Toward Automatic Tolerancing of Mechanical Assemblies: Assembly Analyses

2014 ◽  
Vol 14 (4) ◽  
Author(s):  
Prashant Mohan ◽  
Payam Haghighi ◽  
Prabath Vemulapalli ◽  
Nathan Kalish ◽  
Jami J. Shah ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Feature Recognition ◽  
Tolerance Analysis ◽  
Tolerance Allocation ◽  
Geometric Dimensioning And Tolerancing ◽  
Mechanical Assemblies ◽  
Loop Detection ◽  
Assembly Feature ◽  
Aided Design ◽  
Assembly Analysis

Generating geometric dimensioning and tolerancing (GD&T) specifications for mechanical assemblies is a complex and tedious task, an expertise that few mechanical engineers possess. The task is often done by trial and error. While there are commercial systems to facilitate tolerance analysis, there is little support for tolerance synthesis. This paper presents a systematic approach toward collecting part and assembly characteristics in support of automating GD&T schema development and tolerance allocation for mechanical assemblies represented as neutral B-Rep. First, assembly characteristics are determined, then a tentative schema is determined and tolerances allocated. This is followed by adaptive iterations of analyses and refinement to achieve desired goals. This paper will present the preprocessing steps for assembly analysis needed for tolerance schema generation and allocation. Assembly analysis consists of four main tasks: assembly feature recognition (AFR), pattern detection, directions of control, and loop detection. This paper starts with identifying mating features in an assembly using the computer-aided design (CAD) file. Once the features are identified, patterns are determined among those features. Next, different directions of control for each part are identified and lastly, using all this information, all the possible loops existing in an assembly are searched.

Toward Automatic Tolerancing of Mechanical Assemblies: First-Order GD&T Schema Development and Tolerance Allocation

2015 ◽  
Vol 15 (4) ◽  
Author(s):  
Payam Haghighi ◽  
Prashant Mohan ◽  
Nathan Kalish ◽  
Prabath Vemulapalli ◽  
Jami J. Shah ◽  
...  
Keyword(s):  
Feature Recognition ◽  
Reference Frames ◽  
Geometric Analysis ◽  
Tolerance Allocation ◽  
First Order ◽  
Geometric Dimensioning And Tolerancing ◽  
Mechanical Assemblies ◽  
Schema Development ◽  
Design Function ◽  
Acceptance Rates

Geometric and dimensional tolerances must be determined not only to ensure proper achievement of design function but also for manufacturability and assemblability of mechanical assemblies. We are investigating the degree to which it is possible to automate tolerance assignment on mechanical assemblies received only as STEP AP 203 (nominal) geometry files. In a previous paper, we reported on the preprocessing steps required: assembly feature recognition, pattern recognition, and extraction of both constraints and directions of control (DoC) for assembly. In this paper, we discuss first-order tolerance schema development, based purely on assemblability conditions. This includes selecting features to be toleranced, tolerance types, datums, and datum reference frames (DRFs), and tolerance value allocation. The approach described here is a combination of geometric analysis and heuristics. The assumption is that this initial geometric dimensioning and tolerancing (GD&T) specification will be sent to a stack analysis module and iterated upon until satisfactory results, such as desired acceptance rates, are reached. The paper also touches upon issues related to second-order schema development, one that takes intended design function into account.

Tolerances Modeling in Assemblies: An Approach Based on Graphs

2014 ◽  
Vol 902 ◽  
pp. 378-384
Author(s):  
R.L. Avila Rondón ◽  
R. Pérez Rodríguez ◽  
A. Cordovés García ◽  
R.P. Avila Alfaro ◽  
Z. Mendoza Núñez ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Mechanical Design ◽  
Tolerance Analysis ◽  
Functional Requirements ◽  
Mechanical Assemblies ◽  
Decisive Importance ◽  
Common Task ◽  
Design Systems ◽  
Aided Design ◽  
Graph Map

In the mechanical design process, the interpretation of geometrical and dimensional tolerances is a common task in a products life cycle because tolerances are of decisive importance in the decisions related to cost and quality. At present, there are numerous approaches and investigations related to the modeling of tolerances in mechanical assemblies, related to Computer Aided Design Systems. The goal of this paper is to show a method to modeling an assembly based on a graph map structure, to guarantee the resolution of dimensional chains and tolerance analysis. In this process, which is based on a graph map structure, the dimensional chains associated to the functional requirements that influence the relative location of the parts are determined. A subset of a belt conveyor as an example, illustrates the proposed method.

