Objectives
Develop and demonstrate adaptive control algorithms for laser hybrid applications with variable joint fit-up conditions in stainless steel and aluminium alloy.
Establish the tolerance limits when adaptive welding on butt joints with different joint fit-up conditions.
Demonstrate adaptive control algorithms for the multi-pass welding of steel.
Project Outline
The proposed project will seek to develop hybrid laser-arc welding procedures using a fibre laser integrated to new seam tracking/monitoring equipment, for joining aluminium and stainless steel, with the objective of achieving improved weld quality in medium/thick sections (5-8mm plate). The joining of laser cut edges, as well as machined edges will be investigated. The work will demonstrate adaptive control to accommodate variable gap and joint fit-up at levels representative of welded fabrications.
Work on thicker section C/Mn steels will involve multi-pass welds on nominally 16mm plate to compare with earlier MAG welding work. Butt welds will be produced with joint preparations appropriate to the hybrid process to demonstrate the potential for the deeper penetration welds with lower overall heat input. Again the adaptive control system will be used to accommodate variable gap.
The work will be conducted using an integrated hybrid welding system, comprising an IPG fibre laser in the region of 5 to 7kW power capacity, a Servo-Robot laser vision and joint tracking system, a Kawasaki robot and an ESAB MIG/MAG welding set. The laser vision system will be located ahead of the laser welding system to detect the seam position, orientation, geometry and joint gap. Welding trials will be conducted with adaptive control of wire feed speed, travel speed or laser parameters, to compensate for joint variations. For adaptive control of wire feed speed, a communication interface, between the arc power source and robot control system, will need to be developed.
Hybrid laser-arc welding parameters will be optimised on square edge butt joints with a closed gap in the thinner materials and with the appropriate joint preparation in the thicker material for multi-pass welds. These will be set up to provide a stable process resulting in geometrical characteristics acceptable to weld quality B, further referred to as stringent weld quality, in accordance with BSENISO 13919:1997. The maximum joint gap tolerated using the optimised parameters will then be determined by producing welds with variable gaps, to determine at what gap the conditions will result in sub-standard welds.
Welding parameters will then be re-optimised on the same material/joint configurations with various fixed joint gaps, by adjusting one parameter (eg wire feed speed or travel speed) from the optimised conditions for closed gap joints. The range of gaps tolerated at these welding parameters will also be determined by producing fully penetrated welds at each selected joint configuration.
Based on the parameter sets obtained for the joint gaps examined, control algorithms will then be developed for adaptive control of wire feed speed or travel speed. Hybrid adaptive control welding will be performed on each material/joint combination, to achieve fully penetrating welds of a uniform stringent weld quality, in samples with various engineered joint gaps. Welding will be performed in two ways, using stepped or continuous adaptive control of the welding parameters, based on measurements of real time gap information obtained from the laser vision system.
Relevant Industry Sectors
Oil, gas, chemicals, Power generation, Construction and engineering
Technical and Economic Benefits
Improved quality and consistency.
Industrial Member Report
Access the Industrial Member Report resulting from this programme:
Hybrid Laser-MIG Welding of Aluminium Alloy Butt Joints with Adaptive Control
Hybrid Laser-arc Weld Quality Enhancement by Seam Tracking, Adaptive Control and Weld Bead Inspection