Ben Whiteside

Electro-activated surface micropattern tuning for microinjection molded electrically conductive shape memory polyurethane composites

Shape memory polymers with surface micropatterns have seen rising demand for high value applications such as adjustable adherence surfaces, dynamic micro-geometries for cell culture studies and switchable information carriers. Recently, microinjection molding has emerged as an efficient way to manufacture devices which contain surface micro-features using a wide range of polymers with high accuracy. In this study, shape memory polyurethane–carbon nanotube composites were prepared by twin-screw melt extrusion and subsequently processed using microinjection molding to obtain components with surface micropatterns. Then an electro-activated surface micropattern tuning system was developed which could recover the original micropatterned surface of the components after a thermal deformation by applying a current which heats the component using resistive heating. In order to optimize the technique, three key areas were investigated in this work: conductivity of the microinjection molded microparts, the retention of shape memory micropatterns on the surface of microparts during annealing treatment, and the macroscopic area shrinkage of microparts after thermal treatment. It has been found that the electrical conductivity of microinjection molded parts is relatively low due to the high shear rates prevalent in the process. An annealing treatment improves the electrical conductivity by several orders of magnitude, but can be detrimental to the dimensional stability of the micropatterns, which depends significantly on the micro-injection molding parameters, especially the mold temperature. Increasing the mold temperature, melt temperature, injection speed and injection pressure result in better retention of the micropattern and improved dimension stability during annealing treatment. This work demonstrates the potential of electro-activated surface micropattern control for microinjection molded electrically conductive shape memory polymer composites, which could be a promising technology for a range of application areas including electro-adjustable adherence, information storage, and anti-counterfeiting technology.

Real-time process monitoring of micromoulding using integrated ultrasonic sensors

Real-time, non-intrusive and non-destructive process monitoring of micromoulding has been performed using novel ultrasonic sensors integrated onto the barrel and mould insert with an ultrasonic pulse-echo technique. The relative variation of the polymer melt temperature inside the extrusion barrel can be obtained using the ultrasonic velocities of the melt measured at the barrel during extrusion. Melt flow arrival in the mould, and solidification, shrinkage and detachment of the polymer inside the mould cavity are also successfully monitored. The presented ultrasonic sensors and technique enable optimizing the micromoulding process, and improving quality of the moulded parts and process efficiency.

Real-time ultrasonic diagnosis of polymer degradation and filling incompleteness in micromoulding

Abstract Injection moulding techniques have been miniaturised and refined to achieve micromoulding which aims to satisfy the need for mass production of low-cost micro- and nanoscale components. However, the microscale mould cavity features and extreme processing conditions which are inherent in the process can result in larger process variations than conventional injection moulding, with a corresponding increase in the probability of producing an unsatisfactory product. Accurate process diagnosis is required to ensure process reliability but integration of sensors onto the small and highly detailed mould units can be problematic and alternatives may need to be sought. Piezoelectric film ultrasonic transducers were integrated onto the extrusion barrel and mould insert of a micromoulding machine for real-time, non-destructive and non-intrusive process diagnosis with an ultrasonic pulse-echo technique. Polymer degradation owing to excessive heating at the extrusion barrel was successfully probed by measuring the ultrasonic velocities in the polymer at the mould insert. Filling incompleteness of the mould cavity was also sensitively detected by monitoring the ultrasonic energy variation transmitted into the part at different points along the melt flow length. The developed ultrasonic sensors and technique enable optimisation and in-process quality assurance of the moulded parts which ensures that maximum process efficiency can be achieved.

Micromoulding : extreme process monitoring and inline product assessment

Abstract Advances in micromoulding technology are now allowing mass production of complex, three-dimensional functional products having sub-milligram masses and carefully tailored surface finishes. In order to create a viable manufacturing process for these components, accurate process monitoring and product evaluation are essential in order to highlight process problems and production of substandard parts. The present study describes work implementing a suite of sensors on a commercial micromoulding machine for detailed process interrogation. Evaluation of demoulded products is performed with a single camera based system combined with custom software to allow for three-dimensional characterisation of products during the process.

Optical imaging metrology for micromoulding cavity flows and products

Abstract Process imaging of micromoulding cavity flows has been performed using a transparent mould and high speed camera system creating a powerful method of studying the flow behaviour, shrinkage and internal stresses of polymeric materials during the micromoulding process. Results of these measurements will be presented with discussion of how they may be exploited to further understand crucial process parameters and physical models. An inline optical inspection technique currently under development is described in detail, along with initial results. This system offers 100% product inspection in three dimensions for microscale features.

