Syed H. Masood

Numerical investigation of mixing in microchannels with patterned grooves

Mixing in microchannels with patterned grooves was studied numerically by CFD simulations and particle tracking technique. Point location, velocity interpolation and a fourth-order adaptive Runge–Kutta integration scheme were applied in the particle tracking algorithms. Using these algorithms, Poincare maps were calculated from the 3D velocity field exported from a CFD package for microfluidics (MemCFD™). For small aspect ratio (α = 0.05) grooves, the results showed that there was no significant irregularity in the Poincare map, and indicated little chaotic effect. For high aspect ratio (α = 0.30) grooves, the flow pattern became more jumbled, but there was no apparent evidence that indicated the flow was chaotic, for Reynolds numbers up to five. However, Poincare maps could still be used to evaluate the performance of this type of micro-mixer. The particle trajectories recorded in the Poincare maps were circular-like patterns. By counting the number of dots to form one circle in the Poincare maps, the length of the channel to enable one recirculation could be calculated. The results indicated that this length had an exponential relation to the aspect ratio of grooves, and it was independent of the flow velocity. The CFD simulation showed that the transverse motion could fold and stretch fluids to increase their interfacial area. The results showed that micro-mixers with patterned grooves caused rotation of the fluid streams. This rotation can reorient the folding in the depth direction, and can enhance passive mixing in microfluidic devices with shallow channels.

A generic algorithm for a best part orientation system for complex parts in rapid prototyping

Abstract This paper presents a generic mathematical algorithm to determine the best part orientation for building a part in a layer-by-layer rapid prototyping (RP) system. The algorithm works on the principle of computing the volumetric error (VE) in a part at different orientations and then determining the best orientation based on the minimum VE in the part. The algorithm is shown to work for a part of any shape and complexity, with any slice thickness, and for the orientation of a part about any selected axis. The part orientation system based on this algorithm graphically displays the VE at different part orientations and recommends the best part orientation. The system will help RP users in creating RP parts with a higher level of accuracy and surface finish.

A rule based expert system for rapid prototyping system selection

Abstract The availability of a growing number of rapid prototyping (RP) systems with wide ranging capabilities has created a problem of selecting an appropriate RP system for industry as well as educational sector to suit their requirements. This paper presents an expert system based RP system selection program incorporating 39 RP systems commercially available from 21 RP manufacturers worldwide. The program allows the user to choose one of the four options, namely, quick selection, detailed selection, build technology or machine style for system selection, with each option considering a systematic selection criteria. The program is a rule based expert system, and recommends the RP system along with its full specifications on the basis of interactive question–answer session with the user. The system is believed to be the first expert system based RP selection program and has the potential for future expansion into a full-fledged RP selector system.

Intelligent rapid prototyping with fused deposition modelling

Explains that fused deposition modelling is a rapid prototyping technology by which physical objects are created directly from a CAD model using layer by layer deposition of extruded material. The technology offers the potential of producing parts accurately in a wide range of materials safely and quickly. In using this technology, the designer is often confronted with a host of conflicting options including achieving desired accuracy, optimizing building time and cost and fulfilling functionality requirements. Presents a methodology for resolving these problems through the development of an intelligent rapid prototyping syste integrating distributed blackboard technologies with different knowledge based systems and feature based design technologies.

Error analysis of FDM fabricated medical replicas

Purpose – Recent advancement in fused deposition modelling (FDM) rapid prototyping technology has made it a viable technology for application in reconstructive surgery. The purpose of this paper is to investigate the errors generated during the fabrication stage of complex anatomical replicas derived from computed tomography coupled with the technique of FDM.Design/methodology/approach – An evaluation on the errors generated during the fabrication process of two anatomical parts (skull or mandible) for different human sizes (infant, female or male) is carried out. A comparison between the linear measurements of 11 landmarks on the virtual model of a skull and nine for the mandible of patient specific and its replica is conducted. Furthermore, eight landmarks are chosen to evaluate the bone thickness variation over the fabricated replicas.Findings – Although the FDM technology proved the ability to manufacture and to fit prosthesis to a patients unique proportions quickly and with relatively low cost, the...

