General-purpose Computer-aided Design Research Articles

3D-printed custom tray for maxillofacial implant assisted partial denture.

This technique presents a new fabrication workflow for a three-dimensional (3D) printed custom tray, which duplicates the morphology of the treatment denture for maxillofacial prostheses using an intraoral scanner, computer-aideddesign (CAD) software, and a 3D printer. A 70-year-old man underwent reconstruction of segmental mandibulectomy for mandibular osteoblastoma, followed by implant placement and secondary surgery. During the surgical treatment, a treatment denture was fabricated to restore oral function and determine the morphology of the definitive denture. To create the definitive denture with the same morphology as the treatment denture a custom tray was fabricated with the denture morphology after chairside adjustments. The oral cavity was scanned using an intraoral scanner, and the data acquired were imported into general-purpose CAD software, adjusted, and imported into a 3D printer to produce the custom tray. This was fitted into the patient's mouth without any issues, and closed tray impressions were made with impression caps for the locator attachments on the implant body. The morphology of the treatment denture was replicated in the definitive denture by making a silicon impression of the cameo surface at the fabrication of the cast after impression making. In this technique, the morphology of the treatment denture was transferred accurately to the definitive implant partial denture by leveraging existing digital technology. This method represents a practical approach for partial denture fabrication, including maxillofacial defects with complex denture configurations.

CNC Machining of Reverse Engineered Pseudo-symmetric Sculptured Surface Models

Replicating the complex sculptured surfaces with fair degree of precision cannot be accomplished without the use of reverse engineering technologies. The modern Computer Aided Design (CAD) systems offer variety of tools to manipulate 3D data of the reverse engineered parts/surface features so that these can be manufactured using multi-axis machining systems. Objectives: In the present work an attempt has been made to use the 3D scanning, CAD and Computer Numeric Control (CNC) technologies together for the machining of pseudo-symmetrical sculptured models. The 3D scanned models have been first converted to a triangulated/ STereoLithography (STL) data model of suitable accuracy. Methods/Statistical Analysis: The developed STL models are further manipulated in the Pro-E CAD environment for making machinable STL model suitable for a custom developed CNC tool path planning software code. The CNC tool path code takes the modified STL model as input to generate the roughing and finishing tool path data required for actual machining. The validity of the developed CNC tool path data files is verified using a 3D graphical CNC simulator before machining. Findings: The design details of the complex sculptured parts can be captured from initial handmade / crafted models using 3D scanning technologies. The scanned data can be used to generate the 3D CAD model of the scanned part using the general purpose CAD modelling software. Finally the sculptured artistic models are machined on a 3-axis CNC milling lathe. The machined sculptured surface models closely matched the design intend of the scanned parts, which proves the validity of the procedure followed for the machining of complex pseudo-symmetric surface models. Application/Improvements: To machine the complex sculptured surfaces. Five axis CNC milling can be use to machine the Bezier and Non-Uniform Rational B-Spline (NURBS) surfaces instead of STL. *

Generating cutter paths for marine propellers without interference and gouging

We generate cutter paths free of interference and gouging for manufacturing model propellers using a five-axis numerical control (NC) machine. Our approach is faster than using a general-purpose computer-aided design (CAD)/computer-aided manufacturing (CAM) system. A roughing cut is made using only three axes for efficiency, and the finishing cut is made using all five axes to avoid collisions. Elements of the cutter path that might produce gouging are eliminated and the pose of the cutter is adjusted to eliminate interference. A number of models, including surface-piercing propellers, have been manufactured.

Introducing real world design problems into the undergraduate electromagnetic curriculum

General-purpose CAD (computer-aided design) programs have been used to teach electromagnetics to undergraduates at Carnegie Mellon University. The focus of the instruction is the use of real-world design problems to teach basic electromagnetics concepts. Students use computers to set up and solve a variety of electrostatics, magnetostatics, eddy current, and microwave problems. This gives them the opportunity to visualize EM fields and to interact with real-world devices and issues. Experience shows that solving such problems by means of electromagnetic CAD tools boosts student motivation and leads to a better grasp of key technical concepts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the use of a general-purpose CAD program for molecular graphics

It is suggested that general-purpose computer-aided design software can be of good use in producing high-quality molecular graphics. Such software is often widely available. Besides being an alternative to existing programs, hard copy creation is facilitated by this approach.

A unified framework for computer-aided noise analysis of linear and nonlinear microwave circuits

A unified theoretical concept for noise analysis in analog and microwave circuits is introduced. Based on the adjoint system approach an analysis technique for general-purpose CAD (computer-aided design) applications is presented. The algorithm is easy to implement into existing CAD tools, and exploits the advantages of sparse matrix techniques. As an example, in a linear SPICE-analysis of an amplifier, only an additional forward and backward substitution for each port, two 2*2 matrix multiplications for each transistor, and the outer product of two two-dimensional vectors for a resistor are needed. >

A fast, general three-dimensional device simulator and its application in a submicron EPROM design study

The implementation, functionality, and use of MAGENTA, a three-dimensional semiconductor device simulator. Version 1.0 of the program solves the nonlinear Poisson equation. The program possesses the attributes of numerical efficiency, structural generality, and ease of use required to be an effective general-purpose CAD (computer-aided design) tool. The utility of MAGENTA is demonstrated in a study of EPROM (erasable programmable read-only memory) design issues. Strong three-dimensional effects which impact threshold voltage, programming characteristics, and cell capacitances are characterized. Implications of these effects for submicrometer EPROM design are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

State of the art and present trends in nonlinear microwave CAD techniques

The authors present a survey of modern nonlinear CAD (computer-aided design) techniques as applied to the specific field of microwave circuits. A number of fundamental aspects of the nonlinear CAD problem, including simulation, optimization, intermodulation, frequency conversion, stability, and noise, are addressed and developed. For each one it is shown that either well-established CAD solutions are available, or at least a solution approach suitable for implementation in a general-purpose CAD environment can be outlined. Also, the discussion shows that the various subjects are not just separate items, but rather can be chained in a strictly logical sequence. Finally, an elementary treatment of vector processing is given, to show that supercomputers can handle the involved large-size numerical problems efficiently. >

Computer-Aided Design of Industrial Electrical Distribution Networks

The paper presents general-purpose computer-aided design system for the determination of the optimal design of the industrial, electrical distribution system. A cost-effective structure for such a network io often a multilovol, hierarchical structure with one or more voltage levels and several kinds of equipment. It consists of main supply point, transformer substations and/or switchboards together with supplying lines (which all together form a “backbone network“) and cable feeders connecting demand points to backbone network (local networks). A distribution planning model is formulated using graph theory and discrete programming. Decisions can be taken on two levels - the first concerns backbone network, the second specifies assignments of demand points to particular elements of the backbone. The model is rather general - backbone can be any of loopless structure. The problem structure typically leads to heuristic solutions of an iterative nature. A kind of such method is implemented in a general-purpose software package letting on automatic design of industrial electrical distribution systems.

Efficient method for computing noise in a general purpose CAD program in APL

An efficient technique is implemented in a general-purpose CAD (computer-aided design) program to compute noise in electric circuits. In this method, a preordered, sparsely stored circuit matrix is transposed in an easy but subtle manner. As a consequence, one frequency-domain (AC) analysis is needed to compute noise at an output regardless of the number of noise sources. Unlike other programs that compute noise, the Interactive Circuit Design Program used allows arbitrary type of noise expressions that could be functions of an arbitrary set of parameters, voltages, currents, and frequency, and therefore the most common noise sources are covered. Examples are given.