Prospect of Making Ceramic Shell Mold by Ceramic Laser Fusion

Manufacturing prototypical castings by conventional investment casting not only takes several weeks, but also is prohibitively expensive. Z Corporation in USA, EOS GmbH and IPT in Germany employ the techniques of 3DP and SLS respectively to make directly ceramic shell molds for metal castings. Although those techniques dramatically reduce time expenditure and production cost, each layer cannot be thinner than 50 µm because of using powder to pave layers. The dimensional accuracy and roughness of the castings still cannot meet the specification of precision casting. Therefore, in this paper the ceramic laser fusion (CLF) was used to pave layers. Each layer can be thinner than 25 µm, so that the step effect can be diminished and the workpiece surface can be smoother; drying time will be shortened dramatically. Moreover, the inherent solid-state support formed by green portion has the capability of preventing upward and downward deformation of the scanned cross sections. In order to make shell mold which meets the roughness requirement (Rq=3.048µm) of the precision casting, following issues have to be further studied: (1) design a proper ceramic shell mold structure, (2) design a paving chamber for paving a complete green layer which can be easily collapsed, (3) cut down drying time, (4) optimize laser scanning process parameters with the smallest distortion, (5) eliminate sunken area, (6) reduce layer thickness to less than13µm, (7) control power to guarantee the energy uniformly absorbed by workpiece, and (8) develop a method which can directly clean green portion in cavity from gate.Mechanical Engineerin

Active Auxetic Heel Support for Achilles Tendon Therapy

The Achilles tendon, which stretches from the calf to the ankle, can be injured due to repeated daily activities or overstretching. In severe cases a tear in the tendon can prevent athletes from performing in games as well as individuals from completing their daily tasks. Achilles tendon injuries affect millions of people. The severe pain that occurs upon injury can take months to improve and for the Achilles tendon to heal. Our goal is to design an auxetic support to provide comfort, help heal the tendon, and allow the individual to continue to be active through the natural healing process. The auxetic will help protect from further injury when the individual is active because when force is applied longitudinally it results in expansion laterally leading to a shortening of the tendon, which promotes healing. This support is fabricated using elastomer molds that incorporate auxetic patterning, which was determined through testing, to make the device active while the individual is moving while wearing the support. The pieces are individually made, then pieced together to form the heel portion of the support, which is the crucial component for Achilles tendon healing. With compression testing we discovered that the Young’s modulus of our auxetic structure is similar to that of the calcaneus tissue so it will be comfortable for the user. With shock absorption testing we were able to compare the energy absorption off our auxetic structure compared to bulk elastomers and foams. Overall, we believe the optimal auxetic heel support is comfortable and shock absorptive and heel supports should be made so they are capable of facilitating healing and protect from further injury of the Achilles tendon when an individual is active

Modification of bauxite residue with oxalic acid for improved performance in intumescent coatings

Valorization of bauxite residue (BR) enhances the dynamics of its application in intumescent coating for fire retarding systems. This BR, an alumina production waste could contain up to 45% ferrous oxide along with residual aluminous minerals. In an attempt to optimize the fire retardant properties of these minerals in intumescent systems, BR was treated in oxalic acid, varying the heating temperature between 50 °C and 100 °C at a constant pH of 2.65. X-ray florescence spectrometry revealed up to 80% reduction in iron content and total dissolution of desilication products (DSPs). The process temperature was found to affect the efficiency with which iron oxide was removed and with which the dissolved DSPs were precipitated as aluminum hydrates. X-ray diffraction revealed increased crystallinity and a gibbsite-dominated compound. Incorporation of the modified bauxite residues into a control intumescing formulation resulted in improved endothermic cooling, increased char expansion and char reinforcement. An inverse relationship appeared to exist between aluminum hydrates and iron as removal of iron led to enhanced intumescence and increased char expansion while higher iron content led to a compact, less expanded char. A balance of the fire retarding minerals occurred at a leaching temperature of 75 °C in oxalic acid. Best heat shielding performance thus occurred at XBR75-IC5 as char expansion increased by 12% and the substrate temperature reduced by 31% over the control IC system. Thus, BR may act as alternative fire retardant filler for intumescing systems

Kaedah pembelajaran lukisan kejuruteraan berasaskan simulasi

Kajian yang dijalankan ini adalah untuk melihat kebolehgunaan sebuah perisian pendidikan yang menerapkan Kaedah Pembelajaran Lukisan Kejuruteraan Berasaskan Simulasi bagi menyelesaikan masalah kurang faham , kurang minat dan kebergantungan yang terlalu memusat kepada guru di kalangan pelajar Tingkatan 4, Sekolah Menengah Ungku Aziz, Sabak Bernam, Selangor . Justeru, penyampaian isi kandungan yang bersesuaian dengan tahap pemikiran atau kognitif pelajar, aspek minat dan motivasi serta pembelajaran ala akses kendiri dirasakan sebagai faktor utama yang ingin dikenal pasti dalam perisian yang dibangunkan bagi menyelesaikan masalah tersebut. Macromedia Authorware versi 6.5 dipilih sebagai bahasa pengarangan bagi membangunkan perisian pendidikan ini. Seramai 30 responden dipilih untuk mendapatkan maklum balas terhadap kajian ini. Data yang didapati telah dianalisis menggunakan perisian Statistical Package for Social Science (SPSS) versi 11.0 menggunakan kaedah deskriptif min. Hasil kajian mendapati bahawa maklum balas adalah positif terhadap faktor-faktor yang telah dikaji

