Compensation of distortion in the bottom exposure of stereolithography process

The rapid prototyping (RP) process is the fastest and most feasible method for prototype construction. However, with the use of any material or build method the phenomenon of volume shrinkage is unavoidable. It is known that volume shrinkage and curl distortion are the major causes that lead to poor accuracy of the built prototype. Subsequently, in order to improve the precision of dimension and volume shrinkage, more expensive equipment is used on the market. Also, it is expensive and inefficient to obtain better process parameters through trail and error in the RP process. In order to improve the precision of dimension, reduce the processing cost and the frequency of trail and error, this study first induces the concept of computer-aided engineering (CAE) into the processing of RP, which uses a dynamic finite element simulation code to simulate the photopolymerization process, so as to reduce the time for selecting the processing parameters and obtain the distortion data. Second, by means of reverse distortion compensation to obtain a new CAD model, then it is sent to a RP machine for the actual prototyping processes, so as to obtain a more accurate precision. Finally, in order to confirm this method and restriction in experimental equipment, the stereolithography process and simple laser scanning path are chosen as examples. The results of the simulation and experiment prove that the method proposed herein is effective. It not only can reduce the cost of equipment but also obtain a better precision of dimension on final-parts at the same time. Besides, it is believed that this research method can be promoted to other materials or build methods in RP fabrication .     

Rapid prototyping in the development of optical pickup unit

Rapid prototyping (RP) has already proven itself in the electronics industry as a method for shortening the product development time cycle. In the development of the optical pickup unit (OPU), extremely high precision is needed to make a functional model. Very often, in the design phase of the product development cycle, the prototype of the OPU is machined from a single piece of aluminium block to make the working sample. In this project, a comparison of the machined aluminium sample, RP samples from various RP processes and that moulded out from the injection moulding machine is made on surface finishing as well as dimensional accuracy. Finally, a comparison of tooling cost, piece part cost and lead time of obtaining the parts is also discussed on the different prototyping and manufacturing processes.     

Rapid Sheet Metal Manufacturing. Part 2: Direct Rapid Tooling

The traditional methods adopted for tool design and production in the sheet metal forming industry usually carry a high cost and long lead time resulting in cost justification problems for short production runs. Rapid tooling (RT) technology is capable of justifying the cost of tooling suitable for short production runs or design evaluation purposes. In Part 1 of this work, a new process termed rapid sheet metal manufacturing (RSMM) for the production of soft tooling suitable for prototyping, tool development, and short production runs was introduced. In addition, an indirect RT method employing rapid prototyping (RP), rapid soft tooling, and casting for the fabrication of non-ferrous tools was presented. The current work, Part 2, presents an alternative technique for RSMM whereby metal forming tools are fabricated directly from the RP system via selective laser sintering (SLS).     

A decision support system for the selection of a rapid prototyping process using the modified TOPSIS method

As a new technology that fabricates a three-dimensional (3D) physical model from computer-aided design (CAD) data using an additive process, rapid prototyping (RP) has been developed to reduce product development time and cost. Recently, many newly emerging techniques of RP have been commercialized worldwide. This paper deals with the selection of an optimal RP system that best suits the end use of a part by using multiple-attribute decision making and the test part designed with conjoint analysis to reflect users’ preference. Evaluation factors include only the major attributes that significantly affect the performance of an RP system such as accuracy, roughness, strength, elongation, part cost and build time. Crisp values such as accuracy and surface roughness are obtained with a new test part developed in this study. The part cost and build time are identified as falling within approximate ranges due to varying costs and many variable parameters. They are presented as linguistic values that can be described with triangular fuzzy numbers. Based on the evaluation values obtained, an appropriate RP process for a specific part application can be selected using a modified technique of order preference by a similarity to ideal solution (TOPIS) method given crisp data and linguistic variables as the alternatives of attributes. Finally, each attribute’s weight is assigned using a pairwise comparison matrix. Determined using these weights, the final ranking order aids in the selection of the RP system.     

Rapid tooling technology. Part 2. A case study using arc spray metal tooling

In this case study of arc spray metal tooling, the feasibility of implementing arc metal spraying on a master, produced using an RP technique, to produce the tool is tested. This tool is then used to produce plastic parts in injection molding. In this project, the tool was completed in less than 2 weeks and at an approximate cost of $4180. Compared to traditional tool shop methods, this method would provide time and cost savings of at least 50%.     

