Investigation of the Integrity of aC:H Coatings on Stainless Steel Micro-Moulds during Thermal Cycling

Micro-injection moulding (µIM) is a key technology for scaling down larger geometry components and can include functional features at the micrometre scale and as far as the sub-micrometre length scale. Thermal cycling of amorphous hydrogenated carbon (aC:H) coated Stainless Steel (SS) has been investigated to simulate long-term micro-injection moulding (µIM) wearing and damage. Micro indentations and cracks were made into the mould and predictions of the crack behaviour were made using thermal expansion models. Validation of the results was performed with multiple heating and cooling cycles along with hardness measurements of the damage to the coating. The undamaged surfaces showed no major deformation but the cracks were shown to propagate and change in behaviour. The first two heat cycles of the testing had the most significant effect on the substrate with varying thermal expansions of materials being the main cause. The aC:H is shown to have excellent properties for mould tool applications but delamination could occur in areas susceptible to damaged and periodic surface inspection will be required preserve tool life

Carbon-based coatings for the modern plastics industry

Doutoramento em Engenharia MecânicaEm Portugal, uma das indústrias com maior expressão e competitividade é, sem dúvida, a indústria de moldes. A aposta em produtos de maior valor acrescentado e em nichos de mercado tem sido fomentada e extremamente valorizada. É neste contexto que surge a micromoldação. Uma tecnologia de produção, também cíclica, com todas as vantagens da moldação por injecção, que abre novos mercados, mas que requer conhecimento tecnológico especifico nas diferentes vertentes: equipamento, processo, ferramentas. Neste contexto, para as ferramentas de moldação urge solucionar problemas tecnológicos que se prendem com questões processuais intrínsecas à micromoldação, nomeadamente dificuldades de escoamento em micro-canais, desmoldação, etc. No que concerne a interface fluído/ferramenta moldante, deve referir-se que esta deve promover um mínimo de adesão, por forma a não comprometer a frente de enchimento e a operação de desmoldação. As ferramentas de moldação devem portanto ser de materiais com alta dureza, baixo coeficiente de atrito e uma condutividade térmica elevada. Uma forma de obter tais características é utilizar revestimentos duros, tais como revestimentos de diamante, que possuem um conjunto de propriedades físicas excepcionais, podendo minimizar substancialmente a necessidade de manutenção no molde. Tais propriedades são ainda de importância crucial de forma a garantir a qualidade final das peças. O presente trabalho visa apresentar uma solução para alguns dos problemas acima apontados, bem como estabelecer a metodologia de operação e os limites de validade e ou viabilidade da aplicação de filmes finos de diamante em ferramentas micro-estruturadas para a industria de moldes.Molds industry in Portugal is one of the most dynamic sectors in the national economy. For that reason, its competitiveness is of utmost importance and requires further insight into the development of high value products and new markets. The latter has been pointed out, quite often, as a gateway to improve the sectors performance. Micromolding is, within this context, seen as an area of great potential. Nevertheless, when such a dimensional reduction is considered, the tools are also subjected to problems due to melt flow characteristics on micro-channels. In what concerns the melt flow/molding tool interface it’s worth referring the requirements for minimum adhesion to avoid compromising the flow front advancement or demolding operations. Molding tools have therefore strict requisites in what concerns high hardness, low friction coefficients and high thermal conductivity materials. In order to attain the above, the use of hard coatings, such as diamond, which display outstanding physical properties, may minimize substantially the need for mold intervention. The latter is required to reestablish the surface finish to guarantee part quality. The present work has as its fundamental objective to evaluate the viability and the added value of the diamond coatings on molding tools for thermoplastic micromolding

Investigation of the Integrity of aC:H Coatings on Stainless Steel Micro-Moulds during Thermal Cycling

Micro-injection moulding (µIM) is a key technology for scaling down larger geometry components and can include functional features at the micrometre scale and as far as the sub-micrometre length scale. Thermal cycling of amorphous hydrogenated carbon (aC:H) coated Stainless Steel (SS) has been investigated to simulate long-term micro-injection moulding (µIM) wearing and damage. Micro indentations and cracks were made into the mould and predictions of the crack behaviour were made using thermal expansion models. Validation of the results was performed with multiple heating and cooling cycles along with hardness measurements of the damage to the coating. The undamaged surfaces showed no major deformation but the cracks were shown to propagate and change in behaviour. The first two heat cycles of the testing had the most significant effect on the substrate with varying thermal expansions of materials being the main cause. The aC:H is shown to have excellent properties for mould tool applications but delamination could occur in areas susceptible to damaged and periodic surface inspection will be required preserve tool life

Temperature effects on DLC coated micro moulds

Microinjection moulding is a key enabling technology for replicating miniaturized components and parts with functional features at the micrometer and even sub-micrometer length scale. The micro moulding tools used in the process chain are critical for delivering high quality parts for the duration of the product life cycle, and recently tool coatings such as Diamond-like carbon (DLC) have been used to extend their use and enhance the performance. The micro injection moulding process has high injection speeds with cyclic heat transfer characteristics, and little is understood on how the localised heat transfer at the surface will influence the DLC surface coating delamination and cracking. In this research a microinjection moulding process using three different polymers, Polypropylene (PP), Acrylonitrile butadiene styrene (ABS) and Polyether ether ketone (PEEK) is studied. Finite element analysis (FEA) simulation is utilised to identify the process temperature factors that lead to tool thermal expansion and dimensional changes that directly impact the life cycle of the coating. The theoretical and FEA results show that the mould material and the two coatings experience a significantly different thermal expansion from each other. It has also been shown that at the micro scale heat loss at the tool surface is dominant, and the variation in heat has a significant influence on the different thermal expansion rates. In particular the DLC coated micro rib features are particularly susceptible to high variations in heat transfer. The research identifies areas of the tool surface that experience sudden heat variation across the part surface, and concludes that through process optimisation it is possible to reduce the potential for DLC coating delamination and cracking during service

Remanufacturing and Advanced Machining Processes for New Materials and Components

"Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems.

Remanufacturing and Advanced Machining Processes for New Materials and Components

Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems