articles+ search results

Rapid prototyping processes produce parts layer by layer directly from the CAD model. The processes proceed by first slicing the geometric model of a part into layers. A standard interface is necessary to convey varied geometric descriptions from numerous CAD packages to Rapid Prototyping (RP) systems. The STL (STereoLithography) format is the most commonly used interface for this purpose. Unfortunately, it is an approximate model and is frequently not robust. Therefore, other interfaces are proposed to be used for RP systems. This paper, Part 1, will discuss several existing interfaces including the STL file for the RP systems. The strengths and weaknesses of these formats when used for RP systems are analysed. Furthermore, a new improved format is proposed by the authors in Part 2. In that paper, the design considerations and data structure of the new format are introduced. [ABSTRACT FROM AUTHOR]

The STL (STereoLithography) file format, as developed by 3D Systems, has been widely used by most Rapid Prototyping (RP) systems and is supported by all major computer-aided design (CAD) systems. However, it is necessary to improve the STL format to meet the development needs of RP technologies. In Part 1, several existing and proposed formats have been discussed. This paper, Part 2, will present an improved interface between CAD and RP systems. The new interface is a file format that supports the STL format, removes redundant information in the STL format and adds topological information to balance storage and processing cost. In addition to supporting facet boundary models, the new interface supports precise models by using the edge-based boundary representation. This paper discusses the design considerations of the new interface and data structures for both facet models and precise models. Finally, a comparison of the new interface and the STL file format will be made. [ABSTRACT FROM AUTHOR]

Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The “Four-wall-header” is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach. [ABSTRACT FROM AUTHOR]

In recent years, new surgical techniques have been developed to improve the quality of operations, reduce the risk to patients and reduce the pain experienced by patients. Prominent developments include minimally invasive surgery, robot-assisted hip operations, computer-assisted surgery (CAS) and virtual reality (VR). These developments have helped surgeons operate under difficult visual conditions. Rapid prototyping (RP) technology has also found applications in medicine. The RP technique is able to fabricate a representative, physical 3D model. This 3D model can enhance interpretation, visual and physical evaluation, and the rehearsal and planning of the surgical steps before a surgical operation is carried out in order to eradicate the trauma. This paper presents the procedures involved in the conversion of computerised tomography (CT) scan data to a useful physical model. A case study of a CT scanned file of a patient who had an injury to the right eye socket is presented. Three different RP systems (SLA, SGC and LOM) are benchmarked for comparison in terms of the surface finish, accuracies, visual appearance and processing speed. Because of the ability of RP to fabricate models that are complex in design with intricate features that may be hidden by undercuts, as demonstrated in this paper, the results of this research can be extended to applications in general engineering. One specific area of application would be reverse engineering. [ABSTRACT FROM AUTHOR]

A new approach to remove point data with Delaunay triangulation is introduced to deal with the size problems of the STL file and the difficulties in the operation of the rapid prototyping (RP) process. The selection of a group of triangles, based on the angle, is used for a robust and reliable implementation of the Delaunay triangulation method. The developed software enables the user to specify the criteria for the selection of the group of triangles by the angle between triangles, the percentage of reduced triangles, and the allowable area. This approach can be used to reduce the measuring data from the laser scanner, thus save the handling time of point data during the modelling process and is useful for verifying and slicing the STL model during the RP process. [ABSTRACT FROM AUTHOR]

PROTOTYPES, COMPUTER-aided design, COMPUTERS in engineering, INTERNET, WIDE area networks, and ENGINEERING design

The STL file, which is de facto standard for the rapid prototyping industries, has too large a file size. This paper proposes an improved interface between CAD and rapid prototyping systems, i.e. a CS (compressed STL) file that has very low data storage redundancies and is completely compatible with the STL file. The CS file is about a quarter of the size of the original binary STL file, without any model information loss. This is very suitable for file transferring via the Internet. Removing coordinate data of duplicate vertices, bit-compression technology, and a comparison of the size and compressed performance of the STL and the CS are also discussed. [ABSTRACT FROM AUTHOR]

FLEXIBLE manufacturing systems, PETRI nets, MATERIAL requirements planning, PROCESS control systems, PRODUCTION engineering, and PRODUCTION scheduling

Manufacturing systems are faced with ever-increasing customisation and unstable demand. The traditional hierarchical control structures for shop floor (pre-release planning, scheduling, dispatching and activity control) are often inflexible in responding to unexpected scenario changes and are thus not robust to system disturbances. In this paper, an object-oriented approach to modelling of FMS dynamic tool allocation and control under a non-hierarchical shop floor control scheme using coloured Petri nets is presented. A client–server paradigm is used in the proposed modelling method. The complete FMS model is partitioned into individual classes (machines, magazines, tool transport system, SGVs, tool storage, etc.) thereby significantly reducing the complexity of the model to a tractable size. The system performance under different tool request selection rules is also evaluated using coloured Petri net simulation. The proposed method can provide the designer of a tool management system with a high-level and structured representation of the tool-sharing control. It also provides an effective method for prototyping and evaluating performance of object-oriented shop floor control software. [ABSTRACT FROM AUTHOR]

