Paul G. Sanders

A Low-Cost Open-Source Metal 3-D Printer

Technical progress in the open-source self replicating rapid prototyper (RepRap) community has enabled a distributed form of additive manufacturing to expand rapidly using polymer-based materials. However, the lack of an open-source metal alternative and the high capital costs and slow throughput of proprietary commercialized metal 3-D printers has severely restricted their deployment. The applications of commercialized metal 3-D printers are limited to only rapid prototyping and expensive finished products. This severely restricts the access of the technology for small and medium enterprises, the developing world and for use in laboratories. This paper reports on the development of a open-source metal 3-D printer. The metal 3-D printer is controlled with an open-source micro-controller and is a combination of a low-cost commercial gas-metal arc welder and a derivative of the Rostock, a deltabot RepRap. The bill of materials, electrical and mechanical design schematics, and basic construction and operating procedures are provided. A preliminary technical analysis of the properties of the 3-D printer and the resultant steel products are performed. The results of printing customized functional metal parts are discussed and conclusions are drawn about the potential for the technology and the future work necessary for the mass distribution of this technology.

Low-Cost Open-Source Voltage and Current Monitor for Gas Metal Arc Weld 3D Printing

Arduino open-source microcontrollers are well known in sensor applications for scientific equipment and for controlling RepRap 3D printers. Recently low-cost open-source gas metal arc weld (GMAW) RepRap 3D printers have been developed. The entry-level welders used have minimal controls and therefore lack any real-time measurement of welder voltage or current. The preliminary work on process optimization of GMAW 3D printers requires a low-cost sensor and data logger system to measure welder current and voltage. This paper reports on the development of a low-cost open-source power measurement sensor system based on Arduino architecture. The sensor system was designed, built, and tested with two entry-level MIG welders. The full bill of materials and open source designs are provided. Voltage and current were measured while making stepwise adjustments to the manual voltage setting on the welder. Three conditions were tested while welding with steel and aluminum wire on steel substrates to assess the role of electrode material, shield gas, and welding velocity. The results showed that the open source sensor circuit performed as designed and could be constructed for <

Cascade Bayesian Optimization

100 in components representing a significant potential value through lateral scaling and replication in the 3D printing community.

The Influence of Low Temperature Clustering on Strengthening Precipitation in Al-Mg-Si Alloys

Multi-stage cascade processes are fairly common, especially in manufacturing industry. Precursors or raw materials are transformed at each stage before being used as the input to the next stage. Setting the right control parameters at each stage is important to achieve high quality products at low cost. Finding the right parameters via trial and error approach can be time consuming. Bayesian optimization is an efficient way to optimize costly black-box function. We extend the standard Bayesian optimization approach to the cascade process through formulating a series of optimization problems that are solved sequentially from the final stage to the first stage. Epistemic uncertainties are effectively utilized in the formulation. Further, cost of the parameters are also included to find cost-efficient solutions. Experiments performed on a simulated testbed of Al-Sc heat treatment through a three-stage process showed considerable efficiency gain over a naive optimization approach.

Hypoeutectic Aluminum–Silicon Alloy Development for GMAW-Based 3-D Printing Using Wedge Castings

Heat-treatable 6000 series aluminum alloys are the most commonly extruded materials in the world. The precipitation process in these alloys is both complex and well characterized. The earliest clustering stage has been shown to have a large effect on subsequent strengthening precipitation, however little is known about the influence of clustering as a function of composition and processing parameters. The current work examines this influence considering the factors of relative and absolute magnesium and silicon content, and the extent of natural aging. Billets were cast and extruded prior to heat-treatment, and the hardening response was evaluated with hardness, conductivity, and transmission electron microscopy (TEM). This work advances the current understanding of Al-Mg-Si precipitation by correlating the kinetics of age hardening to composition and processing, and may lead to further optimization of 6000 series alloy strength and toughness.

