Experimental assessment of hybrid mould performance

Hybrid moulds are a novel approach for rapid tooling of injection moulds that combines conventional machining for the mould structure and rapid prototyping techniques for the moulding blocks (core and cavity). In this study, two routes were used for producing the moulding blocks: selective laser sintering of stainless steel-based powder (hard tool) and epoxy resin vacuum casting (soft tool). The experimental work was based on a complex tridimensional commercial part. The mouldings were made in polypropylene, and the processing performance was monitored online in terms of pressure and temperature at the impression. The performance of the moulding blocks was analysed in terms of thermal and cycle performance and structural integrity. The epoxy tooling route is more adequate for fine detailing than selective laser sintering but is not adequate for parts with extensive ribs or deep bosses. The structural integrity of the less costly epoxy composite can be compromised during ejection, this suggesting the need to evaluate the stress field by simulation at the design stage of the mould.     

3D printed tooling for vacuum-assisted resin transfer moulding

Three-dimensional printing (3DP) is widely considered to be one of the low-cost additive manufacturing (AM) processes. In this paper, the suitability of 3DP for making tooling for the vacuum-assisted resin transfer moulding (VARTM) process is considered. This combination has potential advantages, since VARTM has significant prototyping benefits if it can be combined with a fast and low cost tooling option. This paper presents a new process chain for the manufacture of closed mould composite parts using the VARTM process. It will be shown that 3DP tooling is significantly less accurate than CNC machined tooling, but there is a cost and time advantage to making tooling with 3DP. The mould life is also limited to typically 15 to 30 parts since significant wear occurs in the manufacturing process. Quantitative data are presented to show the effect of treating the mould surface to improve the surface roughness and to determine the mould life. An aspect often lacking in AM research is cost estimation. Here, the first cost model for rapid tooling for VARTM using 3DP moulds is presented and compared to actual results. It is shown that the model is suitable for design for manufacture analysis.     

A scaffolding architecture for conformal cooling design in rapid plastic injection moulding

Cooling design of plastic injection mould is important because it not only affects part quality but also the injection moulding cycle time. Traditional injection mould cooling layout is based on a conventional machining process. As the conventional drilling method limits the geometric complexity of the cooling layout, the mobility of cooling fluid within the injection mould is confined. Advanced rapid tooling technologies based on solid freeform fabrications have been exploited to provide a time-effective solution for low-volume production. In addition, research has made attempts to incorporate conformal cooling channel in different rapid tooling technologies. However, the cooling performance does not meet the mould engineer’s expectations. This paper proposes a novel scaffold cooling for the design of a more conformal and hence more uniform cooling channel. CAD model for constructing the scaffolding structure is examined and cooling performances are validated by computer-aided engineering (CAE) and computer fluid dynamics (CFD) analysis. An erratum to this article can be found at     

<Emphasis Type="Bold">A Rapid Manufacturing Method for Water-Saving Emitters for Crop Irrigation Based on Rapid Prototyping and Manufacturing</Emphasis>

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.     

Tool wear prediction models during end milling of glass fibre-reinforced polymer composites

Composite products are often subjected to secondary machining processes as integral part of component manufacture. However, rapid tool wear becomes the limiting factor in maintaining consistent machining quality of the composite materials. Hence, this study demonstrates the development of an indirect approach in predicting and monitoring the wear on carbide tool during end milling using multiple regression analysis (MRA) and neuro-fuzzy modelling. Although the results have indicated that acceptable predictive capability can be well achieved using MRA, the application of neuro-fuzzy yields a significant improvement in the prediction accuracy. It is apparent that the accuracies are pronounced as a result of nonlinear membership function and hybrid learning algorithms. Using the developed models, a timely decision for tool re-conditioning or tool replacement can be achieved effectively.     

