Variation propagation of bench vises in multi-stage machining processes

Comunicación presentada a MESIC 2019 8th Manufacturing Engineering Society International Conference (Madrid, 19-21 de Junio de 2019)Variation propagation has been successfully modeled by the Stream of Variation (SoV) approach in multistage machining processes. However, the SoV model basically supports 3-2-1 fixtures based on punctual locators and other workholding systems such as conventional vises are not considered yet. In this paper, the SoV model is expanded to include the fixture- and datum-induced variations on workholding devices such as bench vises. The model derivation is validated through assembly and machining simulations on Computer Aided Design software. The case study analyzed shows an average error of part quality prediction between the SoV model and the CAD simulations of 0.26%

Obtención de gráficos tangibles mediante técnicas de Prototipado Rápido: el volumen como elemento compositivo de diseño

Se presentan los sistemas de producción de Prototipado Rápido, y se exponen algunas de sus aplicaciones prácticas en el ámbito de la realización de gráficos tangibles para su utilización por personas con discapacidad visual. Se refieren sintéticamente los procesos de fabricación más empleados en la actualidad para realizar este tipo de gráficos en relieve, y se analizan las distintas técnicas desarrolladas para la impresión de objetos físicos en volumen y su modo de realización con técnicas de diseño asistido por ordenador. Se describen los antecedentes y experiencias más significativos en este ámbito, y se plantean algunos aspectos de la teoría compositiva del diseño, que posibilitan un mejor aprovechamiento de estas técnicas.Rapid prototyping systems are described, along with practical applications in the production of tangible graphics for people with visual disability. The article summarises the most popular and recent manufacturing methods for this type of relief graphics and analyses the techniques developed to print physical objects in three dimensions, drawing from computer-assisted design software. A description of the most significant precedents and experiences in the field is followed by a discussion of the particulars of the «compositional theory of design» that facilitate more effective use of these techniques

Aplicación de la fabricación aditiva en la obtención de moldes para termoconformar gráficos tangibles orientados a personas con discapacidad visual

Los gráficos tangibles obtenidos mediante termoconformado de láminas de plástico son un tipo de producto muy común en los distintos ámbitos relativos a la educación y al acercamiento a la cultura de las personas con discapacidad visual, fundamentalmente para la realización de gráficos en relieve. Este tipo de gráficos tangibles termoconformados requieren de un molde para su fabricación, el cual suele ser caro para realizar series de producción media y grande. Las cada vez más habituales técnicas de fabricación aditiva, popularmente conocidas como «impresión en 3D», abren un amplio campo de posibilidades para la realización de gráficos tangibles de forma directa, rápida y económica. En este trabajo se presenta un estudio sobre la viabilidad técnica y económica de la aplicación de las técnicas de fabricación aditiva de bajo coste para la obtención de moldes para el termoconformado de gráficos tangibles.Use of additive manufacturing to obtain moulds to thermoform tactile graphics for people with visual disability. The raised graphics obtained by thermoforming plastic membranes are standard items in educational and cultural activities geared to people with visual disability. Manufacturing this type of thermoformed tactile graphics calls for moulds, which are fairly expensive for medium and large production runs. Increasingly popular additive manufacturing or «3D printing» techniques are paving the way for the direct, speedy, and inexpensive production of tactile graphics. This article discusses a study on the technical and economic feasibility of using low-cost additive manufacturing technology to produce moulds for thermoformed tactile graphics

Manufacturing variation models in multi-station machining systems

In product design and quality improvement fields, the development of reliable 3D machining variation models for multi-station machining processes is a key issue to estimate the resulting geometrical and dimensional quality of manufactured parts, generate robust process plans, eliminate downstream manufacturing problems, and reduce ramp-up times. In the literature, two main 3D machining variation models have been studied: the stream of variation model, oriented to product quality improvement (fault diagnosis, process planning evaluation and selection, etc.), and the model of the manufactured part, oriented to product and manufacturing design activities (manufacturing and product tolerance analysis and synthesis). This paper reviews the fundamentals of each model and describes step by step how to derive them using a simple case study. The paper analyzes both models and compares their main characteristics and applications. A discussion about the drawbacks and limitations of each model and some potential research lines in this field are also presented

