Computer-aided Manufacturing Applications Research Articles

Patient Satisfaction with Implant-Supported Monolithic and Partially Veneered Zirconia Restorations.

The digital workflow and the application of Computer-Aided Manufacturing (CAM) to prosthodontics present the clinician with the possibility of adopting new materials that confer several advantages. Especially in the case of zirconia, these innovations have profoundly changed daily practice. This paper compares the satisfaction and perception of patients who received implant-supported single crowns (SC) and fixed partial dentures (FPD) made from zirconia, either monolithic or partially veneered, after 3 years of follow-up; the success and survival rate of these restorations were also measured. Forty patients, who had been previously treated with implant-supported SC or FPD, either monolithic or partially veneered, and submitted to a yearly maintenance program, were recalled 3 years after their treatment and requested to complete an 8-question questionnaire regarding their perceptions of the treatment. Any mechanical or biological complication that had occurred from the time of delivery was also recorded. Patients that experienced ≥1 complication were less likely to be prone to repeat the treatment. The 3-year success rate was 92.6% for monolithic restoration and 92.3% for partially veneered restoration, while the survival rate was 100% for both restorations. The 3-year follow-up found that monolithic and partially veneered zirconia restorations are both well-accepted treatment options, and patients preferred the veneered restorations (0.76, p < 0.05) from an aesthetic point of view. According to our results, monolithic and veneered zirconia restorations are both reliable treatment options and are both equally accepted by patients.

A Graphics Processor Unit-Accelerated Freeform Surface Offsetting Method for High-Resolution Subtractive Three-Dimensional Printing (Machining)

Machining is one of the major manufacturing methods having very wide applications in industries. Unlike layer-by-layer additive three-dimensional (3D) printing technology, the lack of an easy and intuitive programmability in conventional toolpath planning approach in machining leads to significantly higher manufacturing cost for direct computer numerical control (CNC)-based prototyping (i.e., subtractive 3D printing). In standard computer-aided manufacturing (CAM) packages, general use of B-rep (boundary representation) and non-uniform rational basis spline (NURBS)-based representations of the computer-aided design (CAD) interfaces make core computations of tool trajectories generation process, such as surface offsetting, difficult. In this work, the problem of efficient generation of freeform surface offsets is addressed with a novel volumetric (voxel) representation. It presents an image filter-based offsetting algorithm, which leverages the parallel computing engines on modern graphics processor unit (GPU). The compact voxel data representation and the proposed computational acceleration on GPU together are capable to process voxel offsetting at four-fold higher resolution in interactive CAM application. Additionally, in order to further accelerate the offset computation, the problem of offsetting with a large distance is decomposed into successive offsetting using smaller distances. The performance trade-offs between accuracy and computation time of the offset algorithms are thoroughly analyzed. The developed GPU implementation of the offsetting algorithm is found to be robust in computation, and demonstrates a 50-fold speedup on single graphics card (NVIDIA GTX780Ti) relative to prior best-performing algorithms developed for multicores central processing units (CPU). The proposed offsetting approach has been validated for a variety of complex parts produced on different multi-axis CNC machine tools including turning, milling, and compound turning-milling.

Computing the topology of an arrangement of parametric or implicit algebraic curves in the Lagrange basis

The study of arrangements of geometric objects is a problem of great interest in combinatorial and computational geometry, and in CAGD, with applications in computer-aided manufacturing, geometric modeling, robotics, NC-machining, molecular modeling, etc. [2, 3] We present a new algebraic method for computing the topology of the arrangement of a finite family of planar algebraic curves. The curves are given either by their implicit equations or by polynomial parametrizations. As far as we know, none of the previous works on this problem include the treatment of parametrized curves. The input of the method is assumed to be given as Lagrange data, i.e., by the values of the polynomials defining the curves, at a suitable set of nodes. The output is a graph representing critical points of the curves, all the intersection points between curves, and segments joining some of these points isotopic to the arcs of the curves. The method follows a sweep-line algorithm. To find critical points, intersections and self-intersections we use Bezout matrices. We take advantage of the existence of a basis of the nullspace of a Bezout matrix that has a nice and useful structure (see [4]). We use algebra by values techniques, which means that all computations (Bezout matrices, polynomial derivatives, etc.) are done in the Lagrange basis [5, 1]. This approach reduces the computational cost of manipulating high degree polynomials, and avoids conversion between different basis, which is known to be a numerically unstable procedure. To compute the roots of the determinant of a Bezout matrix we apply linearization, i.e., we use a straightforward procedure to build (in the Lagrange basis) a companion matrix pencil whose generalized eigenvalues are the roots of the aforementioned determinant. The algorithm has been tested using Maple 17, showing that it is accurate and quite efficient.

