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Efficiency Improvements for Aluminium Coil Processing

Aluminium coils are made up of rolled sheets of aluminium, with a hollow cylinder inside upon which the material is wound to create the interior diameter, as shown in Figure 1. Various industry sectors rely on coils made from aluminium for a myriad of applications, including those for construction, electronics, automotive, healthcare, food, manufacturing, aerospace, and more.

Depending on the requirements for each application, the aluminium coil can be surface treated before fabrication into end products. This is achieved in a continuous, efficient and automated process known as coil coating, which improves the corrosion resistance of the material as well as the aesthetic appeal of the coil material.

The coil coating process begins by unwinding the initial coil as it undergoes different stages of the coating line, such as cleaning, etching, anodising, colouring and sealing before being rewound for shipment. However, because of the non-continuous feed of sheet material, the end of one coil needs to be joined to start of the next. Adhesive taping is usually used to perform this joint, which due to its non-conductive nature, requires the shutdown of the production line while this joint passes through each treatment station. This leads to significant manufacturing downtime, material waste and introduces an element of risk when resuming production.

The ideal solution for this application is a rapid, reliable, electrically conductive joining method that delivers excellent mechanical properties and a flush or flat surface finish.

Figure 1. Aluminium coils
Figure 1. Aluminium coils

A potential solution to this costly and time-consuming challenge for aluminium coated sheet manufacture is to use refill friction stir spot welding (Refill FSSW). Initially developed for the aerospace industry to replace riveted joints, Refill FSSW is a fully automated process which offers a number of advantages over mainstream single-point joining processes. As a development from the conventional friction stir spot welding process, refill FSSW offers improved functionality by allowing for the independent vertical movement of the tool components. This allows for the refilling of the exit hole with displaced material to create flush welds (see Figure 2) as well as the versatility of welding different materials and thicknesses using the same tool setup.


The advantages of refill friction stir spot welding for aluminium coated coil manufacture include:

  • Zero consumables
  • High speeds (<1s per spot)
  • Can be gantry or robot mounted (see Figure 3)
  • Works with dissimilar gauges and Al grades
  • Near-flush surface finish
  • Produces high conductivity/low resistance joints
  • No fumes/arc/melting/spatter/EMF
  • Fully automated and monitored mechanical process

Please contact us, below, to find out more about how this process could improve your aluminium coil manufacturing process.

Figure 2. RFSSW top side surface finish (with zero marking on lower side)
Figure 2. RFSSW top side surface finish (with zero marking on lower side)
Figure 3. Refill FSSW equipment
Figure 3. Refill FSSW equipment
Avatar Dr Pedro Santos IEng Pedro Santos - Senior Project Leader

After finishing high school in STEM subjects such as Mathematics, biology, physics and chemistry, Pedro received his MSc Degree in Mechanical Engineering from NOVA School of Science and Technology in Portugal. As part of his industrial placement at The Welding Institute (TWI, Ltd), his MSc thesis focused on the optimisation of Friction Stir Welding process parameters and industrialization to produce tailor welded blanks for lightweight transport application, a project sponsored by Innovate UK (LightBlank).

His PhD research, co-funded by the Industrial Members of TWI as part of the Core Research Programme and Coventry University, focused on the development of the Refill Friction Stir Spot Welding (Refill FSSW) process for lightweight aerospace applications.Pedro is currently working as a senior project leader in TWI’s Friction and Forge Processes section, managing client relationships and the delivery of projects involving friction welding technologies, predominantly for the aerospace and space sectors.

Due to his experience in engineering projects, Pedro is affiliated with the Engineering council and The Welding Institute. As an active STEM ambassador, he frequently presents and supports workshops on engineering related topics to audiences ranging from Year 1 to sixth form students.