TURBINE blades, PROTOTYPES, ROTATIONAL motion (Rigid dynamics), EMBEDDED computer systems, ELECTRIC generators, ELECTRIC power, and FEASIBILITY studies

This paper presents the methodology for quantifying the blade assembly process with the future objective of fully automated assembly planning. The proposed method is aimed at eliminating the expensive and time-consuming physical prototyping needs by analysing and evaluating the feasibility of the blade assembly process using a CAD-based virtual prototype. The virtual prototype of the entire assembly operation is created for the blade assembly from a torque converter of an automobile transmission system. This model development is implemented using ProEngineer. Owing to the modelling requirements, the design intents, pertinent parameters, and their relationships in the entire blade assembly process must be captured and integrated into the model. The virtual assembly prototyping package developed is capable of computing and offering computer animated simulations of the interference of the blade tabs with the turbine and the pump shell during the assembly process. The work focuses on quantifying the blade assembly process by expertly defining some benchmarks and indices based on the kinematic behaviour of the assemblages. The benchmarks can also be used for documenting, evaluating, and comparing the blade assembly designs in various assemblages of torque converters to improve and transfer the experiences of the designers embedded in the model, for the torque converter industry. The model developed in this work has been tested and verified to be effective with a real torque converter model built at a local company. The results of the experiments are discussed. [ABSTRACT FROM AUTHOR]

TISSUE engineering, DESIGN, PROTOTYPES, POWDER metallurgy, CONCURRENT engineering, and MANUFACTURING processes

In tissue engineering (TE), a porous scaffold structure may be required as a template to guide the proliferation, growth and development of cells appropriately in three dimensions. Although TE scaffolds can be created using one of many conventional techniques available, most will suffer from a lack of mechanical strength and/or uniformity in pore distribution and sizes. This study is focused on creating scaffolds using rapid prototyping (RP) techniques. Utilising these novel techniques, a computer-aided design (CAD) of the scaffold structure must first be modelled. The scaffold structure is then fabricated directly from CAD data using a RP system. The objective of this research is to (1) investigate and select various polyhedral shapes suitable for scaffold modelling, (2) classify the selected unit cells, (3) create a parametric library of scaffold structures and (4) verify by building the CAD models using the selective laser sintering process. The first two objectives are covered in Part 1 of this two-part paper. The remaining objectives will be described and discussed in Part 2. [ABSTRACT FROM AUTHOR]

TISSUE engineering, PROTOTYPES, CONCURRENT engineering, FEASIBILITY studies, BIOMEDICAL engineering, COMPUTER-aided design, and MANUFACTURING processes

Rapid prototyping (RP) techniques have been found to be advantageous for tissue engineering (TE) scaffold fabrication due to their ability to address and overcome the problems of uncontrollable microstructure and the feasibility issues of complex three-dimensional structures found in conventional processing techniques. This research proposes a novel approach for TE scaffold manufacture using RP techniques. The approach involves the integration of medical imaging devices (CT/MRI) for the acquisition of anatomic structural data, three-dimensional CAD modelling for designing and creating the digital scaffold models and RP for fabricating the physical scaffolds. To aid the user in CAD modelling, a standard parametric library of scaffold structures is designed and developed. With the library, a user can select the geometry of the scaffold unit cell and size it to suit the end application of the TE scaffold. A developed application program will then assemble the scaffold structure from the selected unit cell, following the surface profile of the anatomic structure to be replicated. A physical scaffold will then be built using an RP system. [ABSTRACT FROM AUTHOR]

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]

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]

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]

SPRAY nozzles, PROTOTYPES, COMPUTER-aided design, ALGORITHMS, MODELS & modelmaking, and ATOMIZERS

This study aims to build a triangular-mesh model directly from scanned 3D data points, which then generate the stereolithography (STL) file, thus avoiding the troublesome task of producing a CAD model. Accuracy of the triangular-mesh model is achieved because the pitch between data points is generally very small. In addition, the paper proposes a multi-nozzle path algorithm to increase both spraying efficiency and part accuracy. The processing procedure includes: (1) Establishing the triangular-mesh model from scanned data points, which are retrieved by means of contact- or non-contact type measuring machines as well as developing the algorithm to add the radius of the probe automatically. (2) Equally slicing the triangular-mesh solid model and plan spraying paths. (3) Determining the amount and diameter of nozzles appropriate for each slice to generate multi-nozzle spraying paths. [ABSTRACT FROM AUTHOR]