ALGORITHM AND IMPLEMENTATION OF AUTO-SEARCHING WELD LINE FOR WELDING MOBILE ROBOT

An algorithm of auto-searching weld line for welding mobile robot is presented. Auto-searching weld line is that the robot can automatically recognize a weld groove according to the characteristics of the weld groove before welding, and then adjust itself posture to the desired status preparing for welding, namely, it is a process that the robot autonomously aligns itself to the center of welding seam. Firstly, the configuration of welding mobile robot with the function of auto-searching weld line is introduced, then the algorithm and implementation of auto-searching weld line are presented on the basis of kinematics model of the robot, at last trajectory planning among auto-searching weld line is investigated in detail. The experiment result shows that the developed welding mobile robot can successfully implement the task of auto-searching weld line before welding, tracking error precision can be controlled to approximate ±1.5 mm, and satisfy the requirement of practical welding project.

Study on intelligent welding mobile robot with the function of auto-searching weld line

The development of welding robots suitable for specially unstructured working enviroments has been become an important development direction of industrial robot application because large-scale welding structures have been used more and more widely in modern industry. In this paper, an intelligent mobile robot for welding of ship deck with the function of autosearching weld line was presented. A wheeled motion mechanism and a cross adjustment slider are used for the welding robot body. A sensing system based on laser-PSD （position sensitive detector） displacement sensor was developed to obtain two dimensional deviation signals during seam tracking. A full-digital control system based on DSP and CPLD has also been realized to implement complex and high-performance control algorithms. Furthermore, the system has still the function of auto-searching weld line according to the characteristics information of weld groove and adjusting posture itself to the desired status preparing for welding. The experiment of auto-searching welding line shows that the robot has high tracing accuracy, and can satisfy the requirement of practical welding project.

Control algorithm based on trajectory and orientation of oblique intersection line welding-cutting robot

Working principle for a four-axis oblique intersection line welding robot is analyzed. A mathematical model for welding torch orientation angle is established, and an interpolation algorithm based on time division is proposed. The algorithm makes all interpolation points fall on a required curve in theory with no accumulated errors and a direct interpolation control on the saddle-shaped curve trajectory and space orientation angle can be achieved. It is shown by MATLAB simulation that the algorithm is real-time and fully meets the precision requirement. The algorithm has been applied to real robots.

Study on general inverse kinematics of rotating/tilting positioner for robotic arc welding off-line programming

Off line programming provides an essential link between CAD and CAM, whose development will result in greater use of robotic arc welding. An arc welding system with a robot and a rotating/tilting positioner is one of the most typical workcells. The inverse kinematics of robot and positioner is the foundation of the off line programming system. The previous researchers only focused on a special solution of the positioner inverse kinematics, which is the solution at down hand welding position. In this paper, we introduce a method for representing welding position. Then a general algorithm of rotating/tilting positioner inverse kinematics is presented, and an approach to find the unique solution of the inverse kinematics is discussed. The simulation experiment results show that the general algorithm can improve the ability of robotic arc welding off line programming system to program all types of welding positions.

Numerical Study on Welding Line Behavior of Deep Drawing TWB Process

The FEM technology is used to analyze the welding line movement behavior of deep drawing TWB sheet with different thickness. It is found that high stress fields are concentrated around the welding line and large residual stresses are left. The effect of the welding line movement is like a rigid string and the selected nodes of the thin part near the welding line show the related larger strain.

Numerical simulation method for weld line development in micro injection molding process

In order to reduce the "trial-mold" risk and cost,numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 mm(depth) ×0.4 mm(width) ×12 mm(length) in test area was selected as the objective part,and polypropylene(PP) as the experimental material. Respectively with specific commercial software(Mold Flow) and general computational fluid dynamic(CFD) software(Comsol Multiphysics) ,the simulation experiments for development of weld line in micro injection molding process were executed and the real comparison experiments were also carried out. The results show that during micro injection molding process,the specific commercial software for normal injection molding process is not valid to describe the micro flow process,the shape of flow front in micro cavity flowing which is important in weld line developing study and the contact angle due to surface tension are not able to be simulated. In order to improve the simulation results for micro weld line development,the general CFD software,which is more flexible in user defining function,is applied. The results show better effects in describing micro fluid flow behavior. As a conclusion,as for weld line forming process,the numerical simulation method can give a characteristic analysis results for processing parameters optimizing in micro injection molding process;but for both kinds of softwares quantitative analysis cannot be obtained unless the boundary condition and micro fluid mathematic model are improved in the future.

Mechanism of weld-line movement within hydroforming of tailor-welded tube

To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analyzed between the thicker and thinner tubes,as well as the property of the axial strain. During TWT hydroforming,tensile strain along axial direction happens on the thinner tube. On the contrary,compressive strain happens on the thicker tube. Experiments are conducted to varify the weld-line movement regularity and strain distribution. It indicates that the weld-line moves from the thinner part to the thicker during TWT hydroforming. The thinning ratio of the thinner tube is bigger than that of the thicker tube,especially in the zone near weldline. Stress ratio difference between the thicker tube and the thinner tube is the main reason of weld-line movement and non-uniform thinning ratio distribution.

