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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

3-D Conformance Analysis of Manufacturing Plans Using M-Maps, by Explicating Formal GD&T Schema from the Process Plan

January 2015 (has links)
abstract: A process plan is an instruction set for the manufacture of parts generated from detailed design drawings or CAD models. While these plans are highly detailed about machines, tools, fixtures and operation parameters; tolerances typically show up in less formal manner in such plans, if at all. It is not uncommon to see only dimensional plus/minus values on rough sketches accompanying the instructions. On the other hand, design drawings use standard GD&T (Geometrical Dimensioning and tolerancing) symbols with datums and DRFs (Datum Reference Frames) clearly specified. This is not to say that process planners do not consider tolerances; they are implied by way of choices of fixtures, tools, machines, and operations. When converting design tolerances to the manufacturing datum flow, process planners do tolerance charting, that is based on operation sequence but the resulting plans cannot be audited for conformance to design specification. In this thesis, I will present a framework for explicating the GD&T schema implied by machining process plans. The first step is to derive the DRFs from the fixturing method in each set-up. Then basic dimensions for the features to be machined in each set up are determined with respect to the extracted DRF. Using shop data for the machines and operations involved, the range of possible geometric variations are estimated for each type of tolerances (form, size, orientation, and position). The sequence of manufacturing operations determines the datum flow chain. Once we have a formal manufacturing GD&T schema, we can analyze and compare it to tolerance specifications from design using the T-map math model. Since the model is based on the manufacturing process plan, it is called resulting T-map or m-map. Then the process plan can be validated by adjusting parameters so that the m-map lies within the T-map created for the design drawing. How the m-map is created to be compared with the T-map is the focus of this research. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2015
2

Automating GD&T Schema for Mechanical Assemblies

January 2016 (has links)
abstract: Parts are always manufactured with deviations from their nominal geometry due to many reasons such as inherent inaccuracies in the machine tools and environmental conditions. It is a designer job to devise a proper tolerance scheme to allow reasonable freedom to a manufacturer for imperfections without compromising performance. It takes years of experience and strong practical knowledge of the device function, manufacturing process and GD&T standards for a designer to create a good tolerance scheme. There is almost no theoretical resource to help designers in GD&T synthesis. As a result, designers often create inconsistent and incomplete tolerance schemes that lead to high assembly scrap rates. Auto-Tolerancing project was started in the Design Automation Lab (DAL) to investigate the degree to which tolerance synthesis can be automated. Tolerance synthesis includes tolerance schema generation (sans tolerance values) and tolerance value allocation. This thesis aims to address the tolerance schema generation. To develop an automated tolerance schema synthesis toolset, to-be-toleranced features need to be identified, required tolerance types should be determined, a scheme for computer representation of the GD&T information need to be developed, sequence of control should be identified, and a procedure for creating datum reference frames (DRFs) should be developed. The first three steps define the architecture of the tolerance schema generation module while the last two steps setup a base to create a proper tolerance scheme with the help of GD&T good practice rules obtained from experts. The GD&T scheme recommended by this module is used by the tolerance value allocation/analysis module to complete the process of automated tolerance synthesis. Various test cases are studied to verify the suitability of this module. The results show that software-generated schemas are proper enough to address the assemblability issues (first order tolerancing). Since this novel technology is at its initial stage of development, performing further researches and case studies will definitely help to improve the software for making more comprehensive tolerance schemas that cover design intent (second order tolerancing) and cost optimization (third order tolerancing). / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016
3

Méthode de recalage non rigide : application au contrôle géométrique de pièces souples à l'état libre ayant une spécification limitant les forces de montage / Nonrigid registration method : application for the inspection of compliant components with assembly force requirements