Crystallization Temperature Dependence of Cavitation and Plastic Flow in the Tensile Deformation of Poly(ε-caprolactone)

In situ small-, ultrasmall-, and wide-angle X-ray scattering measurements were performed to investigate the structural evolution of crystalline lamellae and cavities as a function of deformation ratio during tensile deformation of isothermally crystallized poly(ε-caprolactone). The cavities were modeled as cylinder-shaped objects which are oriented along the stretching direction and randomly distributed in the samples, and their dimensions were evaluated by direct model fitting of scattering patterns. At small deformations, the orientation of these cavities at the onset of cavity formation was related to the isothermal crystallization temperature. Upon further stretching, the cavities were found to cluster in the interfibrillar regions at moderate strains where the long spacing of the newly developed lamellae along the stretching direction remained essentially constant. At large orientations, the cooperative deformational behavior mediated via slippage of fibrils was evidenced, the extent of which depended on the cavity number, which could be traced back to the significantly different coupling forces imposed by chains connecting adjacent fibrils. Furthermore, wide-angle X-ray scattering results revealed that a fraction of the polymer chains with their orientation perpendicular to the stretching direction were still preserved even at large macroscopic strains.

A service based wireless sensor networks architecture for high value-added process monitoring

Current research in high value-added manufacturing processes, such as the Micro Injection Molding (μIM) process, focuses on the monitoring of the machine process data., which could potentially affect the quality of the end product. Up until now, machine process monitoring has been limited to the machine level and has often bypassed the ambient environmental factors and pre manufacturing factors, which could have direct impact on the end product quality. In light of this, extending the monitoring of high value-added processes to include the ambient manufacturing environment would have numerous benefits in terms of process monitoring accuracy, material condition and product quality. In this paper, we present a novel Service Orientated Architecture (SOA) for monitoring a high value-added manufacturing process and its ambient environment using Wireless Sensor Networks (WSN). The proposed architecture applies the SOA to a network of wireless sensor nodes installed in the uIM machine and the industrial micro-molding environment. Here we present; the generic architectural design, system integration, user interfaces, and initial test results for an experimental testbed system.

Ultrasonic density measurement of polymer melts in extreme conditions

In-line real time monitoring and measurement of density of manufactured products is very important in various industrial applications, especially during extrusion of polymer melts. In this case measurements must be performed in very complex conditions, for example at high temperature (up to 400°C), high pressure (up to 10 MPa) and high chemical activity of the medium, mechanical impacts. Such extreme conditions limit the number of measurement techniques which can be used. The objective of this work was to develop and investigate an in line ultrasonic density measurement technique of polymer melts.

Simplified three-dimensional finite element hot-spotting modelling of a pin-mounted vented brake disc: an investigation of hot-spotting determinants

Hot spotting is a thermal localisation phenomenon in which multiple hot regions form on a brake disc surface during high-energy and/or high-speed braking events. As an undesired problem, hot spots can result in high-order brake judder, an audible droning noise and thermal cracking. This paper presents a finite element model for hot-spot modelling which introduces the classical axisymmetric assumptions to the brake pad in three dimensions by scaling the material properties combined with a subroutine to simulate the heat generation instead of modelling the rotation of the brake pad. The results from the initial feasibility models showed significant improvement in the computing efficiency with acceptable accuracy when compared with a traditional finite element model without such simplifications. This method was then applied to three-dimensional simulations of hot spotting on a realistic ventilated brake disc–pad pair, and the results showed good correlation with the experiments. In order to improve the understanding of the hot-spotting mechanism, parametric studies were performed including the effects of a solid-disc geometry and a ventilated-disc geometry, the rotational speed and energy, the pins, the disc run-out and the brake pad length. Based on the analysis of the results, it was identified that the vents and the pins affected the hot-spot distribution. The speed was shown to be more important in the hot-spot generation time and the hot-spot distribution than either the pressure or the total energy input was. The brake disc run-out was shown to affect the magnitude of both the hot-spot temperature and the hot-spot height because of the non-linear relationship between the local deformation, the contact pressure and the heat generation. Finally, increasing the brake pad length generated fewer hot spots, but the temperature of each hot spot increased.

An IoT and business processes based approach for the monitoring and control of high value-added manufacturing processes

Whilst the concept of IoT has already started to expand to some industrial environments, one industrial environment which still has not much exposure is the plastics industry environment made up of the Injection Moulding (IM), Micro Injection Moulding (μIM) and Extrusion line manufacturing processes. These processes would directly benefit from the IoT concept by making the environmental and high resolution process data available in real-time over the internet. This would have numerous benefits in terms of process monitoring, material and product quality, tracking, tracing and integration with other business components of an enterprise. In this paper we build upon a novel architecture for monitoring the μIM process using: IoT devices; distributed Service Orientated Architecture (SOA), with the Enterprise Service Bus (ESB) at its core; Business Processes for linking with other standard processes and Google Applications for web monitoring. This approach applies the SOA to IoT gateway node in the micro-moulding environment, NI high speed data acquisition devices connected to μIM machines and simulated material drying processes. Evaluation results from the extended architecture show that the BPEL orchestration framework successfully invokes simulated business processes based on the environmental conditions. The ESB successfully initiates the orchestration of business processes whereas the googles gadget API successfully visualizes the results. Here we present; architectural design, system integration, and results for an initial test scenario.