Ángel Fernández

Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript.

The Influence of Different Recycling Scenarios on the Mechanical Design of an LED Weatherproof Light Fitting

This paper analyzes the high relevance of material selection for the sustainable development of an LED weatherproof light fitting. The research reveals how this choice modifies current and future end of life scenarios and can reduce the overall environmental impact. This life cycle assessment has been carried out with Ecotool, a software program especially developed for designers to assess the environmental performance of their designs at the same time that they are working on them. Results show that special attention can be put on the recycling and reusing of the product from the initial stages of development.

Environmentally Conscious Polishing System Based on Robotics and Artificial Vision

Polishing process is one of the manufacturing issues that are essential in the production flow, but it generates the major amount of defects on parts. Finishing tasks in which polishing is included are performed in the final steps of the manufacturing sequence. Any defect in these steps impliesrejection of the part, generating a big amount of scrap and generating a huge amount of energy consumption, emission, and time to manufacture and replace the rejected part. Traditionally polishing process has not evolved during the last 30 years, while other manufacturing processes have been automated and technologically improved. Finishing processes (grinding and polishing), are still manually performed, especially in freeform surface parts, but to be sustainable some development and automation have to be introduced. This research proposes a novel polishing system based on robotics and artificial vision. The application of this novel system has allowed reducing the failed parts due to finishing process down to zero percent from 28% of rejected parts with manual polishing process. The reduction in process time consumption, and amount of scrapped parts, has reduced the energy consumption up to 30% in finishing process and 20% in whole manufacturing process for an injection moulded aluminium part for automotive industry with high production volumes.

Surface Roughness Evolution Model for Finishing Using an Abrasive Tool on a Robot

The polishing process is the final step in the manufacturing workflow for many parts and tools. While previous tasks have evolved technically, the finishing of freeform surfaces is still effected mostly by hand. Many parts are rejected because no control of the process is possible. The main problems are geometrical shape deviations and no repeatability of the process. A new methodology has been developed for the passes of the abrasive on the polished part. This research focusses on the feasibility of robotic polishing and the development of a new evolution model pertaining to the surface roughness for an abrasive tool mounted on a spherical robot. The polishing principle is mechanic and based on dry friction. The tool is multilayered with a compressive foamed core. The combination of rotational and translational movement requires the creation of a model that can predict the footprint on the polished surface. The mathematical model developed for the evolution model permits for making a prediction of the final surface quality in the function of the programmed polishing parameters. Furthermore, the model described allows for setting up polishing parameters in order to reach a desired final roughness with less than 15% deviation. Repeatability is assured and polishing time is reduced down to 1/5 of manually effected procedures.

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.

Influence of Packing Phase Parameters in the Optimization of Mechanical, Weight Reduction and Dimensional Properties of Microcellular Foaming Injection Molding of Polypropilene

Microcellular foaming of injected plastics offers the possibility to manufacture parts with reductions in costs and weight if compared with conventional injection molding. For this reason there is an increasing interest in challenging applications such as HEV (hybrid and electrical vehicles) and lightweight material applications in general. Complexity of microcellular injection molding is very high because the final properties of the material obtained depend largely on the processing conditions and these in turn unalterable factors such as mold design and manufacturing. The shrinkage of the molded part must be applied as an oversize of the mold cavity in the design phase. Shrinkage of a microcellular foam depends on the reduction of foam density. Moreover, the piece is designed to get a mechanical performance and meet the dimensional tolerances. Knowing that the reduction of foam density implies a reduction of the mechanical properties and influences the final piece dimensions the conclusion is that the microcellular injection process has a very small process window to fit all these factors. This research focuses on two objectives. First is the variation of post-molding shrinkage in terms of reduction of weight to determine the process window. Second is the determination of mechanical properties which do not show a proportional reduction but exponentially with weight reduction components. The results obtained with a 750 Tons. injection moulding machine equipped with a MuCell plastication unit and a large spiral mold have shown small variations in the dimensions for a predetermined process window and smaller reduction of mechanical properties with weight reductions for 20% talc filled polypropylene. The goal of this applied research is that all experiments have been developed with scaled-industry tools (large injection molding machine, Mucell unit and mold and test parts) comparing with conventional injection molding.

