Sharif Digital Repository

Purpose - Dimensional accuracy analysis of wax model created by room temperature vulcanization (RTV) silicone rubber molding to be used in investment casting is presented. The purpose of this paper is to discuss the effective parameters of dimensional accuracy in RTV tooling technique. Design/methodology/approach - After producing a pattern by stereolithography (SLA) and then creating the RTV silicone rubber mold by the SLA pattern, dimensional accuracy of wax models produced by RTV tool are analyzed. Design of experiments (DOE) using the Taguchi approach is used for analysis and determination of optimum condition. Findings - Experiments show that the dimensional accuracy in RTV technique is... 

A rapid wax injection tool of a gearbox shift fork was designed, simulated, and manufactured using rapid prototyping and rapid tooling technology to save time and cost of producing wax models used for the investment casting process. CAE simulation softwares, in particular, MoldFlow, are used to get wax injection moulding parameters such as filling parameters, temperature profiles, freeze time, speed, and pressure. The results of this research were compared with conventional wax model production methods. The criteria of such comparison were based upon parameters such as time, cost, and other related characteristics, which resulted in saving of 50% in time and 60% in cost. In this research,... 

In the present work, the densification and microstructure of M2 high speed steel powder processed by direct laser sintering method was studied. Test specimens were produced using a 200 W continuous wave CO2 laser beam at different scan rates ranging from 50 to 175 mm s-1. The building process was performed under argon and nitrogen atmospheres in order to evaluate the role of sintering atmosphere. It was found that the sintered density strongly depends on the laser scan rate and thus on the duration time of the laser beam on the surface of the powder particles. Generally, with a decrease in the scan rate higher densification was obtained. However, formation of large cracks and delamination of... 

In this paper, a feedforward proportional-integral-derivative (PID) controller is developed to effectively control the clad height in laser solid freeform fabrication (LSFF). The scanning velocity is selected as the input control variable and the clad height is chosen as the output. A novel knowledge-based Hammerstein model, including a linear dynamic and a nonlinear memoryless block, is developed, and its parameters are identified offline using experimental data. The architecture of the controller consists of a PID and a feedforward module, which is the inverse of the identified model. The advantage of adding a feedforward path to the PID controller is evaluated experimentally, in which the... 

This paper presents a prototype of a high-throughput 4x4 64-QAM MIMO receiver consisting of a channel matrix QR decomposition, a soft-output K-Best MIMO detector and a Convolutional Turbo Code decoder. The proposed MIMO receiver provides low processing latency and a pipelined architecture scalable to a larger number of antennas and constellation order. Therefore, it is suitable for LTE-Advanced and IEEE 802.16m broadband wireless standards. A rapid prototyping platform interfacing MATLAB with Xilinx ISE was used in the development of the 4x4 64-QAM MIMO receiver. The receiver utilizes 96% of the slice LUTs and 78% of slice registers on Virtex-5 FX130T FPGA, operating at a maximum frequency... 

Purpose: An important challenge of the osteotomy procedures, particularly in the case of large and complex corrections, is the fixation of the osteotomy site. The purpose of this study is to propose a practical and cost-effect methodology for the plate adapting problem of osteotomy surgery. Design/methodology/approach: A novel patient-specific plate contouring methodology, based on rapid prototyping (RP) and multi-point forming (MPF) techniques, was developed and evaluated. In this methodology, a female mold is fabricated by RP, based on the geometry of the osteotomy site and estimation of the plate spring back. The mold is then used to configure a MPF die, which is then used for press... 

All Rapid Prototyping and CNC material removal processes use information which is extracted from a CAD system. There are several ways to convert CAD data into usable manufacturing information. In this paper, five methods of translating CAD data into a usable manufacturing format are explained. These five methods are data translation from CAD files in STL, DXF, STEP-NC, and IGES formats as well as a platform-dependent area method of manufacturing information in a desirable format. For each method, algorithms and details about the CAD data translation into usable manufacturing and prototyping processes formats are presented. Finally, applications of each approach and its pros and cons are... 

Purpose - The purpose of this paper is to present an improved methodology for design of custom-made hip prostheses, through integration of advanced image processing, computer aided design (CAD) and additive manufacturing (AM) technologies. Design/methodology/approach - The proposed methodology for design of custom-made hip prostheses is based on an independent design criterion for each of the intra-medullary and extra-medullary portions of the prosthesis. The intra-medullar part of the prosthesis is designed using a more accurate and detailed description of the 3D geometry of the femoral intra-medullary cavity, including the septum calcar ridge, so that an improved fill and fit performance... 

A choreography specifies activities and interactions among a set of services from a global point of view. From this specification, local implementations or peers can be automatically generated. Generation of peers that precisely implement the choreography specification is not always possible: this problem is known as realizability. This paper presents an encoding of the Chor choreography calculus into the FSP process algebra. This encoding allows to: (i) validate and verify Chor specifications using the FSP toolbox (LTSA), (ii) generate peer protocols from its choreography specified in Chor, (iii) test for realizability of the Chor specification, and (iv) generate Java code from FSP for...