金属粉末激光成形基体表面粘结性研究

金属粉末激光成形技术作为一种新的快速成形技术 ,将传统快速原型技术与激光熔覆技术相结合 ,用于研究具有任意复杂形状或者复杂材料组分金属材料零件 /模具的快速制造技术 ,并可以直接成形金属功能零件。成形加工过程中成形零件与基体表面的粘结牢固性直接决定加工是否可以顺利完成。采用低碳钢作为基体材料 ,基体表面经过打磨、刨削、氧化和磷化等四种不同处理方式进行粘结性试验 ,试验表明磷化表面粘结性能最佳并能成功地应用到金属粉末激光成形工艺中。     

Research on Injection Mould Intelligent Cost Estimation System and Key Technologies

The manufacturing cost of injection-moulded parts is mainly decided by the cost of the injection mould. Thus if we can ascertain the cost of the injection mould as early as possible, it will be a great contribution to an injection mould cost evaluation system and research on the economics of injected part manufacture. In this paper, related work on injection mould cost estimation has been discussed. A case-based reasoning (CBR) approach is used for evaluating the manufacturing cost of injection moulds. Case indexing, neural network-based case retrieval, knowledge-abundant case-adaptation and knowledge-absent case-adaptation strategies, and case learning are all considered. A comprehensive cost model including mould manufacturing costs, tax costs and general administrative costs is also discussed. The model is valuable for the price estimation of injection moulds. The application of the system is illustrated with an example.     

快速模具技术在现代制造技术中的应用

快速模具技术随着工业化生产的发展而产生,一直受到模具界的广泛重视。文中概括地介绍了快速模具技术在现代制造技术中的应用,对于快速模具技术的应用与发展,具有重要的现实意义。     

Manufacture of an injection mould with rapid and uniform cooling characteristics for the fan parts using a DMT process

The aims of the present study is to manufacture an injection mould with a pair of conformal cooling channels in each blade of the mould for a plastic fan part via laser-aided direct metal tooling (DMT) process to achieve both rapid and uniform cooling characteristics. The features of the design and the manufacturing process for the injection mould as well as the characteristics of the manufactured mould were discussed. Three-dimensional injection moulding analyses were performed to obtain a proper design of the conformal cooling channels. Injection moulding experiments were carried out to investigate the practical applicability of the fabricated mould and the influence of the cooling time on the qualities of the moulded product. The results of the experiments showed that a plastic fan part with superior qualities can be fabricated from the designed mould when the cooling time is 13 s. The efficiency of the designed mould was examined through a comparison of the product from the newly designed mould and that from a previously designed mould with linear cooling channels in terms of product qualities as well as the cooling and cycle times. The results of the comparison showed that the newly designed mould can remarkably reduce the positional error distributions and the eccentricity of the moulded product. In addition, it was shown that the cooling and cycle times of the designed mould can be shortened to 35.0 % and 25.7 % of those of the previously designed mould, respectively.     

Automated Process Planning for the Manufacture of Lifters

This paper presents the methodology of a computer-aided process planning system IMOLD  FCAPP for the manufacture of injection moulded components, which will facilitate the standardisation of process planning and significantly reduce lead-time. The main components of the mould such as the slider, the lifter and the mould base are considered in this system. In this paper, the automated process planning for the manufacture of a lifter is described. A combination of the generative and variant approach (hybrid approach) is used for the development of the system. The input to the system is a 3D lifter model. First, the system classifies the lifter types and extracts the feature parameters from the model. Each lifter type refers to a standard process plan template, in which a set of processes is presented in sequence. Secondly, the system selects the machines, cutters, fixtures, and cutting parameters for each process in the plan template, based on the actual dimensions of the features and constraints and rules defined in the system and the available machining resources. The process plan execution is then simulated on the screen step by step.     

Integrating rapid prototyping and tooling with vacuum casting for connectors

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.     

汽车覆盖件冲压模具辅助报价系统的研究

本文从汽车覆盖件冲压模具的制造特点出发,充分考虑了汽车覆盖件冲压模具的结构特点和影响其价格的因素,通过对三种常用报价方法的比较,选择了以制造工时为基础 汽车覆盖件冲压模具报价方法,并借助于现代网络技术开发出一套汽车覆盖件冲压模具辅助报价系统。     

The effects of machining process variables and tooling characterisation on the surface generation

The paper presents a novel approach for modelling and simulation of the surface generation in the machining process. The approach, by integrating a dynamic cutting force model, regenerative vibration model, machining system response model and tool profile model, models the complex surface generation process. Matlab Simulink is used to interactively perform the simulation in a user-friendly, effective and efficient manner. The effects of machining variables and tooling characteristics on the surface generation are investigated through simulations. CNC turning trials have been carried out to evaluate and validate the approach and simulations presented. The proposed approach contributes to comprehensive and better understanding of the machining system, and is promising for industrial applications with particular reference to the optimisation of the machining process based on the product/component surface functionality requirements.     

