High Speed Sintering - Early Research into a New Rapid Manufacturing Process

Rapid Manufacturing (the production of end use products by layer manufacturing techniques) has grown significantly in recent years and has started to revolutionise some areas of manufacturing. Among the main drawbacks for commercially available techniques are machine cost and build speed. This paper describes some initial research into a new process called High Speed Sintering. The High Speed Sintering process (UK patent No. 0317387.9) involves the sintering of 2D profiles of layers of powder without the need for a laser. Experiments performed on a simple lab apparatus have shown how the addition of carbon black to standard nylon powder can increase the rate of sintering such that an entire layer may be sintered in 5 seconds using an infra-red lamp. The effects of composition of carbon black on material properties are shown and may be traded off against build speed. Thermal control of the process is vital and the effects of altering the position and power used with an infra-red lamp are presented. Eliminating a laser reduces machine cost and build time, combining these factors will make the High Speed Sintering process suitable for high volume manufacture. Cost predictions show that the process will be viable for the manufacture of standard products in volumes over 100,000.Mechanical Engineerin

High Speed Sintering – Continuing Research into a New Rapid Manufacturing Process

High Speed Sintering (HSS) is an emerging layer manufacturing technique aiming to break into the lucrative field of Rapid Manufacturing (RM). The process is likened to Selective Laser Sintering (SLS), however, instead of a laser dictating the sintered cross sectional area of each layer, the desired area is first printed using a Radiation Absorbing Material (RAM) and then sintered using an inexpensive infrared lamp. This paper begins by describing the sintering process in more detail and then outlining the overall manufacturing cycle. It then continues by describing the experiments performed to investigate the current problem concerning the hardness of excess powder within the powder bed. This problem arose due to the continual exposure of the whole bed to infrared radiation from the lamp. The experiments showed that as the power of the IR lamp increased, the hardness of the bed also increased. Furthermore, at higher IR power levels it was found the excess powder produced a solid tile which could only be broken down by a glass bead blaster.Mechanical Engineerin

Geochemical Insights into Crustal Melting in the Bhutan Himalaya

Crustal melting and granitic intrusions are characteristics of many continental collision zones. The processes, sources and timing of melt generation in collision zones are critical to understanding crustal and tectonic evolution. In the Himalaya, multiple Oligocene-Miocene leucogranite bodies intrude the Greater Himalayan Series (GHS), a lithotectonic package of high-grade metamorphosed sediments. This package is underthrust by a chemically distinct metasedimentary package, the Lesser Himalayan Series (LHS). Multiple elemental and isotopic techniques provide insight into leucogranite source and petrogenesis in central Bhutan (eastern Himalaya). Whole-rock major and trace elemental abundances confirm that all studied leucogranites are the product of muscovite breakdown between 640 and 760°C. Sr-Nd signatures suggest that most samples were sourced from the GHS; however several samples yield signatures more comparable with those from the LHS, an observation that currently appears unique to Bhutan. O, U-Pb, Hf isotopes in zircon confirm previous whole-rock findings that melting in the eastern Himalaya took place over 20 Myr, from 31 to 11 Ma. Increasingly radiogenic Nd and Hf isotope signatures are observed in younger leucogranites, which suggest a deeper source, and potentially more contribution from melting LHS. Importantly, O-Hf isotopic signatures indicate that there is no mantle input into eastern Himalayan melting, a finding important for heat budget calculations and for crustal growth models in orogenic belts. Stable Rb and Sr isotopic analyses from both whole-rock leucogranites and mineral separates establish, for the first time, that mass-dependent isotopic fractionation occurs during the formation of highly evolved crustal melts. Consistent Sr fractionation of up to 2.51‰ is observed between plagioclase, K-feldspar and micas. These observations have implications for the application of stable isotopes as petrogenetic indicators and for Rb-Sr geochronology. Together, the findings of this study provide new insights into both Himalayan and global tectonic evolution and the geochemical nature of melt generation

Investigating Dielectric Properties of Sintered Polymers for Rapid Manufacturing

Selective Laser Sintering (SLS) of polymers is the leading technology in the growing field of Rapid Manufacturing. High Speed Sintering (HSS) is a process that offers the potential to reduce costs and processing times and thus open significant new markets for Rapid Manufactured parts. Much academic research has been performed with respect to mechanical properties of Rapid Manufactured parts, however the area of electrical properties has received little attention to date. Electrical properties are obviously important in applications that will involve embedding of circuits with Rapid Manufactured 3D objects. However electrical properties are also important for a wide variety of electrical products where Rapid Manufactured parts can be used as housings etc. This paper focuses on the dielectric properties of parts made by SLS and HSS and compares properties with those for conventionally processed polymers. Dielectric strength results show that SLS parts are comparable with injection moulded parts, while HSS parts are inferior to SLS parts. Dielectric constant and dissipation factor results show that HSS parts are comparable with injection moulded parts, whilst SLS parts have superior properties. The presence of porosity (SLS and HSS) and the presence of carbon (HSS) are suggested as reasons behind the variation in dielectric properties when compared with injection moulded parts.Mechanical Engineerin

