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RAPID prototyping, PROTOTYPES, RAPID tooling, MANUFACTURING processes, FLEXIBLE manufacturing systems, and SURFACE roughness

As the race to launch a product successfully into the market increases in speed, the drive to reduce metal tooling lead time will become more important. Time reduction for fabricating metal tools depends on fast, efficient, and flexible manufacturing processes that dramatically reduce lead times while not sacrificing mechanical properties. A novel process of rapid tooling, non-baking of ceramic moulding, was studied. It uses a casting mould made from ceramic slurry and rapid prototyping to form a metal tool. It provides a quick, accurate, and relatively cost-effective route for producing metal parts or tools. The process and key technologies are analysed in detail. The process has been used in the automotive, consumer products, casting, and toy industries. Applications show that the total costs for new products can be reduced by as much as 40–60%, and lead times can be reduced by 50–60%. The surface roughness is approximately Ra = 3.2, and it can be improved to better that Ra = 1.6 by polishing. The dimensional accuracy relative to size is about ±0.1 mm for dimensions less than 200 mm. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, PROTOTYPES, RAW materials, SHEAR waves, PHOTOPOLYMERIZATION, MANUFACTURING processes, and FINITE element method

Stereolithography is one of the rapid prototyping processes which uses a photopolymer as the raw material to build prototypes. The photopolymer absorbs energy by selective laser exposure. The curing effect starts when the absorbing energy exceeds a critical value, and the process is called photopolymerisation. The photopolymerisation changes the phase from liquid to solid. The cured volume can expand and then shrink on cooling. The process parameters such as the scanning speed, scanning path, scanning pitch, and the slicing thickness, lead to different shrinkage and curl distortion, so, the photopolymerisation process is a dynamic material behaviour. In this study, a dynamic finite element simulation code has been developed to simulate the photopolymerisation process. The simulated result for a suspended beam which corresponds to the process parameters shows that a short raster causes less curl distortion than a long raster. The experimental result agrees very well with the simulated result. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, NEW product development, COATING processes, MANUFACTURING processes, LARGE scale systems, and CONCURRENT engineering

Many technological difficulties exist in the field of rapid prototyping (RP) technology when making large-scale prototypes. The manufacturing efficiency is the main problem, and the process implemention and RP equipment also present difficulties. In this paper, the concept of divisional parallel scan is presented. Laminated object manufacturing (LOM) technology is used for the basic forming process and has been improved continuously through practice. Static divisional scan technology was also better developed to dynamic divisional scan technology, which can help in achieving the object of improving work efficiency and optimising design. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, COMPUTER-aided design, METAL spraying, METAL coating, MANUFACTURING processes, and CONCURRENT engineering

In order to build the complex built-in labyrinth design of an emitter which is a key element in water-saving devices, rapid prototyping and manufacturing (RP&M) is used to design the emitters and to manufacture corresponding rapid tooling (RT). Detailed CAD design of the emitter, CAD process design, and the generation of RT process modelling of the emitter have been carried out using parameterised design. Prototypes have been built using RP techniques to perform the rapid verification and modification of the emitter design; rapid tooling (RT) for the emitter has been fabricated using a metal spraying process to carry out trial-production. Finally, with the fabrication ofa precision mould as the basis, emitter mould design and manufacturing have been completed. As a result, the integration of design/verification/manufacturing of a mould and its products is realised. [ABSTRACT FROM AUTHOR]

LIQUID crystal displays, LIQUID crystal devices, NEW product development, MANUFACTURING processes, LITHOGRAPHY, RAPID prototyping, FINITE element method, and COMPUTER simulation

In many investigations, a liquid crystal display (LCD) has been used as the photo mask in a stereolithography system. The LCD mask has the potential to increase the speed of rapid prototyping (RP) fabrication as well as to reduce the system cost. Compared to the conventional laser-scanning technique used in 3D systems stereolithography apparatus (SLA), the reaction heat of layer curing is released as the area is exposed, and it is higher than that of the laser scanning in which the reaction heat only releases point-by-point. On the other hand, mask type stereolithography has a more serious shrinkage effect than the other methods and requires further analysis. This paper analyses the shrinkage deformation of the mask type stereolithography process. A simulation code based on the dynamic finite-element method has been developed to predict the 3D shrinkage and to monitor the RP fabrication, which consists of three stages of simulation which include the pre-processor, the analytic processor and the post-processor. In order to fabricate experimental parts, a mask type stereolithography system has been assembled. The principle of the experimental apparatus is also briefly described. For evaluation of the experimental and simulation results, a thin shell wall rectangular part was fabricated and measured. The simulation program developed has been proved to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

TESTING-machines, COORDINATE measuring machines, RAPID prototyping, REVERSE engineering, COMPUTER-aided design, PARAMETER estimation, and NUMERICAL analysis

