Predictive Methodology for Quality Assessment in Injection Molding Comparing Linear Regression and Neural Networks

The use of recycled polypropylene in industry to reduce environmental impact is increasing. Design for manufacturing and process simulation is a key stage in the development of plastic parts. Traditionally, a trial-and-error methodology is followed to eliminate uncertainties regarding geometry and process. A new proposal is presented, combining simulation with the design of experiments and creating prediction models for seven different process and part quality output features. These models are used to optimize the design without developing additional time-consuming simulations. The study aims to compare the precision and correlation of these models. The methods used are linear regression and artificial neural network (ANN) fitting. A wide range of eight injection parameters and geometry variations are used as inputs. The predictability of nonlinear behavior and compensatory effects due to the complex relationships between this wide set of parameter combinations is analyzed further in the state of the art. Results show that only Back Propagation Neural Networks (BPNN) are suitable for correlating all quality features in a single formula. The use of prediction models accelerates the optimization of part design, applying multiple criteria to support decision-making. The methodology is applied to the design of a plastic support for induction hobs. Furthermore, this methodology has demonstrated that a weight reduction of 27% is feasible. However, it is necessary to combine process parameters that differ from the standard ones with a non-uniform thickness distribution so that the remaining injection parameters, material properties, and dimensions fall within tolerances

Sustainable supply chain management: The influence of disposal scenarios on the environmental impact of a 2400 L waste container

This paper analyzes the influence of the supply chain management on the environmental impact of a 2400 L waste disposal container used in most cities of Spain. The studied functional unit, a waste disposal container, made up mostly of plastic materials and a metallic structure, and manufactured in Madrid (Spain), is distributed to several cities at an average distance of 392 km. A life cycle assessment of four different scenarios (SC) has been calculated with the software EcoTool v4.0 (version 4.0; i+: Zaragoza, Spain, 2015) and using Ecoinvent v3.0 database (version 3.0; Swiss Centre for Life Cycle Inventories: St. Gallen, Switzerland, 2013). The environmental impact has been characterized with two different methodologies, recipe and carbon footprint. In order to reduce the environmental impact, several end of life scenarios have been performed, analyzing the influence of the supply chain on a closed-looped system that increases recycling. Closed loop management of the waste and reuse of parts allows companies to stop selling products and start selling the service that their products give to the consumers

Life cycle assessment of a plastic part injected with recycled Polypropylene: a comparison with alternative virgin materials

Plastics recycling is becoming a common action to reduce our products and processes'' environmental impact, and it is of the utmost importance to introduce circular economy strategies. However, for most of the different types of thermoplastics, recycling is not currently its usual end of life due to the technical difficulties in the sorting and recycling processes. This paper presents the complete life cycle assessment of an industrial component made with three different thermoplastics; two virgin thermoplastics typically used for similar parts in the market as Polyamide 6 and Polypropylene, and an alternative source of 100% recycled Polypropylene. All life cycle stages are included in the study. After carrying out the life cycle inventory, calculations of the environmental impact of each life cycle steps have been performed with ReCiPe 2016 EndPoint (H/A) v1.03/World and with IPCC 2013 GWP 100a v1.03 methodologies, comparing all three materials under the same conditions. A sensibility assessment has also been performed, calculating a worst-case scenario of the recycled material, and considering higher material acquisition distances. This study shows that recycled Polypropylene contributes to reducing the overall environmental impact of the component life cycle by 29.8% under ReCiPe, and by 42.8% under Carbon Footprint when compared to virgin Polypropylene. For the worst-case scenario, these reductions in the environmental impact of the component life cycle are also significant: 23.2% and 36.4%, respectively, showing that the use of recycled polymers is a key approach to reduce the environmental impact of plastic components

Influence of mechanical design on the evolution of the environmental impact of an induction hob

