Procedimiento para el análisis automatizado de la manufactura de la pieza de plástico y del molde de inyección

El proceso de manufactura mediante moldes de inyección de plástico es uno de los métodos de producción más versátiles y extendidos para la fabricación de piezas de plástico. Actualmente, existe una amplia variedad de software tipo CAD/CAE/CAM para el análisis y diseño asistido de piezas de plástico y moldes de inyección. Sin embargo, estas herramientas comerciales aún requieren de interacción humana y acceso a información geométrica interna de la pieza de plástico vinculada a su modelo CAD. La presente tesis doctoral propone una metodología universal basada en algoritmos automatizados de tipo geométrico – experto que, mediante el análisis de la geometría discreta de la pieza de plástico (malla en formato discreto definida por los elementos notables nodos y facetas), mejore y optimice el proceso actual de análisis, diseño y dimensionamiento del molde de inyección, sin recurrir a técnicas heurísticas e interacción manual por parte del usuario.Plastic injection molding is one of the most versatile and widespread manufacturing process for the plastic parts manufacture. Nowadays, there is a wide variety of CAD/CAE/CAM type software for the analysis and aided design of plastic parts and injection molds. However, these commercial tools still require human interaction and access to internal geometric information (geometric features) of the plastic part linked to their CAD model. The present PhD thesis proposes a universal methodology based on automated geometrical - expert algorithms that, by means of the analysis of the plastic part discrete geometry (mesh in discrete format defined by notable elements nodes and facets), improve and optimize the current analysis, design and dimensioning process of the injection mold, without resorting to heuristic techniques and manual interaction by the user.Tesis Univ. Jaén. Departamento Ingeniería Gráfica, Diseño y Proyectos. Leída el 3 de mayo de 2019

A New Conformal Cooling System for Plastic Collimators Based on the Use of Complex Geometries and Optimization of Temperature Profiles

The paper presents a new design of conformal cooling channels, for application in collimator-type optical plastic parts. The conformal channels that are presented exceed the thermal and dynamic performance of traditional and standard conformal channels, since they implement new sections of complex topology, capable of meeting the high geometric and functional specifications of the optical part, as well as the technological requirements of the additive manufacturing of the mold cavities. In order to evaluate the improvement and efficiency of the thermal performance of the solution presented, a transient numerical analysis of the cooling phase has been carried out, comparing the traditional cooling with the new geometry that is proposed. The evolution of the temperature profile versus the thickness of the part in the collimating core with greater thickness and temperature, has been evaluated in a transient mode. The analysis of the thermal profiles, the calculation of the integral mean ejection temperature at each time of the transient analysis, and the use of the Fourier formula, show great improvement in the cycle time in comparison with the traditional cooling. The application of the new conformal design reduces the manufacturing cycle time of the collimator part by 10 s, with this value being 13% of the total manufacturing cycle of the plastic part. As a further improvement, the use of the new cooling system reduces the amount of thickness in the collimator core, which is above the ejection temperature of the plastic material. The improvement in the thermal performance of the design of the parametric cooling channels that are presented not only has a significant reduction in the cycle time, but also improves the uniformity in the temperature map of the collimating part surface, the displacement field, and the stresses that are associated with the temperature gradient on the surface of the optical part.This research work was supported by the University of Jaen through the Plan de Apoyo a la Investigación 2021-2022-ACCION1a POAI 2021-2022: TIC-159

A numerical and experimental study of a new Savonius wind rotor adaptation based on product design requirements