One objective of this work is to determine the optimal combination of the probe diameter and grid distance for freeform surface measurement, and another is to determine the optimal parameters for the local Shepard interpolation. The optimal combination of the probe diameter and grid distance for freeform surface measurement was determined through a Taguchi matrix experiment. The smaller the probe diameter and grid distance, the better the accuracy of the surface normal based on the configured matrix experimental result. The optimal parameters, namely the exponent μ and the radius R, for the local Shepard interpolation were determined by using the minimisation method of the root-mean-square normalised error (RMSNE) between the measured data points and the theoretical data points on a standard steel ball surface. The optimal parameters determined were actually applied to the measurement of a freeform surface (mouse surface) on a coordinate measuring machine (CMM). The local Shepard interpolation method was used to interpolate 16 control points from 1054 measured data points. Bi-cubic Bezier- and B-spline surface CAD models were constructed through these interpolated control points. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, LASERS, INDUSTRIAL engineering, and MANUFACTURING processes

To meet the requirement of faster and precise slicing in rapid prototyping, a direct slicing approach from AutoCAD solid models is proposed. The sliced layers are saved in ASCII DXF files. Lines, arcs and circles are used to describe the section contours. This approach can be used in stereolithography, selective laser sintering, fused deposition modelling, and other rapid prototyping processes, e.g. laminated object manufactu-ing. [ABSTRACT FROM AUTHOR]

SIMULATION methods & models, MODELS & modelmaking, BOTTLENECKS (Manufacturing), PRODUCTION scheduling, MANAGEMENT, and THREE-dimensional imaging

Filling lines are too complex to allow realistic models of them to be evaluated analytically. In this paper, the requirements for designing filling lines are analysed, and a directed graph-based modelling formalism which unifies object oriented analysis methods, and the 3D geometry and mechanism required for the simulation is proposed. A framework of a virtual simulation system is proposed, and the architecture and main modules of the prototyping tool are introduced. These provide an integrated tool for the design and optimisation of filling lines. Entire facilities and filling line can be modelled in the modelling and simulation environment to evaluate alternatives, and to identify physical bottlenecks. An example is given. [ABSTRACT FROM AUTHOR]

SILICA sand, TEMPERATURE, CALCIUM, ALUMINUM, MAGNESIUM, and MELTING points

Silica sand is commonly used in the foundry industry. With a high melting point of 160°C, the silica sand is normally sintered in a high-temperature furnace. However, silica with contents of calcium, aluminium, magnesium, and chlorine, etc. can form low-melting point eutectics. Therefore, a relatively low-power laser can be used to sinter the silica sand directly. The investigation of the mechanism and process for direct laser sintering of the silica sand, without any binder, is presented in this paper. Combined with rapid prototyping (RP) technology, the laser sintering of the silica sand can be used to directly fabricate a sand casting mould, called a rapid sand casting mould. By avoiding the time-consuming process of fabricating a pattern, the rapid sand casting mould process has the potential of further reducing the lead time for producing a casting product. Some important issues, such as the lead time of producing a sand mould, its accuracy, and surface finish, etc., are discussed. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, MANUFACTURING processes, ASYNCHRONOUS transfer mode, SMALL business, TECHNOLOGICAL innovations, and INFORMATION resources management

Faced with today's competitive market, the development of innovative product needs to be accelerated. But this is limited by heterogeneous systems and a distributed environment. A way of utilising network technology to this end must be found. In this paper, we use a new approach, called asynchronous and synchronous coupling, which is a network-based product development approach. This is then applied to rapid-response manufacturing by small- and medium-sized enterprises in a distributed environment. It demonstrates integrated thinking, high development speed and a transparent development process. Visual technology and real-time monitoring technology are used to solve asynchronous process and data management problems. An ICE (integrated collaborative environment) is also created to support synchronous collaboration. [ABSTRACT FROM AUTHOR]

DESIGN, RAPID prototyping, INTERACTIVE computer systems, SURFACES (Technology), DEFORMATION of surfaces, COMPUTER-aided design, and MODELS & modelmaking

There is an increasing demand in conceptual design for more intuitive methods for creating and modifying freeform curves and surfaces in CAD modeling systems. The methods should be based not only on the change of the mathematical parameters but also on the user's specified constraints and shapes. This paper presents a new surface representation model for freeform surface deformation representation. The model is a combination of two functions: a displacement function and a function for representing an existing NURBS surface called a parent surface. Based on the surface model, the authors develop several novel deformation methods which are named SingleDef (Single-point constraint based deformation method), MultiDef (Multiple-points constraints based deformation method), CurDef (Curve constraints based deformation method) and FeatDef (Feature constraint based deformation method). The techniques for freeform surface deformation allow conceptual designers to modify a parent surface by directly applying point constraints, curve constraint or a surface constraint to the parent surface. The deformation methods are implemented in an experimental CAD system. The results show that designers can easily and intuitively control the surface shape. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, PRODUCTION engineering, MACHINING, RAPID prototyping, INDUSTRIAL engineering, ALLOYS, NEW product development, and METAL products