Special Issue: Advances in Computer Aided Manufacturing

Special Issue: Advances in Computer Aided Manufacturing

Management and control of information flow in CIM systems using UML and Petri nets

In this paper, we develop a systematic design methodology for control modules to manage and control the information flow among existing and new manufacturing application systems in CIM by synthesizing object-oriented modelling and net analysis (Petri net [PN]) methods. Due to the importance of objects in managing and controlling information flow, transformation rules from unified modelling language (UML) object dependencies and flows to PN were defined to extend the existing transformation rules between UML activity diagrams and PNs. The goal is to use the configurable graphic interface and the mathematical analysis methods of the PN to verify the logic correctness of the flow control mechanism and then apply the standard modelling and implementation capabilities of UML to transform the control specifications into desired computer codes with specified logic and configuration. The PN models were analysed by performing efficient algorithms that solve recursively corresponding integer programming (IP) problems to discover structural errors in the models. This design methodology was then used to build a prototype of the control module for CIM that took into account commercially available computer-aided manufacturing application systems to demonstrate its applicability.

An Algorithmic Strategy for Automated Generation of Multicomponent Software Tools for Virtual Manufacturing

Abstract This paper describes an algorithmic strategy to facilitate the generation of multicomponent software tools for computer-aided manufacturing (CAM) and virtual manufacturing (VM). Components that are often used to build CAM and VM applications include a wide range of domain-specific knowledge sources and also more general utility components with often very heterogeneous characteristics. The identification of a suitable and compatible set of these components is the first and arguably most important step during the development process of any CAM or VM application. This paper presents an algorithmic strategy that automates this development step by solving a time-expanded network problem, referred to as the component set identification (CSI) problem. A definition of the CSI problem, a mathematical formulation, a solution procedure, and some computational results are presented. Finally, an application to predict hole quality in drilling is used to illustrate the functionality of the proposed algorithmic strategy.

Development of drilling optimization strategies for CAM applications

Abstract The selection of economic cutting conditions in machining operations is becoming increasingly important in modern computer based-manufacturing. Using a generic deterministic approach, the optimization analyses, strategies and software for selecting the economic cutting conditions in drilling operations are presented based on the criteria typified by the maximum production rate (or minimum production time per hole) and incorporating a range of machine tool constraints. The deterministic optimization approach involving mathematical analyses and graphical presentation of economic characteristics provides clearly defined optimization strategies that ensure the global optimum solution. Numerical simulation studies have verified the optimization strategies and demonstrated the economic benefits of using optimization in process planning as well as the suitability of the developed optimization strategies for on-line applications in computer-aided manufacturing (CAM).

Constant-time algorithms for constrained triangulations on reconfigurable meshes

A number of applications in computer-aided manufacturing, CAD, and computer-aided geometric design ask for triangulating pieces of material with defects. These tasks are known collectively as constrained triangulations. Recently, a powerful architecture called the reconfigurable mesh has been proposed: In essence, a reconfigurable mesh consists of a mesh-connected architecture augmented by a dynamically reconfigurable bus system. The main contribution of this paper is to show that the flexibility of the reconfigurable mesh can be exploited for the purpose of obtaining constant-time algorithms for a number of constrained triangulation problems. These include triangulating a convex planar region containing any constant number of convex holes, triangulating a convex planar region in the presence of a collection of rectangular holes, and triangulating a set of ordered line segments. Specifically with a collection of O(n) such objects as input, our algorithms run in O(1) time on a reconfigurable mesh of size n/spl times/n. To the best of our knowledge, this is the first time constant time solutions to constrained triangulations are reported on this architecture.