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Highly efficient & flexible remote welding systems for advanced welded structures

Deliverables

The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. Between January 1st 2001 and December 30st 2003 CRF has been involved in the joint finder realisation. The main objectives were: - Accurate and rapid reading; - Automatic offset of the machine trajectory; - User-friendly, non-contact and cost effective; - Front optics and sensor protected against fume and dust generated by the process. The system use the same camera employs for autofocus and acquire at the beginning of the process the workpiece position onto the clamping device. In the next components the algorithm acquire the workpiece component and compare the new position respect the "reference". The algorithm adjusts the weld path in real time.
The REMOWELD project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. During the project period from January 2001 to December 2003 CRF realised the tests for a process-monitoring prototype. The main activities were: - A spectral analysis of radiation emitted from laser process. - To define which the wavelength permit to evaluate the process quality and which sensor is necessary to use. - The hardware set-up. - To realise software monitoring. At the end of these activities CRF carried out a prototype with four sensors. The results obtained with these configurations have permitted to evaluate the welds quality (porosity, lack of penetration and difference of penetration). The intensive tests have permitted to optimise the sensors positions. In particular, the sensor used (only one) is mounted near the focal len.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. CRF has been involved in the realisation of the autofocus prototype. CRF after preliminary tests has realised the prototype. The prototype employs: - CCD camera mounted in front off the remote black box; - Two laser He-Ne mounted in front off the focussing lens; - The acquisition system. Two spots He-Ne laser are coincident in the focus position and during the len movement the spots increases or decreases the distance. The software evaluated in real time the spot distance (z position) and optimised the focus position onto the workpiece.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. A prototype of a Remote Laser Welding Station in robot configuration, mainly dedicated to the manufacturing of non-automotive components has been realised and installed at the end user Salvagnini. The main standard components of the station are: - A solid state Nd:YAG diode pumped laser with an output power of 4,4 kW and a beam quality of 12mm.mrad; - An optical fiber beam delivery system; - An industrial robot; - A miniaturized Remote Welding System (RWS) mounted on the arm of the robot and able to move and focalize the laser beam over the work-piece.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. In this part of the project the main task of Rofin-Sinar-Laser is the development of an advanced Nd:YAG-laser scanning system. Based on the experience of scanner systems for medium laser power and 2-dimensional applications, a high power version for 3-dimensional welding application has been developed and has been set up. The scanner head has been successfully tested with a laser power of more than 4kW in long term running. The scanner-head is a very compact device with dynamic beam-scanning capabilities, which includes a zoom telescope, a bending mirror, scanner mirrors, an f-theta optic, protecting window and a cross jet. There is the possibility to adapt process-monitoring devices behind the mentioned bending mirror. The working volume is 100mm x 100mm x 40mm. The working distance is about 210mm. The spot size at the work-piece is about 0.65mm. The scanner-optics is moved by a specially designed scanner-control, which is connected, to the laser-control and the robot-control. Welding applications were demonstrated on the fly together with the adapted Comau M1-robot.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. In this project the main task of UPATRAS was the development of remote laser welding process simulation models. The main results that have been achieved through the Project’s lifetime include: - Literature research on previous analytical conventional laser welding simulation models. - Modification of existing laser welding simulation models as to integrate the remote approach. - Geometrical analysis and modelling of the CO2 and Nd:YAG remote welding scanning systems in order to evaluate the beam profiles for different incidence angles inside the working volume. - Realization of experiments with the CO2 RWS on three different welding combinations (automotive and non-automotive). - Realization of experiments with the Nd:YAG RWS on two different welding combinations (non-automotive). The investigated process parameters included the laser power, the welding speed, the incidence angle, the air knife direction and the air pressure. The measured characteristics include the weld depth and width, the weld angle and the undercut for the Volvo material. - Application of statistical modelling using the method of statistical design of experiments. - Application of empirical modelling of the weld characteristics using the results from the experimental work. These results contain process models that provide quality characteristics of the welds as functions of the process parameters for different weld combinations and materials required by the end users. UPATRAS aims to disseminate the obtained results to the scientific and academic community through at least two publications – presentations in conferences and workshops. A PhD thesis and two student theses projects will be completed 12 months after the completion of the project. The achieved results can be directly implemented by off-line programming software codes developed for laser processing (remote or not). The potential end users that could respond to the results obtained on Remote Welding process modelling involve software developers for programming and controls, developers of process monitoring systems and direct remote laser welding and conventional laser welding users (automotive and non-automotive) for optimisation and controlling of the process. The main innovation featured by the referred results is related to the remote (inclined) approach of the laser beam to the workpiece, which distorts the laser power density and affects significantly the quality characteristics of the resulting welds. Such phenomenon and others as well that derive from the remote (inclined) approach haven’t been investigated so far in theoretical or/and experimental level.