Effect of process parameters and mathematical model for the prediction of bead geometry in pulsed GMA welding

Pulsed gas metal arc welding is one of the most widely used processes in the industry. It offers spray metal transfer at low average currents, high metal deposition rate, versatility, less distortion, and the ability to be used in automated robotic welding systems. The weld bead plays an important role in determining the mechanical properties of the weld. Its geometric parameters, viz., width, reinforcement height, and penetration, are decided according to the welding process parameters, such as wire feed rate, welding speed, pulse current magnitude, frequency (cycle time), etc. Therefore, to produce good weld bead geometry, it is important to set the proper welding process parameters. In the present paper, mathematical models that correlate welding process parameters to weld bead geometry are developed with experimental investigation. Taguchi methods are applied to plan the experiments. Five process parameters, viz., wire feed rate, plate thickness, pulse frequency, pulse current magnitude, and travel speed, are selected to develop the models using multiple regression analysis. The models developed were checked for their adequacy. Results of confirmation experiments show that the models can predict the bead geometry with reasonable accuracy.     

Development of an automatic arc welding system using SMAW process

In end milling of pockets, variable radial depth of cut is generally encountered as the end mill enters and exits the corner, which has a significant influence on the cutting forces and further affects the contour accuracy of the milled pockets. This paper proposes an approach for predicting the cutting forces in end milling of pockets. A mathematical model is presented to describe the geometric relationship between an end mill and the corner profile. The milling process of corners is discretized into a series of steady-state cutting processes, each with different radial depth of cut determined by the instantaneous position of the end mill relative to the workpiece. For the cutting force prediction, an analytical model of cutting forces for the steady-state machining conditions is introduced for each segmented process with given radial depth of cut. The predicted cutting forces can be calculated in terms of tool/workpiece geometry, cutting parameters and workpiece material properties, as well as the relative position of the tool to workpiece. Experiments of pocket milling are conducted for the verification of the proposed method.     

Optimization of flux-cored arc welding process parameters by using genetic algorithm

The effect of flux-cored arc welding (FCAW) process parameters on the quality of the super duplex stainless steel (SDSS) claddings can be studied using Taguchi L9 design of experiments. In this experimental investigation, deposits were made with 30 % bead overlap. Establishing the optimum combination of process parameters is required to ensure better bead geometry and desired properties. The above objectives can be achieved by identifying the significant input process parameters as input to the mathematical models like welding voltage (X ₁), wire feed rate (X ₂), welding speed (X ₃), and nozzle-to-plate distance (X ₄). The identified responses governing the bead geometry are bead width (W) and height of the reinforcement (H). The mathematical models were constructed using the data collected from the experiments based on Taguchi L9 orthogonal array. Then, the responses were optimized using non-traditional nature-inspired technique like genetic algorithm (GA).     

Solving a new mathematical model for a hybrid flow shop scheduling problem with a processor assignment by a genetic algorithm

This paper presents a new mathematical model for a hybrid flow shop scheduling problem with a processor assignment that minimizes makespan (i.e., C _max) and cost of assigning a number of processors to stages. In this problem, it is assumed that there are a number of parallel identical processors which are assigned to all of the stages with an unlimited intermediate storage between any two successive stages. To solve such a hard problem, first a new heuristic algorithm is proposed to compute the makespan that is embedded in the proposed genetic algorithm in order to find the best sequence of jobs, and then processors are assigned to the stages simultaneously. A number of test problems have been solved and related results are illustrated and analyzed.     

