Progress of remanufacturing engineering and future technology

After development for decades, abroad remanufacturing has formed a complete industrial system. At present, the research emphases are on marking logistics management and market cultivation theory of remanufacturing products, and so on. The Chinese remanufacturing starts fairly late. After 10 years of development, it formed a remanufacturing mode with Chinese characteristics that is sustained by high-tech industries, using the surface engineering
technology to restore the size and improve properties, and combining manufacturing, study and research together. The remanufacturing mode is not only circular but also economic. With the development of science and technology, future remanufacturing technology will break the previous limits, explore and understand the limits of micro machining. It will carry out the waste product remanufacturing in the micro-nano scale, and extend the remanufacturing industry to a more broad space.     

Overlaying welding technology and performance of axle tube remanufacturing

Screw failure is one of the main scrap forms for rear axle tube, and thread turning after surfacing is a common means of remanufacturing. This paper takes rear axle tube as the main research topic, which is made of 40Mn and provided by an axle company. Manual electric arc welding, CO2 shielded arc welding and argon shielded arc welding are carried to overlay the damaged thread. The deposited metal consists of two welding material lays.Welding process and overlay properties are characterized by the test and analysis of microstructure, residual stress and hardness of surfacing layers. The results show that
argon shielded arc welding is an effective method to repair the failure thread; its microstructure of fusion area is meticulous and uniform; its residual compressive stress (absolute value) of welding surface is the biggest among the three welding methods; its hardness curve is relatively flat and appropriate for turning.     

先进的熔化极气体保护焊焊接技术发展

GMAW由于其自身诸多优点,在焊接生产中已经占主要地位。但焊接过程线能量较大、成型不如GTAW、飞溅问题和全位置焊接性不佳,成为限制其在高端产品上应用的弱点。随着先进的电力电子技术和数字化控制技术的发展,先进的GMAW焊接技术有望解决上述问题。本文综述了目前国际先进的GMAW焊接技术,重点介绍了德国CLOOS的CP技术,EWM的Coldarc焊接技术,福尼斯的CMT(包括CMT-Pluse MIX)技术以及PLT的Super-MIG技术,上述方法通过先进的逆变技术和控制技术在溶滴过渡、送丝控制、降低热输入等方面有效地改善了GMAW的上述弱点,在降低焊接过程线能量、改善焊接过程飞溅和焊缝成型、提高焊接质量和效率等方面取得了很好的效果。     

On the attractiveness of sorting before disassembly in remanufacturing

We examine the attractiveness of simple sorting procedures characterized by limited accuracy just before disassembly and remanufacturing of used products. That type of quick sorting is often made possible through the installation of simple electronic devices in new products, which record basic usage data and provide information about the remanufacturability of the product without the need for its disassembly. We study a two-level reverse supply chain with remanufacturing and we concentrate on the single-period setting. There is uncertainty about the remanufacturability of used products and we derive the conditions under which quick sorting is economically justifiable. We show that the economic attractiveness of sorting depends on the costs of transportation, disposal, disassembly, the cost and accuracy of the sorting procedure and the expected quality of the returned items.     

GMAW焊接熔池的流场及其对熔池形状的影响

采用数值分析方法研究了ＧＭＡＷ焊接熔滴状,射流过渡时焊接池的流场,分析了流场对熔池形状的影响。实验表明,焊缝尺寸的计算值和实测值吻合良好,建立的数值分析模型可精确地模拟ＧＭＡＷ焊接熔池的流场,这对控制焊接成形,提高焊接质量具有重要意义。     

Optimal acquisition decision in a remanufacturing system with partial random yield information

When making decisions to acquire used products or components (cores), a remanufacturer faces limited information on the quality or proportional yield of cores during the recovery process. In this paper, we propose and analyse a robust optimisation model for studying the remanufacturing decision problem with partial random yield information, that is, when the quality information of cores is partly unknown in a remanufacturing system. Regarding the impacts of unknown yield information, we only require the support and mean of the proportional yield rather than the true distributions. The closed-form solutions of acquisition quantities are derived based on the minimax regret approach. In addition, to validate the effectiveness of the analytical results, particularly the acquisition of yield information, numerical experiments are designed and implemented using (1) the support and mean of the proportional yield based on the manufacturer’s knowledge and (2) a sampling inspection to evaluate the performance of the robust optimisation approach, the benchmark, and the naïve approach. We observe that the minimax regret approach slightly underperforms compared to the benchmark but performs much better than the naïve approach. As an acceptable choice, this approach is less complicated and extremely easy to implement to meet the needs of practical situations based on its robust closed-form solutions.     

