María del Cristo González Marrero

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.

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.

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.

The Archaeology of the Early Castilian Colonialism in Atlantic Africa. The Canary Islands and Western Barbary (1478–1526)

Towards the end of the fifteenth century, the Crown of Castile decided to become directly involved in the conquest of the three Canary Islands which remained rebellious: Gran Canaria (1478–1483), La Palma (1492–1493) and Tenerife (1494–1496). This was the beginning of an authentic state-driven project of colonization that is traditionally considered to have been completed in 1526. Significantly, 1526 also marked the end of the Castilian attempts to colonize the neighbouring African coast, the Western Barbary.

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

New Development in Computer Aided Electroforming for Rapid Prototyping Applications

Electroforming enables metallic parts manufacturing with good mechanical properties and high level of accuracy and reproducibility. A thin metallic shell is deposited on a model and later released from it. There are several applications of electroforming combined with rapid prototyping: injection moulds, EDM electrodes, moulds for rotational moulding, complex metallic parts, etc. However the two main disadvantages of electroforming are the non uniform thicknesses distribution and high time of shell manufacturing. The paper focuses on a new development in order to achieve uniform thickness and otherwise a faster shell manufacturing. A new device and software have been developed, named Elecform3D™. The device is an automatic machine controlled by computer and assembled into the electroforming equipment. Otherwise the software not only controls the device but also simulates and calculates the optimal positions of the cathode based in the electrolytic parameters of the bath. The software recommends an automatic program of movements or allows the operator to decide another alternatives programs if necessary. Elecform 3D is an important step beyond electroforming so far. RP 3D printer combined with Elecform 3D is a cheaper alternative for high quality metallic parts manufacturing in comparison with SLS-SLM technologies or high speed machining, mainly for rapid tooling and even rapid manufacturing.© 2008 ASME

Design and Testing of Innovative Rotational Mould Heated by Thermal Fluid

Rotomoulded plastic parts have no internal stresses, as it is a process carried out at lower temperatures than injection moulding and no pressure is applied. The main disadvantage is the high cycle times needed. This paper focuses on reducing this cycle time and in producing a mould using standardized parts. For cycle time reducing, it is proposed to heat the mould by thermal fluid in continuous circulation; heat transfer processes have been studied for over 20 different configurations of the oil’s inlet – outlet, obtaining acceptable results with a manifold with 25 perforations in the front and rear faces. This configuration has been optimized by computational fluids dynamics, allowing reducing heating and cooling time and improving the energetic efficiency and the uniformity of heating. Design, simulations and testing of a 100 mm3 cube have been carried out in order to produce a standardized mould; this mould consists in some standardized parts and a nickel shell, obtained by rapid prototyping and electroforming process. This shell can be removed from the rest of elements in the mould, allowing thus to obtain parts with any other geometry just by changing the nickel shell. An experimental machine for testing has been developed as well.Copyright

Behaviour of Vacuum Casting Plastic Composites Under Different Treatments of Banana Fibres

Nowadays, the natural fibres market is having an important growth due to the commitment of contemporary society with the sustainable development that leads the natural resources preservation and the environment protection. Fibres from banana food wastes provide high mechanical properties related to other natural fibers such as flax, sisal, hemp, etc. The aim of the present research work is to compare different banana fibres processing in order to improve the matrix fibre adhesion and behavior of fibre under processing conditions. Simple Anova analysis has been implemented on four different formulations: 1. No fibre processing, 2. Alkaline processing with Caustic Soda (NaOH), 3 Maleic Anhydride, 4. Combination of Soda and Maleic Anhydride. Several samples of MTT 8040 resin, under vacuum casting, with silicone moulds, conditions, have been done. Mechanical properties and efficiency factors of adhesion fibre-matrix have been determined and compared.Copyright