The Quality Analyzing System Based On Dynamic Resistance For Resistance Spot Welding

Resistance spot welding (RSW) is one of the most efficient techniques for the fabrication of sheet metal assemblies. The process is used extensively in the fabrication of body in white structures and railroad vehicle components. The major advantages of spot welding are high speed and adaptability for automation in high-volume production. Despite these advantages, RSW suffers from a major problem of inconsistent quality from weld to weld. This problem results from both the complexity of the basic process as well as from numerous sources of variability, noise, and errors. Any or all of these complicate automation, reduce weld quality, demand over-welding and drive up production costs.Welding defects inevitably are implied in procedure parameters (monitoring parameters) in spot welding process. Lots of procedure parameters (monitoring parameters) in spot welding process, such as welding current, welding voltage across electrodes, welding resistance, electrode force and electrode displacement, can reflect the process of forming weld spots and are affiliated with the quality of weld spots. So they are used in quality monitoring. If we monitor some procedure parameters those which are susceptible to welding defects, it is a stitch in time saves nine in the evaluation of welding quality.Practice proves up to the hilt, it is effectively to advance the quality evaluation of spot welding, if procedure parameters are acquired comprehensive and accurately. Besides, the more procedure parameters we acquire, the more accurately welding quality is reflected. Along with the development of computer technology and artificial intelligence, fully using the quality information provided by monitoring parameters, building reasonable mathematical models and working out rational evaluation to the welding quality have been hotspots in study of spot welding.In order to meet these needs, the paper has researched quality analyzing system based on dynamic resistance for resistance spot welding, which can real time monitor spot welding current,welding time and welding voltage across electrodes. It acquires welding resistance and welding energy by calculation. With relative analysis of the information of all parameters beside perfective and defective weld spots, it will output an ideal curve of dynamic resistance for resistance spot welding and ideal value of all parameters by mathematics statistics. So this system can judge and analyze the quality of weld spot by using what it outputs before.Current signal is acquired by rogowski coil sensor in quality analyzing system, and is tackled by an integrator in subsequent signal processing board. however, Voltage signal acquired from electrodes directly is sent to Analog signal Isolation Transmitter, and then is input to ADC. Industrial control computer based on Windows NT system is used as monitoring platform, because of it's stability and friendly Interface.The paper takes Visual C++ 2003 as the software development circumstance to design the measurement software, realizing the aim of collecting multi-parameters and data disposal, calculating the quality information. The function of quality analyzing system mainly include:â‘ The process of realization of the real-time acquisition, display, storage of the spot welding current, electrode voltage.â‘¡Calculating the effective value of welding current, weld time, welding energy, dynamic resistance and time-domain diagram of heat welding, and storing the various parameters to the appropriate database if the weld spot without defect.â‘¢The training function, that is, with the accumulation of a certain number of parameters whose welding quality are perfect, the spot welding quality analysis system automatically extracts data of non-defective welding joint from the parameter tables of the welding database, then it execute intelligence analysis to identify the law of value of various parameters without defect and establish the standards whether welding joints are perfect or not.â‘£Since standards are established, the spot welding quality analysis system can immediately do on-line monitoring and analysis the quality of welding joints.After the whole system finish, it is necessarily to do a series of performance tests, mainly include the measurement accuracy, the quality analytical ability and stability of the quality analysis systems. The system can be used as an on-line monitoring platform in actual production, with combination of the specific production process, it can be designed with personalization based on the user's specific requirements. With fast acquisition, high accuracy and storage capacity, high reliability, the quality analysis system, as spot welding parameters real-time monitoring and on-line quality analysis platform, can be used for experimental study of spot welding and on-site production and so on. Particularly, through a certain number of qualified training, the system can analyze multi-parameters intelligently by using the principle of mathematical statistics, and format the basis whether the welding joint is non-defective or not. At the same time, the program of the system, compiled by Visual C + + language, holds general performance and low computer hardware requirements. It has a high cost-effective and broad prospects for development in the field of on-line quality assessment.