Purpose: This paper studies the influence of the mechanical design of five different induction hob generations (G1 to G5), which are currently installed in several million homes, on the evolution of their environmental impact. Methods: Life cycle assessment (LCA) has been applied using SimaPro 8.0.3.14 and EcoInvent v2.2 database. Samples of each design were obtained to generate a life cycle inventory. These induction hobs have been developed and produced in Zaragoza (Spain). The functional unit has been defined as all of the components influenced by the mechanical design of a cooktop with four induction hobs and a width of 60 cm, including every component except the electronic boards and the use phase, as they are not affected by the mechanical design. The limits of the LCA model include the production of the raw materials and energy, the manufacture and production processes, the distribution, and the end of life. Results and discussion: This study has revealed that the differences in mechanical design highly affect the environmental impact, especially in the environmental categories of abiotic depletion and human toxicity due to the consumption of copper, steel, and plastics. The manufacturing phase highly affects human toxicity, mainly due to the variation in PPS use. There is a decreasing tendency in the environmental impact from the first (G1) to the last generation (G5), as G5 causes the lowest burden in 8 out of 11 analysed categories. The different generations analysed in this paper show that the compact designs of induction hobs help to decrease the environmental impact, especially thanks to the reduction in wiring lengths. It is also important to enhance the wiring separation at the end-of-life phase, avoiding designs that hinder recycling processes. Conclusions: Compact designs and reduced wiring lengths help to reduce the environmental impact. The consumption of copper, steel, aluminium, and polymers creates considerable impact, although the end-of-life phase reduces the burden created by metals, thanks to recycling. Manufacturing processes such as injection moulding also produce a noteworthy impact, especially in ozone layer depletion due to the inclusion of solvents in EcoInvent’s injection moulding dataset. The impact caused by the distribution phase for this product is almost negligible in most categories

Influence of composition on the environmental impact of a cast aluminum alloy

The influence of alloy composition on the environmental impact of the production of six aluminum casting alloys (Al Si12Cu1(Fe), Al Si5Mg, Al Si9Cu3Zn3Fe, Al Si10Mg(Fe), Al Si9Cu3(Fe)(Zn) and Al Si9) has been analyzed. In order to perform a more precise environmental impact calculation, Life Cycle Assessment (LCA) with ReCiPe Endpoint methodology has been used, with the EcoInvent v3 AlMg3 aluminum alloy dataset as a reference. This dataset has been updated with the material composition ranges of the mentioned alloys. The balanced, maximum and minimum environmental impact values have been obtained. In general, the overall impact of the studied aluminum alloys varies from 5.98 ˆ 10 ´1 pts to 1.09 pts per kg, depending on the alloy composition. In the analysis of maximum and minimum environmental impact, the alloy that has the highest uncertainty is AlSi9Cu3(Fe)(Zn), with a range of ¿9%. The elements that contribute the most to increase its impact are Copper and Tin. The environmental impact of a specific case, an LED luminaire housing made out of an Al Si12Cu1(Fe) cast alloy, has been studied, showing the importance of considering the composition. Significant differences with the standard datasets that are currently available in EcoInvent v3 have been found

Clima escolar y problemas de asistencia: el papel mediador de la competencia académica e interpersonal del estudiante

A positive school climate promotes regular attendance through strong relationships, a sense of belonging, diversity promotion, clear rules, and safety, leading to improved relational and educational outcomes. This study explores how perceived academic and interpersonal competence mediate the relationship between school climate components and absenteeism, using Havik’s(2015) model. A cross-sectionalstudy of 539 Italian high school students employed structural equation modelling with latent variables to examine these mediations. Results indicated that perceptions of interpersonal competence mediated the relationship between Peer Connectedness ( =.16,p<.01) and Affirming Diversity ( =-.05, p<.05) with Truancy. Perceived academic competence mediated the relationship between School Connectedness and Subjective Health ( =-.12, p<.01), Truancy ( =-.14, p<.01), andSchool Refusal ( =-.14, p<.01). The findings highlight the importance of promoting a positive school climate and enhancing students’ competences to reduce absenteeism.Un clima escolar positivo promueve la asistencia regular a través de relaciones sólidas, un sentido de pertenencia, promoción de la diversidad, reglas claras y seguridad, lo que conduce a mejores resultados relacionales y educativos. Este estudio explora cómo la competencia académica e interpersonal percibida media la relación entre los componentes del clima escolar y el ausentismo, utilizando el modelo de havik (2015). Un estudio transversal de 539 estudiantes de secundaria italianos empleó modelos de ecuaciones estructurales con variables latentes para examinar estas mediaciones. Los resultados indicaron que las percepciones de competencia interpersonal mediaron la relación entre la conexión con los pares ( =.16, p<.01) y la afirmación de la diversidad ( =.05, p<.05) con el absentismo escolar. La competencia académica percibida medió la relación entre la conectividad escolar y la salud subjetiva ( =-.12, p<.01), el absentismo escolar ( =-.14, p<.01) y el rechazo escolar ( =-.14, p<.01). Los hallazgos resaltan la importancia de promover un clima escolar positivo y mejorar las competencias de los estudiantes para reducir el absentismo.&nbsp

Analysis of the Influence of Microcellular Injection Molding on the Environmental Impact of an Industrial Component