Determination of optimal build direction in rapid prototyping with variable slicing

Several important factors must be taken into consideration in order to maximize the efficiency of rapid prototyping (RP) processes. The ability to select the optimal orientation of the build direction is one of the most critical factors in using RP processes, since it affects part quality, build time, and part cost. This study aims to determine the optimal build-up direction when a part is built with the variable layer thickness for different RP systems. The average weighted surface roughness (AWSR) that is generated from the stair stepping effect, the build time, and the part cost using the variable layer thickness are all considered in the process. Using the multi-attribute decision-making method, the best orientation is determined among the orientation candidates chosen from the convex hull of a model. The validity of the algorithm is illustrated by an example. The algorithm can help RP users select the best build-up direction of the part and create an efficient process planning.     

<Emphasis Type="Italic">Rapid Moulding Using Epoxy Tooling Resin</Emphasis>

Rapid prototyping (RP) is fast becoming a standard tool in today’s product design and manufacturing environment. Significant benefits in terms of lead time and cost savings have been reported with the use of RP technology. However, these benefits can be derived only during the design and planning stages of a new product where RP parts are produced in small quantities for design evaluation, form fitting, and marketing analysis. The high cost of raw material stock used in current RP systems makes them economically unsuitable even for small-batch production during the product evaluation and manufacturing stages. Further to this, the difference between the mechanical and physical properties of RP and traditional manufacturing materials limits the functionality of RP end products. Rapid tooling (RT) technology has opened up new cost-effective solutions for small-batch production. In this paper, a technique using a rapid soft-tooling approach, namely, aluminium filled epoxy resin tooling for injection mould preparation is successfully explored. An aluminium filled epoxy resin mould is evaluated and the characteristics of the injection-moulded end products are presented.     

Tool deflection error compensation in five-axis ball-end milling of sculptured surface

Manufacturing of aircraft structural parts have the characteristics of complex process, large variety, small batch, and frequent change of production status. In order to shorten lead time and reduce cost, high-efficiency communication and collaboration among manufacturing departments are required. However, in the existing research literature, tool/fixture design, manufacturing simulation, and online machining process monitoring are not fully taken into account for collaboration. In order to address these challenging issues, this paper proposes a collaborative manufacturing framework based on machining features and intelligent software agents. The components of the proposed framework include a machining process planning agent, a numerical control (NC) programming agent, a simulation and verification agent, a tool/fixture design agent, a cost estimation agent, a production management agent, and an online machining process monitoring agent. Machining features are used as information carrier for communication and collaboration among these agents. This paper particularly focuses on the collaboration between tool/fixture design and NC programming, as well as the collaboration between online machining processes and related departments. The proposed approach has been implemented through a prototype system and tested in a large aircraft manufacturing enterprise with some very promising results.     

Rapid tooling technology. Part 1. A comparative study

Rapid tooling (RT) is the technology that adopts rapid prototyping (RP) techniques and applies them to tool and die making. Research into RT techniques has shown that it is gaining more importance and is starting to pose a serious threat to conventional machining. In this paper, several popular RT techniques are discussed and then classified. A comparison is also made on these techniques based on tool life, tool development time and cost of tool development.     

Adaptive rapid prototyping/manufacturing for functionally graded material-based biomedical models

In this paper, research on developing adaptive rapid prototyping/manufacturing (RP/M) algorithms for functionally graded material (FGM)-based biomedical models is reported. Non-uniform rational B-spline and FGM-based features have been proposed to present the models. Innovative algorithms for tool path optimization in RP/M have been developed, including: (1) a mixed tool path algorithm to generate contour/offset tool paths to represent varying material composition along the boundary of each sliced layer of a model and zigzag tool paths to present the internal area of a single material to simplify computing and processing and (2) adaptive algorithms to control the RP/M nozzle/print head to minimize the build time of each sliced layer according to the geometrical characteristics of the model. Case studies of FGM-based biomedical models have been used to verify and demonstrate the performance of the research in terms of algorithm effectiveness.     

经济型快速成形系统研究

基于模块化与取代相接合的原则,提出经济型快速成形系统的概念。这种快速成形系统以用户现有的ＣＮＣ数控机床及三维ＣＡＤ造型软件为基础,配置切片处理软件和必要快速成形运动部件所构成。探讨该系统的组成特点。理论分析和开发实践表明,经济型快速成形系统不但能大大降低设备的投资费用,将降低ＲＰ技术的应用难度,加快该技术推广。     

Integrated simulation of the injection molding process with stereolithography molds

Functional parts are needed for design verification testing, field trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process holds the best promise of reducing the time and cost needed to mold low-volume quantities of parts. The potential of this integration of injection molding with RP has been demonstrated many times. What is missing is the fundamental understanding of how the modifications to the mold material and RP manufacturing process impact both the mold design and the injection molding process. In addition, numerical simulation techniques have now become helpful tools of mold designers and process engineers for traditional injection molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for verification, which show that the present scheme is well suited to handle RP fabricated stereolithography (SL) molds.     

