The main expected deliverables were 2 prototypes able to work under industrial environment, which would comprise the integration of electrical sensing and acoustic emission technologies, and a software program where a quality algorithm would be implemented. Specifications of the prototypes as well as working manuals were also expected as deliverables.
Actually 2 prototypes able to work under industrial environment were developed. The prototype system is able to monitor and control the electrical, force and acoustic parameters of the resistance welding process and give a prediction of the weld spot quality in terms of its shear stress or point diameter The analysis of the relationship between process parameters and product quality features is done through a quality algorithm integrated in the system software. The prototypes have similar capabilities although its hardware basis presents some differences. It can be concluded, in general terms, that the final outcome remained substantially as originally planned. In more detailed terms, it can be said that the prototypes development was an evolution process, since the original specifications were updated during the 28 months of project duration to comply with industrial requirements and technological developments. A learning module was also developed in order to teach the system to analyse and evaluate the quality of the production.
The resistance welding processes is widely used in different industrial sectors for several years due tc the high productivity rates and economical assembling process achieved for metal joining in particular. Although technical developments have been achieved in the last years concerning the process technology, the quality control of the welds produced has not yet been completely dominated. In fact, the quality control of resistance welding joints is not fully controlled during the joining process. On-line interferences can occur leading to defective joints even during the welding process. In the other hand, the weld quality control is usually carried out by conventional inspection techniques, destructive (metallographic and mechanical testing) or non destructive (ultrasonic or xray techniques). The first one is the most industrially used, carried out after the weld is performed in laboratory environment and/or on-line production (wrench tests), using a random criteria and being time consuming. The later one, is not of common practice in industry due to the high costs associated, low on-line inspection time and low joint quality reliability. For various reasons, non of the above mentioned techniques has been so far successful. Although some electrical monitoring devices have been found in the market, they do not present the required reliability needed by the industrial end-users. The aim of this project is to develop an friendly use prototype which is aimed at on line process monitoring and control the quality of resistance spot welds in industrial environment. It is envisaged to integrate two different control technologies based on acoustic emission and electrical sensors, which will allow to check the quality of each spot and simultaneously will monitor all the important parameters of the resistance spot welding process. The integration of both technologies will enable an more accurate quality evaluation resulting from the combination of the quality specifications evaluation provided by each of them. This prototype will promote the implementation of "intelligent welding machines" in industrial online production, reducing the level of rejected welds, thus production costs, and increasing the European competitiveness within the industrial sectors involved, providing therefore a cost effective device for monitoring and quality control of resistance spot welding. The present proposal addresses to the research areas 1.1 and 2.3 of the BRITE-EURAM Programme.
Funding SchemeCRS - Cooperative research contracts
06120 Halle - Saale
40024 Castel San Pietro Terme
78250 Oinville Sur Montcient