Revisiting the design intent concept in the context of mechanical CAD education

[EN] Design intent is generally understood simply as a CAD model¿s anticipated behavior when altered. However, this representation provides a simplified view of the model¿s construction and purpose, which may hinder its general understanding and future reusability. Our vision is that design intent communication may be improved by recognizing the multifaceted nature of design intent, and by instructing users to convey each facet of design intent through the better-fitted CAD resource. This paper reviews the current understanding of design intent and its relationship to design rationale and builds on the idea that communication of design intent conveyed via CAD models can be satisfied at three levels provided that specialized instruction is used to instruct users in selection of the most suitable level for each intent.Otey, J.; Company, P.; Contero, M.; Camba, J. (2018). Revisiting the design intent concept in the context of mechanical CAD education. Computer-Aided Design and Applications. 15(1):47-60. https://doi.org/10.1080/16864360.2017.1353733S476015

A Contribution to Conveying Quality Criteria in Mechanical CAD Models and Assemblies through Rubrics and Comprehensive Design Intent Quantification

Esta investigación examinó el uso de rúbricas de ensamblaje, describiendo su evolución a partir de rúbricas de piezas, y estudió cómo afectan a la autoevaluación de los estudiantes. También se valoró la evaluación de los estudiantes por los instructores, encontrando que, mientras que las rúbricas de ensamblaje fueron parcialmente comprendidas y utilizadas de manera eficiente por los estudiantes, éstas fueron usadas con más éxito por los instructores. En esta investigación se han abordado estrategias diseñadas para mejorar la comunicación de la intención de diseño en modelos CAD, acrecentando así su calidad, con directrices dirigidas a evaluar su eficiencia. Es evidente que se necesitan métricas dirigidas hacia la instrucción de la intención de diseño, ya que la intención de diseño transferida a través de modelos CAD puede realizarse en tres etapas con criterios contradictorios que deben ser equilibrados para llegar a la mejor estrategia de modelado. La investigación ha incluido el desarrollo de un método de validación que demuestra que las rúbricas son dispositivos útiles para garantizar una comunicación consistente de la intención de diseño, y son fundamentales no sólo para evaluar, sino también para comunicar las expectativas del instructor. En esta investigación se examinó cómo definir claramente las cualidades de la intención de diseño para permitir una más fácil evaluación de un ensamblaje CAD. Para todas las dimensiones de la rúbrica, se encontró más concordancia y correlación entre instructores que entre instructores y estudiantes. Existe una correlación moderada/fuerte entre los instructores para las dimensiones de la validez, completitud, concisión y claridad, mientras que existe una ligera correlación para las dimensiones de consistencia e intención del diseño. En segundo lugar, las rúbricas también pueden ser descritas como estáticas o dinámicas. Las rúbricas estáticas, existen sólo en papel, no proporcionan retroalimentación inmediata al educando. Las rúbricas dinámicas realizan cálculos que proporcionan observaciones de evaluación inmediatas al usuario. Además, pueden adaptarse a situaciones específicas dependiendo de la capacidad del usuario. Las rúbricas electrónicas son ideales para rúbricas dinámicas, y permiten el uso y desarrollo de rúbricas adaptativas y adaptables, como se describe a continuación. En tercer lugar, las rúbricas deben ser adaptables lo que debería hacerlas fácilmente comprensibles y fáciles de usar, y adaptativas. Las rúbricas de evaluación se usan cuando un experto determina el progreso pedagógico de un educando, mientras que las rúbricas formativas son empleadas por los propios estudiantes, para trazar su progreso e identificar las deficiencias escolares para las que necesitan apoyo. Las rúbricas se deben refinar y mejorar de forma continuada, en un proceso iterativo y colaborativo, hasta que se alcance un acuerdo satisfactorio, tanto entre evaluadores como entre evaluadores y alumnos. Por ello, se desarrollaron mapas de aserciones que ilustran el modo en que la estrategia de expansión-contracción adapta las rúbricas al progreso del aprendiz de CAD, a la vez que ayudan a comprender las diferentes dimensiones de la rúbrica. Basándose en los experimentos con las rúbricas de ensamblajes, es evidente que las pequeñas diferencias entre los instructores sugieren que la rúbrica de ensamblajes propuesta es lo suficientemente sofisticada como para proporcionar una evaluación acumulativa imparcial del desempeño del alumno. En consecuencia, se puede afirmar con confianza que los evaluadores pueden usarse indistintamente sin sacrificar la precisión. Sin embargo, la rúbrica de ensamblaje posee una eficacia finita para producir una autoevaluación formativa de las habilidades de ensamblaje CAD para nuevos alumnos.This research examined the use of assembly rubrics, described how they evolved from parts rubrics, and studied how they affect student self-evaluation. Instructor assessment of students was also evaluated, finding that while the assembly rubrics were partially understood and effectively used by the students, they were more successfully utilized by the instructors. Strategies designed to improve design intent communication in CAD models, in order to enhance their quality, with guidelines targeted to evaluate efficiency, have been addressed with this research. It is apparent that metrics directed toward the instruction of design intent are needed, since design intent transferred through CAD models can be performed at three stages with competing tradeoffs that must be balanced to arrive at the best modeling strategy. Research included the development of a validation approach that reflects that rubrics are valuable devices to expedite consistent design intent communication, and are vital not only for evaluation, but also for the communication of instructor expectations. This research examined how to clearly define qualities of design intent to enable