A new way to produce conformal cooling channels by RPT for moulding blocks of the hybrid moulds

Prémio de melhor artigo com interesse para a indústria.Hybrid moulds are an increasingly considered alternative for prototype series or short production runs. In this solution of injection moulds the moulding elements (blocks or other inserts) are manufactured in alternative metallic materials or in synthetic materials. One of the main issues associated to the use of these alternative materials is their thermal behaviour. For instance, in order to allow uniformity in the cooling of the moulded part, and a significant cooling time reduction, conformal channels are recommended as an efficient solution. The layout of the channels should contour the geometry of the impression, and has to be easily implemented during the production of the moulding blocks. This paper reports on a case study involving the use of conformal cooling channels obtained in wax by 3D-impression. An injection hybrid mould of a simple geometry production was used for testing several possibilities of conformal cooling construction. The discussion of cure parameters of the epoxy-based composite resin that can have influence on the wax thermal properties is presented alongside with recommendations for the use of this rapid tooling technique

Is there any chance for polypropylene/clay nanocomposites in injection molding?

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Making an impact with nanocomposites

Nanoclays can improve the performance of injection-molded polypropylene components likely to be subjected to impact in servic

The use of a three-point support flexural test to predict the stiffness of anisotropic composite plates in bending

http://www.sciencedirect.com/science/journal/01429418Anisotropic polymeric matrix composite discs supported on three points were subjected to a non-destructive bending test to study their behaviour in complex flexural loading situations. The results show that the flexural behaviour of the composites depends on several factors, such as fibre orientation, laminate stacking, surface waviness and moulding temperature. The experimental data were compared with those obtained from the finite element program software Algor. Differences up to 13% were found between the experimental and simulated values of the flexural stiffness. In spite of that, it was concluded that the non-destructive test used is a useful tool to predict the behaviour of anisotropic composites and to validate the results obtained from computer FEM analysis

Rapid prototyping and tooling in the manufacture of mould elements for large parts

In the last two decades the advances in rapid prototyping and tooling (RPT) technologies made possible the use of materials alternative to steel in some mould components. They also have allowed novel fabrication strategies and new ways of thinking on the production of injection moulds for short series of plas-tics parts. These technologies induced a new generation of toolmaking techniques. In the scope of the devel-opment project Hybridmould 21 the pros and cons of some RPT technologies were studied to fabricate moulding blocks and inserts for hybrid injection moulds for large plastics parts. Essentially, the studies aimed at finding the best solution for quick production and compliance with specific product requirements, such as complex features, complex cooling layout and large size (around 1 m2) in short production series. This paper discusses the main advantages and disadvantages associated to a number of different RPT technologies for the manufacture of moulding element.Program QREN - ‘Concessão de Incentivos Financeiros no âmbito do Sistema de Incentivos à Investigação e Desenvolvimento Tecnológico’ (contract 2010/013307) – Project Hybridmould 2

The use of birefringence for predicting the stiffness of injection moulded polycarbonate discs

Polycarbonate discs were injection molded with different sets of molding conditions. The parameters studied were the flow rate, melt- and mold-temperature. The discs were subjected to three point support flexural tests. Those tests are specially intended for injection molded discs because of their inherent non-flatness. The through-thickness molecular orientation was assessed by birefringence measurements along and across the flow direction using the wedge method. This method is ideal to measure the birefringence of materials that are difficult to cut with a microtome. The through-thickness stiffness of the discs was calculated from the measured birefringence distributions. A composite model of the disc was used in the Algor finite element method (FEW package to simulate the flexural tests