Incorporation of form deviations into the matrix transformation method for tolerance analysis in assemblies

Comunicación presentada a MESIC 2019 8th Manufacturing Engineering Society International Conference (Madrid, 19-21 de Junio de 2019)Mathematical models for tolerance representation are used to assess how the geometrical variation of a specific component feature propagates along the assembly, so that tolerance analysis in assemblies can be carried out using a specific tolerance propagation method. Several methods for tolerance analysis have been proposed in the literature, being some of them implemented in CAD systems. All these methods require modelling the geometrical variations of the component surfaces: parametric models, variational models, DoF models, etc. One of the most commonly used models is the DoF model, which is employed in a number of tolerance analysis methods: Small Displacement Torsor (SDT), Technologically and Topologically Related Surfaces (TTRS), Matrix Transformation, Unified Jacobian–Torsor model. However, none of the DoF-based tolerance analysis methods incorporates the effect of form deviations. Among the non DoF-based methods, there are two that include form tolerances: the Vector Loop or Kinematic method and the Tolerance Map (T-Map) model, although the latter is still under development. In this work, a proposal to incorporate form deviations into the matrix transformation method for tolerance analysis in assemblies is developed using a geometrical variation model based on the DoF model. The proposal is evaluated applying it to a 2D case study with components that only have flat surfaces, but the proposal can be extrapolated to 3D cases

Design and implementation of a function block-based holonic control architecture for a new generation flexible manufacturing system

In this research work a control architecture which gives response to the requirements of new generation of flexible manufacturing systems in terms of flexibility, reconfigurability, robustness and autonomy is designed and implemented. To do so the main principles of the Holonic Manufacturing paradigm are applied using the IEC61499 function block (FB) technology. Unlike other similar research proposals, in this work FBs are not relegated to low-level control but are used to model manufacturing execution and control high-level control tasks. This is done with the objective of evaluating the viability of using FBs to develop holonic architectures in comparison to more established technologies like multi-agent systems. Moreover, the proposed control architecture also focuses on better integrating and exploiting the products’ information to enhance its flexibility and adaptability. For this STEP-NC (ISO14649) is used to model richer process plans which include manufacturing alternatives and could be easily integrated in the control itself

Design of a machine to rectify ceramic tiles for laboratory tests

Ponència presentada a 9th Manufacturing Engineering Society International Conference (MESIC 2021) 23rd-25th June 2021, Gijόn, SpainThe tile rectification process, also called squaring, consists of machining the edges of the tile to make them straight, parallel two by two and perpendicular to the other two in addition to controlling the size of the tile (calibrating). The current industrial lines are based on multiple heads (abrasive wheels) where the characterization of the process in terms of product quality and power consumption is hard to be conducted. In this work we present a laboratory machine equipped with a single grinding wheel to be used for testing and simulating the working conditions of a conventional rectification tile. The specifications of the machine that are required and the analysis of the different functional systems designed (clamping and motion, cutting, cooling, structure/enclosure, and electrical/control system) is reported. This machine may lead researchers to characterize the rectification process and propose actions for improving the efficiency and the sustainability of the industrial process

Influencia de los defectos geométricos en la superficie de contacto de un disipador de calor, orientado a la asignación de sus tolerancias de fabricación