Abenhaim, Gad Noriel January 2014 (has links)
Résumé : En dépit des nombreuses recherches pour réduire le coût d'inspection des pièces à l'aide d'outils numériques, l'inspection de pièces souples demeure un défi. La raison est que les pièces souples peuvent prendre à l'état libre une forme substantiellement différente de leur géométrie nominale. Il en résulte que l'inspection de ce type de pièces nécessite des outils dédiés et coûteux, comme un gabarit d'inspection. Cette thèse détaille les défis associés au contrôle de ces pièces, pour proposer ensuite une méthode permettant l'inspection à l'état libre de pièces souples ayant une spécification limitant les forces de montage. L'approche proposée combine la méthode par éléments finis, les méthodes de traitement d'images ainsi que les démarches du domaine de l'optimisation. Essentiellement, la méthode proposée transpose (maps) le nuage de points représentant la pièce à l'état libre dans une configuration correspondant à sa géométrie installée sur son gabarit d'inspection. La méthode n'exige pas la conversion du nuage de points en modèle d'éléments finis, et veille à ce que les forces de montage ne dépassent pas leurs limites spécifiées, tout en tolérant des incertitudes dans la position des points de fixation simulant l'interface de montage. Ceci est accompli par le biais d'une optimisation par contrainte des déplacements des points de fixation. La contrainte de l'optimisation limite l'étendue des valeurs des forces de montage. La performance de la méthode d'inspection numérique proposée est évaluée à partir de cas d'études simulés, ainsi qu'à partir de deux pièces réelles du secteur de l'aéronautique. // Abstract : Despite extensive research to reduce the cost of inspection of parts using computational tools, inspection of compliant parts remains a challenge. The reason is that in a free-state, compliant parts can take on different shapes compared to their design model. It follows that the inspection of such parts requires dedicated and expensive inspectionfixtures. This thesis details the challenges associated with the inspection of these partsto then propose a fixetureless inspection method for compliant parts for which theirfunctional requirements mandate to limit the restraining forces imposed during assembly. The proposed approach combines the finite element method, image processing andoptimization techniques. Essentially, the proposed method maps the point cloud, representing the part in a free-state, to a configuration corresponding to its shape mounted onto its inspection fixture. The method does not necessitate the conversion of the point cloud into a finite element model, ensures that restraining forces do not exceed their specified limits, and accepts uncertainties in the position of features simulating the mounting interface. This is done through an constrained optimization on the displacements of the fixing points. The optimization constraint bounds the restraining forces values. The performance of the proposed computational inspection method is evaluated on simulated case studies, as well as on two aeronautics workpiece.
4

Reconciling The Differences Between Tolerance Specification And Measurement Methods

January 2014 (has links)
abstract: Dimensional Metrology is the branch of science that determines length, angular, and geometric relationships within manufactured parts and compares them with required tolerances. The measurements can be made using either manual methods or sampled coordinate metrology (Coordinate measuring machines). Manual measurement methods have been in practice for a long time and are well accepted in the industry, but are slow for the present day manufacturing. On the other hand CMMs are relatively fast, but these methods are not well established yet. The major problem that needs to be addressed is the type of feature fitting algorithm used for evaluating tolerances. In a CMM the use of different feature fitting algorithms on a feature gives different values, and there is no standard that describes the type of feature fitting algorithm to be used for a specific tolerance. Our research is focused on identifying the feature fitting algorithm that is best used for each type of tolerance. Each algorithm is identified as the one to best represent the interpretation of geometric control as defined by the ASME Y14.5 standard and on the manual methods used for the measurement of a specific tolerance type. Using these algorithms normative procedures for CMMs are proposed for verifying tolerances. The proposed normative procedures are implemented as software. Then the procedures are verified by comparing the results from software with that of manual measurements. To aid this research a library of feature fitting algorithms is developed in parallel. The library consists of least squares, Chebyshev and one sided fits applied on the features of line, plane, circle and cylinder. The proposed normative procedures are useful for evaluating tolerances in CMMs. The results evaluated will be in accordance to the standard. The ambiguity in choosing the algorithms is prevented. The software developed can be used in quality control for inspection purposes. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2014
5

