QCOALA Quality Control Of Aluminium Laser-welded Assemblies A collaboration between: LASAG, Precitec, CIT and SAFEL, Flisom, SolarPro and VW, Ruhr-Universität Bochum, Fraunhofer ILT and TWI An idea from :
QCOALA Call & Consortium FoF.ICT.2010-10-1 Smart Factories: ICT for agile and environmentally friendly manufacturing Duration: 47months (until July 2014) 10 participants from 5 countries Industry involvement in R&D: 30% RTD 40% SMEs (laser manufacture, process monitoring, NDT, end-user) 30% LE (solar energy, automotive)
Our Consortium
QCOALA Outline What? Why? Develop a dual-wavelength laser platform for the welding of thin-gauge Al and Cu To establish capability to provide a reliable, high speed, low-cost and high-quality joining solution Electric car battery, and Thin-film PV interconnections Courtesy of Volkswagen (automotive end-user) Courtesy of Flisom (solar cell end-user)
Technical Basis Steen, 2003
The actual solution Precitec dual (Red-Green) wavelength processing head Processing head integrated with the pulsed q-switched green laser
Project Outputs 8 Defined Exploitable Outcomes (as per final report) ~30 Events attended (10 by industrial partners) 4 IPR outputs 2 patents 1 1 Design Cost-Benefit Analysis
Cost-Benefit Analysis (Auto. Battery) Two seams for each terminal / busbar interconnection (6m/min welding speed) One manufacturing shift - 450 units Automated unit assembly Screwing: Laser-welding: 3 stations 1 station Screwing (Existing) GreenMix Laser (QCOALA) Investment for manufacturing concepts Space requirements for manufacturing concepts Product weight reduction by using laser welding Fibre Laser (Red laser)
Dissemination and Promotion of the Project Results Dissemination activities:
Dissemination and Promotion of the Project Results
Exploitable Result 1 Dual Wavelength-Laser for reliable spot welding of copper Innovation Single laser source capable to deliver Green and IR wavelength at the same time. Proportion of Green and IR radiation is set online via pulse shaping. LASAG Customers target Electronics industry (Ribbon and wire bonding). Solar industry (thin film bonding). Benefits More reliable and reproducible copper welding process. Higher yield, less pre-processing costs.
Exploitable Result 2 Dual-wavelength laser welding head with sensor interfaces Precitec TWI Innovation Using green laser radiation improves the quality of laser welding of copper because of the higher absorption of this wavelength. The dual-wavelength laser welding head provides the facility to combine the green and infrared laser wavelength for high quality laser welds even in thicker materials. Additionally all interfaces are offered to attach sensor systems for in-process quality monitoring. Customers target End-users (Laser welding companies) Machine integrators R&D facilities Benefits Quality enhanced for laser welding of copper. Reproducible results and less quality fluctuations
Exploitable Result 3 Know-how for laser welding copper and aluminium thin sheets (monometallic and dissimilar joining) Safel RUB TWI Innovation The laser process development allowed to develop a tool or procedure for assisting in equipment and process selection for micro laser welding of copper and aluminium for electrical connections. A dual-wavelength laser welding head was used to deliver combined green and infrared laser sources, due the perceived innovative capability of this system to address the battery application, in terms of penetration and welding speed required. Customers target The transport sector as well as other industry sectors involving electronic assemblies using Copper and Al materials. Benefits Quality enhanced laser welding of copper (monometallic) and copper to copper dissimilar joining. Reproducible results and less quality fluctuations. A tool procedure to guide industry on selection of the appropriate process window to laser weld copper and aluminium thin sheets (eg reduced formation of melt ejections, blow holes).
Exploitable Result 4 & 5 Indirect measurement of penetration depth in continuous-wave welding of copper for quality assurance ILT Innovation Indirect measurement of penetration depth is researched by analysing the relationship of penetration with measurable process quantities such as radiation in visible spectrum or dimensions of the liquid material. The investigation results are novel for this wavelength of the laser radiation and material, due to the intricate nature of laser welding. Customers target OEM / End-users Machine integrators Benefits Assuming enough accuracy and precision of the measurement technique for an application, the weld can be quality assured synchronously with the processing with regard to penetration depth. After further research closed-loop controls can enable welding of new geometries requiring rapid adjustment, e.g. of laser power. Eddy Current Inspection of Battery Electrode Welds TWI Innovation Eddy current probe design (micro sized coils), operating procedure for thin metal welds. Customers target Users of critical laser welds on thin non-magnetic materials or coatings. Benefits Improved inspection allowing operation for thin materials in more critical conditions.
Exploitable Result 6 Thin wall material NDT digital radiography inspection system Innovation The ability to inspect laser welded thin material made of Aluminium or copper or composite material can be inspected with this technology. CIT Customers target Solar panel manufactures. Aircraft manufacturing companies using composite material products. Benefits Improvement in product quality with reduced cost or ownership. Risk mitigation with evidence of product quality that reduces liability protection.
Exploitable Result 7 Welding of busbars on flexible solar modules FLISOM CIT Innovation Welding of busbars on flexible solar modules to collect and extract the current Customers target Solar panel manufactures Aircraft manufacturing companies using composite material products Benefits Improved and more stable contacting of the busbar with the solar modules Courtesy of Flisom
Exploitable Result 8 Laser welded battery terminal connection with copper materials for weight and volume optimisation VOLKSWAGEN Innovation Laser welding process by using the combination of a green q-switch laser and a high power continuous infrared laser for high volumes productions with In-line weld inspection for welding quality of battery terminals Customers target High volume battery system manufacturer Benefits Laser welding of copper with high process stability Economical production of connected battery cells for high production rates Courtesy of Volkswagen
Standards and Regulations Several standards exist for laser weld quality not specifically relevant The most relevant, EN ISO 13919-2:2001, Welding Electron and laser beam welded joints Guidance on quality levels for imperfections, Part 2, relates to electron and laser beam welding of aluminium alloys. It should be noted that ISO 13919-2:2001 is non-application specific and relates to welds with penetration depths of 1mm. No recognised international standards for laser weld quality QCOALA components and materials New to industry application of laser welding to battery terminals and solar module electrical interconnections; in-house quality criteria for such joints are in the process of being developed. For the QCOALA applications, key quality requirements identified: Minimum spatter from the surface of the welds to maintain a clean production environment. This requirement will be reflected in a lack of blow holes and melt ejections from the surface of the lap-welds produced. For Cu-to-Al dissimilar welding minimised formation of cracks due to intermetallic phase formation between the two metals.
Project Management and Governance Constant battle within the consortium about following DoW vs Doing the relevant thing RTO/University [keep EC happy] vs Industrial partners [solve their problems] Consensual decisions were made SolarPro left the consortium at M24 due to external environment (rather than project progress) Approached the EC for a single amendment (M24) which was accepted Did ignore / not include new side-ground developments (i.e. can use Red lasers solely)
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