In mold laser welding for high precision polymer based optical components

“Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”To Assemble a complete subsystem as a rear lamp, is necessary to have different machines and to perform several tasks. This necessity obliges the companies to have large structures to support all the assembling process. These huge structures are very costly and have as a consequence the reduction of the competitiveness of the companies. The process presented in this document has the intention of reducing the number of tasks needed to produce the final subsystem/product. To achieve this goal were combined several technologies, as in-mould assembling, laser welding and LEDs (light-emitting diode). One of the advantages of this process was the utilization of only one injection molding machine with three injection units to do all the assembling process. To achieve the main objective, firstly, the rear lamp was designed according to with the legislation of UNECE Vehicle Regulations - 1958 Agreements; Regulation No. 50 -Rev.2 - Position lamps, stop lamps, direction indicators for motorcycles. Posterior several polymeric materials were studied at different levels. Initial were studied several concentrations of carbon nanotubes mixed with PC (polycarbonate). This had the objective of determine, if these materials are suitable to conduct the necessary electric current to turn on the different LEDs. One of the main advantages of this process is the use of the laser transmission welded process. Since, with this welding technology is possible reduce the complexity of the final part. To understand the potentialities of this technology a combination of two materials was studied. The studied showed that all materials presented a high transparency to the laser beam. In terms of weld process, the study showed that the best welding conditions are the lowest velocity, diameter and power. With these studies was possible conclude that this new process is suitable to be implemented at the industrial level

Combination of laser welding with in-mould assembling into a single process

The search of a process capable of produce and assemble complex subsystems in a short period is the goal of any company. In the market it is possible to found several solutions. They go from simple glue to the complexes systems that use moulds, robot and other. These systems are part of a complex assembling line. In these lines are several different processes as welding, plastic and assembling process. This complex structure is costly, and in countries where the labour cost is high. To maintain the cost the companies are obliged to go overseas. The process presented had the objective of reducing the complexity of an assembling line. The reduction of the complexity is achieved through the combination of the in-mould assembly and the laser welding. The in-mould assembly is used to produce in the same mould several components. Laser welding is used to join different polymers. To study the viability of the process I was chosen a case study, in this case, a rear lamp. Firstly, it was modified to this new process, and then each component was studied individually. Finally, all the processes were combined and it was concluded that this process has viability and to make it possible producing a complex subsystem in one process

Microinjection of polipropylene with nanoclays

Polypropylene (PP)/montmorillonite (MMT) nanocomposites micro samples was produced by micro injection molding at concentrations 2, 6 and 10% of Nanomax. The dispersion of the nanoclay particles in polypropylene was characterized using optical microscopy in polarized light, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) and the mechanical characterisation was performed using the tensile test. The results of x-ray diffraction indicated the formation of nanocomposites with partially exfoliated or intercalated structures, depending on the concentration of clay, with a maximum basal spacing of 6.217 nm. The micrographs obtained by scanning electron microscopy of fractured nanocomposite showed good dispersion of clay in polymer matrix without the presence of clusters. The tensile strength of PP/MMT is not much improved compared with pure PP but deformation increased significantly

In mould laser welding for high precision polymer based optical components

Assembling a complete subsystem as a rear lamp, it is necessary several different machines and tasks, for producing the final product. The technology presented in this paper has de capability to reduce the number of tasks needed for producing a final subsystem/product. In this case will be necessary only one injection moulding machine with three injection units. This was achieved by combining several technologies, as in-mould assembling, laser welding and LEDs. The challenges began by studying several polymeric materials, for understanding their behavior when they are welded by a laser beam. This was helpful also for determine the best welding properties. At the same time were analyzed different conductive polymers. This had the objective to determine their suitability for conducting the electric current between the different LEDs. The development of the rear lamp was made take in consideration the legislation of UNECE Vehicle Regulations - 1958 Agreement; Regulation No. 50 -Rev.2 - Position lamps, stop lamps, direction indicators for motorcycles. The results obtained present good input for producing in the same machine a complete and functional rear lamp

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

Formation of Atomic Carbon Chains from Graphene Nanoribbons

The formation of one-dimensional carbon chains from graphene nanoribbons is investigated using it ab initio molecular dynamics. We show under what conditions it is possible to obtain a linear atomic chain via pulling of the graphene nanoribbons. The presence of dimers composed of two-coordinated carbon atoms at the edge of the ribbons is necessary for the formation of the linear chains, otherwise there is simply the full rupture of the structure. The presence of Stone-Wales defects close to these dimers may lead to the formation of longer chains. The local atomic configuration of the suspended atoms indicates the formation of single and triple bonds, which is a characteristic of polyynes.Comment: 4 pages, 5 figure

Fiber reinforced thermoplastics compounds for electromagnetic interference shielding applications

Market demands for lightweight and lower cost products drive manufacturers to improve current product portfolios. In the case of electronic devices, the most significant weight originates from the enclosure, traditionally in steel or aluminum, that ensures excellent mechanical and electromagnetic shielding performance. The use of thermoplastics filled with electrically conductive fibers, such as carbon or stainless steel, was investigated as a lightweight and cost-effective alternative to steel sheet for creating electromagnetic interference (EMI) shielding enclosures for electronic devices. This paper presents an EMI shielding analysis workflow for the development of plastic enclosures for an electronic device. The workflow starts by measuring the fiber-reinforced thermoplastic compounds shielding effectiveness (SE) with an experimental method in the 30 MHz–3 GHz frequency band. This analysis helps to filter a vast list of materials with a wide range of shielding performance, 20–100 dB, and allows to obtain empirical data for the second phase of the workflow, computer simulations. Simulations with experimentally adjusted material properties were used to validate the design concept of an enclosure in its early development phase. Results from this study showed that the selected material has better EMI SE performance than a steel sheet venting grid.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by Portugal Incentive System for Research and Technological Development, Project no 36265/2013

Influence of the local morphology on the surface tension of injection molded polypropylene

Publicado em “Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”In this work, we investigate the development of the morphology of an injection molding polypropylene under the local thermomechanical environment imposed during processing, and its effect on the contact angle and, hence, on the surface tension of the moldings. Melt and mold temperatures were varied in two levels. The local thermomechanical environment was characterized by mold filling computational simulations that allow the calculation of thermomechanical variables (e.g., local temperatures, shear stresses) and indices (related to the local morphology development). In order to investigate the structural hierarchy variations of the moldings in the thickness direction, samples from skin to core were used. The molecular orientation and degree of crystallinity were determined as function of the thickness, as well as the contact angle. The variations of the degree of crystallinity were assessed by differential scanning calorimetry. The level of molecular orientation was evaluated by birefringence measurements. The contact angles were measured in deionized water by sessile drop (needle in) method at room temperature, to determine the wettability of the samples. The contact angles were found to vary along the molding thickness in the skin, transition and core layers. These variations are related to the local morphologies developed. Results suggest that water contact angle increases with the level of molecular orientation and for finer microstructures