Comunicación presentada en el XXI Congreso Nacional de Ingeniería Mecánica, celebrado en Elche en Noviembre de 2016.Las desviaciones de la geometría real en los componentes fabricados respecto de la geometría ideal tratada durante el diseño provocan la aparición de anomalías durante el funcionamiento de componentes ensamblados, siendo necesario limitar estas desviaciones mediante una apropiada síntesis de tolerancias (su especificación y la asignación de sus valores) de modo que se garantice la funcionalidad. Esta síntesis de tolerancias se deberá llevar a cabo efectuando un estudio detallado de cómo las desviaciones de fabricación afectan a la función, y asignando valores de las tolerancias atendiendo a criterios de capacidad y de costes de fabricación. Sin embargo, las relaciones entre el valor de las tolerancias y la calidad de funcionamiento no están siempre claras, por lo que las tolerancias se especifican asignando valores "habituales" o recomendados. Este proceder es frecuente y lleva a que se establezcan, con gran frecuencia, esquemas inconsistentes de tolerancias, que conducen a asignar valores para las tolerancias excesivamente estrechos. Como consecuencia de todo ello las piezas resultan caras y el propio funcionamiento del conjunto puede incluso no quedar garantizado. En este trabajo se analiza un sistema compuesto por un circuito integrado (CI) y un disipador de calor sobre él montado, estudiando cómo influyen los errores de fabricación presentes en la superficie del disipador en la capacidad de transmisión de calor en la zona de contacto entre CI y disipador, siendo el requisito funcional la transmisión de una cantidad de calor Q definida bajo unas condiciones de contorno ambientales. Como resultado se obtendrán las ecuaciones funcionales que ligan el RF con la tipología y magnitud de los errores, particularizado para el caso concreto de los defectos de rugosidad superficial en la superficie del CI

Estudio de los factores de transmisión de la variabilidad dimensional en la fabricación de baldosas cerámicas

Comunicación presentada en el XXI Congreso Nacional de Ingeniería Mecánica, celebrado en Elche en Noviembre de 2016.Uno de los principales problemas en la fabricación de pavimento en la industria cerámica es la variabilidad dimensional tras la cocción del producto cerámico que ocasiona la clasificación del producto en diferentes calibres o calidades dimensionales. A pesar del conocimiento extenso del proceso de fabricación de las baldosas cerámicas, pocos son los trabajos que buscan analizar las interacciones entre las diferentes etapas del proceso para estimar la variación dimensional final del producto. Un análisis global del proceso permitiría realizar modificaciones de puntos de operación en ciertas etapas para minimizar la variabilidad, o estudiar en detalle las etapas críticas del proceso sobre las que implementar acciones de mejora. Este trabajo muestra un estudio del proceso global de fabricación de las baldosas cerámicas y la aplicación de la metodología Stream-of-Variation para el modelado de la propagación de errores entre las diferentes etapas del proceso.Este trabajo ha sido financiado por la Generalitat Valenciana en su programa de ayudas a proyectos de I+D para grupos emergentes convocatoria 2015, proyecto GV/2015/091

Analysis of the hardness ratio effect on the tribological performance of NiCrBSi coating/debris particles using the Stribeck Curve

This work aims to propose an approach to estimate the final surface roughness as a function of the hardness ratio between coating and debris (Hpin/Hdebris = Hp/Hd) under lubricated conditions employing pin-on-disc configuration. Using this approach provides a better understanding and prediction of the lubrication regime (Stribeck Curve) compared with the traditional approach that uses the initial surface roughness. Our results demonstrate that a lower hardness ratio induces a higher friction coefficient and contributes to a marked increase in wear rate in lubricated conditions. To find an effective method for simulating the debris effect, four types of NiCrBSi powders were used as a source of debris: two metallic powders with a completely spherical morphology but different Cr concentrations and two other NiCrBSi (15.25%Cr) powders mixed with different concentrations 40 and 60% of ceramic, Zr + 7% Y2O3 (ZSP), composed of spherical particles morphology. Therefore, a set of four sources of debris material specimens were simulated by different types of particles with a similar size distribution but different average hardness. Each of these particles was dispersed in an oil lubricant. Observation of the worn surfaces using a rugosimeter and scanning electron microscope suggested that, together with the shape, size and number of debris, the hardness ratio must be considered when studying the tribological behavior of machine components. The proposed methodology may help to predict the variation in lubrication regime parameters (Stribeck curve) by controlling the hardness ratio.Funding for open access charge: CRUE-Universitat Jaume