动态分区并行扫描方法研究

如何制造大型原型零件是目前快速成形技术(RP)研究的热点之一。分层实体制造工艺(LOM)在直接制造大型原型方面具有独特的优势。造型周期长是制造大型原型的困难之一,针对LOM工艺提出了动态分区并行扫描成形的方法。分析和试验结果表明,采用该方法可以有效提高成形效率,是实现直接制造大型原型的可行途径之一。     

An intelligent concurrent design task planner for manufacturing systems

Product design is an integral component of manufacturing systems. This paper presents a prototype intelligent concurrent design task planner, which combines the strength of genetic algorithms and an iterative design analyser for the scheduling of a complex design process of a manufacturing system. It accounts significantly for shortening the time-to-market of a product, and hence, improves the agility of a manufacturing system. The proposed prototype attempts to schedule the design process inherently containing iteration, which is caused by the interdependencies among tasks and leads to prolonged lead-time and increased cost on the whole time-span of introducing a product. Genetic algorithm (GA), as one of the effective optimisation techniques, is embodied in the prototype to search for the optimal schedule for a design process for the goal of satisfying the managerial objective under resource constraints. The iterative design analyser, which is basically an analytical tool for design iteration, is utilised to estimate the time and engineering cost spent on the design process for each candidate schedule. Considering the unpredictable length of a schedule for iterative design process, a novel chromosome representation scheme and unique crossover and mutation operators have been introduced. A case study conducted on a burn-in system of a manufacturing company has illustrated the effectiveness of the proposed prototype.     

三角Bézier曲面建模的RE系统与RP系统集成

为解决复合三角Bezier曲面与快速原型系统接口,以便实现两者集成,提出了按给定精度从复合三角Bezier曲面模型产生STL文件数据的方法,并在原型系统上得到验证,将推动反求工程与快速原型技术的进一步应用。     

EDM石墨电极快速研磨成型研具的开发研究

简介Hauseman研磨研具的特点、制造要求和制造方法;对研具配方进行深入的理论分析,在此基础上,通过实验获得研具制造的最佳配方,并进行了研磨实验给予验证。     

集成环境下数控机床虚拟样机的建造与实现

分析了虚拟样机技术的优势和特点,研究了数控机床虚拟样机技术的实现策略.将数控机床划分为有机关联的单学科系统模型,分别由不同学科专家在支撑软件上并行建模,实现在集成环境下数控机床虚拟样机的建造与实现.     

高速扫描机在产品开发中的应用

介绍一种高速扫描机，取代传统的数字化扫描技术和昂贵而难以普及的激光扫描机。共扫描机可对样件进行连续扫描，使无法用数学方式定义的表面，通过扫描，快速而准确地转化为数学模型，再与ＣＡＤ／ＣＡＭ技术相结合。大大地加快了新产品开发周期，降低了开发成本，使ＣＡＤ／ＣＡＭ技术得到更广泛的应用。     

基于STEP-NC加工工步的优化

研究了基于精英选择遗传算法的加工工步序列优化技术。传统的加工工艺路线是以工序为制造单元,而在基于STEP-NC的加工中,是以加工工步为制造单元,并且面向数控加工中心的一种加工过程,由加工工步变换所带来的零件转位、刀具更换等所消耗的辅助加工时间为最短作为优化目标,来进行加工工步序列的优化,并对加工工步序列的优化算法进行了验证。     

Study of Trapped Material in Rapid Prototyping Parts

Since the launch of the first commercial system in 1988, rapid prototyping (RP) technology is fast being accepted in the fields of product design and development, in the tool and die making industry and recently, for biomedical applications. Although, in theory, RP is able to produce an object of any complexity, problems such as having material trapped inside parts with hollow features still frequently occur during normal operation. This research project seeks to achieve a better understanding of the formation of trapped material inside RP parts, with the eventual aim of developing an algorithm to avoid this problem. In this paper, the causes and effects of trapped material will be discussed for stereolithography apparatus (SLA), solid ground curing (SGC), selective laser sintering (SLS), and laminated object manufacturing (LOM). Finally, current remedies will be presented.