An oriented feature extraction and recognition approach for concave-convex mixed interacting features in cast-then-machined parts

2018 ◽  
Vol 233 (4) ◽  
pp. 1269-1288 ◽  
Author(s):  
Haichao Wang ◽  
Jie Zhang ◽  
Xiaolong Zhang ◽  
Changwei Ren ◽  
Xiaoxi Wang ◽  
...  
Keyword(s):  
Feature Extraction ◽  
Computer Aided Design ◽  
Feature Recognition ◽  
Freeform Surface ◽  
Layer By Layer ◽  
Computer Aided Process Planning ◽  
Computer Aided ◽  
Machined Parts ◽  
Aided Design ◽  
Interacting Features

Feature recognition is an important technology of computer-aided design/computer-aided engineering/computer-aided process planning/computer-aided manufacturing integration in cast-then-machined part manufacturing. Graph-based approach is one of the most popular feature recognition methods; however, it cannot still solve concave-convex mixed interacting feature recognition problem, which is a common problem in feature recognition of cast-then-machined parts. In this study, an oriented feature extraction and recognition approach is proposed for concave-convex mixed interacting features. The method first extracts predefined features directionally according to the rules generated from attributed adjacency graphs–based feature library and peels off them from part model layer by layer. Sub-features in an interacting feature are associated via hints and organized as a feature tree. The time cost is reduced to less than [Formula: see text] by eliminating subgraph isomorphism and matching operations. Oriented feature extraction and recognition approach recognizes non-freeform-surface features directionally regardless of the part structure. Hence, its application scope can be extended to multiple kinds of non-freeform-surface parts by customizing. Based on our findings, implementations on prismatic, plate, fork, axlebox, linkage, and cast-then-machined parts prove that the proposed approach is applicable on non-freeform-surface parts and effectively recognize concave-convex mixed interacting feature in various mechanical parts.

Effects of Immersion on Virtual Reality Prototype Design Reviews of Mechanical Assemblies

2018 ◽  
Author(s):  
Luis de Casenave ◽  
José E. Lugo
Keyword(s):  
Computer Aided Design ◽  
Virtual Prototype ◽  
Point Of View ◽  
Human Computer Interface ◽  
Design Decisions ◽  
Mechanical Assemblies ◽  
Accurate Design ◽  
Virtual Prototypes ◽  
Aided Design ◽  
Prototype Design

The proficiency of Computer Aided Design (CAD) to save, communicate and render realistic virtual prototypes allows for easier communication and review of proposed design decisions via design reviews. However, the use of virtual prototypes is limited by the realism of the human computer interface. This paper builds on previous research investigating if increasing the realism of input and output interactions between subjects and virtual prototypes will affect user’s ability to analyze an assembly for errors. For this end, two experiments were conducted which asked participants to perform design reviews on assembly models and identify errors in the assembly. The first experiment tested virtual prototype output display factors through subject point of view movement and virtual prototype rotation. The second experiment tested human input factors using different controller setups. It is expected the more realistic virtual prototype rendering and controller input experience will result in more accurate design reviews.

Design System Mfk—An Important Step towards an Engineering Workbench

1993 ◽  
Vol 207 (2) ◽  
pp. 105-116 ◽  
Author(s):  
H Meerkamm
Keyword(s):  
Computer Aided Design ◽  
Tolerance Analysis ◽  
Design System ◽  
Product Model ◽  
Cad System ◽  
Knowledge Based ◽  
Different Types ◽  
Analysis Design ◽  
Aided Design ◽  
Production Tolerance

The Design System mfk will support the designer by an object-orientated synthesis of parts and an integrated knowledge-based analysis. An own-product model which is completely independent from the data structure of the used computer aided design (CAD) system contains all necessary information on geometry, technology, function and organization. It allows different types of analysis: design for production, tolerance analysis, cost and stress calculation, repeated component search, etc. Usable for products of higher complexity the Design System can be seen as an approach to an engineering workbench.