Interoperability of Geometric Dimension & Tolerance Data between CAD Systems through ISO STEP AP 242

January 2016 (has links)
abstract: There is very little in the way of prescriptive procedures to guide designers in tolerance specification. This shortcoming motivated the group at Design Automation Lab to automate tolerancing of mechanical assemblies. GD&T data generated by the Auto-Tolerancing software is semantically represented using a neutral Constraint Tolerance Feature (CTF) graph file format that is consistent with the ASME Y14.5 standard and the ISO STEP Part 21 file. The primary objective of this research is to communicate GD&T information from the CTF file to a neutral machine readable format. The latest STEP AP 242 (ISO 10303-242) “Managed model based 3D engineering“ aims to support smart manufacturing by capturing semantic Product Manufacturing Information (PMI) within the 3D model and also helping with long-term archiving of the product information. In line with the recommended practices published by CAx Implementor Forum, this research discusses the implementation of CTF to AP 242 translator. The input geometry available in STEP AP 203 format is pre-processed using STEP-NC DLL and 3D InterOp. While the former is initially used to attach persistent IDs to the topological entities in STEP, the latter retains the IDs during translation to ACIS entities for consumption by other modules in the Auto-tolerancing module. The associativity of GD&T available in CTF file to the input geometry is through persistent IDs. C++ libraries used for the translation to STEP AP 242 is provided by StepTools Inc through the STEP-NC DLL. Finally, the output STEP file is tested using available AP 242 readers and shows full conformance with the STEP standard. Using the output AP 242 file, semantic GDT data can now be automatically consumed by downstream applications such as Computer Aided Process Planning (CAPP), Computer Aided Inspection (CAI), Computer Aided Tolerance Systems (CATS) and Coordinate Measuring Machines (CMM). / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016
6

Tolerance Maps for Patterns of Profiles

January 2014 (has links)
abstract: This thesis contains the applications of the ASU mathematical model (Tolerance Maps, T-Maps) to the construction of T-Maps for patterns of line profiles. Previously, Tolerance Maps were developed for patterns of features such as holes, pins, slots and tabs to control their position. The T-Maps that are developed in this thesis are fully compatible with the ASME Y14.5 Standard. A pattern of square profiles, both linear and 2D, is used throughout this thesis to illustrate the idea of constructing the T-Maps for line profiles. The Standard defines two ways of tolerancing a pattern of profiles - Composite Tolerancing and Multiple Single Segment Tolerancing. Further, in the composite tolerancing scheme, there are two different ways to control the entire pattern - repeating a single datum or two datums in the secondary datum reference frame. T-Maps are constructed for all the different specifications. The Standard also describes a way to control the coplanarity of discontinuous surfaces using a profile tolerance and T-Maps have been developed. Since verification of manufactured parts relative to the tolerance specifications is crucial, a least squares fit approach, which was developed earlier for line profiles, has been extended to patterns of line profiles. For a pattern, two tolerances are specified, and the manufactured profile needs to lie within the tolerance zones established by both of these tolerances. An i-Map representation of the manufactured variation, located within the T-Map is also presented in this thesis. / Dissertation/Thesis / M.S. Mechanical Engineering 2014
7

Integration of Machining Inspection Sensors and Software

Sawula, Alan D. 04 1900 (has links)
<p>Ideally, the nominal design of a part or assembly, created with 3D Computer-Aided Design and Manufacturing (CAD/CAM) software, can be consistently fixtured and machined. In reality, process conditions vary, and feedback and correction methods such as integrated on-machine inspection, analysis, and process adjustment, are required.</p> <p>On-machine inspection based on touch trigger probes is well established, but limited motion control computing capability restricts analysis to simple arithmetic. This prevents on-line use of known whole part mathematical analysis software that implements the part salvaging intentions of modern Geometric Dimensioning and Tolerancing (GD&T) standards. Additionally, no CNC integrated method exists for geometrically adjusting nominal tool paths so that an in-tolerance final part is produced. Machine tool support for high data rate sensors such as laser scanners is also lacking.</p> <p>This thesis reports progress towards bidirectional integration of machine tool mounted inspection sensors with GD&T analysis software, and subsequent toolpath adjustment. The concepts are demonstrated using a fixture consisting of three datum spheres and a workpiece. The fixture is clamped in the CNC machine, datum spheres are measured, and after mathematical data fitting and registration, an in-tolerance final part is produced. To facilitate multiple tests, a tool path is split into four and machined in four poses with measurement and tool path adjustment for each pose. Preliminary integration of a laser scanner with axis scales and computer software was also accomplished.</p> / Master of Applied Science (MASc)
8

