Thermoelectrical regulation of microinjection moulds

Microinjection is one of the major replication techniques for producing low cost micro parts. The small scale of the microinjection processes presents different challenges from those usually encountered in conventional injection moulding. One particular aspect, very important for part quality, is mould temperature control. In conventional injection moulding, the temperature control system is set to a fixed value during the injection cycle. In microinjection moulding such behaviour is not acceptable, which as lead to the development of “active” control temperature of the mould named “variotherm” systems. In the present paper a study will be presented for the implementation of thermo electric elements in dynamic temperature control of microinjection moulds and its impact on the process cycle time and part quality

Yield, impact and fracture performance of injected metallic looking polypropylene parts

Innovation, cost and weight reduction are some factors for the replacement of metals by plastics. Plastics continue to offer attractive solutions for design engineers. The metallic effect obtained by incorporation of metal particles in polymers by injection moulding has the advantage of eliminating postprocessing techniques reducing production cost and time. Nevertheless, undesired defects in the final appearance of parts are common. These defects occur due to inhomogeneous orientation and anisotropy of the metal particles. Very few studies are reporting the influence of metallic particles on the morphology development of PP parts. Therefore, this study is focused on the production of parts made of PP/metallic pigments (aluminium) by injection moulding in order to understand the influence of metallic particles on the aesthetic, morphological and mechanical properties of the parts

Isolation of hydrodynamic parameters for the fibre length attrition in injection-moulded short-fibre polymer composites

A comprehensive study of the fibre breakage mechanisms during mould filling in injection moulding of short-fibre polymer composites requires the isolation of the main parameters promoting fibre length attrition. In this work, hydrodynamic parameters such as injection flow rate and residence time in the range of injection moulding were isolated, and their effect on fibre length attrition was studied. Fibre breakage was quantified by means of a capillary rheometer attached to an injection moulding machine minimising fibre-equipment interactions. Fibre breakage increased linearly as a function of injection flow rate in the range of 30–120 cm3.s−1. It was also found that residence time in the order of milliseconds had a significant effect on fibre breakage. The results shown that longer fibres had less breakage probability, which contradicts the buckling failure theory for brittle fibres in a simple shear flow. This result was attributed to the similar rotation period of the fibres in comparison with the test residence times.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the “Universidad Nacional de Mar del Plata” (ING560/19, 15/G575) and the “Agencia Nacional de Promoción Cient´ıfica y Tecnológica” (PICT-2014-3228, PICT-2017-2458

Simulación mediante ordenador de movimientos bidimensionales en medios resistentes

We have accomplished a simulation program of mechanics; it is developed in laboratory practice by students in their first years of physics studies ata University level. Its aim is a better understanding of the influence of the variable forces of friction in bidimensional movements. We have verified the effectiveness of this teaching method through the evaluation of the students' progress during the courses in which we have carried out this practice

Characterization of microinjection moulded composites of polyamide 6 and carbon nanotubes

Microinjection molding is a powerful technology in micro-manufacture, providing millimeter scale parts at large scale production rate. In order to produce homogeneous composite parts, good dispersion of the nanoreinforcement in the polymer matrix is required. In the present work the carbon nanotube (CNT) reinforcement was dispersed in polyamide 6 (PA6) using a mini twin-screw extruder. Nanocomposites were prepared with different compositions (1% and 4,5%) of pure CNT (p-CNT) and functionalized CNT (f-CNT).Fundação para a Ciência e Tecnologi

Spectral Bandwidth and WEC Performance Assessment

This paper investigates the dependency of wave energy conversion on the spectral bandwidth of sea-states. To this aim, the performance of an axisymmetrical Wave Energy Converter is assessed in the frequency domain by using a stochastic model in two far different wave climates (Portugal and North Sea) both represented by more than 23000 energy spectral densities obtained from measurements. The correlation between the performance and various bandwidth parameters found in the literature is observed. Then, refined methods for predicting the long-term converted wave energy based on wave statistics including spectral bandwidth are compared to more common procedures and conclusions are drawn

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