easier CAD assembly assessment. It has been found that there is more inter-rater agreement and correlation between instructors than between instructors and students, for all rubric dimensions. There is strong to moderate correlation between instructors for the dimensions of validity, completeness, conciseness, and clarity, while slight correlation exists for the dimensions of consistency and design intent. Secondly, rubrics can also be described as being either static or dynamic. Static rubrics, existing in paper form only, do not provide immediate feedback to the learner. Dynamic rubrics perform calculations that provide immediate evaluative observations to the user. Besides, they can be independently adapted to specific situations depending on the capability of the user. Electronic rubrics are ideally suited for dynamic rubrics, and permit the use and development of both adaptable and adaptive rubrics, as described next. Thirdly, rubrics need to be adaptable which should make them easily understood and user-friendly, and adaptive (rubric can change itself, depending on the usage pattern). Evaluative rubrics are used when an expert determines the pedagogical progress of a learner, while formative rubrics are employed by the learners themselves, in order to chart their progress and identify scholastic deficiencies that are in need of remediation. Rubrics must be continually refined and improved, in an iterative, collaborative process, until satisfactory agreement is attained, both between raters, but also between raters and learners. Thus, assertions maps were developed, illustrating how the expand-contract strategy adapts the rubrics to CAD trainee progress, while assisting the understanding of the different rubric dimensions. Based on the assembly rubric experiments, it is apparent that the small differences between instructors suggests that the proposed assemblies rubric is sufficiently sophisticated to furnish an unbiased accumulative assessment of student performance. Accordingly, it can be confidently stated that raters can be used interchangeably without sacrificing accuracy. However, the assembly rubric possesses finite efficacy to produce formative self-evaluation of CAD assembly skills for new learners.Aquesta investigació examinà l'ús de rúbriques de acoblament, descrivint la seua evolució a partir de rúbriques de peces, i estudià cóm afecten a la autoavaluació dels estudiants. També es va valorar la avaluació dels estudiants per els instructors, trobant que, mentre que les rúbriques de acoblament van ser parcialment compreses i fetes servir de manera eficient per els estudiants, van ser usades amb mes èxit per els instructors. En aquesta investigació s'han abordat estrategues dissenyades per a millorar la comunicació de la intenció de disseny en models CAD, creixentat així la seua qualitat, amb directrius dirigides a avaluar la seua eficiència. Es evident que es necessiten mètriques dirigides cap a la instrucció de la intenció de disseny, ja que la intenció de disseny transferida a través de models CAD pot realitzar-se en tres etapes amb criteris contradictoris que deuen ser equilibrats per a arribar a la millor estratègia de modelatge. La investigació ha inclòs el desenvolupament de un mètode de validació que demostra que las rúbriques son dispositius útils per a garantir una comunicació consistent de la intenció de disseny, i son fonamentals no només per a avaluar, però també per a comunicar les expectatives de l'instructor. En aquesta investigació s'examinà com definir clarament les qualitats de la intenció de disseny per a permetre una mes fàcil avaluació de un acoblament CAD. Per a totes les dimensions de la rúbrica, es va trobar mes concordança i correlació entre instructors que no pas entre instructors i estudiants. Existeix una correlació moderada/fort entre els instructors per a les dimensions de la validesa, completesa, concisió i claredat, mentre que existeix una lleugera correlació per a les dimensions de consistència i intenció del disseny. En segon lloc, les rúbriques també poden ser descrites com estàtiques o dinàmiques. Les rúbriques estàtiques, existeixen sòls en paper, no proporcionen retroalimentació immediata a l'educand. Les rúbriques dinàmiques realitzen càlculs que proporcionen observacions de avaluació immediates al usuari. A mes, poden adaptar-se a situacions específiques dependent de la capacitat de l'usuari. Les rúbriques electròniques son ideals per a rúbriques dinàmiques, i permeten l'ús i desenvolupament de rúbriques adaptatives i adaptables, como es descriu a continuació. En tercer lloc, les rúbriques deuen ser adaptables, el que deuria ferles fàcilment comprensibles i fàcils d'usar, i adaptatives. Les rúbriques d'avaluació se usen quant un expert determina el progrés pedagògic de un educand, mentre que les rúbriques formatives son fetes servir per els propis estudiants, per a traçar el seu progrés i identificar les deficiències escolars para a les que necessiten suport. Les rúbriques es deuen refinar i millorar de forma continuada, en un procés iteratiu i col·laboratori, fins que se arriba a un acord satisfactori, tant entre avaluadors como entre avaluadors i alumnes. Por això, es desenvoluparen mapes de assercions que il·lustren el mode en que la estratègia de expansió-contracció adapta les rúbriques al progres del aprenent de CAD, a la vegada que ajuden a comprendre les diferents dimensions de la rúbrica. Basant-se en els experiments amb les rúbriques de acoblaments, es evident que les xicotetes diferencies entre els instructors suggereixen que la rúbrica de acoblaments proposta es lo suficientment sofisticada com per a proporcionar una avaluació acumulativa imparcial del acompliment de l'alumne. En conseqüència, es pot afirmar amb confiança que els avaluadors poden usar-se indistintament sense sacrificar la precisió. No obstant, la rúbrica de acoblaments posseeix una eficàcia finita per a produir una autoavaluació formativa de les habilitats de acoblament CAD per a nous alumnes.Otey, JM. (2017). A Contribution to Conveying Quality Criteria in Mechanical CAD Models and Assemblies through Rubrics and Comprehensive Design Intent Quantification [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94627TESI