This paper presents the numerical-experimental study carried out on a new rotor adapted from a Savonius rotor. Aesthetic, ergonomic and functional requirements have been incorporated into it in order to be part of sustainable consumer products. The new rotor consists of a parametric model adaptable to the dimensions and geometry of the products which it will be part of. A set of translation, symmetry, rotation and scaling operations have been applied to the bucket sections of the Savonius rotor by means of transforming the initial cylindrical buckets into topological surfaces with an organic shape. The new modified Savonius rotor and the conventional Savonius with the same Aspect Ratio have been tested in an open jet wind tunnel in order to verify the influence level of product design parameters on rotor performance, in terms of power coefficient, torque coefficient and mechanical power generated. Experimental tests have been carried out for Reynolds values in the range of [3,430·104 and 1,419·105]. A numerical analysis using an incompressible unsteady Reynolds average Navier Stockes model has been validated by means of the experimental results. Experimental and numerical results coincide with a 3.5% error. The behavior of the turbine has been analyzed by varying the angle of rotation for the sections of its buckets. Using a rotation angle of 45 ° the power coefficient values improve by 32% compared to the values obtained using an angle of 0 °. The rotor has been dimensioned for its application in a patented consumer product of small dimensions and requirements of lateral accessibility to its interior. Under these limited conditions the rotor meets the small-scale energy requirements of the product. The new rotor is designed as an aid to the energy consumption of the product in which it is incorporated, maintaining the advantages of a conventional Savonius rotor as self-starting, easy manufacture and maintenance, obtaining at the same time a product that sells better, is more able to integrate into its environment and is customizable for the consumer.This work has been supported by the University of Jaen through the project titled ”Diseño de un bastón ecológico de senderismo generador eólico hidráulico” Project Code (AC20/2015-12) and (R1A7/2017). The authors would like to thank the Mechanical Engineering Departmentat Jaen University for using the wind tunnel to achieve the experimental study

A new method for the automated design of cooling systems in injection molds

This paper presents a new method for the automatic design of the cooling system in injection molds, based on the discrete geometry of the plastic part. In a first phase the new algorithm recognizes the discrete topology of the part, obtaining its depth map and detecting flat, concave regions and slender details which are difficult to cool. The algorithm performs an automatic analysis of the heat transfer, taking into account functional parameters, in order to guarantee a uniform cooling of the part. Based firstly on the limit range distance from which the horizontal straight channels lose cooling effectiveness and secondly on the depth map data, the algorithm provides an optimal layout for the cooling system of the part by adapting it to its geometry. By means of adapting the precision of the algorithm to the molded geometry, both horizontal straight channels for low concavity areas and baffle matrixes for concave regions are used. In a second phase, the parameters of the cooling system such as channel diameter, channel separation etc, are dimensioned by means of genetic optimization algorithms. A second genetic optimization algorithm ensures uniformity and balance in the layout of the cooling system for the plastic part. The result is the design of the cooling system for the plastic part with the same performance as the conformal system. A constant distance between the cooling channels and the part surface is maintained, and at the same time the manufacturing of the mold using CNC techniques and traditional metal materials could be achieved. Complementarily, the algorithm performs an interference analysis with other parts of the mold such as the ejection system. The method does not need a subsequent CAE analysis since it takes into account functional and technical parameters related to heat transfer in its design, thus ensuring its functionality. The algorithm is independent of the CAD modeler used to create the part since it performs a recognition analysis of the part surfaces, being able to be implemented in any CAD system. The data obtained in the design can be used additionally in later applications including the automated design of the injection mold.This work has been supported by the Consejeria de Economia, Innovación, Ciencia y Empleo (Junta de Andalucia-Spain) through the project titled “A vertical design software for integrating operations of automated demoldability, tooling design and cost estimation in injection molded plastic parts. (CELERMOLD)” (Project Code TI-12 TIC 1623). The authors would like to thank the reviewers for comments that improved the exposition

Experimental and Numerical Analysis for the Mechanical Characterization of PETG Polymers Manufactured with FDM Technology under Pure Uniaxial Compression Stress States for Architectural Applications

This paper presents the numerical and experimental analysis performed on the polymeric material Polyethylene Terephthalate Glycol (PETG) manufactured with Fused Deposition Modeling Technology (FDM) technology, aiming at obtaining its mechanical characterization under uniaxial compression loads. Firstly, with the objective of evaluating the printing direction that poses a greater mechanical strength, eighteen test specimens were manufactured and analyzed according to the requirements of the ISO-604 standards. After that, a second experimental test analyzed the mechanical behavior of an innovative structural design manufactured in Z and X–Y directions under uniaxial compression loads according to the requirements of the Spanish CTE standard. The experimental results point to a mechanical linear behavior of PETG in X, Y and Z manufacturing directions up to strain levels close to the yield strength point. SEM micrographs show different structural failures linked to the specimen manufacturing directions. Test specimens manufactured along X present a brittle fracture caused by a delamination process. On the contrary, test specimens manufactured along X and Y directions show permanent plastic deformations, great flexibility and less strength under compression loads. Two numerical analyses were performed on the structural part using Young’s compression modulus obtained from the experimental tests and the load specifications required for the Spanish CTE standards. The comparison between numerical and experimental results presents a percentage of relative error of 2.80% (Z-axis), 3.98% (X-axis) and 3.46% (Y-axis), which allows characterizing PETG plastic material manufactured with FDM as an isotropic material in the numerical simulation software without modifying the material modeling equations in the data software. The research presented here is of great help to researchers working with polymers and FDM technology for companies that might need to numerically simulate new designs with the PETG polymer and FDM technology.This research was funded by the University of Jaen grant number [ACCION1 PAIUJA2019-20: TIC-159] through the Research Support Plan 2019-2020. The APC was funded by the University of Jaen

