts; Chemical and Mechanical toner production. The chemical production method utilises a process, Evaporative Limited Coalescence, to produce an engineering toner in the desired 20-50μm range. It was found that during the chemical production process the negatively charging polymer was converted to charge positive. Analytical assessment of the toner was carried out to explain the change in polarity. Mechanical milling trials were also conducted under both ambient and cryogenic conditions, as well as a novel method to reduce the feed-stock material to the desired particle size range. The results suggest a significant increase in efficiency compared to prior research. Printing trials were conducted using the mechanically milled toner to assess the mechanical properties for different heating, pressure and stand-off distance conditions. It was found that, due to insufficient heating and applied pressure the final samples suffered from high porosity and poor tensile strength

Rub, fold, and abrasion resistance testing of digitally printed documents

The life cycle of commercially printed digital documents (in particular, marketing and promotional items, direct mailers, business communications, and on-demand color books) was examined to find stress points where potential permanence problems could exist. The stress and life cycle overview covers the stages of processes in printing and finishing, mailing preparation and fulfillment, distribution, usage, and recycling. Stress points found in the different stages of the life cycle, whether physical or chemical, include (but are not limited to) scratching, rubbing, cracking, solvent exposure, light exposure, moisture exposure, heat exposure, and air contamination exposure. Tests for abrasion resistance, folding resistance, solvent resistance, light-fastness, water-fastness, thermostability, and gas/ozone fastness were researched. Based on a survey given to randomly selected printers, printing press vendors, and print buyers, the tests for abrasion resistance, folding resistance, and rub resistance were selected. Using offset lithography as a benchmark, three commercial digital presses as well as high-speed ink jet technology were included in this testing. Using a combination of solid circular test targets and the “Three Musicians” test target (an image for visual comparisons), the Taber Abraser testing method, the Sutherland Rub testing method, and a folding procedure outlined in ASTM document F 1351 were used to examine and to compare the five presses in this study (three commercial digital presses, one offset lithographic press, and one high-speed ink jet press). After testing was performed, visual ranking, changes in density, Delta E, and the abrasion resistance index were used as the criteria to evaluate results. Testing results showed that the high-speed ink jet held up the best in each test performed during this research; however, the image quality of the high-speed ink jet press was less than the image quality of any other press in this study. The second best performer in the testing was the offset lithographic press. The test performance of these particular presses, as compared with the commercial digital presses, was attributed to the different drying methods in each of the different printing technologies. In the ink jet and lithographic presses, the evaporation, absorption, and oxidation drying methods seemed to hold up better to the testing performed than the drying method of toner-based technology. With oxidation and evaporation, the image (i.e., the ink) actually becomes a part of the paper after drying, whereas, in toner technology, the image (i.e., the toner) is fused to the paper and actually sits on top of it. Within the digital printing industry, coatings have been put in place to alleviate some of these problems, but they have not been tested here. This research shows that offset lithography is the dominant technology in terms of offering abrasion and folding resistance of its printed product

The application of a thermoplastic recording material to holographic filtering

Imperial Users onl

Performance improvement of professional printing systems : from theory to practice

Performance Improvement of Professional Printing Systems: from theory to practice Markets demand continuously for higher quality, higher speed, and more energy-efficient professional printers. In this thesis, control strategies have been developed to improve the performance of both professional inkjet and laser printers. Drop-on-Demand (DoD) inkjet printing is considered as one of the most promising printing technologies. It offers several advantages including high speed, quiet operation, and compatibility with a variety of printing media. Nowadays, it has been used as low-cost and efficient manufacturing technology in a wide variety of markets. Although the performance requirements, which are imposed by the current applications, are tight, the future performance requirements are expected to be even more challenging. Several requirements are related to the jetted drop properties, namely, drop velocity, drop volume, drop velocity consistency, productivity, and reliability. Meeting the performance requirements is restricted by several operational issues that are associated with the design and operation of inkjet printheads. Major issues that are usually encountered are residual vibrations in and crosstalk among ink channels. This results in a poor printing quality for high-speed printing. Given any arbitrary bitmap, the main objective is to design actuation pulses such that variations in the velocity and volume of the jetted drops are minimized. Several model-based feedfoward control techniques using an existing model are implemented to generate appropriate input pulses for the printhead. Although the implementation of the model-based techniques shows a considerable improvement of the printhead performance compared with the current performance, further improvements are still necessary. We observe that besides the pulse shape the state of the ink surface at the nozzle plate (speed, position) at the start of the pulse influences the drop velocity considerably. This state at firing depends also on previous pixels in the bitmap of the image. Consequently, any pulse design has to guarantee almost the same initial state when firing a drop. Based on these facts, a model-free optimization scheme is developed to minimize the drop velocity variations taking into account the bitmap information. Experimental results show the effectiveness of the optimized pulses. Laser printing systems are highly depending on the appropriate combination of several design factors so as to become functional in a desired working range. The physical printing process involves multiple temperature set points at different places, precise electro-magnetic conditions, transfer of toner through certain pressures and layouts, and many other technical considerations. In the laser printing system there are several challenging issues and unknown disturbances. They originate from different sources, such as the printer itself (unknown phenomena appear, disturbances that are not foreseen, wear, contamination, failures, bugs), the environment of the system (power supply variations, temperature, humidity, vibrations), and the printing media (weight, coating, thermal properties, humidity characteristics, and initial temperature). These issues have a negative effect on the stability and performance of the laser printing system. The objective is to design a control scheme to achieve printing quality requirements and a high productivity. Good printing quality means that the fusing temperature should track a certain reference signal at different operating conditions. Based on the printing system behavior, we propose two different control schemes to cope with the large parameter variations and disturbances, namely, a Model Reference Adaptive Controller (MRAC) and a nonlinear (scheduled) observer-based output feedback control scheme. Both control techniques yield considerable performance improvements compared with the present industrial controller