A Framework Using Tangible Interaction for Automatically Capturing and Embedding Design Intent in Parametric Models

The objective of this research is to address some of the challenges of parametric design associated with defining a model’s frameworks using mathematics and computer programming. This work proposes a tactile-based approach to automate the generation of such information. A design-based research method is implemented for this work, which involves developing research prototypes consisting of Tangible User-Interfaces (TUIs) to demonstrate and test the digital-physical workflow. Five prototypes were created each generating a type of information for setting up parametric models, including; linear and polynomial mathematical equations, algorithmic rules and seed configurations for a Cellular Automata (CA) component, geometric transformations (single and compound), and Non-Uniform Rational Basis Spline (NURBS) objects. During the progress of the work, prototypes were improved to include a higher level of automation by performing multiple and more complex modeling tasks. This research includes two levels of evaluation. The first is system correctness, which tests the prototypes for translating tangible interaction with design objects into modeling information. The second is a qualitative comparison between the developed method and the conventional parametric modeling approach using graph-based and/or text-based programming applications. The results of the research have shown the plausibility of the workflow and its potential benefits for parametric modeling practice and education. This work provides a proof-of-concept for a novel approach that translates design intents into mathematical and algorithmic modeling information for establishing parametric frameworks. The outcomes of this research include; detailed workflows describing algorithmic procedures for interpreting analog data, TUI specifications, and an overall theoretical framework of the method