Studies on the mouldability of structural foams in hybrid moulds

In the context of the research project Hybridmould 21, studies on the mouldability of structural foams using hybrid moulds have been carried out. Hybrid injection moulds are an increasingly considered alternative for prototype series or short production runs of large dimension parts. In this solution for injection moulds the moulding elements (blocks or other inserts) are manufactured in alternative metallic materials or in synthetic materials typically using rapid prototyping techniques. Structural foams, known since the 70s, are moulded by injection moulding without using the high pressures typically used in injection moulding. The formation of the structural foam results from the dispersed gaseous phase, which derives from the expansion of a chemical blowing agent usually compounded in a compatible masterbatch. In this project various thermoplastics and thermosets were used, namely, PP, ABS and PUR, us-ing a hybrid mould instrumented for the monitoring of temperature, pressure and expansion force. The mould-ing block was manufactured by vacuum casting of an epoxy composite. In this paper are mainly discussed the results obtained on liquid injection moulding polyurethane resins in the hybrid mould.QREN contract 2010/013307 – Project Hybridmould 2

Hybrid moulds : the use of combined techniques for the rapid manufacturing of injection moulds

"Virtual modeling and rapid manufacturing : advanced research in virtual and rapid prototyping : proceedings of the 2nd International Conference on Advanced Research and Rapid Prototyping, Leiria, Portugal, 28 September - 1 October, 2005 (VR@P 2005)". ISBN 0-415-39062-1Injection moulding is the major polymer processing technique. The mould is a key element of this process and its characteristics have a key importance on the parts produced. The fabrication of products with higher added value, especially in terms of production time and costs, is essential for the success of the mouldmaking industry within a global competitive environment. This paper presents the concept of hybrid mould, a recent concept for injection moulding of prototype and short series. Direct and indirect rapid tooling technologies can be used for the fabrication of these moulds. Hence, new design guidelines need to be defined to produce these moulds as well to assess its performance. Epoxy tooling and selective laser sintering are the two rapid tooling technologies explored to produce inserts for hybrid-moulds. This work studies the fabrication of hybrid-moulds through these rapid tooling technologies, as well its mechanical and thermal behaviour.(undefined

Fracture toughness of injection moulded organoclay reinforced polypropylene composites

The fracture behavior of polypropylene reinforced with different amounts of PP/50% organoclay masterbatch was studied. Test pieces were prepared using a two-gated hot runner injection mould. Morphology of final pieces was analyzed by polarized optical microscopy, Xray diffraction and transmission electron microscopy. Fracture toughness was evaluated under quasi-static conditions at different positions in the molded pieces. The brittle mode of failure of PP became more ductile with increasing the amount of clay. However, the midthickness region (core) of “ductile” samples underwent brittle fracture while the surface layers (skin) behave in a ductile way, exhibiting elongation, necking and ductile tearing, probably due to differences in thickness and crystalline structure found in skin layers of composite pieces. Different Fracture Mechanics approaches were applied to characterize the fracture behavior: fracture toughness initiation value was assessed by means of the stress intensity factor at 5% non-linearity, KIq, and fracture toughness propagation value was obtained by means of the propagation strain energy release rate, Gcp. It was found that fracture initiation neither depends on clay content nor on test piece location. On the other hand, clay reinforcement increased fracture propagation values away from weld line region. This toughening effect was found to be dependent on the clay content and reinforcement orientation induced by the processing technique

Impact behavior of injected PP/nanoclay parts

This work attempts to contribute to bridge the gap between scientific challenges and industrial stakes regarding PP/nanoclay composites. Pieces of nanocomposites were obtained by direct injection of commercial PP mixed with a commercial MB of PP with 50% of organoclay, with a double-gated hot runner mould, which produced mouldings with a weld line. The moulding microstructure was assessed by POM and XRD, while the distribution and exfoliation grade of clay was evaluated by TEM and XRD. The typical skin-core structure was found, with a skin thickness wider in bulk than in weld line zones. Regarding clay platelets mostly intercalated structures were seen. The impact properties at room temperature were assessed by means of tensile and biaxial tests. Properties were monitored at different sites of the mouldings. At the weld line zone less energy was consumed under tensile conditions and exhibited higher apparent impact toughness under biaxial conditions than the bulk zone. Visual inspection of biaxially impacted samples showed that the orientation of polymer molecules and clay platelets induced by melt flow prevailed, and the weld line was not the determinant of the toughness of the mouldings. An optimum in impact performance was found for moulding with 3% of clay, since at larger clay contents platelets agglomerated and acted as stress raisers