A numerical and experimental study of the compression uniaxial properties of PLA manufactured with FDM technology based on product specifications

This paper presents a numerical and experimental study of the compression uniaxial properties of PLA material manufactured with FDM based on product specifications. A first experimental test in accordance with the requirements and conditions established in the ISO 604 standard characterizes the mechanical and elastic properties of PLA manufactured with FDM technology and product requirements in a uniaxial compression stress field by testing six specimens. A second experimental test allows analyzing the structural behavior of the industrial case, evaluating the compression stiffness, the compression yield stress, the field of displacements and stress along its elastic area until reaching the compression yield stress and the ultimate yield stress data. To improve the structural analysis of the case study, a numerical validation was carried out using two analytical models. The first analytical model applies an interpolation procedure to the experimental results of the tested specimens in order to characterize the uniaxial tension-compression curve versus the nominal deformations by means of an 8-degree polynomial function. The second model defines the plastic material as elastic and isotropic with Young's compression modulus constant and according to the guidelines established in ISO standard 604. The comparison between experimental tests and numerical simulation results for the study case verify that the new model that uses the proposed polynomial function is closer to the experimental solution with only an 0.36% error, in comparison with the model with Young's compression modulus constant that reaches an error of 4.27%. The results of the structural analysis of the mechanical element indicate that the elastic region of the plastic material PLA manufactured with FDM can be modeled numerically as an isotropic material, using the elastic properties from the experimental results of the specimens tested according to ISO standard 604. In this way it is possible to characterize the PLA FDM material as isotropic, obtaining as an advantage its easy definition in the numerical simulation software as it does not require the modification of the constitutive equations in the material database. SEM micrographs have indicated that the fracture of the failed test specimens is of the brittle type, mainly caused by the separation between the central plastic filament layers of the specimens. The results presented suggest that the use of FDM technology with PLA material is promising for the manufacture of low volume industrial components that are subject to compression efforts or for the manufacture of components by the user.This work has been supported by the University of Jaen through the project titled ” Design of a mechanical plastic device for the displacement of collection sheets for olive harvesting” Project Code (AC20/2016-10) and (ID228-R2 A8 2018)

A new hybrid method for demoldability analysis of discrete geometries

In this paper, a new method for demoldability automatic analysis of parts to be manufactured in plastic injection is presented. The algorithm analysis is based on the geometry of the plastic part, which is discretized by a triangular mesh, posing a hybrid discrete demoldability analysis of both the mesh nodes and facets. A first preprocessing phase classifies mesh nodes according to their vertical dimension, assigning each node a plane perpendicular to the given parting direction. By selective projection of facets, closed contours which serve as the basis for calculating the demoldability of the nodes are created. The facets are then cataloged according to demoldability nodes that comprise demoldable, non-demoldable and semi-demoldable facets. Those facets listed as semi- demoldable are fragmented into demoldable and non-demoldable polygonal regions, causing a redefinition of the original mesh as a new virtual geometry. Finally, non-demoldable areas are studied by redirecting the mesh in the direction of the sliding side, and again applying the processing algorithm and cataloging nodes and facets. Resoluble areas of the piece through mobile devices in the mold are obtained. The hybrid analysis model (nodes and facets) takes advantage of working with a discrete model of the plastic part (nodes), supplemented by creating a new virtual geometry (new nodes and facets) that complements the original mesh, providing the designer not only with information about the geometry of the plastic piece but also information on their manufacture, exactly like a CAE tool. The geometry of the part is stored in arrays with information about their manufacture for use in downstream applications.This work has been supported by the Consejeria de Economia, Ciencia y Empleo (Junta de Andalucia—Spain) through the project titled ‘‘A vertical design software for integrating operations of automated demoldability, tooling design and cost estimation in injection molded plastic parts. (CELERMOLD)’’ (Project Code TI- 12 TIC-1623). The authors would like to thank the reviewers for comments that improved the exposition