Line balancing and simulation of an automated production transfer line

Purpose – This paper presents an investigation on the line balancing of an automated cylinder block production transfer line in order to reduce the total cycle time and increase machine utilization in an automotive plant. Results were verified by computer simulation, which showed increased throughput and higher machine utilization as a result of line balancing.Design/methodology/approach – Three main operation lines of the transfer line were identified as critical and having the highest cycle time and were chosen for optimisation study. Strategies of re‐sequencing of existing operations and tools were used to reduce the cycle time of these critical operations and to balance the line. Results of a simulation study using Simul8 software are also presented to demonstrate the increase in machine utilisation and throughput as a result of line balancing.Findings – Owing to line balancing, the cycle time of cylinder block line was reduced from 293.9 to 200 s, an almost 32 per cent reduction. This also resulted i...

A volumetric approach to part-build orientations in rapid prototyping

Abstract This paper presents the development of a part-build orientation system for rapid prototyping by considering the volumetric error (VE) encountered in parts during the building process. The methodology involves a primitive volume approach, which assumes a complex part to be constructed from a combination of basic primitive volumes. First, the VE in a number of primitive volumes such as cylinders, cubes, hemispheres, cones and pyramids is considered. Then, the VE in parts made from a combination of these primitives is determined. The system graphically displays the VE at different orientation of any part and recommends the best orientation for the minimum VE in the whole part. This paper will illustrate the methodology by considering the case of the orientation problem of a cone and the parts made from different primitives.

Tensile Properties of Processed FDM Polycarbonate Material

Knowledge of the mechanical properties of parts processed by Fused Deposition Modelling (FDM) rapid prototyping process is essential for engineering applications of such parts as the mechanical strength of parts depends heavily on the FDM process parameters selected during part fabrication. Little knowledge is available for the Polycarbonate (PC) material used in the FDM systems. This paper presents results of the experimental work on the effect of the FDM process parameters such as air gap, raster width, and raster angle on the tensile properties of PC. Results show that FDM made parts have tensile strength in the range of 70 to 75 % of the moulded and extruded PC parts. The results will be valuable for different functional applications of FDM produced parts and assemblies.

Thermal characteristics of a new metal/polymer material for FDM rapid prototyping process

– Presents development and characterisation of a new metal/polymer composite material for use in fused deposition modelling (FDM) rapid prototyping process with the aim of application to direct rapid tooling. The work represents a major development in reducing the cost and time in rapid tooling., – The material consists of iron particles in a nylon type matrix. The detailed formulation and characterisation of the thermal properties of the various combinations of the new composites are investigated experimentally. Results are compared with other metal/polymer composites used in rapid tooling., – The feedstock filaments of this composite have been produced and used successfully in the unmodified FDM system for direct rapid tooling of injection moulding inserts. Thermal properties are found to be acceptable for rapid tooling applications for injection moulding., – Introduces an entirely new metal based composite material for direct rapid tooling application using FDM RP system with desired thermal properties and characteristics. This will reduce the cost and time of manufacturing tooling inserts and dies for injection moulding.

Application of fused deposition modelling in controlled drug delivery devices

Purpose – This paper seeks to present an investigation on building controlled drug delivery device (DDD) matrix using fused deposition modelling (FDM) rapid prototyping (RP) process. The focus of the study is on the effect of FDM fabricated macro‐features of reservoir‐matrix DDD models on the drug release rates through the diffusion process.Design/methodology/approach – Using various parameters involved with FDM, polymeric DDD matrices with different macro‐features are designed and fabricated on the FDM3000 machine. Experiments are conducted to study the release characteristics and porosity of the fabricated models with a model drug and to see how they are affected by FDM build parameters.Findings – Experimental results show that FDM parameters, raster gap and raster angle, play significant roles in controlling the structure and drug release characteristics of the FDM fabricated DDDs. The experimental observations reveal that appropriate FDM parameters can be selected to fabricate controlled DDD device wi...