to extract the information of droplet detachment will guarantee real time control for smooth metal transfer.

4. Imaging of a weld pool can be reliably triggered by a delayed flag signal generated during the period of a base current. In a cycle, droplet detachment and image acquisition can be compatibly accomplished.

5. In addition to other image processing routines, worm tracing and scanning are developed for calculating the area of a weld pool image. The procedure developed for processing a weld pool image includes its boundary extraction and area calculation and provides the possibility for real time quantifiable monitoring and control of the weld pool penetration state in the future.

ACKNOWLEDGEMENT

The author expresses his great acknowledgement to the supports of Mechanical Engineering Department of Southern Methodist University, Dallas, Texas and Edison Welding Institute, Columbus, Ohio.

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OPTIMIZATION OF PGMAW USING ONLINE OBSERVATION

AND STATISTICAL DATA

S. Nordbruch 1,2, A. Gräser

2

ABSTRACT

In this paper a monitoring system that simplifies the finding of optimal welding parameters, the analysis and the optimization of pulsed gas metal arc welding (PGMAW) is described.

The system allows the visual online observation of all states of the welding process, including the droplet transfer, without an additional lighting unit. Additionally, the synchronized measurement of the welding current and welding voltage signals during image recording and the extraction of characteristic parameters of the signals is possible. Furthermore, the system allows the visual analysis of the material transition images.

For an analysis and optimization of the process the systems computes statistical data of all collected and calculated visual and electrical data of a recording sequence.

KEYWORDS

PGMAW, droplet transfer, online observation, visual data, electrical welding data, statistical data

INTRODUCTION

The pulsed gas metal arc welding process is an important component in many industrial and manufacturing operations. It is highly suited to a wide range of applications. Due to the complex processes, the extreme brightness of the welding arc, the high number of different welding tasks, etc., the finding of optimal parameters, the test of new welding parameter combinations or the analyses by process errors is difficult.

For the solution of the problems the visual observation of the droplet transfer in combination with the measurement of electrical welding parameters is an approach. Typically, the droplets should be even and in uniform size and the material transition should be splashless. The visual observation of the material transition has been used extensively. Normally digital Charge-Coupled-Device (CCD) high-speed cameras in combination with an optical laser are used. Due to the extreme brightness these approaches are using the shadowgraphing technique, described by Allemand et. al. (Ref. 1).

For the mentioned problems the systems are unsuitable due to a set of disadvantages. The most important are:

>> The necessity of the lighting unit and the limited possibilities of observation caused by this (shadowgraphing technique).

The acquisition and maintenance costs are very high.

2

Friedrich-Wilhelm-Bessel-Institut Forschungsgesellschaft m.b.H, Postfach 106364, 28063 Bremen, Germany University Bremen, Institute of Automation (IAT), Kufsteiner Str. NW1, 28359 Bremen, Germany