基于互联网的机器人远程实验系统

将互联网技术、机器人远程控制技术和计算机技术有机结合起来，建立了一个基于互联网的机器人远程实验系统。操作者可以在任何时间和任何地点通过互联网来控制和操作机器人臂手集成系统。用户通过互联网可以进行机器人语言的学习、编程及直接控制机器人关节运动，完成一些简单的操作，也可以利用带有力觉和触觉反馈的人机交互设备，在虚拟仿真规划的基础上，完成复杂的操作任务。本系统的建立同时也为有限或贵重设备的共享及异地协同实验研究提供了技术支持。     

Predicting of bead undercut defects in high-speed gas metal arc welding (GMAW)

In the gas metal arc welding (GMAW) process, when the welding speed reaches a certain threshold, there will be an onset of weld bead undercut defects which limit the further increase of the welding speed. Establishing a mathematical model for high-speedGMAWto predict the tendency of bead undercuts is of great significance to prevent such defects. Under the action of various forces, the transferred metal from filler wire to the weld pool, and the geometry and dimension of the pool itself decide if the bead undercut occurs or not. The previous model simplified the pool shape too much. In this paper, based on the actual weld pool geometry and dimension calculated from a numerical model, a hydrostatic model for liquid metal surface is used to study the onset of bead undercut defects in the high-speed welding process and the effects of different welding parameters on the bead undercut tendency.     

Experimental investigation on the effects of process parameters of GMAW and transient thermal analysis of AISI321 steel

Gas metal arc welding (GMAW) develops an arc by controlling the metal from the wire rod and the input process parameters. The deposited metal forms a weld bead and themechanical properties depend upon the quality of the weld bead. Proper control of the process parameters which affect the bead geometry, the microstructures of the weldments and the mechanical properties like hardness, is necessary. This experimental study aims at developing mathematical models for bead height (HB), bead width (WB) and bead penetration (PB) and investigating the effects of four process parameters
viz: welding voltage, welding speed, wire feed rate and gas flow rate on bead geometry, hardness and microstructure of AISI321 steel with 10 mm thickness. The transient thermal analysis shows temperature and residual stress distributions at different conduction and convection conditions.     

Development of remaining life prediction of crankshaft remanufacturing core

This paper reviewed the main research work in the field of remaining life prediction of crankshaft remanufacturing core by Science and Technology on Remanufacturing Laboratory. Based on the results of finite element analysis, the R angle zone of crankshaft was determined as a major measuring position. A special measuring probe is developed, and bending fatigue bench tests were carried out to collect electromagnetic damage information during
fatigue process. A neural network model was established to identify damage degree of crankshaft core, and a damage evaluation equipment for crankshaft core was developed.     

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.     

机器人刚度控制及实验研究

采用腕力传感构成力反馈和刚度控制策略。在五自由度机械手Ｍｏｖｅｍａｓｔｅｒ－ＥＸ上实现了垂直方向，水平方向和任意斜方的扦轴入孔装配作用。     

Plasma transferred arc forming technology for remanufacture

The plasma transferred arc (PTA) forming remanufacturing technology was introduced in this paper.This technology includes plasma surfacing, deposition and rapid forming technology. With self-developed plasma forming system, the thrust of engine cylinder body was remanufactured by PTA powder surfacing. In the concrete,the Ni15 alloy was deposited on the thrust face of the body in order to recover its dimension. In addition, the remanufacturing forming with Fe-based, Inconel 625 alloy was studied. The microstructure and hardness of the as-deposited materials were investigated.     

Uncapacitated production planning with multiple product types, returned product remanufacturing, and demand substitution

This paper investigates an uncapacitated multi-product production planning problem with returned product remanufacturing and demand substitution, where no backlog and no disposal are allowed. Both the production of new products and the remanufacturing of returned products are considered to meet time-varying demands in a finite time horizon. Setup costs are taken into account when a new product is manufactured or a returned product is remanufactured. The problem is to determine when and how many returned products are remanufactured and new products are manufactured so as to minimize the total cost, including manufacturing, remanufacturing, holding and substitution costs. We first develop an optimization model to formulate the problem. We then propose a dynamic programming approach to derive the optimal solution in the case with large quantities of returned products. We further propose an approximate approach for the general problem to compute a near-optimal solution. The proposed approaches are evaluated by computational experiments and the effectiveness of the approximate approach is verified. Some managerial insights regarding the effects of remanufacturing/substitution are also obtained from the computational studies. This work was partly supported by the National Science Foundation of China under Grant No. 70329001, 70321001, China Postdoctoral Science Foundation under Grant No. 2003034020, 70501014, SRF for ROCS, SEM (2004) and Hong Kong Research Grants Council under Earmarked Grant No. CUHK 4170/03E. We wish to express our sincere appreciation to the Special Issue Editor and the two referees for their constructive comments and suggestions to help improve our paper.     

Mechanical and Metallurgical Studies in Double Shielded GMAW of Dissimilar Stainless Steels

In the present work, a simple arrangement is made to provide double layer shielding gas supply in addition to primary shielding during gas metal arc welding (GMAW) of two dissimilar stainless steels, i.e., AISI 316 and duplex 2205. Influences of double layer shielding in addition to five more process parameters like welding current, voltage, material of the electrode wire, the type of primary shielding gas, and flow rate on joint tensile strength and fusion zone microhardness are studied. An experimental design technique is used to design the experimental conditions and the results are analyzed to observe the influences of each process parameter and their interactions. The tensile strength is more influenced by the electrode material and the type of shielding, whereas current, interaction between current × voltage and current × flow rate significantly influence microhardness. Welding voltage influences both tensile strength and microhardness. Double layer shielding with CO₂ as an outer shielding layer helps in controlling the cooling rate which improves the tensile strength and microhardness. Microstructural observations by scanning electron microscopy reveal that moderate to low heat input with a single layer of shielding results in poor joint strength and severe damage or lack of fusion, and the duplex 2205 filler gives the maximum joint strength due to the presence of a ferrite structure.     