Generalized CAPP and synthetic evaluation strategy for production line of accuracy welding

This paper presents generalized CAPP （G-CAPP） method which deals with macro process planning for multiobjective in the planning stage of production line of accuracy welding （PLAW） based on the features of accuracy welding production （ AWP ）. G-CAPP offers foundations for prototype design and general equipment sorting, production capacity predication and production analysis by means of simulation and optimization. A synthetic hierarchy evaluation （SHE） model for G-CAPP established according to the planning objective is utilized to estimate the alternate processing plans by using membership function and analytic hierarchy process （AHP） of operational theory. The assembly welding line of hydraulic torque converter （HTC） is as an example of typical A WP to explicate G-CAPP and synthetic evaluating strategy of PLAW. The feasible and rational process configuration strategies of HTC assembly welding line are pointed oat under different planning objective.

On-line measurement of electrical variables of the transducer during ultrasonic welding and cutting

A measurement system for high power electrical variables with ultrasonic frequency was established. It can measure the effective values of the voltage and the current, the active power, the phase difference of voltage and current, the frequency of the transducer during ultrasonic welding and cutting. In sampling circuits of the system, the measured current is sensed by using a no capacitance and no inductance precision resistor and is treated with a difference amplifier, the measured voltage is processed by using a proportional amplifier. For achieving good amplitude frequency characteristics and rapid measurement of high frequency signals, the resistors, capacitors and amplifiers used in the system are rationally selected. Calibrating experiments show that relative errors are less than 1% for voltage and current effective values and less than 2.5% for active power, and absolute errors are ±1 Hz for frequency and ±1.7° for phase difference of voltage and current in the range of 17～23 kHz .

Study of fractal character of the fusion line in dissimilar welded joint

The fractal dimension of the fusion line in different dissimilar welded joints is measured with Box Dimension Method.The non scale region of the fusion line with fractal character is calculated. The fusion line in the dissimilar welded joint is proved to be a fractal structure. The change and influence factors of the fractal dimension of the fusion line are studied.

Automatic girth welding and performance evaluation of the joints of hot-induction-bend and line pipes with different wall thickness

During the process of laying long-distance oil and gas transmission pipelines, the hot-induction-bend method is extensively used when the direction has to be changed. By considering the pipeline＇ s ongoing processing and loading states during service, the pipeline that is generally used exhibits thicker walls than those that are observed in the line pipe. As such, during pipeline construction, hot-induction-bend and line pipes with different wall thickness are girth-welded. The chemical composition of hot-induction-bend and line pipes differs, with the carbon content being particularly higher in the hot-induction-bend pipe;it also depicts a higher carbon equivalent, which makes it possible to modify the girth of the pipe. In this study, using Baosteel＇ s standard X70M UOE hot- induction-bend and line pipes, solid-wire automatic gas-metal-arc girth welding was performed and the performance of the girth-welded joint was evaluated. Furthermore,the weldability of the pipeline girth and the microstructure of the girth-welded joint were analyzed. The results reveal that Baosteel＇ s standard UOE hot-induction-bend and line pipes exhibit good girth weldability, and their technical quality can be guaranteed in case of consumer field- construction applications.

Development of the High Toughness Spirally Submerged Arc Welded Pipe Line

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Off-line simulation of robot welding of radar pedestal

A study of the interference simulation based on robot welding of the radar pedestal was carried out by using the KUKA Sim Pro simulation software and off-line program technology. Compared with the actual robot welding process, it was found that the trajectory of the simulated robot welding process in line with that recorded in the actual welding process, and the actual limit and interference appeared at the same place as the simulation process. There was no interference phenomenon on the outside weld-seam; on the internal weld-seam, especially on the weld-joint of support plate connected to the cylinder, a phenomenon of interference appeared. It was helpful to use the simulation method to guide the actual robot welding so as to protect robot from impacting and reduce the weld defects.

Path Planning of Planar Kinked Line Seam by Visual Servoing for Robotic Welding

Welding path planning can substitute for the manual teaching process of the robot and can promote the autonomous level of the robotic welding. A path planning method by visual servoing was presented, in which the optimal angle of charge-coupled device (CCD) camera was also planned. Aiming at planning two forms of kinked line seams, obtuse angle seam and right angle seam, a practicable solution was put forward. In this solution, the intersection of two adjacent straight segments is detected in each local seam image, and if intersection is found, the seam errors are calculated using the next straight segment. The experimental results show that kinked line seam can be well planned using this solution.

Study on path planning and compensation of off-line programming for thick walled curve welding

Thick walled curve welding are usually joined by multi-layer and multi-pass welding, which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programming welding path was decreased due to the deviation between the off-line planned welding path and the actual welding path. A path planning algorithm and a path compensation algorithm of multi-layer and multi-pass curve welding seam for off-line programming of robot welding are developed in this paper. Experimental results show that the robot off-line programming improves the welding efftcieney and precision for thick walled curve welding seam.