Konstruktionsbegleitende Toleranzsimulation mit CETOL 6 σ unter Verwendung der GPS-Strategie DIN EN ISO 14638 und DIN EN ISO 8015

Bruns, Christoph 06 June 2017 (has links) (PDF)
Die geometrische Produktspezifikation (GPS) ist für Unternehmen eine wesentliche Triebfeder um sich in Konstruktions- und Entwicklungsprozessen neu auszurichten. Mit der 3-dimensionalen Bemaßung an der CAD-Geometrie sollen alle Aspekte der Geometriebeschreibung datenneutral umgesetzt werden. Dazu gehören Toleranzdefinitionen die den Anspruch der Funktion, der Fertigbarkeit und der Messtechnik erfüllen. Die verfügbaren Werkzeuge zur normgerechten Toleranzdefinition am 3D-Teil haben sich in Creo 4 mit dem GD&T Advisor nochmals deutlich erweitert. Dies wird in diesem Vortrag mit dem Fokus auf die Toleranzanalyse in Creo 4 und der neuen CETOL Version 9 aufgezeigt.
9

Konstruktionsbegleitende Toleranzsimulation mit CETOL 6 σ unter Verwendung der GPS-Strategie DIN EN ISO 14638 und DIN EN ISO 8015

Bruns, Christoph 06 June 2017 (has links)
Die geometrische Produktspezifikation (GPS) ist für Unternehmen eine wesentliche Triebfeder um sich in Konstruktions- und Entwicklungsprozessen neu auszurichten. Mit der 3-dimensionalen Bemaßung an der CAD-Geometrie sollen alle Aspekte der Geometriebeschreibung datenneutral umgesetzt werden. Dazu gehören Toleranzdefinitionen die den Anspruch der Funktion, der Fertigbarkeit und der Messtechnik erfüllen. Die verfügbaren Werkzeuge zur normgerechten Toleranzdefinition am 3D-Teil haben sich in Creo 4 mit dem GD&T Advisor nochmals deutlich erweitert. Dies wird in diesem Vortrag mit dem Fokus auf die Toleranzanalyse in Creo 4 und der neuen CETOL Version 9 aufgezeigt.
10

Creating Competitive Advantage by Rethinking B2B Software Pricing / Skapa konkurrensfördel genom att utvärdera B2B-prissättning av mjukvara

Adelstrand, Carl, Brostedt, Emil January 2016 (has links)
The choice of pricing model for software products is a complex procedure due to the different characteristics compared to physical products. This thesis investigates and compares software pricing models in a B2B setting, and describes how KAM plays a role in executing a pricing model. The research has been conducted as an opportunist case study on Adebro, a technology company in the B2B sector. The thesis have come to the following conclusions, with data from interviews and literature: Perpetual license is, and will continue to be, an attractive pricing model for Adebro. However, a subscription-based usage independent pricing model is also attractive for the future. Implications of switching pricing model would be largest when changing between a perpetual and subscription model, where revenue will have the most visual impact. The most important task for KAM is to communicate the change to current and new customers. KAM and the pricing model must also be structured to support each other to be successful. The thesis contributes to science by providing research on pricing models for manufacturing related software. However, studies concerning the weighting of importance for different pricing parameters would be of interest for the future.

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