High-speed machining is known as one of the most effective rapid prototyping and/or manufacturing (RPM) processes that provides the various machining materials with excellent quality and dimensional accuracy. However, the high-speed machining process is not suitable for the rapid realization of 3D-shaped product because a considerable amount of time is required for the work piece fixturing process. High-speed rapid prototyping (HisRP), a new type of RPM technology, will be presented in this paper. The proposed HisRP has been developed using a combination of a multi-face high-speed machining process and a flexible fixturing technique. Low melting point metal alloys are used to hold the work piece during multi-face machining. An automatic set-up device, mounted and fixed to the work table, has also been developed to guarantee positional accuracy during a series of multi-face machining operations. This set-up device is expected to be beneficial for successive multi-face high-speed machining of working materials, for example for two-face or four-face machining. The proposed HisRP process has been shown to be a useful method for manufacturing 3D metal products with reduced lead time. [ABSTRACT FROM AUTHOR]

CONCURRENT engineering, INDUSTRIAL engineering, RAPID prototyping, MATHEMATICAL optimization, ENGINEERING tolerances, NONLINEAR statistical models, NONLINEAR theories, and MACHINE tools

A new method for optimal concurrent process tolerance is proposed. Information related to process planning is used during the structure design stage of a product. The functional tolerances of the assembly of a product are considered process tolerances. A nonlinear optimal concurrent process tolerance model has been established to minimize the total manufacturing cost with different weight factors for the operations of the product. The constraints include concurrent process tolerance chains, the standard coefficient of process tolerance, and the economical maximum tolerance of the machine tools. In order to obtain optimal process tolerances, a new approach based on grey difference degree is presented in this paper. This approach takes the sequence consisting of the optimal value of every objective as the standard sequence, and that consisting of the actual values as the objective sequence. Thus, grey difference degree is calculated and used as the objective of the function. Finally, a practical example is introduced to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, ENGINEERING design, ENGINEERING models, COMPUTER-aided design, and PRODUCTION engineering

Most rapid prototyping (RP) processes adopt a solid CAD model sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually the stacked layers form a physical part of the model. A new RP process called the Transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-st) has been developed to reduce building time and to improve the surface finish of parts with thick layers and sloping surfaces. The objective of this study is to develop a method for calculating the rotation angles (θx, θy) of a linear hotwire cutter in the three-dimensional space for the VLM-st process using inverse kinematics. The method for calculating the rotation angles (θx, θy) of the four-axis hotwire cutter to VLM-st was applied and verified for a variety of free surface bodies. [ABSTRACT FROM AUTHOR]

REVERSE engineering, STATISTICAL sampling, COMPUTER-aided design, THREE-dimensional imaging, OPTOELECTRONIC devices, and PROTOTYPES

The process of capturing the shapes of objects through surface data sampling and generating a 3D CAD model is termed reverse engineering (RE) because the process is the reverse of the normal design and manufacturing sequence. The digitisation process can be achieved through spatial measurements taken by a coordinate measuring machine (CMM). The way of capturing data in a CMM can be divided into contact or non-contact methods. Diode-lasers or CCD cameras are commonly applied in non-contact measuring, while touch probes are applied in contact measuring. There are limitations in obtaining data for complex objects (for under-cut or inner structures) by means of the two abovementioned methods. Therefore, we have designed and assembled a novel device, called an abrasive computed tomography (ACT) apparatus, to overcome the abovementioned limitations. The ACT apparatus uses an abrasive method to remove the inlaid object layer by layer and to capture the cross-sectional image of each layer with a CCD camera. A numerical scheme is applied to obtain the Bezier curve of the boundary in each layer. The combination of all cross-sectional boundaries is used to reconstruct the 3D CAD model of the object. The 3D CAD model can then be transmitted to generate the tool paths in a CNC machine or produce rapid prototyping in a RP machine. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, RAPID prototyping, JOB analysis, TRIANGULATION, ASSEMBLY line methods, and LASERS