A holistic decision support tool for remanufacturing: end-of-life (EOL) strategy planning

Remanufacturing is a key enabler for sustainable production due to its effectiveness in closing the loop on material flows, extending product life cycle and reducing production waste and emission. In this paper, a holistic decision support tool to facilitate the product end-of-life (EOL) strategy planning, specifically using remanufacturing as a key strategy is presented. The proposed model incorporates checklist methods to evaluate the viability of conducting remanufacturing for a product and its components. An optimization model for determining the Pareto set of optimal EOL strategies that correspond to maximum economic profit and minimum environmental impact is presented. Since determination of this Pareto set via enumeration of all EOL strategies is prohibitively time-consuming, even for a product with a small number of components, genetic algorithm (GA), specifically NSGA-II has been utilized to achieve rapid calculation of the set of optimum EOL strategies. This NSGA-II method permits extensive sensitivity analysis to understand thoroughly the impact of situational variables, such as reverse logistic cost, technology and replacement part availability, etc., on the EOL decision making, i.e., Pareto front, and thus leading to improved strategy planning and better productdesign. The case study involving EOL treatment of two types of desktop phones is described to illustrate the utility of the proposed methodology.     

Robotic disassembly sequence planning using enhanced discrete bees algorithm in remanufacturing

Increasing attention is being paid to remanufacturing due to environmental protection and resource saving. Disassembly, as an essential step of remanufacturing, is always manually finished which is time-consuming while robotic disassembly can improve disassembly efficiency. Before the execution of disassembly, generating optimal disassembly sequence plays a vital role in improving disassembly efficiency. In this paper, to minimise the total disassembly time, an enhanced discrete Bees algorithm (EDBA) is proposed to solve robotic disassembly sequence planning (RDSP) problem. Firstly, the modified feasible solution generation (MFSG) method is used to build the disassembly model. After that, the evaluation criterions for RDSP are proposed to describe the total disassembly time of a disassembly sequence. Then, with the help of mutation operator, EDBA is proposed to determine the optimal disassembly sequence of RDSP. Finally, case studies based on two gear pumps are used to verify the effectiveness of the proposed method. The performance of EDBA is analysed under different parameters and compared with existing optimisation algorithms used in disassembly sequence planning (DSP). The result shows the proposed method is more suitable for robotic disassembly than the traditional method and EDBA generates better quality of solutions compared with the other optimisation algorithms.     

Determining the critical transition current for metal transfer in gas metal arc welding (GMAW)

It is of great significance to determine the critical transition current from globular transfer to spray transfer in gas metal arc welding (GMAW) because metal transfer modes affect the weld quality and welding productivity. In this study, a simple model is developed to calculate the critical transition current based on the analysis of various forces exerted on a pendent droplet at the electrode tip. It is found that the force exerted by the incoming molten metal from the wire on the drop, i.e., the term ṁ _c v _c, plays an important role in determining the critical transition current. For mild steel wires and argon shielding gas, the critical transition current is predicted with different levels of wire diameter and extensions. The calculated results match the experimental ones.     

机器人触觉识别系统的研究

介绍了一种机器人触觉识别系统。该系统具有智能抓握功能，能抓握各种机械零件及鸡蛋、玻璃器皿等易碎物体。在抓握物体的同时可自动获取、处理该物体的触觉图象，从而可以自动识别某些规则物体。该系统的建立将为智能机器人提供实用化技术。     

A strategic framework for the design and implementation of remanufacturing operations in reverse logistics

Reverse logistics (RL) is a systematic process that manages the flow of products/parts from the point of consumption back to the point of manufacturing for possible recycling, remanufacturing, or disposal. Although the concept of RL is well-known in logistics and supply chain management, the available holistic literature and theory of RL are scarce. This paper surveys current RL literature and identifies the present state of theory in RL by formulating the propositions for strategic factors. The approach used is grounded theory development. The strategic factors are in turn delineated and evaluated in terms of specific sub-factors associated with each factor by the use of interview protocol and within the context of an in-depth analysis of two companies in different industries that are engaged in remanufacturing/recycling operations within RL systems. The analysis of these case studies, using the grounded theory approach, resulted in insights regarding their RL practices. Based on these insights and strategic factors and sub-factors, a framework for effective design and implementation of remanufacturing/recycling operations in RL is provided. This framework allows for the determination of the viability of returned products/parts in the RL system. The findings outline how our RL theory is enhanced and how our understanding of RL practices with respect to remanufacturing/recycling operations is improved. In conclusion, managerial implications and future research directions are presented.