接管马鞍形自动焊焊接工艺方案

核反应堆压力容器的接管和接管段之间的焊缝是马鞍形曲线,为此焊缝的焊接研究出接管马鞍形埋弧自动焊接工艺,成功地实现了这一焊接,为我公司生产核压力设备做出了贡献。     

Optimization of weld bead geometry in the activated GMA welding process via a grey-based Taguchi method

We optimized the weld bead geometry of 6061 aluminum alloy welds pre-coated with activating flux before gas metal arc (GMA) welding. In this activated GMA welding process, there were five single component fluxes used in the initial experiment to evaluate the penetration capability of bead-on-plate GMA welds. Based on the higher penetration of weld bead, two single component fluxes were selected to create mixed component flux in next stage. The grey-based Taguchi method was employed to obtain the optimal welding parameters that were considered with multiple quality characteristics such as penetration, depth-to-width ratio (DWR) and fusion area of GMA welds. The experimental procedure of the proposed approach not only increases penetration of 6061 aluminum alloy welds, but also improves the DWR and fusion area of GMA butt-joint welds simultaneously.     

金属密封垫自动点焊成型机的研制

目前制造行业中基本都是采用DN系列手动点焊机将金属密封垫进行焊接,这与工业现代化生产极不匹配,亟需改进和发展。研制开发一种新型金属密封垫自动点焊成型机,对于增加安全保障,减少劳动强度,提高产品品质显得尤为必要。通过将DN系列点焊机手端脚踏的人工操作方式用运动控制器+伺服驱动器+交流伺服电机及气动、点焊系统组成的自动装置来代替的方法,实现产品自动化控制,节省人工、提高产量及合格率。     

Development of a genetic algorithm for scheduling products with a multi-level structure

This paper develops a genetic algorithm for scheduling products with a multi-level structure. The proposed approach explicitly considers due dates of products, operation sequences among items, and capacity constraints of the manufacturing system. The objective of the approach is to seek the minimum cost of both production idle time and tardiness or earliness penalty of an order. A representative example is illustrated to compare the GA-based approach with mixed integer programming (MIP). The results demonstrate that the suggested approach is satisfactory in producing effective schedules.     

Optimization of arc-start performance by wire-feeding control for GMA welding

The wire feeding system for gas metal arc welding usually consists of a wire feeder and a torch. In many industries, the distance between the wire feeder and the torch is generally 3 m to 5 m. In a conventional wire feeder, a direct current (DC) motor is used for wire feeding. However, a significant problem with this system is the impossibility of feedback control because of inner or outer impedance. In this paper, a digital wire feeder was developed by using a DC encoder motor and a push-pull torch. An optimized wire-feeding system was also developed by experiment. The welding process was observed using a high-speed camera. The resulting wire-feeding system exhibits low spatter generation and arc stability.     

液压支架结构件自动焊接工艺的研究

针对机器人自动化焊接液压支架结构件批量生产中存在的开坡口对接焊接缺陷问题,进行了焊接试验并观察金相显微组织,结果表明:多层多道焊缝中板条马氏体、贝氏体等组织被针状铁素体、交叉分布的下贝氏体等组织均匀分割,原因是前层焊道对后续焊道起预热作用,后续焊道对前层焊道有再加热作用,显微组织不均匀。针对开坡口对接焊接缺陷问题进行缺陷分析,原因是在自动化批量生产中工件拼装间隙的不均匀,造成了未熔合缺陷,因此提出了先人工局部溜缝+机器人焊接的工艺解决方案。为液压支架结构件焊接制定合理的焊接工艺提供理论依据,也进一步拓宽了焊接机器人的应用范围。     

A genetic algorithm for solving a multi-floor layout design model of a cellular manufacturing system with alternative process routings and flexible configuration

This paper presents a novel integer linear programming model for designing multi-floor layout of cellular manufacturing systems (CMS). Three major and interrelated decisions are involved in the design of a CMS; namely cell formation (CF), group layout (GL), and group scheduling (GS). A novel aspect of this model is concurrently making the CF and GL decisions to achieve an optimal design solution in a multi-floor factory. Other compromising aspects are: multi-floor layout to form cells in different floors is considered, multi-rows layout of equal area facilities in each cell is allowed, cells in flexible shapes are configured, and material handling cost based on the distance between the locations assigned to machines are calculated. Such an integrated CMS model with an extensive coverage of important manufacturing features has not been proposed before and this model incorporates several design features including alternative process routings, operation sequence, processing time, production volume of parts, duplicate machines, machine capacity, new machine purchasing, lot splitting, material flow between machines, intra-cell layout, inter-cell layout, multi-floor layout and flexible configuration. The objective is to minimize the total costs of intra-cell, inter-cell, and inter-floor material handling, new machines purchasing and machine processing. Two numerical examples are solved by the Lingo software to verify the performance of the proposed model and illustrate the model features. Sensitive analysis is also implemented on some model parameters. An improved genetic algorithm (GA) is proposed to derive near-optimal solutions for the integrated model because of its NP hardness. It is then tested using several problems with different sizes and settings to verify the computational efficiency of the developed algorithm in comparison to a classic simulated annealing algorithm and the Lingo software. The obtained results show the efficiency of proposed GA in terms of objective function value and computational time.     