An Expert System for Concurrent Product and Process Design of Mechanical Parts

1994 ◽  
Vol 208 (3) ◽  
pp. 167-172 ◽  
Author(s):  
H S Abdalla ◽  
J Knight
Keyword(s):  
Expert System ◽  
Process Design ◽  
Computer Aided Design ◽  
Feature Recognition ◽  
Design For Manufacturability ◽  
Design System ◽  
Mechanical Parts ◽  
Extensive Information ◽  
Product And Process ◽  
Aided Design

A new approach for concurrent product and process design of mechanical parts is presented in this paper. This approach enables designers to ensure that the product will be manufactured with the existing manufacturing facility at high quality and lowest cost. It is composed of an integrated expert and CAD (computer aided design) system that meets the requirements for accomplishing the concept of design for manufacturability or concurrent engineering. The system is based mainly on three tasks: firstly, developing a technique for automated feature recognition from the database of a solid modeller; secondly, interfacing the expert system tool-kit with the solid modelling system; finally, building an expert system that contains extensive information about both manufacturing facilities and product features. The expert system provides feedback about manufacturing concerns such as process limits or design inconsistencies. This work is part of the present extended research plan for developing a generic system suitable for various manufacturing practices based on design for manufacturability strategy.

A Novel Model for the Tolerancing of Nonrigid Part Assemblies in Computer Aided Design

2019 ◽  
Vol 19 (4) ◽  
Author(s):  
Mehdi Tlija ◽  
Anis Korbi ◽  
Borhen Louhichi ◽  
Abdelmajid Benamara
Keyword(s):  
Computer Aided Design ◽  
Tolerance Analysis ◽  
Physical Factors ◽  
Worst Case ◽  
Manufacturing Defects ◽  
Computer Aided ◽  
Aided Design ◽  
Novel Model

In the design step, the realistic modeling of the product represents an industrial requirement and a digital muck up (DMU) improvement. Thus, the tolerance integration in the computer aided design (CAD) model with the neglect of important physical factors, such as the components’ deformations during the mounting and assembly operation, causes a deviation between the numerical and the realistic models. In this regard, this paper presents a new model for the tolerance analysis of CAD assemblies based on the consideration of both manufacturing defects and deformations. The dimensional and geometrical tolerances are considered by the determination of assemblies’ configurations with defects based on the worst case tolerancing. The finite elements (FEs) simulation is realized with realistic models. An algorithm for updating the realistic mating constraints, between rigid and nonrigid parts, is developed. The case study of an assembly with planar and cylindrical joints is presented.

Microstructure Feature Recognition for Materials Using Surfacelet-Based Methods for Computer-Aided Design-Material Integration

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Namin Jeong ◽  
David W. Rosen
Keyword(s):  
Computer Aided Design ◽  
Feature Recognition ◽  
Computational Method ◽  
Geometric Features ◽  
Material Microstructure ◽  
Control Material ◽  
Computer Aided ◽  
Aided Design ◽  
And Control ◽  
Material Information

With the material processing freedoms of additive manufacturing (AM), the ability to characterize and control material microstructures is essential if part designers are to properly design parts. To integrate material information into Computer-aided design (CAD) systems, geometric features of material microstructure must be recognized and represented, which is the focus of this paper. Linear microstructure features, such as fibers or grain boundaries, can be found computationally from microstructure images using surfacelet based methods, which include the Radon or Radon-like transform followed by a wavelet transform. By finding peaks in the transform results, linear features can be recognized and characterized by length, orientation, and position. The challenge is that often a feature will be imprecisely represented in the transformed parameter space. In this paper, we demonstrate surfacelet-based methods to recognize microstructure features in parts fabricated by AM. We will provide an explicit computational method to recognize and to quantify linear geometric features from an image.

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