An incremental constraint-based approach to support engineering design.

Constraint-based systems are increasingly being used to support the design of products. Several commercial design systems based on constraints allow the geometry of a product to be specified and modified in a more natural and efficient way. However, it is now widely recognised the needs to have a close coupling of geometric constraints (i.e. parallel, tangent, etc) and engineering constraints (Le. performance, costs, weight, etc) to effectively support the preliminary design stages. This is an active research topic which is the subject of this thesis. As the design evolves, the size of the quation set which captures the constraints can get very large depending on the complexity of the product being designed. These constraints are expected to be solved efficiently to guarantee immediate feedback to the designer. Such requirement is also necessary to support constraint-based design within Virtual Environments, where it is necessary to have interactive speed. However, the majority of constraint-based design systems re-satisfy all constraints from scratch after the insertion of a new design constraint. This process is time consuming and therefore hinders interactive design performance when dealing with large constraint sets. This thesis reports research into the investigation of techniques to support interactive constraint-based design. The main focus of this work is on the development of incremental graph-based algorithms for satisfying a coupled set of engineering and geometric constraints. In this research, the design constraints, represented as simultaneous sets of linear and non-linear equations, are stored in a directed graph called Equation Graph. When a new constraint is imposed, local constraint propagation techniques are used to satisfy the constraint and update the current graph solution, incrementally. Constraint cycles are locally identified and satisfied within the Equation Graph. Therefore, these algorithms efiiciently solve large constraint sets to support interactive design. Techniques to support under-constrained geometry are also considered in this research. The concept of soft constraints is introduced to represent the degrees of freedom of the geometric entities. This is used to allow the incremental satisfaction of newly imposed constraints by exploiting under-constrained space. These soft constraints are also used to support direct manipulation of under-constrained geometric entities, enabling the designers to test the kinematic behaviour of the current assembly. A prototype constraint-based design system has been developed to demonstrate the feasibility of these algorithms to support preliminary desig

Analyzing the Effects of Incentives and Model Attributes on CAD Model Creation and Alteration

Modern computer-aided design (CAD) systems have contributed significantly towards product development cycle time reduction and product quality improvement. To enhance the performance of CAD systems engineers must be able to create CAD models of conceptual designs quickly; at the same time CAD models must be easy to alter, so as to accommodate the rapid changes that the design undergoes through the lifecycle. However, there is no agreement in the way CAD models should be created to accomplish these goals. This work attempts to assess the effects of incentives on CAD model attributes during model creation and alteration; the effects of CAD model attributes on alteration are also investigated. Its aim is to derive prescriptions based on empirical evidence to improve CAD model creation and alteration efficiency. The CAD models under study are created by three sets of participants – students from a junior level CAD course, students from a senior level CAD course and experienced engineers involved in product development activities. The participants are incentivized to create and alter CAD models of designs they are provided with. The results indicate that upon removal of incentives, engineers (both students and professionals) tend to compromise on proper modeling procedures. Experts are quicker and adhere to commonly agreed correct modeling procedures during CAD model creation and alteration than students. The results also indicate that it is beneficial for alteration to construct a model with several simple features as opposed to a few complex features and that these features be fully constrained. Maintaining the traditional feature sequence improves the perception of the model. The retention and alteration of features (as opposed to deletion) is also shown to be positively correlated with model perception ratings