Rapid manufacturing techniques in the development of an axial blood pump impeller
Abstract This paper presents a comparison of manufacturing techniques used in the development of an axial blood pump impeller. In this development process the impeller was designed and its performance was evaluated with the aid of computational fluid dynamics (CFD). Prototypes of those designs where the CFD results show promise were needed in sufficient quantities at a low cost for experimental validation of the CFD results. As the impeller is less than 16 mm in diameter with a maximum blade thickness of about 1.5 mm, innovative manufacturing techniques are explored in this paper to determine the best process for quick fabrication of prototypes that are dimensionally accurate, structurally robust and low in cost. Four rapid prototyping techniques were explored. The completed parts were compared on the basis of manufacturing time, quality and strength of parts obtained, manufacturing cost and also in vitro performances. Based on these studies, it was concluded that selective laser sintering (SLS) is the most appropriate method for the quick production of prototype parts for evaluation of pump performance.
Effect of Workpiece Volume on Shell Wall Thickness Reduction in Rapid Casting of Aluminum using Three-Dimensional Printing
The purpose of the present work is to study the effect of workpiece volume on reducing the shell wall thickness in rapid shell casting based upon three-dimensional printing 
(3DP) technology, and to evaluate the dimensional accuracy and mechanical properties of aluminum (Al) castings obtained as per the ISO standard UNIEN 20286-I (1995). Starting from the identification of component/benchmark, castings of different volumes (corresponding to workpieces of ɸ60 mm, ɸ50 mm and ɸ40 mm) were produced with different shell wall thicknesses. Measurements on a coordinate measuring machine (CMM) allowed the calculation of the dimensional tolerances of the castings produced. Some important mechanical properties were also compared to verify the suitability of the castings. The research proved that having a shell wall thickness with a value less 
than that recommended (12 mm) is more suitable from a dimensional accuracy and economic point of view (irrespective of the workpiece volume within the given selected range). All the castings produced with different shell thicknesses are acceptable as per the ISO standard. The results of the study suggest that workpiece volume has an unnoticeable effect on reducing the shell wall thickness for the selected range of volumes of casting. Furthermore, the hardness of castings produced is almost same for 
all shell wall thicknesses, from 12 mm to 1 mm. The results are supported by cooling (time-temperature) curves, which show unnoticeable changes in the rate of heat transfer 
at different shell wall thicknesses. Keeping in mind the cost effectiveness of the process, one (1) mm shell wall thickness has been recommended for the production of castings. For a 1 mm shell wall thickness, the production cost and time are reduced by 67.38% and 44.87% (for ɸ60 mm workpieces), 64.51% and 44.62% (for ɸ50 mm workpieces), and 69.50% and 59.64% (for ɸ40 mm workpieces), respectively.
Self-sustained flow oscillations and heat transfer in radial flow through co-rotating parallel disks
An experimental study was conducted to determine the fluid flow and heat transfer characteristics in a passage formed by two parallel rotating disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two rotating disks were visualized by using paraffin mist and a laser-light sheet. 
 
It was disclosed that 1) the self-sustained laminar flow separation which is characteristic of the stationary disks still exists even when the disks are set in motion, giving significant influence to the heat transfer. 2) For small source flow Reynolds number, Re, and large rotational Reynolds number, Reω, rotating stall dominates the heat transfer. 3) Heat transfer for steady laminar flow occurs only when both the source-flow and rotational Reynolds numbers are small: Re < 1200 and Reω < 20.