基于UG电话上盖注塑模具设计与数控加工

以电话机上盖塑件为例,在对塑件的结构工艺性进行分析的基础上,采用UG中的模具设计与加工模块,进行塑件的模具设计与模具的数控模拟加工。通过实例表明,模具设计与制造的一体化应用,缩短了模具设计与制造的周期,提高了生产效率。     

面向熔射快速制模的机器人自动研磨系统的开发

为解决熔射制造大中型汽车覆盖件模具过程中人工研磨时间长、劳动强度大等问题,建立了面向熔射快速制模的机器人自动研磨系统.在该系统上进行机器人研磨工艺参数实验研究,得到了研磨角度、机器人行走速度和路径对研磨表面质量的影响规律;在此基础上选择合适的研磨条件,在通过等离子熔射制造的模具表面皮膜上进行了研磨实验.实验研究结果表明,保持适当的研磨压力,选取合理的机器人行走速度、研磨角度、进给量,可得到较好的研磨效果.该机器人自动研磨系统适用于熔射制造的模具及一般模具的研磨过程.     

Early castability evaluation using analytical hierarchy process

Design for manufacture usually implies applying various guidelines derived from previous experience to improve part design so it is more compatible with the capabilities of the selected process, resulting in better quality and lower cost. The guidelines can be formulated as dimensionless criteria, enabling quantitative evaluation of a particular aspect of part design. There is, however, no good way to compare two or more designs for all aspects, considering that they may not be equally important. In this work, we employ analytical hierarchy process to determine the relative weights of various criteria for castability evaluation. The criteria are categorised in a three-level hierarchy, with the middle level comprising mould, feeding and gating groups. The prioritisation of criteria along with consistency checking of pair-wise comparisons enables a systematic evaluation of alternative product designs for manufacturability. The methodology is illustrated by modifying the product and tooling design of a grey iron bracket casting and estimating the improvement in manufacturability. The results are supported by experiments.     

Enhancing moulds manufacturing by means of reverse engineering

Modern CAD/CAM techniques together with five-axis high-speed milling allow to reduce moulds manufacturing time and costs. Nevertheless, in order to put a mould into use, operations of manual finishing and fitting are still always required. Such operations, performed manually by mould makers, modify the milled surfaces of moulds. Reverse engineering techniques can be employed in quality control to evaluate dimensions and geometrical tolerances on moulds after machining and fitting. Changes in the product’s shape are sometimes decided after a mould has already been machined. In such cases, if possible, the mould maker directly modifies the mould. Thus the final real geometry of the mould does not reflect the one of the original CAD model. The aim of this paper is to point out the benefits of non-contact quality control and to illustrate a procedure, based on reverse engineering techniques, to reconstruct and update the mathematical model of the mould after it has been polished and fit. The procedure was tested on a mould for the production of a plastic camera body that was previously inspected by means of a structured light scanner.     

基于数控加工原型的快速模具制造工艺

提出一种将常规数控加工技术与精密材料成形技术结合应用于快速模具制造的新工艺。工艺路线为在CAD环境中对零件的CAD数据进行前期误差补偿,用普通加工中心快速加工出精密成形用的专用蜡基或泡沫塑料基模具原型,并优化其加工工艺和后处理工艺,最后通过精密铸造工艺制造出模具,使之在少量加工或者不加工条件下能用于实际生产。     

L-Shaped Curved Hole Creation by Means of Electrical Discharge Machining and an Electrode Curved Motion Generator

The study deals with the manufacture of curved holes for water channels in moulds, which are difficult to machine. As holes are generally formed by drilling operations, curved holes are formed approximately as a combination of straight holes, which leads to interference with the smooth stream of coolant and also the low efficiency and unstable performance of cooling of the mould. To solve the problem and to create a curved hole, we devised a simple mechanism, which consists of a helical compression spring, wires, pulleys, and an electrode for electrical discharge machining, which is installed on an electrical discharge machine (EDM). The device allows the electrode to move along a curved line. From experimental results, it is found that the device enables the machining of a curved hole. In addition, the device can make an L-shaped curved hole by connecting two curved holes machined from two perpendicular directions.     

CAGD AND NC MILLING OF THE CASTING MOULD OF HELICAL INTAKE PORT

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