Antonio N. Benítez

Predictability of Plastic Parts Behaviour Made from Rapid Manufacturing

One of the most important issues to resolve in parts manufactured from rapid manufacturing (RM) technologies is to know their behavior working under real conditions. Total quality manufacturing (TQM) is only possible if mechanical properties are well known in the design stage depending on the processing parameters. This work is mainly focused on testing of several samples made with different selective laser sintering (SLS) parameters and technologies. This procedure is the starting point to establish a basis for designing for RM and the standardization of RM testing. The experiments and the analysis of variance (ANOVA) analyzed the effects of several factors on mechanical properties. The SLS technologies were 3DSystem and EOS. The results show which factor has a large effect on the variables and the interaction between them. The conclusions are very useful for developing rules for designing (designing for RM) and creating new standard rules (ISO, AISI, and DIN) for RM materials and parts testing. The ANOVA gives a better knowledge of the effects of these factors and eliminates unimportant parameters.

Banana and Abaca Fiber-Reinforced Plastic Composites Obtained by Rotational Molding Process

Natural fibers can be used in rotational molding process to obtain parts with improved mechanical properties. Different approaches have been followed in order to produce formulations containing banana or abaca fiber at 5% weight, in two- and three-layer constructions. Chemically treated abaca fiber has also been studied, causing some problems in processability. Fibers used have been characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), optical microscopy, and single-fiber mechanical tests. Rotomolded parts have been tested for tensile, flexural, and impact properties, demonstrating that important increases in elastic modulus are achieved with these fibers, although impact properties are reduced.

Advantages of Fused Deposition Modeling for Making Electrically Conductive Plastic Patterns

There are many applications where electrically conductive plastic patterns are needed. The most usual way to make electrically conductive patterns is coating a plastic part by a thin layer of metal. It’s well known the different procedures for metalizing plastic parts but most of them aim to obtain either aesthetic or functional metallic coating with high level of adherence, finishing and electrical conductivity if necessary. This aim requires complex process and time expense, however in the present research work only electrical conductivity is needed. This particular requirement allows to develop a simplified process of coating adapted to a specific target: electroforming starting from rapid prototyping (RP) metalized parts. Additive technologies based on extrusion such as Fused Deposition Modeling(FDM) provide patterns or prototypes suitable to be metalized by electroless plating and to be used as patterns for making electroforming. A different behavior of ABS FDM parts has been found in terms of metalizing procedure. This paper is focused on the proposed simplified method of electroless plating for obtaining patterns with high level of electrical conductivity and reproducibility of original RP plastic part.

Rapid prototyping applied to a new development in moulds for rotational moulding

The aim of this work has been to adapt and apply the advantages of rapid prototyping and electroforming technologies to try to achieve an innovative mould design for rotational moulding. The new innovative design integrates an electroformed shell, manufactured starting from a rapid prototyping mandrel, with different designed standard aluminium tools. The shell holder enables mould assembly with high precision manufacture of a shell in a few minutes. The overall mould cost is significantly decreased because it is only necessary to manufacture one or two shells each time; however, the rest of the elements of the mould are standard and usable for an infinite number of shells, depending on size.

New lightweight optimisation method applied in parts made by selective laser sintering and Polyjet technologies

The continuous evolution of materials and technologies of additive manufacturing has led to a competitive production process even for functional parts. The capabilities of these technologies for manufacturing complex geometries allow the definition of new designs that cannot be obtained with any other manufacturing processes. An application where this capability can be exploited is the lightening of parts using internal structures. This allows to obtain more efficient parts and, at the same time, reduce the costs of material and manufacturing time. A new lightweight optimisation method to optimise the design of these structures and minimise weight while keeping the minimal mechanical properties is presented in this paper. This method is based on genetic algorithms, metamodels and finite element analysis (FEA). This combination reduces the number of FEA simulations required during the optimisation process, thereby reducing the design time. This methodology is experimentally applied to a reference geometry oriented both for selective laser sintering (SLS) and Polyjet technologies. In both cases, an optimised and a non-optimised design are manufactured and tested in order to experimentally compare the stiffness results between them. The optimum design achieved a specific stiffness 72.82% higher than the non-optimised design in the SLS case study, and 3.14 times higher in the Polyjet case study.

