Simplification of Feature Based Models for Tolerance Analysis

1992 ◽  
Author(s):  
Peter Martino
Keyword(s):  
Data Structure ◽  
Graph Model ◽  
Tolerance Analysis ◽  
Solid Modeling ◽  
Computational Effort ◽  
Tree Graph ◽  
Graph Data ◽  
Computer Aided ◽  
Feature Based ◽  
Analysis Models

Abstract This paper presents a method for eliminating unnecessary parts, features, and dimensions from feature based models in computer aided tolerance analysis systems. A typical tolerance analysis involves a dozen or so parts, or subassemblies. Each part may have dozens of features, and hundreds of dimensions. Many of these subassemblies, parts, features, and dimensions do not effect the tolerance analysis, and therefore are not needed. Computational effort can be reduced by eliminating the unnecessary items from the model. Currently, tolerance analysis models are implicitly simplified by the user. The user examines the problem, and determines which parts, features, and dimensions can be ignored. The user then constructs his model, leaving out the unneeded items. This is true whether the analysis is accomplished with a computer aided tool, or with paper and pencil. Simplification of the model is essential. Practical tolerance analysis problems become overwhelmingly complex if every detail is included. The method discussed in this paper is intended for use in computer aided tolerance analysis systems that use feature based, and dimension driven, solid modeling. It uses a combined tree and graph data structure. The tree structure represents the hierarchy of assemblies, parts, and features in the model. The graphs represent the dependence between features in a part, or parts in an assembly. An algorithm has been developed that searches this tree/graph model, locating the parts and features needed to accomplish the tolerance analysis.

scholarly journals A NURBS-based solid modeling to enhance rapid prototyping in the restoration of decorative elements

2020 ◽  
Author(s):  
Michele Calì ◽  
Salvatore Massimo Oliveri ◽  
Placido Calì ◽  
Rita Ambu
Keyword(s):  
Experimental Data ◽  
Rapid Prototyping ◽  
Tolerance Analysis ◽  
Solid Modeling ◽  
High Accuracy ◽  
Three Dimensions ◽  
Reconstruction Method ◽  
Solid Modelling ◽  
Analysis Model ◽  
Computer Aided

Abstract In this research, we describe a computer-aided approach to improve the reconstruction method of decorum in architectural surfaces and sculpture. The effects of withdrawal caused by catalysis of mold in silicone was evaluated and simulated by a NURBS-based solid modelling. A tolerance analysis model was developed to predict manufacturing precision levels. In particular, differential increment along three dimensions was performed considering different volume distributions. The methodology was validated by experimental data obtained during the coffered ceiling restoration of Teatro Massimo Vittorio Emanuele in Palermo. The proposed methodology allowed the reconstruction of decorations or fragments of decoration with high accuracy.

Structural Analysis of Product and Computer-Aided Assembly Planning in AssemBL Software Package

2018 ◽  
pp. 11-33
Author(s):  
A. N. Bozhko
Keyword(s):  
Computer Aided Design ◽  
State Of The Art ◽  
Graph Model ◽  
Design System ◽  
Assembly Planning ◽  
Complex Products ◽  
Assembly Sequences ◽  
Computer Aided ◽  
Cad Cam ◽  
Aided Design

Computer-aided design of assembly processes (Computer aided assembly planning, CAAP) of complex products is an important and urgent problem of state-of-the-art information technologies. Intensive research on CAAP has been underway since the 1980s. Meanwhile, specialized design systems were created to provide synthesis of assembly plans and product decompositions into assembly units. Such systems as ASPE, RAPID, XAP / 1, FLAPS, Archimedes, PRELEIDES, HAP, etc. can be given, as an example. These experimental developments did not get widespread use in industry, since they are based on the models of products with limited adequacy and require an expert’s active involvement in preparing initial information. The design tools for the state-of-the-art full-featured CAD/CAM systems (Siemens NX, Dassault CATIA and PTC Creo Elements / Pro), which are designed to provide CAAP, mainly take into account the geometric constraints that the design imposes on design solutions. These systems often synthesize technologically incorrect assembly sequences in which known technological heuristics are violated, for example orderliness in accuracy, consistency with the system of dimension chains, etc.An AssemBL software application package has been developed for a structured analysis of products and a synthesis of assembly plans and decompositions. The AssemBL uses a hyper-graph model of a product that correctly describes coherent and sequential assembly operations and processes. In terms of the hyper-graph model, an assembly operation is described as shrinkage of edge, an assembly plan is a sequence of shrinkages that converts a hyper-graph into the point, and a decomposition of product into assembly units is a hyper-graph partition into sub-graphs.The AssemBL solves the problem of minimizing the number of direct checks for geometric solvability when assembling complex products. This task is posed as a plus-sum two-person game of bicoloured brushing of an ordered set. In the paradigm of this model, the brushing operation is to check a certain structured fragment for solvability by collision detection methods. A rational brushing strategy minimizes the number of such checks.The package is integrated into the Siemens NX 10.0 computer-aided design system. This solution allowed us to combine specialized AssemBL tools with a developed toolkit of one of the most powerful and popular integrated CAD/CAM /CAE systems.