Welding technique and quality of large diameter X70 line pipe for gas transmission of China

X70 grade large diameter line pipe with helical and longitudinal seam SAW was developed and used in West-East Pipeline Project of Petrochina. The operation pressure of the pipeline was designed as 10 MPa, with diameter of 1016 mm OD. This project represents the first high-pressure, large diameter and high strength grade gas pipeline in China. All the factors affecting the safety of the pipeline shall be considered. The welds quality of line pipe is very important for safety of the pipeline. Acicular ferrite type X70 grade pipeline steel was adopted for the base material. The welds performances of X70 line pipes with 1016mm OD and 14.6-21.0 mm WT has reached a very high level, especially of low temperature Charpy V impact toughness of welds metal. Welding technique and quality status of X70 line pipe of China are investigated in this paper.

浅析新版长输管道定期检验规则的修订理念及意义

近年来,随着管道技术发展和相关法规标准的不断完善,TSG D7003—2010版中部分内容已不再适用。为满足长输管道检验工作需求,市场监管总局对TSG D7003—2010版进行了修订。本文详细阐述了此次修订的背景、修订原则、修订过程、主要变化和重要意义,以期为广大管道检验检测和管理人员更好地理解长输管道定期检验规则提供帮助。

纤维增强注塑熔接线强度预测模型与实验研究

熔接线是影响注塑制品强度的关键因素之一,而目前以汇合角预测熔接线强度的力学模型并没有体现注塑工艺的影响。为了科学定量地认识熔接线区域强度的变化规律,准确预测熔接线力学性能,首先对带扇形孔的制品进行注塑模拟分析,研究了注塑温度、注射速率以及保压压力对熔接线汇合角的影响,结果显示注塑温度、保压压力不是通过改变熔体前沿汇合角来影响熔接线强度。基于此,为全面体现注塑工艺、汇合角对熔接线强度的影响,在现有模型基础上通过引入注塑工艺影响因子重新构造了体现注塑工艺、汇合角对熔接线区域强度影响的预测模型。设计并制造了用于成型扇形孔制品的注射模具,开展了不同工艺条件下30%长玻纤增强聚丙烯扇形孔制品注塑实验,根据实验结果推导出了体现注塑温度和保压压力影响的注塑工艺影响因子数学表达式,利用实验数据拟合确定了模型中的相关参数,并对模型进行了回归分析。结果表明,新构建的强度预测模型可以准确计算不同注塑温度、保压压力下熔接线不同位置的强度。

含氢环境中X80管线钢焊接接头氢脆敏感性研究

为了探究管线钢焊接接头在氢气环境下断裂力学性能的变化,采用缺口拉伸原位充氢方法对X80钢母材、焊缝和热影响区进行12 MPa总压,0.36 MPa氢分压下的氢脆敏感性研究,采用高压慢应变速率拉伸试验机进行缺口拉伸测试,采用高压断裂韧性试验机和高压腐蚀疲劳试验机对X80钢分别进行断裂韧性试验和疲劳裂纹扩展速率试验。结合断裂韧性试验和疲劳裂纹扩展速率试验对X80钢的裂纹扩展行为进行研究。结果表明:在相同条件下,相比母材和热影响区,焊缝位置的断面收缩率明显下降,表现出较高的氢脆敏感性;与常温常压空气中的原始数据相比,在0.36 MPa氢分压环境中焊缝位置的裂纹尖端张开位移(CTOD)值变化较小,断裂表面未出现二次裂纹;与在空气环境中相比,X80钢焊缝在0.36 MPa氢分压环境中的疲劳裂纹扩展速率增加了1个数量级,说明氢气能够增大材料的疲劳裂纹扩展速率,但根据实际管道压力波动情况,在0.36 MPa氢分压条件下X80钢的氢脆敏感性较小。

基于响应曲面的卡盖双浇口工艺参数优化与模具设计

车用电源卡盖结构复杂与多加强筋的结构特征,在其注塑成型过程可能会阻碍了材料的流动诱发熔接线、翘曲变形等问题,影响产品的表面质量和结构强度。因此,本文将理论算法与有限元仿真相结合开展卡盖制品注塑成型工艺优化与模具设计研究。研究结果如下:首先,根据产品特征确定了点浇口及位置,进而结合Moldflow开展单浇口和双浇口的对比分析并确定了双浇口;其次,以熔接线长度为优化目标,建立响应曲面法实验方案并开展仿真分析;然后,利用最小二乘法、方差分析、回归分析等,确定了以熔接线为优化目标的最优工艺组合,即塑料制品的熔体温度(A)为260℃、模具温度(B)为65℃、注射时间(C)为1.5 s、保压压力(D)70 MPa及保压时间(E)10 s,此时的熔接线最大长度约为5.8 mm,相比于初始分析方案的31.5 mm降低了81.6%;最后,采用UG进行了卡盖的注塑模具设计并进行生产验证,产品填充完整且表面质量良好,为生产提供指导意义。