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Real-time dynamic control system for laser welding

Periodic Reporting for period 3 - RADICLE (Real-time dynamic control system for laser welding)

Reporting period: 2017-02-01 to 2018-10-31

The overall aim of the Radicle projects is to develop a laser welding adaptive control system which can integrate sensor data from 3 loops in real time by adjusting laser parameters to deliver welded joints with zero defects. The control system will include in process monitoring control, fault prevention / fixing pre and post welding measurement.
Radicle project partners include four large, end user partners which includes Roll Royce, GE, GKN and CRF (Fiat). The successful implementation of Radicle technology through Project Partners and the wider industry, will enable the project to have the following impacts:-
• An increase in Health & Safety benefits
• An increased productivity of up to 30% resulting in reduced emissions, reduced energy usage, reduced rework and a reduction in the need for final NDE testing
• Reduce floor space requirements by removing the need for large welding room enclosures

The Radicle project contributes to the wider European 2020 targets by:-
• Reducing energy usage and greenhouse gas emissions
• Increasing employment for 20-64 year olds
• Increasing R&D spend
• Increasing education, particularly third level education

Laser welding is a high performance joining process which provides significant benefits over more conventional methods, such as arc based welding. The global market for using laser equipment for material processes has grown 50% since 2004 and is valued in excess of €10 billion per annum. The automotive industry has led in the implementation of laser welding for structures such as BIW (Body in White). The aerospace industry are now also using this process for various applications in joining reactive metals such as titanium alloys. Welds in the aerospace undergo 100% post weld inspections using X-ray technologies and welds with greater levels of porosity than relevant standards specify, have to undergo rework which can severely impact the economic benefits of laser welding processes.

Figure 1: Overview of the Radicle Concept

Radicle is a 45 month project and is delivered in three distinct phases. Phase 1 was about the specification and preparation of samples and components for initial characterisation and subsequent testing. Phase 2 , development of sensors and the algorithm whilst phase 3 is the integration, demonstration and validation of the RADICLE system, firstly in the lab and subsequently on MTC’s laser welding cell.

The final RADICLE system developed in the project delivers a new laser welding monitoring and adaptive control architecture integrating multi-sensor data to deliver high–quality weld joints. This will help companies across different industry sectors produce laser welded components – Smarter, Faster and to Higher Quality, Reducing Post Manufacturing Inspections Costs.

The RADICLE project has created:

- A modular system allowing users to configure the system to their specific applications. The system includes:
o Photodiodes (off-axis and co-axial)
o Seam tracking camera
o Permatrack software that provides live weld quality feedback to the operator on welding stability.
o Co-axial process zone imaging camera
o Keyhole depth monitoring sensor
o Microphone for acoustic emission analysis

- Welding process widows for a number of ferrous and non-ferrous materials and joint configurations, supported by welding data from industrial case studies;
- Weld data handling and analysis routines to extract valuable information from the welding process monitoring sensors;
- The development of the architecture for a multi sensor adaptive control system for laser welding including a machine learning algorithm able to:
o Interpret raw sensor data and associated welding quality parameters.
o Generate the process window heatmap from the sensor data.
o Allow in line weld quality limits to be set and monitored live and provide an alarm when weld quality has deviated from the acceptable limits.

Figure 2: Final project leaflet
The project has summarised which commercially available sensors, including those measuring the intensity of the back-scattered laser beam, process radiations, keyhole depth and acoustic emissions, were successful in detecting which process deviations and welding defects.

Created process windows identifying suitable welding conditions for the materials and joint configurations under study in the project, and outlining the tolerances of those conditions,

Designed, built, validated and demonstrated the final RADICLE modular laser monitoring system containing a series of sensor packages and sensor control system

Validated the final RADICLE laser welding system for a range of end user application materials.

To conclude, the RADICLE system is capable of process monitoring and alerting the operator to welds that may potentially contain defects (by being made using inappropriate parameters). The RADICLE system will not converge onto ‘good’ parameters, indeed, this a functionality that the consortium consider undesirable and would rather use process window maps to start welds with known, good parameters. RADICLE cannot control parameters beyond the adaption of the seam path to compensate for minor variations in desired seam path. Key weld defects, such as porosity requires measurement and analysis within timeframes that are currently beyond the latency experienced in data acquisition and processing. Furthermore, hardware latency further extends any potential system response time.

Whilst the final Radicle system has not fully delivered on the original project objectives, there has been significant progress made despite the difficulties encountered and the final system gives Permanova and BitAddict a future commercial opportunity with the field of laser weld process monitoring system that is comparable and has additional benefits over existing systems. It also delivers the end users need to have confirmation that acceptable welding quality is being achieved and done repeatedly.

Components of the final Radicle system will be commercially available from Permanova now and are developed to TRL level 8.
Environmental and Societal Impacts

• RADICLE will help to increase economic growth and create new jobs in Europe by means of reducing costs in manufacturing for major employers in Europe.
• Increased output of the OEM manufacturers will have a positive effect for their supply chain, targeting not only large companies but also SMEs. By having large OEM manufacturers in the consortium we can ensure that the RADICLE system is transferred through the entire supply chain of these OEMs.
• Improved Health and Safety as the operator is remote from the laser welding head and therefore, not exposed to fumes and potential injury.
• Training and education opportunities for the partners to upskill their workforce and train other people working in the sector. The training and education gained more relevance in the RADICLE project, since it was seen as a way to increase the visibility of the RADICLE system as well as a way of ensuring a proper uptake of the system by industry. This approach moves from an “in-house” training to a sustainable training/educational program that will be included in the EWF training system that is already running for 25 years.