Through-the-wire Sensor and Real-time Torch-height Control in Waveform Controlled Short-circuit CO_2 Axc Welding-Part Ⅰ : Principle, Data Acquisition and Filtering Algorithm

摘要

The waveform controlled short-circuit CO_2 arc welding, which is provided with less spatter and better weld quality, has been developed and applied in industries widely. As the wire electrode extension during short-circuit is approximately the torch-height, the distance from welding torch to workpiece, it can be used as the sensor to determine and then to control the torch-height. In this paper, a through-the-wire sensor adapted to the real-time torch-height control, to improve further the process stability and weld quality of waveform controlled short-circuit CO_2 arc welding in automatic applications, is proposed. The wire electrode extension is measured during the metaphase of short circuit by sampling and recording the value of voltage as the welding current being constant, where the molten droplet has spread into weld pool completely and the neck in liquid bridge has not formed. The acquired data is filtered by rule-based fuzzy algorithm and/or shift-average method. The experimental results show that the wire electrode extension is direct proportional to the value of short-circuit voltage between welding torch and workpiece The actual detecting accuracy of through-the-wire sensor could be achieved up to ±0.4mm, which can meet the requirements of torch-height control and energy compensation for the melting of wire electrode for waveform controlled short-circuit CO_2 arc welding fully.