Conformal Cooling and Heating Channels using Laser Sintered Tools 490

The EOS Direct Metal Laser Sintering (DMLS) and DTM Rapid Steel 2 processes may be used to create tools incorporating conformal channels behind the tool surface through which fluids may be passed. To date, a significant amount of work has been carried out to investigate the efficiency of using conformal channels to cool tools. This work suggests the use of conformal channels to both cool and heat a single tool. This may appear self-defeating at first but the selective nature by which conformal channels may make this a worthwhile means of generating hitherto unavailable thermal conditions within a tool. Such conditions may then allow the successful production of geometries which had previously been impossible to mould.Mechanical Engineerin

Thermal Effects on Accuracy in the 3DKeltool™ Process

The 3DKeltool™ process has been used to produce injection moulding inserts capable ofproducing millions ofparts with quick cycle times (1). Short lead times are possible however accuracy is reduced for dimensions over 150mm. The use ofroom temperature vulcanising (RTV) silicone rubber in the 3DKeltool™ process is a possible reason for the loss of accuracy in larger parts. Effects of temperature changes during the process are assessed both theoretically and experimentally. The results show close agreement between theoretical predictions and experimental results for dimensional changes. Suggestions which could allow accurate manufacture oflarger 3DKletool™ parts are presented.Mechanical Engineerin

Effect of Sintering Parameters and Flow Agent on the Mechanical Properties of High Speed Sintered Elastomer

High Speed Sintering (HSS) is an Additive Manufacturing process that creates parts by sintering using inkjet and infra-red lamp technology rather than laser systems employed in Laser Sintering (LS). This research investigated the effects of machine parameters (sintering power, bed temperature) and the addition of fumed silica flow agent on the tensile properties of thermoplastic elastomer parts processed using HSS. The results showed improved elongation at break values by a factor of more than 2X compared to reported values for LS of the same thermoplastic elastomers. At constant parameters, improved tensile strength and tensile modulus were observed with the addition of flow agent into the sintering mixture.Mechanical Engineerin

Rapid prototyping for direct manufacture

Advances in rapid prototyping and machining have resulted in reduced lead times for injection moulding tooling. Comparisons between aluminium and stereolithography (SL) tools are made with regard to the ejection forces required to push mouldings from the tools, heat transfer through the tools and the surface roughness of the tools. The results show that ejection forces for both types of tools are increased when a longer cooling time prior to ejection is used. The ejection forces required from a rough aluminium tool are considerably higher than those from a smooth aluminium tool. SL tools do not appear to be subjected to any smoothing as a result of moulding polypropylene parts, this is explained by the fact that the tool’s surface acts in a rubber like manner during part ejection. The rubber like nature of the tool’s surface is as a direct consequence of the low glass transition temperature and low thermal conductivity of the tool material. Further potential benefits of the low thermal properties of the tool are discussed

Effect of Greyscale/Print Density on the Properties of High Speed Sintered Nylon 12

High Speed Sintering is an Additive Manufacturing process that creates parts by sintering using inkjet and infra-red lamp technology, rather than the laser systems employed in Laser Sintering. This research investigated the effects of altering the dosage of ink (greyscale/print density) on the properties of parts produced. A clear pattern emerges that shows a ‘sweet spot’ for correct dosage of ink to maximise properties. The work also shows that greyscale allows considerable control of part density that could lead to substantial reductions in part mass beyond those that may be achieved by conventional design optimisation approaches employed today.Mechanical Engineerin

Analysis of rapid manufacturing—using layer manufacturing processes for production

Rapid prototyping (RP) technologies that have emerged over the last 15 years are all based on the principle of creating three-dimensional geometries directly from computer aided design (CAD) by stacking two-dimensional pro les on top of each other. To date most RP parts are used for prototyping or tooling purposes; however, in future the majority may be produced as end-use products. The term ‘rapid manufacturing’ in this context uses RP technologies as processes for the production of end-use products. This paper reports ndings from a cost analysis that was performed to compare a traditional manufacturing route (injection moulding) with layer manufacturing processes (stereolithography, fused deposition modelling and laser sintering) in terms of the unit cost for parts made in various quantities. The results show that, for some geometries, it is more economical to use layer manufacturing methods than it is to use traditional approaches for production in the thousands