Machining Feature-Based CAD/CAPP for STEP-NC

2014 ◽  
Vol 598 ◽  
pp. 591-594 ◽  
Author(s):  
Li Yan Zhang
Keyword(s):  
Process Planning ◽  
Manufacturing Process ◽  
Data Transfer ◽  
Operation Planning ◽  
Computer Aided Process Planning ◽  
Machining Feature ◽  
Computer Aided ◽  
Cad Cam ◽  
Feature Based ◽  
Cam Systems

ISO 14649, known as STEP-NC, is new model of data transfer between CAD/CAM systems and CNC machines. In this paper, the modeling based on machining feature is proposed. The machining feature comes from the manufacturing process considering the restriction of machining technology and machining resource. Then the framework for computer aided process planning is presented, where the algorithms of operation planning is studied. The practical example has been provided and results indicate that machining feature based model can integrate with CAPP and STEP-NC seamlessly.

An Investigation of Vector and Parallel Processing Applied to Solid Modeling

1996 ◽  
Author(s):  
Navin Pai ◽  
Mark Henderson
Keyword(s):  
Data Structure ◽  
Parallel Processing ◽  
Solid Modeling ◽  
Boundary Representation ◽  
Solid Modeler ◽  
Linked Lists

Abstract Solid modeling is a very useful industrial tool in the manufacture and design of industrial parts and assemblies. As a tool in the industrial workplace it has to be able to respond quickly to changes in design. To do this, the intersection algorithms between the solids have to be speeded up. Optimizations such as vector and parallel processing traditionally supported by supercomputers have the potential to solve this problem. A solid modeler was developed based on the boundary representation approach using a half-edge data structure. Those parts of the solid modeler code that could be vectorized were identified. A method was tested which allows loops involving linked lists to vectorize. It was also shown that this solid modeler has an inherent parallelism that can be exploited. Results are presented for vectorization and parallelization. The practical limits to both vectorization and parallelization are highlighted. Improvements to the geometric intersections algorithms are suggested to take advantage of vector and parallel processing. Results of the speedups possible using these algorithms are presented.

Parametric Kinematic Tolerance Analysis of Planar Pairs With Multiple Contacts

1996 ◽  
Author(s):  
Elisha Sacks ◽  
Leo Joskowicz
Keyword(s):  
Efficient Algorithm ◽  
Tolerance Analysis ◽  
Parametric Model ◽  
Worst Case ◽  
Multiple Contacts ◽  
Work Cycle ◽  
Computer Aided ◽  
Kinematic Models ◽  
Range Of Variation ◽  
Different Parts

Abstract We present an efficient algorithm for worst-case limit kinematic tolerance analysis of planar kinematic pairs with multiple contacts. The algorithm extends computer-aided kinematic tolerance analysis from mechanisms in which parts interact through permanent contacts to mechanisms in which different parts or part features interact at different stages of the work cycle. Given a parametric model of a pair and the range of variation of the parameters, it constructs parametric kinematic models for the contacts, computes the configurations in which each contact occurs, and derives the sensitivity of the kinematic variation to the parameters. The algorithm also derives qualitative variations, such as under-cutting, interference, and jamming. We demonstrate the algorithm on a 26 parameter model of a Geneva mechanism.

CATI: A Computer Aided Tolerancing Interface

1992 ◽  
Author(s):  
Rikard Söderberg
Keyword(s):  
Normal Distribution ◽  
Tolerance Analysis ◽  
Distribution Model ◽  
Preliminary Design ◽  
Tolerance Limits ◽  
Cad System ◽  
System A ◽  
Computer Aided ◽  
2D Drawing ◽  
Normal Distribution Model

Abstract This work presents an interface for tolerance analysis in a CAD system. A method for picking up necessary information from a 2D drawing is developed and implemented as an interface in a commercial CAD system. The interface communicates with an external calculation program which determines unknown tolerance limits using the normal distribution model. Results from the calculation program is in the end used by the interface to present measures with tolerances on the drawing. The advantage of using CATI in preliminary design is discussed, and a strategy for treating interrelated tolerance chains is presented.

scholarly journals Text Mining for Industrial Machine Predictive Maintenance with Multiple Data Sources

2021 ◽  
Author(s):  
Giancarlo Nota ◽  
Alberto Postiglione
Keyword(s):  
Data Structure ◽  
Text Mining ◽  
Machine Tool ◽  
Computational Effort ◽  
Data Sources ◽  
Multiple Data Sources ◽  
Log Files ◽  
Multiple Data ◽  
Innovative Methodology ◽  
Industrial Machine

This paper presents an innovative methodology, from which an efficient system prototype is derived, for the algorithmic prediction of malfunctions of a generic industrial machine tool. It integrates physical devices and machinery with Text Mining technologies and allows the identification of anomalous behaviors, even of minimal entity, rarely perceived by other strategies in a machine tool. The system works without waiting for the end of the shift or the planned stop of the machine. Operationally, the system analyzes the log messages emitted by multiple data sources associated with a machine tool (such as different types of sensors and log files produced by part programs running on CNC or PLC) and deduces whether they can be inferred from them future machine malfunctions. In a preliminary offline phase, the system associates an alert level with each message and stores it in a data structure. At runtime, three algorithms guide the system: pre-processing, matching and analysis: Preprocessing, performed only once, builds the data structure; Matching, in which the system issues the alert level associated with the message; Analysis, which identifies possible future criticalities. It can also analyze an entire historical series of stored messages The algorithms have a linear execution time and are independent of the size of the data structure, which does not need to be sorted and therefore can be updated without any computational effort.

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