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. One of the project's tasks consists in remote welding process certification. The main expected results of this work are: - Final definition of assessment testing procedures and rules for qualifying remote welded joints, - Mechanical and metallurgical data for remote welded joints, - Corrosion resistance data for the same welded joints. Mechanical and fatigue tests procedures have been defined. Volvo, who is in charge with corrosion tests for automotive applications, has its own standards, and Salvagnini proposed to use the same procedure for non-automotive applications. Moreover, two technical meetings permitted to define acceptance quality criteria for simple specimen for Volvo, Fiat and Salvagnini applications. All the samples are welded with the Remote Welding System located at CRF, and then sent to IS for mechanical (fatigue, static) and metallurgical (metallographic and corrosion) testing. Different documents were emitted to present results obtained on automotive and non-automotive materials, including Milestone M6.1 distributed at Mid -Term meeting. Broadly speaking, after these investigations, one can say that weld quality was improved between the campaigns of welding, because of a better knowledge in the weld parameters influence. Indeed, small pores and failures due to porosity have decreased significantly. Main results are the next: - Butt configuration is more resistant than lap one for a same material, - High inclination is preferable for lap joints, and low inclination for butt ones, - Main imperfections observed: undercuts, incompletely filled groove, lack of penetration. “Quality and acceptance criteria for remowelded joints”, one of the milestones, are guidelines for estimating the quality of joints welded using Remote Welding process. It was written basing on end-users’ acceptance quality criteria and on all the results obtained during our investigations.
The RemoWeld project aimed to an extended, sustainable and competitive use of remote laser welding systems promoting the development of competitive manufacturing procedures. During the project period from January 2001 to June 2002, a powerful and easy-to-use offline NC programming and simulation base system for Highly Efficient and Flexible Remote Welding System has been developed. Two main types of current welding application, CO2 Laser Gantry System and Nd:YAG Laser Robot Handled System, are planned to be supported by this system. Currently, a gantry station based offline programming system is under running testing. Based on powerful geometry platform, the system possess a variety of CAD model exchange interface: IGES, DXF, CATIA, STEP and BRep. Spot, stitch and continuous welding methods and a number of different welding geometries, e.g. linear, cross, circle, arc, are able to be defined easily from end user point of view. Following the experiment results of the studies on welding process, welding machining sequences, welding cycles and welding process optimisation methodologies will be implemented by developer, as well as welding quality prediction. Furthermore, the whole software development followed object oriented software method, any new functionalities are able to be integrated freely in the future. It is well known that laser welding is a common practice in much industrial area, including automobile area and non-automobile manufacturer. As a result, this offline programming system can be applied both for laser remote welding machining and conventional laser welding machining. The suitable group users are automobile manufacturer and some machinery equipment manufacturer. Compared with conventional laser welding offline programming system, RemoWOPS system could define variant welding targets, simulate the welding process and its quality which concerning remote welding technology - a completely new way of laser welding. It is able to deal with both the gantry system and robot-handled system.
The RemoWeld project has been running for 3 years and during this time Volvo's input has been to supply the project with industrial specs and system requirements. Volvo's Standards for lasers; 5605,517 Laser Welding; 8615,3 Quality Assurance of Laser Welding; and 1027,1375 Corrosion Resistance have been used to a great extent for specifying and for quality assuring laser welding. Welding tests have been performed at VCBC (Volvo Olofstrom), Rofin Sinar and CRF. Cuopons and hat-profiles were welded and examined, shear strength test on coupons were made at LV-material teknik in Gothenburg. Installation of a Remote Laser and a final test period of 6 month have been performed while welding stamped parts. Shear strength (Fmax) for the joint with a weld width of 1.5-2mm is 18-19kN for Volvo's STD flat sheet test objects. Welding of three-piece joints was also done at CRF, Fiat Research Centre, with their Remote laser. In this case the material was DP450 to DP450 and DP600, all zinc coated. Sheet thickness of the welded material was 1.0 with 1.6mm, and 1.6 with 1.6mm. Cross sectioning of the welds and shear rupture testing was also done on these sheet combinations, but here the weld width was changed to suite the remote laser's better beam quality. This allowed weld speed to be increased to 3 - 4 m/min. Weld width was approx. 1mm. The rupture test gave an Fmax of approx. 13kN for the 1 mm and 1.6 mm test bodies. An investigation between cost and production of a line which produce two doors, front LH and RH door with two joining methods, remote laser welding and resistance spot welding have also been made, with following presumptions: - Production rate: 100000 doors in three-shift operation (x2=RH+LH door=200000). - Cycle time 138s/part. - All welds are done with laser in RLW-line and with resistance spot welding in RSW-line. - Number of welds/door: 167 stitches or 171 spots. - Number of details in one door are 11.