Automotive Wrought Aluminium Alloys

Alloy development can simplify low-cost gas metal arc weld (GMAW)-based 3-D printing by making it easier to print quality parts with minimal metallurgical or welding experience. Previous work found good properties in aluminum alloys, particularly in the aluminum–silicon 4943 (Al–5.5%Si–0.4%Mg) and 4047 (Al–11.6%Si) alloys. These alloys were easy to print, but could benefit from alloying to increase ductility and to minimize or redistribute porosity. The purpose of this study was to modify 4943 and 4047 alloys and rapidly screen their performance for use as feedstock for improved 3-D printability. The 4047- and 4943-based alloys were modified with additions of magnesium, strontium, titanium boride, and combinations thereof. Wedge-shaped castings were used to efficiently screen alloying additions over the same ranges of solidification rates as those observed in GMAW-based 3-D printing. The alloying additions were most effective at modifying the high-silicon 4047 alloy, whereas no change in microstructure was observed in the low-silicon 4943 alloy. Strontium was an effective modifier of the high-silicon alloy. Titanium boride was not observed to have a grain-refining effect on aluminum dendrites on its own, although the combination of strontium and titanium boride produced the most refined eutectic structure in the high-silicon alloy. Future work should evaluate the singular effects of strontium, titanium boride, and the combination of strontium and titanium boride additions in weld-based 3-D printing.

Processing and Pore Growth Mechanisms in Aluminum Gasarites Produced by Thermal Decomposition

Abstract In recent years, automotive lightweighting efforts have led to increased use of wrought aluminium alloys for structural and body components. This chapter begins by outlining the incentives for automotive lightweighting and explains why aluminium alloys are currently positioned as the most attractive material choice for a variety of applications. General processing methods and metallurgical considerations are covered next, which pertain to all of the alloys that are subsequently discussed. The chapter focusses on the metallurgy, properties, and application/manufacturing of heat-treatable (6xxx, 2xxx, and 7xxx series) and nonheat-treatable (5xxx series) alloys in automotive design. Due to their overwhelming prevalence, 6xxx and 5xxx series alloys are discussed in detail. In each case, current material and manufacturing limitations are outlined, as well as potential routes to improve properties and applicability in the future.

Austempered ductile iron performance at rail wheel operating conditions

Gasarites are a subclass of metallic foams that have a cylindrical pore morphology created by directional solidification of metals saturated with a gas. Thermal decomposition is an alternative process in which the soluble gas is delivered by decomposition of a particulate gas source. Aluminum gasarites formed through decomposition of titanium and zirconium hydrides were studied to both replicate the results of a previous study and discern pore-formation mechanisms. Replication of the previous study was not achieved, and additional processing enhancements were required to produce gasarite pore morphologies. For the first time, zirconium hydride was utilized to produce gasarites, with porosity levels and pore sizes lower than that from titanium hydride. Maximum average porosity levels of 10 and 6 pct were observed for titanium hydride and zirconium hydride, respectively. Pore-formation mechanisms in aluminum gasarite foams created via thermal decomposition of titanium and zirconium hydrides were evaluated through metallographic analysis and scanning electron microscopy. Definitive evidence of gas–metal eutectic pore growth was not found, but pore morphological characteristics and chemical analysis of particulate at pore surfaces support direct gas evolution from the hydride particles as a contributor to pore formation and growth.

Optimizing limited solar roof access by exergy analysis of solar thermal, photovoltaic, and hybrid photovoltaic thermal systems

As transportation costs rise, rail stock material improvements are critical to improving efficiency, durability, and performance. Steel wheels have been a consistent part of rail equipment, but it may be time to assess potential other alloys and materials in anticipation of future demands. Strength requirements are steadily increasing with rail car capacity, while weight savings in equipment can reduce fuel costs and/or increase carrying capacity. Herein, the current requirements for railroad wheels are discussed and compared with experimental evaluation of a potential alternative material, austempered ductile iron (ADI).ADI is an attractive wheel material because of its higher strength-to-weight ratio (as compared to steel) and its wear resistance. ADI castings are also typically cheaper to produce than steel. While ADI can meet or exceed the strength of steel components, it is also comparable in ductility and impact strength, so conversion to ADI does not bring additional risk of brittle fracture, as is commonly the case when achieving higher strengths.There are challenges with its implementation, however. AAR certification of new materials is costly and time consuming, so adoption is unlikely until there is a very compelling business case. Heat produced during on-tread braking has the potential to damage the heat-treated structure of ADI. The regular exchange of cars across different sections of track and therefore different managing companies requires that new wheel materials be fully backwards compatible, so alterations in design are severely limited. This paper will take initial steps toward assessing the potential of ADI railroad wheels by investigating the performance of ADI at elevated temperatures, and comparing the results to measured and simulated wheel temperatures.Copyright