Tuning PID control of an automatic arc welding system using a SMAW process

A new method to tune the gains of the proportional integral derivative (PID) controller for alternating current shield metal arc welding (SMAW) of automatic arc welding system using a SMAW process is presented in this paper. This method used the genetic algorithm (GA) approach to optimize the gains of the PID auto-tuner and considerably modulated the rate of an electrode feed mechanism that regulates arc current. The proposed controller was verified by simulation and experiments of the transient response in the automatic arc welding system. Finally, the performance indices of the proposed controller are compared with that based on Ziegler–Nichols tuning rules.     

基于数学计算的自动化控制模型设计

自动化控制设备在工作中常常出现控制偏差,造成机械设备加工出现失误,出现控制偏差的主要原因是自动化控制模型通信性能较弱、调度稳定性不好。因此,设计基于数学计算的自动化控制模型,作为自动化控制设备的调度模型,可以有效地较少因自动化控制模型通信性能较弱、调度稳定性不好等原因造成的偏差。通过确定自动化控制模型影响变量,依托数学计算进行自动化控制模型设计,然后对所设计的模型进行校核,最终完成基于数学计算的自动化控制模型设计。试验证明,基于数学计算的自动化控制模型能够改善原有的自动化控制模型中通信性能较弱、调度稳定性不好等性能。     

Simulation of the continuous casting process by a mathematical model

A computational three-dimensional (3D) heat transfer model has been developed and applied to calculate the temperature distribution and solid shell thickness profile of a continous cast slab in a steel plant. This developed model includes non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification. A general thermo-fluidmechanics computer program, PHOENICS, was employed to numerically solve the heat transfer equation with the associated source terms. The thermal profile and solid shell thickness calculated by mathematical model agree with those predicted by an industrial model and experimental measurements. The model could also be used to predict the optimum process parameters on casting speed, heat removal rates and associated water flow rates and roll force. These parameters could be monitored by suitable sensors and controlled through a feed back system that interfaced with the mathematical model and the sensors.     

具有模式识别功能的焊接自动跟踪系统

所研制的焊接自动跟踪系统,通过对不同焊道的模式自动识别,很好地实现了对多道埋弧焊的自动跟踪。     

基于遗传算法的加固机机箱后盖机加工路径优化

针对加固机机箱后盖复杂的机加工特征和加工中心编程人员在编写加工程序时无章可循的问题,通过对加固机机箱后盖的机加工特征和加工工艺分析,将所有机加工特征归纳统一为广义孔特征,建立了基于广义孔特征的数据模型,并在此基础上运用遗传算法对机加工路径进行多级优化,通过实际验证,相比优化前缩短了加工时间,提高了经济效益。     

Multi-objective optimization for optimum tolerance synthesis with process and machine selection using a genetic algorithm

This paper presents a new approach to the tolerance synthesis of the component parts of assemblies by simultaneously optimizing three manufacturing parameters: manufacturing cost, including tolerance cost and quality loss cost; machining time; and machine overhead/idle time cost. A methodology has been developed using the genetic algorithm technique to solve this multi-objective optimization problem. The effectiveness of the proposed methodology has been demonstrated by solving a wheel mounting assembly problem consisting of five components, two subassemblies, two critical dimensions, two functional tolerances, and eight operations. Significant cost saving can be achieved by employing this methodology.