The objective of this research is to investigate the effect of slice thickness on the profile accuracy of the model maker (MM) rapid prototyping (RP) system, layer by layer, through non-contact laser probe measurement. A circular triangulation laser probe, model OTM-3A20, made by Wolf & Beck Co., was mounted on a coordinate measuring machine (CMM), as the non-contact sensor. An adjustment device for the laser probe was designed to minimise the cosine error caused by assembly inaccuracy. The alignment test of the measuring laser beam was carried out using a calibrated specimen. The systematic accuracy of the circular triangulation laser probe with respect to the surface roughness and the surface slope of the RP workpiece was investigated using a HP5529A laser interferometer system. The maximum error of 21/2D RP part profile accuracy can be improved from 220 μm to 131 μm, and the average error can be improved from 78 μm to 46 μm as the slice thickness changed from 0.127 mm (0.005 in.) to 0.0127 μm (0.0005 in). However, the machining time increases by about seven fold based on the experimental results. An overall error of 197 μm as measured by the laser probe is attainable using the finest slice thickness 0.0127 mm (0.0005 in.) for the 3D profile accuracy. To verify the accuracy of non-contact laser probe measurement, the 3D profile of the RP part was also measured by a CNC CMM, with good consistency. [ABSTRACT FROM AUTHOR]

CONCURRENT engineering, COMPUTER-aided design, PROTOTYPES, MANUFACTURING processes, SOLID state physics, and NEW product development

Adaptive slicing varies layer thickness by taking the geometry change of the CAD model in the build direction into account to improve surface finish. Direct slicing generates exact slice contours from the original CAD model and avoids an intermediate representation, known as an “STL file”. At present, most direct slicing approaches are restricted to some CSG solids or some CAD systems. In this paper, an approach toward adaptive direct slicing with non-uniform cusp heights independent of CAD systems for rapid prototyping is presented. First the geometry model is imported into the adaptive direct slicing system from CAD systems using the standard STEP format. Using OpenGL graphics libraries, the solid model is then displayed and the user is prompted to specify the allowable cusp height for each highlighted surface. Lastly, the CAD model is sliced adaptively with different cusp heights (tolerance requirements) for different surfaces. With non-uniform cusp heights, adaptive slicing has a higher efficiency. Implementation details and results are also presented. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, CONCURRENT engineering, SILICONE rubber, METHODS engineering, METAL castings, and PRODUCTION planning

Investment casting (IC) offers an economical method for mass producing complex, shaped metal parts. However, high tooling cost and lead times associated with the fabrication of metal moulds for producing IC wax (sacrificial) patterns result in cost justification problems for customised single casting, small- and medium-quantity production. Rapid prototyping (RP) techniques can reduce the costs associated with single-part or small-quantity production as they can be applied to the fabrication of sacrificial IC patterns containing complex and intricate designs with significant cost and lead-time savings. In this project, a benchmark model is designed to assess the fused deposition modelling (FDM) process for creating sacrificial IC patterns. In addition, an indirect approach toward producing wax patterns via silicone rubber moulding is investigated. Cost and lead time comparisons between the two IC pattern production methods were carried out and presented. The dimensional accuracies of metal castings generated from the RP-produced patterns are also presented. [ABSTRACT FROM AUTHOR]

ELECTRODES, PROTOTYPES, INDUSTRIAL design, POWDER metallurgy, MANUFACTURING processes, and COPPER

This paper describes a collaborative research programme aimed at investigating the use of quick EDM electrodes obtained via appropriate rapid prototyping techniques in finishing laser-sintered tools. Two methods were employed in obtaining the EDM electrodes: copper coating of stereolithography models and copper coating of direct metal laser sintered (bronze) models. The amount of copper deposited on both electrode models proved problematic as the electroplating process was unable to deposit enough copper in the inner cavities of the electrodes, with very gradual reduction in copper layer thickness from the outer faces/surface to virtually no deposition in the inner walls and bottom face. Consequently, the electrodes were not suitable for the envisaged EDM process. [ABSTRACT FROM AUTHOR]

RAPID prototyping, SPRAYING, COATING processes, NEW product development, COMPUTER-aided design, and CONCURRENT engineering

Rapid prototyping processes produce parts layer by layer directly from 3D CAD models. An important technique is required to slice the geometric model of a part into layers and to generate a motion code of the cross-sectional contour. Several slicing methods are available, such as slicing from sterolithgraphy (STL) files, tolerate-error slicing, adaptive slicing, direct slicing, and, adaptive and direct slicing. This paper proposes direct slicing from 3D CAD models and generating a G-code contour of each layer using PowerSOLUTION software (Delcam International, Birmingham, UK). PowerSOLUTION includes two main modules: PowerSHAPE is used to build 3D CAD models and PowerMILL is used to produce G-Code tool paths. It provides macro language, picture files and cutting paths for secondary development work. The authors used macro commands to write an interface generating direct slicing from 3D CAD models and G-code contours for all layers. Most well-known controllers in the market accept the G-Code. Therefore, it is easier to apply this scheme in a CNC-machining center to produce rapid prototyping such as laminated object manufacturing (LOM) for complex geometries. The interface was successfully applied the interface to the UV resin spray rapid prototyping (UVRS-RP) machine that was developed to produce RP. [ABSTRACT FROM AUTHOR]