Solid Modeling and Stereolithography as a Solid Freeform Fabrication Technique at Texas Instruments Incorporated

Over the past 25 years, the CAE/CAD/CAM industry has developed technological advances that have provided industrial users the ability to increase productivity and decrease the cycle time necessary for product development. These technologies include basic wireframe and surface design, specializedapplication software packages, finite element analysis, numerical control, solid modeling, and rapid prototyping. Each of these technologies plays a significant role in industry today. The Defense Systems & Electronics Group of Texas Instruments currently uses these technologies in the mechanical design engineering process. This paper discusses the two specific technologies of solid modeling and rapid prototyping (specifically stereolithography), including their advantages, benefits, and practical applications within the Texas Instruments Defense Systems & Electronics Group. This paper also discusses the use of stereolithography (SLA) rapid~prototype parts within the solid-mold investment~casting process.Mechanical Engineerin

How Insurers Benefit from the Housing Rehabilitation Efforts of NeighborWorks Organizations

Insurance companies have a vested interest in communities and homes that are safe and secure. Through their successful but underutilized housing rehabilitation expertise, NeighborWorks organizations seek to improve the quality of older, unsafe and/or vacant and abandoned properties in the communities they serve

Green Housing = Improved Health: A Winning Combination

The case studies in this paper explore the relationship between housing and health. It explains how building affordable green housing provides health benefits to low-income residentsand it identifies the benefits of green housing for the environment and energy efficiency

Multiscale, thermomechanical topology optimization of self-supporting cellular structures for porous injection molds

Purpose This paper aims to establish a multiscale topology optimization method for the optimal design of non-periodic, self-supporting cellular structures subjected to thermo-mechanical loads. The result is a hierarchically complex design that is thermally efficient, mechanically stable and suitable for additive manufacturing (AM). Design/methodology/approach The proposed method seeks to maximize thermo-mechanical performance at the macroscale in a conceptual design while obtaining maximum shear modulus for each unit cell at the mesoscale. Then, the macroscale performance is re-estimated, and the mesoscale design is updated until the macroscale performance is satisfied. Findings A two-dimensional Messerschmitt Bolkow Bolhm (MBB) beam withstanding thermo-mechanical load is presented to illustrate the proposed design method. Furthermore, the method is implemented to optimize a three-dimensional injection mold, which is successfully prototyped using 420 stainless steel infiltrated with bronze. Originality/value By developing a computationally efficient and manufacturing friendly inverse homogenization approach, the novel multiscale design could generate porous molds which can save up to 30 per cent material compared to their solid counterpart without decreasing thermo-mechanical performance. Practical implications This study is a useful tool for the designer in molding industries to reduce the cost of the injection mold and take full advantage of AM

The Materials Advantage of the SLS Selective Laser Sintering Process

The rapid prototyping market continues to progress in tenns of processes and materials used for the creation of conceptual and functional parts and prototype tooling. As this market continues to mature, the market leaders win be able to offer rapid prototyping processes and materials that provide parts which are accurate, have good surface finish, and provide properties which support fqnctional applications.. The materials used for these parts will be. polymers, metals, and ceramics. '. The strength oithe SLSTM Selective Laser Sintering Process is the. potential to use a wide variety of powdered materials for the creation of models, patterns, and some fonns of prototype tooling. ,This paper will cover the types of materials currently used in the SLS process and their inherent advantages.and discuss current research into the development of new materials.Mechanical Engineerin

Study of Ceramic Slurries for Investment Casting with Ice Patterns

Ice patterns generated by rapid freeze prototyping or a molding process can be used to make ceramic investment molds for metal castings. Due to the use of ice, the ceramic slurries must be poured around the pattern and cured at sub-freezing temperatures. Success of this process depends greatly on the mold strength after the gelation of the slurries. This paper describes the experimental results of the mold strength after the gelation of the slurries under different compositions. The parameters considered include mixing time, alumino-silicate vs. fused silica ratio, volume of binder, and volume of catalyst. The strength of the gelled slurries is examined by breaking test bars on a four-point bending apparatus. Weibull modulus for each trial is calculated based on the breaking strength from four-point bend tests. Analysis of variance for breaking strength and Weibull analysis is performed to evaluate the significance of the effect of each parameter. The casting of a bolt is used to demonstrate that metal castings of complex geometry can be fabricated using investment casting with ice patterns.Mechanical Engineerin