Methodology for architecture development for product design

Thesis (S.M.)--Massachusetts Institute of Technology, System Design & Management Program, 2000.Includes bibliographical references (p. 101-104).An integrative methodology for architecture development in a product development environment is described. The methodology combines the use of the design structure matrix technique with constraint-based modeling to create a process that satisfies the following requirements: 1. Provide a means for modeling the system that provides the capability to gain feedback on proposed decisions. This promotes rapidly system learning. 2. Provide a definition of the linkage between product requirements and design parameters. 3. Provide documentation that makes the architecture explicit and enables others to have access to the architectural knowledge. 4. Increase confidence in the proposed system so that product design can proceed with a minimum of risk. The application of the methodology in the context of the development of the xerographic module architecture for color printing system is described. The project was a clean sheet design using a new color architecture and implementing seven new technologies. A significant result is that once the architecture was accepted and placed under change control, the architecture has not changed in four years. Traditionally, similar projects have had to make significant changes as the design matured. Based on the case study, there is anecdotal evidence to support the hypothesis that the methodology can be successfully used to develop complex systems. It is shown that the methodology is closely aligned to the product development process. During the pre-concept and concept phases, the models were used to develop the system architecture. During the detailed design phase, the models can be used to maintain the integrity of the architecture as the design and technologies mature. Finally, in order for the methodology to be successfully applied it must have the full support of program management and the design and technology organizations.by Michael J. Martin.S.M

Material Issues of the Metal Printing Process, MPP

The metal printing process, MPP; is a novel Rapid Manufacturing process under development at SINTEF and NTNU in Trondheim, Norway. The process, which aims at the manufacturing of end-use products for demanding applications in metallic and CerMet materials, consists of two separate parts; The layer fabrication, based on electrostatic attraction of powder materials, and the consolidation, consisting of the compression and sintering of each layer in a heated die. This approach leads to a number of issues regarding the interaction between the process solutions and the materials. This paper addresses some of the most critical material issues at the current development stage of MPP, and the present solutions to these.Mechanical Engineerin

Investigation of laser printing for 3D printing and additive manufacturing

Additive Manufacturing (AM), popularly called “3D printing,” has benefited from many two-dimensional (2D) printing technology developments, but has yet to fully exploit the potential of digital printing techniques. The very essence of AM is accurately forming individual layers and laminating them together. One of the best commercially proven methods for forming complex powder layers is laser printing, which has yet to be used to directly print three-dimensional (3D) objects above the microscale, despite significant endeavour. The core discovery of this PhD is that the electrostatic charge on toner particles, which enables the digital material patterning capabilities of 2D laser printing/photocopying, is disabling for building defect-free 3D objects after the manner attempted to date. Toner charge is not mostly neutralized with fusing as previously assumed. This work characterizes and substantiates the accumulation of residual toner charge as a primary cause for defects arising in 3D printed bodies. Next, various means are assessed to manage and neutralize residual toner charge. Finally, the complementary implementation of charge neutralization with electrostatic transfer methods is explored

Development of a novel toner for electrophotography based additive manufacturing process.

This thesis is intended to conduct feasibility study of producing 3D objects by printing thermoplastic elastomer using electrophotography technique and thereafter sintering the whole layer using infrared light source .The term Selective laser printing (SLP) has been coined by the author for this new process. This thesis provides the feasibility of developing experimental toner using thermoplastic toner using both mono and dual component print engines

Characterization of color, gloss and mechanical performance of 3D printed structures

The demand for customized products is on a rise. As such, there is a great need for methods to efficiently satisfy this need for customization. Rapid prototyping, also known as 3D printing, is a technology that enables economic production of customized low volume products and enables expedited product development cycles. Given the importance of color as a means to differentiate products generated through 3D printing processes, accurate color reproduction is essential for broad market acceptance. Color reproduction in 2D document printing is itself a complex science; achieving similar results in 3D printing will require significant research. This research work explores the various factors that affect accurate color reproduction in rapid prototyping. More specifically, it studies the effect of process parameters and post-processing techniques on the color reproduction achieved in powder based layer deposition process with a selective binder delivery enabled by an ink-jet print head. A systematic study of a subset of these factors was conducted using a ZCorp Z510 3D printer. The process parameters that were included in the study were color, hue, coverage, layer thickness, and binder saturation. The post-processing technique focused on the use of an infiltrant, which is commonly used to increase the mechanical strength of the printed 3D structure. The response variables of interest for this study included color response, gloss and mechanical strength. A full factorial experiment was designed in order to characterize the effect. Gloss, which contributes to the visual perception, was studied as a qualitative response. Of particular interest was the effect of process parameters and the type of post processing on the tensile strength of the specimen to identify trade-offs between quality of color reproduction and the mechanical strength required for structural integrity. Analysis of the experimental data indicates that the standard process settings, on average, generate samples that have greater color lightness and lower chroma, representing an opportunity for improvement. In addition, layer thickness was found to have a significant effect on the tensile strength as well. The process of infiltration improved both the color reproduction and mechanical properties of the 3D printed samples. The choice of infiltrant did not have a significant effect on the color reproduction but had a significant effect on the tensile strength of the part. In this research, the effect of layer thickness on color reproduction in ink jet based 3D printing has been studied for the first time. Also, adding to the body of current research, the interaction effects of the various factors have been studied. The research intends to serve as a platform to enable color scientists to collaborate with rapid prototyping experts towards achieving full selective color throughout 3D printing in the future