Methodology to Analyze the Influence of Microcellular Injection Molding on Mechanical Properties with Samples Obtained Directly of An Industrial Component

Microcellular injection molding is a process that offers numerous benefits thanks to the internal structure generated, thus many applications are being arising in different fields, especially home appliance. In spite of it, when changing the manufacturing process of a component from conventional injection molding to microcellular injection molding, it is necessary to ensure the mechanical properties of the component. In this paper a study of the mechanical behavior of samples obtained directly from a manufactured component both by conventional injection molding and microcellular injection molding is carried out. This kind of samples take into account the process conditions under the final component is processed and the influence of these conditions on the mechanical properties. For this purpose special devices have been developed taking into account the characteristics of the component and the samples obtained. An X-ray 3D computed tomography is also carried out to validate the internal structure of the microcellular injection molded component. Tensile properties are reduced between 20–22% regarding flow direction when using microcellular injection molding. Impact properties are reduced up to 27%. However, flexural properties reduction for samples processed by microcellular injection is only 6.8%, so microcellular injection molding arises as a very suitable process for components working under this kind of load. Molding and impact tests are carried out by using specially developed devices.

Lightweight Medium-Sized Parts Made of Foamed HDPE Processed via Extrusion Blow Moulding: Analysis of Parison Formation

The manufacturing of medium-sized hollow parts using a foamed high density polyethylene was studied using a conventional accumulator blow extrusion machine and a systematic capture of pictures during the parison formation. To fully monitor the parison formation, several experiments were carried out varying the chemical foaming agent content from 0 wt.% to 2 wt.% and increasing the push extrusion speed. Results pointed out greater wall thickness, diameter, and length of parisons with higher weight percentage of blowing agent and extrusion speed. A full experimental characterisation of parison dimensions was essential to assure a proper prediction of the blowing step. Information was used as input for modelling and simulations of the blowing phase of an industrial container. To validate the proposed methodology, a blow moulding process of a generic container was simulated using Ansys Polyflow v13 software and its finite element analysis which provided an accurate approximation of the wall thickness expected. Further real tests on the simulated container also demonstrated that, in those parisons with a 1 wt.% CFA concentration and higher blowing pressure, there was remarkable improvement on their packaging properties such as decreasing of the total weight of the container and an enhancement of its surface quality.

Surface Quality Improvement and Tool Footprint Analysis in a Robotic Grinding Cell

Finishing process (Grinding and Polishing), is still manually performed, specially in free form surface parts. This involves a series of remaining problems, mainly related with the geometrical shape of the finished part. In traditional manually finishing task, the final quality aspect of the part is the only parameter to be controlled. This supposes a lack in the quality parameter control, mainly in high level parts, as in automotive, aeronautics or mould making parts. Manual finishing has not any control about the amount of material removed, during finishing process, affecting this way to the final geometrical shape of the product. This is the reason why this investigation proposes an exhaustive research of the parameter influencing the finishing tasks, and defining a finishing methodology adapted for an automatic process executed by a spherical robot. Making it an automatic way, and controlling paths, tool, abrasive, and defining a mathematical model for the finishing process, final quality of the part and product will be optimized, from a quality point of view, at the same time process time and cost is reduced.

Influence of the Processing Conditions on the Mechanical Properties of PA 6 - Halloysite Nanotubes Nanocomposites for Injection Moulding

Nowadays polymer based nanocomposites are very interesting to manufacture products of less weight and higher mechanical properties and specific performance depending on the morphology of nanoscaled reinforcement. Most of these potential improvements are focused to the challenges newer products require like HEV (hybrid or electrical vehicles) for example. The development of these new products requires the full characterization of the rheological and mechanical behavior of the materials and the correct preparation of the raw material for further processing. As an example two nanocomposite blends were prepared letting down a masterbach of PA6+30% HNT (Halloysite nanotubes) to 3% and 6% of HNT content in a PA6 matrix of (BADADUR). The letting down process was developed in an extrusion-compounding machine (COPERION ZSK 26) and the rheological behavior was determined in a capillar rheometer obtaining the viscosity curves of the material needed for injection molding simulation. The products obtained were used for injection molding of test specimens in an electrical injection machine (JSW EL II 85). In addition, the letting down process was done directly in the injection machine in order to establish the relevance of the previous extrusion process. The probes obtained were analyzed by DSC and FTIR to determine the functional groups of the resultant product and SEM and TEM to determine the quality of the dispersion of the nanotubes. The probes were finally tested to determine its stiffness and tensile properties. The results showed the feasibility to develop parts made of nanocomposite with improved performance with scaled industry equipment with natural reinforcements..