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The use of stereolithography (SL) as a rapid tooling technique for injection moulding provides a low cost and quick alternative to hard tooling methods when producing a small quantity of parts. However, previous work has shown that different characteristics are developed by crystalline plastic parts produced from SL moulds and those produced from conventional tooling methods. Differing characteristics means that the parts are not truly the same as those that would be produced by hard tooling and highlights a disadvantage to SL tooling. Such differences are due to the cooling rate experienced by the part. Parts produced from SL moulds are cooled more slowly than those from metal tools as a result of the differing thermal conductivity of the mould material itself. This work concerned establishing the extent of the difference in the heat transfer characteristics. The different cooling rates were demonstrated by real-time data acquisition. The results illustrated the very different thermal history imparted on the moulding that is likely to be the cause of characteristic differences in the parts. The work then describes how the thermal conditions experienced in SL moulds can be used to an advantage. A case study details the use of SL moulds for the injection moulding of polyether-ether-ketone, which has high process parameter demands. The results of the case study have shown that not only is the SL rapid tooling method capable of producing a low volume of polyether-ether-ketone parts, but also under conditions that would not be possible using a metal mould. The thermal characteristics of SL moulds allowed fully crystalline polyether-ether-ketone parts to be produced with the mould at room temperature; the equivalent steel mould would require a pre-moulding temperature of about 200°C and much higher injection pressures and speeds. [ABSTRACT FROM AUTHOR]

Multi-Photon Polymerization (MPP) is a technique used to fabricate complex micro-scale 3D structures using ultra-short laser pulses. Typically, MPP is used to manufacture micron-scale components in photopolymer materials. However, the development of micron scale processes that can produce components from multiple materials within a single manufacturing step would be advantageous. This would allow the inclusion of particles that are manipulated and embedded within structures with sub-micron feature sizes. To achieve this, an MPP system was combined with an optical trapping (OT) setup in order to independently manipulate microparticles in the x, y and z planes. Particles were transported into the fabrication site using the OT and encapsulated using the MPP laser. Here it is shown that combining the OT capabilities with an additive manufacturing technique enables the production of complex multi-material artifacts. [ABSTRACT FROM AUTHOR]

Novel textile-like linked structures, realised using a rapid manufacturing (RM) process, have been proposed and developed recently. Various potential applications exist, and in most cases the mechanical performance must be evaluated. The present paper outlines a method to solve this problem by employing finite-element (FE) techniques at two scales, using the results of analysis at the meso-scale (the scale of the repeating unit) to provide equivalent non-linear spring behaviour for each textile link at the macro-scale. Validation with experimental test data from each scale was performed and these results are presented. Initial results overestimated mechanical performance. Microscopy suggested that this may be due to edge porosity in the specimens, and the dimensions of the FE models were adjusted accordingly as an initial approach to account for this. Predictions incorporating this modification exhibited excellent agreement with experimental measurements. The current work demonstrates both a technique, which could be automated for use in the design environment, and the potential value of developing an integrated process simulation to provide local material property data for the FE model. [ABSTRACT FROM AUTHOR]

The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique which allows low volume production by plastic injection moulding. The greatest advantage of the process is that it provides parts that are the same as those that would be produced by metal tooling in a fraction of the time and cost. However, work by the authors demonstrates that the parts possess different characteristics to those produced by metal tooling. This knowledge defies the greatest advantages of the SL injection moulding tooling process – the moulded parts do not replicate parts that would be produced by metal tooling. This work specifically demonstrates that a different rate of part shrinkage is experienced and subsequently investigates the mechanisms in SL tooling that induce these different part properties. The work culminates in different approaches to modifying the moulding process which allow the production of parts whose key morphological characteristics are closer to those that have been produced from metal moulds. [ABSTRACT FROM AUTHOR]

The use of moulds produced by stereolithography (SL) for injection moulding provides a quick route to manufacturing a low volume of parts without expensive hard tooling. However, these parts have been shown to exhibit different material property characteristics than those produced from metal tooling. The aim of the present work is to research methods that would allow SL moulds to produce parts of similar material property characteristics to those from conventional metal tools. This work has identified that the different part characteristics are due to differing levels of crystallinity developed in the parts from the comparative mould varieties (SL and metal). These crystallinity differences have been associated with the cooling rates imparted owing to the thermal properties of the mould material. The latter part of this work concerns controlling and manipulating this degree of crystallinity. After a discussion of possible methods, two approaches are taken to modifying the crystalline content of parts produced by SL moulds. One of the approaches is material based, the other concerns the injection moulding process. Differential scanning calorimetry (DSC) is used to quantify the resulting levels of crystallinity in the parts. The results show that by process modification it is possible to produce parts by SL moulding that possess a similar crystalline content to those moulded from metal tooling. The use of modified materials allows parts created in SL and metal tools to be of a consistent crystalline content. The work concludes that not only are SL moulds capable of producing parts that are more like those from metal moulds but also present some unique opportunities that have been demonstrated to be unachievable in metal moulds. [ABSTRACT FROM AUTHOR]