Computer Cathodic Orientation Device: Functional Properties of Electroformed Nickel Shells

A new developed device, computer cathodic orientation system, was tested to analyze functional properties of electroformed shells of nickel. Several applications, such as rapid tooling, may require thickness uniformity, where the tool or mold is made by electroforming, starting from the 3D model. This system enables the programed movement of the cathode (the model) in front of the anode with the main objective of achieving thickness uniformity. Different strategies were carried out, and parameters such as thicknesses and flexural modulus were measured for each sample. Results showed the apparent influence of this apparatus on the thickness distribution and the flexural modulus. Either the rate of mean thickness or central thickness was improved when the strategy of modifying relative position took place. Also, the flexural modulus was influenced by the approach carried out in the sequence of movement.

Recycling of polymeric fraction of cable waste by rotational moulding

This study focuses on the mechanical recycling of polymeric waste that is produced in considerable amount from the cable industry. Every year large amounts of cables become waste; wires recycling has traditionally focused on metal recovery, while the polymer cover has just been considered as a residue, being landfilled or incinerated. Nowadays, increasingly restrictive regulations and concern about environment make necessary to reduce landfilling as much as possible. Main novelty of the study is that the material used in the research is a post-consumer material and the entire residual material is used, without a previous purification, in contrast with similar studies. Characterization of this residue was performed by thermal analysis, showing that the material is mainly made up of a heavy fraction (84% of the residue), which is not able to melt, fact what makes recycling more difficult. Once characterized, the material was ground, blended with virgin polyethylene and reprocessed by rotational moulding. The influence of the amount of residue and parts structure (1, 2 and 3 layers) was assessed, studying the mechanical behaviour of obtained parts (tensile, flexural and impact properties). It has been found that although mechanical properties get reduced with the increased amount of residue, up to a 35% of residue can be used without an important decrease in mechanical properties. On the other hand, the use of multiple layers in the mouldings allowed obtaining a better external appearance without compromising the mechanical properties.

Rotational Molding Applied to the Manufacturing of Blades of Small Wind Turbine

The small wind energy produces electric energy using power turbines below 100 kW. This technology allows the electrical supply in places isolated, generates energy of way distributed (distributed microgeneration) and permits to produce electricity in the points of consumption. The rotomoulding process is characterized to allow hollow plastics parts, with great surface quality, good homogeneity of thicknesses and suitable mechanical properties, all this with a great freedom of design and a wide variety of materials. The Department of Economy and Competitiveness from Government of Spain, inside the Subprogram INNPACTO 2012, resolved to grant the project of title Development of new blades made for rotational moulding for small wind generators (RotEos). The main purpose of this project is focused on getting a viable and cheaper process to manufacture the blades to small wind generators without reducing the efficiency of them, and trying to increase the competitiveness of these turbines. This research work presents the initial results obtained in the design of the blades, materials characterization and in the manufacturing process of these components.Copyright

Rapid Manufacturing Experience in Training

Rapid Manufacturing (RM) is considered as a set of innovative manufacturing technologies, many of which are in continuous development phases, and are becoming increasingly important to develop new products with high added value. Procesos de Fabricación research group, at the University of Las Palmas de Gran Canaria (ULPGC) is a founding member of the Spanish Rapid Manufacturing Association (ASERM), and has over ten years of expertise in research, transfer and training activities in these new technologies. ASERM, marked among its strategic objectives to promote and support RM training. As a result of this, the association participates in the European Project named Knowledge Transfer of Rapid Manufacturing (KTRM). Ingeniería de Fabricación educational innovation group (GIEIF) from ULPGC is working along other partners in this project and other training activities, because of the knowledge gained in these technologies.

An innovative electroforming process for oil heated rotational moulding tools

Rotational moulding is a method to produce hollow plastic articles. Heating is normally carried out by placing the mould into a hot air oven where the plastic material in the mould is heated. The most common cooling media are water and forced air. Due to the inefficient nature of conventional hot air ovens most of the energy supplied by the oven does not go to heat the plastic and as a consequence the procedure has very long cycle times. Direct oil heating is an effective alternative in order to achieve better energy efficiency and cycle times. This research work has combined this technology with new innovative design of mould, applying the advantages of electroforming and rapid prototyping. Complex cavity geometries are manufactured by electroforming from a rapid prototyping mandrel. The approach involves conformal heating and cooling channels, where the oil flows into a parallel channel to the electroformed cavity (nickel or copper). Because of this the mould enables high temperature uniformity with direct heating and cooling of the electroformed shell. Uniform heating and cooling is important not only for good quality parts but also for good uniform wall thickness distribution in the rotationally moulded part. The experimental work with the manufactured prototype mould has enabled analysis of the thermal uniformity in the cavity, under different temperatures.Copyright