Microcellular injection molding is a process that offers numerous benefits due to the internal structure generated; thus, many applications are currently being developed in different fields, especially home appliances. In spite of the advantages, when changing the manufacturing process from conventional to microcellular injection molding, it is necessary to analyze its new mechanical properties and the environmental impact of the component. This paper presents a deep study of the environmental behavior of a manufactured component by both conventional and microcellular injection molding. Environmental impact will be evaluated performing a life cycle assessment. Functionality of the component will be also evaluated with samples obtained from manufactured components, to make sure that the mechanical requirements are fulfilled when using microcellular injection molding. For this purpose a special device has been developed to measure the flexural modulus. With a 16% weight reduction, the variation of flexural properties in the microcellular injected components is only 6.8%. Although the energy consumption of the microcellular injection process slightly increases, there is an overall reduction of the environmental burden of 14.9% in ReCiPe and 15% in carbon footprint. Therefore, MuCell technology can be considered as a green manufacturing technology for components working mainly under flexural load

Environmental assessment tool to analyse the presence of critical and valuable raw materials

The aim of this paper is show the software 'Sustainable Electronics' (SE), developed in the University of Zaragoza as an environmental impact assessment tool, specially developed to design components taking into account the presence of critical and valuable raw materials consumption; simulating environmental impact and measuring the overall raw material consumption, taking into account material composition of the electronic components. It considers raw material acquisition, manufacturing processes, transports and end of life. This software allows us to easily update and use the datasets provided by Life Cycle Inventory databases, such as, for example, EcoInvent, developed by the Swiss Centre for Life Cycle Inventories. The methodology has been tested through the software in an electronic board of a touch control used in an induction hob. As result, it has been obtained that there is a high consumption of materials such as copper, tin or aluminium

Simulación computacional del fenómeno de relajación de tensiones en polímeros compuestos termoplásticos

Se propone en este trabajo el desarrollo de una metodología que permita abordar el modelado del comportamiento de materiales de componentes de cocinas de inducción que trabajan bajo condiciones de deformación constante, tratando de optimizar la predicción del fenómeno de relajación de tensiones. Se presentan resultados de calibración del modelo inicial

Evaluación del impacto ambiental del proceso de reciclado de materiales plásticos.

