| Resistance spot welding,a high-speed and economical connection method,is widely used in today's manufacturing industry.Especially in the automotive industry,resistance spot welding has completed more than 90 % of the body assembly work.With the widespread application of resistance spot welding technology,its quality control has become more and more important.At present,the quality testing methods for resistance spot welding mainly focus on the welding current,electrode voltage,resistivity,and thermal conductivity during the welding process.However,judging the welding quality from these data is based on the alignment of the spot welding electrode is good.Electrode misalignment can lead to electrode degradation,expulsion during welding and reduce the strength of the joint.So it is necessary to design a set of equipment for measure electrode misalignment quickly and accurately.This paper analyzes the requirements of non-contact centering state detection for resistance spot welding electrodes,defines the electrode centering state as two parts:axial deflection and vertex offset.The profile data of the electrode is measured by laser sensors and related auxiliary equipment.The computer-aided detection results are obtained by computer.Based on this principle,this paper designs two detection schemes: 1.Axial section profile detection method,which uses sensors to measure electrode surface data in two directions perpendicular to each other;2.Radial section profile detection method,which uses a stepper motor to drive the sensor to dynamically scan the electrode surface data.The axial profile detection method consists of a tripod,a 2D laser ranging sensor,a sensor bracket,and a portable computer.The radial profile detection method consists of a tripod,a 2D laser ranging sensor,a stepper motor,a ball screw,a motor control card,a sensor bracket,and a portable computer.Among them,the axial profile detection method collects the axial contours of spot welding electrodes in twodirections that are perpendicular to each other,and builds the collected results into a spatial model.Based on the relationship between the axis and surface data,the particle swarm algorithm is used to calculate the two-electrode axis attitude.The radial profile detection method uses a stepping motor to drive a laser sensor to collect the radial profile of the electrode within a certain range,and builds the acquisition result into a spatial lattice model.According to the projection of the lattice on the YOZ plane,the filter function and The grid search algorithm determines the two-electrode axis attitude.In addition,in both methods,the electrode vertices are determined by comparing the dot matrix data at the top of the electrode to the axis and comparing them,and the two electrode vertices are projected on a plane perpendicular to the upper electrode axis.According to the calculation results,the relative deflection of the upper and lower electrodes is represented by the spatial attitude and relative deflection angle of the two electrodes,and the relative deviation of the upper and lower electrodes is represented by the relative distance and direction of the projection of the two vertices.In this paper,through the axial senction profile detection method and the radial senction profile detection method,the non-contact measurement of the centering state of the electrode space of resistance spot welding is realized.Among them,the axial senction profile detection method has high measurement accuracy,fast measurement speed,and low equipment cost.The radial senction profile detection method has a wider application range and simpler operation.By analyzing the advantages of the two methods,this paper also proposes to combine the data measurement of the radial detection method with the mathematical processing of the axial detection method,and use a single-point laser sensor to measure the spatial alignment state of the electrode,thereby neutralizing the advantages of two methods and reduce the cost of equipment. |
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