New Procedure for BIM Characterization of Architectural Models Manufactured Using Fused Deposition Modeling and Plastic Materials in 4.0 Advanced Construction Environments

This paper presents a new procedure for the building information modeling (BIM) characterization of structural topologies manufactured with plastic materials and fused deposition modeling (FDM) additive technology. The procedure presented here transforms the architectural geometry into an expanded three-dimensional model, capable of directly linking the topology of the plastic structure with the technological, functional and economic requirements for working in advanced construction 4.0 environments. The model incorporates a new algorithm whose objective is to recognize the topological surface of the plastic structural part obtaining in a fully automated way the FDM manufacturing time as well as the manufacturing cost. The new algorithm starts from the voxelized geometrical surface of the architectural model, calculating the manufacturing time from the full geometric path traveled by the extruder in a voxel, the extruder’s speed, the print pattern and the layer height. In this way it is possible to obtain a complete digital model capable of managing and analyzing the plastic architectural object in an advanced BIM 4.0 environment. The model presented in this paper was applied to two architectural structures designed for a real urban environment. The final structural geometries have been obtained through topological processes in order to reduce the raw plastic manufacturing material and to improve the plastic structure strength. The architectural elements have been validated structurally by the means of numerical simulations, following the scenario of loads and boundary conditions required for the real project. The displacement maps point to a maximum value of 0.5 mm according to the project requirements. The Von Mises stress fields indicate maximum values of 0.423 and 0.650 MPa, not exceeding in any case the tensile yield strength of the thermoplastic material

A New Conformal Cooling Design Procedure for Injection Molding Based on Temperature Clusters and Multidimensional Discrete Models

This paper presents a new method for the automated design of the conformal cooling system for injection molding technology based on a discrete multidimensional model of the plastic part. The algorithm surpasses the current state of the art since it uses as input variables firstly the discrete map of temperatures of the melt plastic flow at the end of the filling phase, and secondly a set of geometrical parameters extracted from the discrete mesh together with technological and functional requirements of cooling in injection molds. In the first phase, the algorithm groups and classifies the discrete temperature of the nodes at the end of the filling phase in geometrical areas called temperature clusters. The topological and rheological information of the clusters along with the geometrical and manufacturing information of the surface mesh remains stored in a multidimensional discrete model of the plastic part. Taking advantage of using genetic evolutionary algorithms and by applying a physical model linked to the cluster specifications the proposed algorithm automatically designs and dimensions all the parameters required for the conformal cooling system. The method presented improves on any conventional cooling system design model since the cooling times obtained are analogous to the cooling times of analytical models, including boundary conditions and ideal solutions not exceeding 5% of relative error in the cases analyzed. The final quality of the plastic parts after the cooling phase meets the minimum criteria and requirements established by the injection industry. As an additional advantage the proposed algorithm allows the validation and dimensioning of the injection mold cooling system automatically, without requiring experienced mold designers with extensive skills in manual computing

A New Conformal Cooling Design Procedure for Injection Molding Based on Temperature Clusters and Multidimensional Discrete Models

This paper presents a new method for the automated design of the conformal cooling system for injection molding technology based on a discrete multidimensional model of the plastic part. The algorithm surpasses the current state of the art since it uses as input variables firstly the discrete map of temperatures of the melt plastic flow at the end of the filling phase, and secondly a set of geometrical parameters extracted from the discrete mesh together with technological and functional requirements of cooling in injection molds. In the first phase, the algorithm groups and classifies the discrete temperature of the nodes at the end of the filling phase in geometrical areas called temperature clusters. The topological and rheological information of the clusters along with the geometrical and manufacturing information of the surface mesh remains stored in a multidimensional discrete model of the plastic part. Taking advantage of using genetic evolutionary algorithms and by applying a physical model linked to the cluster specifications the proposed algorithm automatically designs and dimensions all the parameters required for the conformal cooling system. The method presented improves on any conventional cooling system design model since the cooling times obtained are analogous to the cooling times of analytical models, including boundary conditions and ideal solutions not exceeding 5% of relative error in the cases analyzed. The final quality of the plastic parts after the cooling phase meets the minimum criteria and requirements established by the injection industry. As an additional advantage the proposed algorithm allows the validation and dimensioning of the injection mold cooling system automatically, without requiring experienced mold designers with extensive skills in manual computing.This research work was supported by the University of Jaen through the Plan de Apoyo a la Investigación 2019-2020-ACCION1 PAIUJA2019-20: TIC-15