PROCESS MONITORING AND ON-LINE MODELING OF THE GAS METAL ARC WELDING PROCESS This Abstract is brief description o f a thesis on the development o f methods for the Process Monitoring and On-line Modeling o f the Gas Metal Arc Welding Process (GMAW). Progress in development o f Advanced Process and Equipment for GMAW, especially in Automated and Mechanised Welding, requires clear understanding o f the physical phenomena o f the Welding Process [1]. The objective o f this thesis is to design and develop modem experimental facilities capable o f providing instrumentation and photography to record welding phenomena, so as to allow a thorough study o f die physical welding processes. The thesis initially describes the development o f an Experimental Facility for Monitoring die Gas Metal Arc Welding (GMAW) Process. The Facility described consists o f : a) Weld Testing Facilities. b) A Physical Testbed with a Weld Table moving under a stationary GMAW Gun. c) Electronic Monitoring o f the GMAW Parameters including Weld Voltage (V), Weld Current (I), Wire Feed Rate(WFR) and Weld Travel Speed (TS). d) Computer Control o f GMAW Parameters including Weld Voltage, Wire Feed Rate and Weld Travel Speed. e) Weld Visualisation using High Speed Photography with a Communications Link from the High Speed Camera to the Electronic Monitoring System allowing the Camera, when it commences its diming run, to trigger the Electronic Monitoring System, thereby enabling time-correlated Electronic Data and Visual Images to be obtained. The thesis next describes in detail the Weld Testbed and Electronic Monitoring System in terms o f Electronic Hardware, Software Algorithms for Weld Monitoring, Algorithms for Weld Parameter Control and two Graphical User Interface (GUI’s) Packages developed for the Viewing and Analysis o f Weld Data. These Software Packages are: a) ‘Shortmon’: A package for Viewing and Analysing the Parameter Traces o f short bursts o f Welding Data ( < 2 seconds). b) ‘Longmoir : A package for Viewing and Analysing the behaviour and stability o f Weld Parameter Settings over longer welding periods (up to 120 seconds). Both o f the above described Packages also include Computer Controlled Setting o f Weld Parameters. ‘Longmon’ also allows in-weld alteration o f Weld Parameters thus enabling the effects o f Weld Parameter variation to be studied. The verifification o f the MWEF as a facility for GMAW Control Strategy development was achieved through a series o f experimentation in which process irregularities were induced and monitored in Real-time. The next Stage o f the thesis describes the development o f a Graphical User Interface (GUI) for On-line Modeling o f the Welding Process in a single weld run utilising Weld Parameter Feedback for a range o f Computer Controlled Weld Parameter Settings. An important research interest is the development o f Strategies and Models for die effective Real-time Control o f the Welding Gun Standoff (L) (also often referred to as ‘Contact-tip to Workpiece Distance’). The On-line Modeling Package has therefore been initially developed to generate Least-Squares Models of: I = ffV,W FR,L) and also L = f(V,I,WFR) which are intended for use as Real-time Estimators for Current and Standoff Control. This work is funded by die Cooperative Research Centre (CRC) for Materials Welding and Joining as part o f Project 93/12 which is a collaborative research effort in the area o f Welding Automation between the University o f Wollongong, The University o f Sydney and the CSIRO Division o f Applied Physics (Sydney). Please Note that Welding Visualisation with High Speed Photography was developed by Dr. Wee King Soh and Mr. Heman Ratio whilst the Welding Testbed and the Electronic Monitoring and Control o f the Welding Process was developed by the Author under the supervision o f Professor Michael W est

Process monitoring and on-line modelling of the gas metal arc welding process

Microarc welding process commonly encounters many disturbances, thus affecting the weld penetration quality. This paper presents the techniques to monitor the high-frequency and hybrid pulsed micro-TIG weld penetrations by arc electric signal processing. These techniques utilize the mean voltage of arc, the probability density distribution of arc voltage, and arc dynamic voltage-current graph respectively to characterize the microweld penetration. Experimental results show the feasibility of monitoring this penetration by the microarc sensing.

You Hong Xiao

Papers

Sensing gta weld pool geometry by arc voltage signal processing

The welding process, and apparatus for use therein, and method of analysis for the evaluation of welding.