El consumo de plástico a nivel mundial ha sufrido un aumento continuo desde la invención del mismo. Laflexibilidad que ofrece en cuanto a propiedades físicas, métodos de fabricación o coste lo convierten enuno de los materiales más útiles y flexibles a la hora de diseñar productos. Sin embargo, en las últimasdécadas el uso excesivo y el inadecuado tratamiento tras su fase de uso nos ha hecho enfrentarnos alproblema de la gestión de estos residuos.A la vez que el volumen de plástico acumulado en el mundo aumentaba, también lo ha hecho la concienciamedioambiental de la sociedad. Se ha promovido un cambio en el modelo económico y social que obligaa las empresas a hacer frente al reto de generar menos residuos y gestionar de la manera más eficienteposible los generados.El aspecto medioambiental llegó al diseño de producto con una metodología que buscaba disminuir elimpacto ambiental de los productos desde la misma fase de concepción de los mismos. El conocido como“Ecodiseño” propone adicionalmente, mediante diferentes enfoques, la valoración del impacto ambientalcomo un factor más sobre el que se puede influir en la fase de diseño. Algunos de estos enfoques pasanpor seleccionar materiales y procesos de fabricación con cargas ambientales menores a otras alternativasy seleccionar métodos de unión entre componentes que permitan una rápida y fácil separación yreciclabilidad.Esta tesis se centra en la evaluación ambiental del plástico reciclado y en el análisis de viabilidad de su usopara procesos industriales. El impacto ambiental se ha analizado de forma comparativa para una mismaunidad funcional que puede ser fabricada en distintos materiales de origen virgen y un material reciclado,de forma más concreta, buena parte de la tesis doctoral se ha centrado en el estudio de una pieza deplástico utilizada en encimeras de inducción cuyo principal objeto es el alojamiento de placas electrónicasy la gestión del cableado interno del aparato. El resultado, publicado en el artículo “Life Cycle Assessmentof a Plastic Part Injected with Recycled Polypropylene. A Comparison with Alternative Virgin Materials”,muestra la reducción del impacto desglosada en las diferentes etapas del ciclo de vida del producto. Elanálisis parte de la descomposición del proceso completo en fases y el estudio de todos los procesosllevados a cabo para recuperar desechos post-industriales de plástico. Este proceso se realiza hasta laobtención de material reciclado, cuyas características físicas son equiparables, según los resultados de lainvestigación, a las de materiales vírgenes.Esta reducción supone el 30% del impacto, según la metodología ReCiPe, para el caso de la sustitucióndirecta de un material virgen por otro reciclado. Se debe principalmente al descenso de los impactosasociados a la fabricación de la materia prima. Se puede afirmar, por tanto, que en un escenario en el quetécnicamente sea viable el uso de materiales reciclados, se obtendrá un mayor ahorro medioambiental alsustituir dichos materiales vírgenes por su correspondiente alternativa de fuentes recicladas.El análisis de las propiedades mecánicas del material reciclado comienza con la realización de unasimulación del proceso de inyección comparativa entre ambas fuentes de material para una pieza deplástico utilizado como soporte de electrónica y gestión de cableado en encimeras de inducción del grupoBSH. Para la caracterización de las propiedades mecánicas del material se requerían muestras inyectadascon dicho material en un molde ya existente. Para asegurar la factibilidad, se realizó una caracterizaciónreológica y posteriormente una simulación del proceso de inyección. El análisis de la granza demuestrauna mayor viscosidad en el material reciclado que, sin embargo, no afecta de forma considerable alproceso de moldeo por inyección. Los resultados fueron presentados en el 30º Congreso Europeo deModelado y Simulación (EMSS) de 2018 en Budapest, con el artículo titulado: “PROCESSABILITY ANALYSISOF AN INJECTED PART IN VIRGIN OR RECYCLED POLYPROPYLENE”Debido al origen post-industrial de los desechos y al proceso de reciclaje mecánico sufrido para llegar asu nuevo estado, el material reciclado sufre una serie de daños en su estructura interna, como elacortamiento de sus cadenas poliméricas, que pueden alterar, entre otros aspectos, su comportamientodimensional en piezas inyectadas o bien generar alabeos o deformaciones debido a las tensiones internas.En el artículo “Dimensional Stability and Process Capability of an Industrial Component Injected withRecycled Polypropylene” se analizan las variaciones dimensionales sufridas por un componente inyectadoen material reciclado sometido a diferentes ensayos térmicos y comparados con el material original. Secomprueba el efecto del aumento de viscosidad observado en el material reciclado, generando mayorcantidad de tensiones internas en la pieza analizada. Estas tensiones, liberadas ante la aportación deenergía en el calentamiento a diferentes temperaturas, provocan alteraciones dimensionales distintas enpiezas de diferentes materias primas. Esto se ve agravado por la geometría de la pieza por la que seobserva el efecto de la menor rigidez del material reciclado. La mayor contracción se obtiene en lasdimensiones afectadas por geometrías menos rígidas. Sin embargo, la variación dimensional, si bientiende a ser mayor en material reciclado, no es significativa a efectos prácticos, por lo que se hadeterminado viable la utilización de estos materiales para la pieza estudiada.También se realiza un estudio de la estabilidad del proceso de inyección para ambos materiales. Elresultado arroja la viabilidad de utilizar materiales reciclados, obteniendo parámetros aceptables de losvalores de Cp y Cpk en todos los casos. Sin embargo, sí se muestra una mayor variabilidad en las medidasobtenidas en materiales reciclados, estando los resultados de las muestras analizadas en material virgen,comprendidos en un rango de medidas menor.Por último, se analizan las propiedades mecánicas en base a muestras obtenidas a partir de piezasinyectadas en ambos materiales. De nuevo se analizan las propiedades consideradas de mayor interés(tensión de fluencia y módulo elástico) a tres diferentes temperaturas: temperatura ambiente, 50ºC y80ºC Estas temperaturas de análisis se han seleccionado por considerarse situaciones reales durante suetapa de almacenamiento previo a su ensamblaje, y en su etapa de uso.El resultado de éste análisis muestra una pérdida de propiedades del 22% del módulo elástico en elmaterial reciclado con respecto al material virgen y de ambos con respecto a sus fichas técnicas. Estadisminución, sin embargo, tiende a igualarse cuando el material se encuentra a temperaturas mayores,siendo el límite elástico in 13% mayor para el material virgen a 50º y de nuevo un 11% menor con respectoal material virgen a 80ºC.Por tanto, con que esta tesis doctoral se ha logrado evaluar la viabilidad técnica y ambiental del uso dematerial reciclado. Los resultados obtenidos han servido para introducir un PP reciclado en la producciónde encimeras de inducción.<br /