Bobbin Tool Friction Stir Welding

Pinless friction stir welding is basically normal friction stir welding, only the pin is shorter or left out completely. So you weld just with the shoulder over the surface. This is done for thin sheets or when you only need a superficial, smooth weld without fully penetrating the parts. The advantage is that you don't have to worry about a backing bar or anvil because nothing is welded through. You just have to make sure you have enough downforce and the parts are cleanly clamped, otherwise the weld wanders or you don't get a proper bond. If the material is too thin or the shoulder gets too hot, you can quickly push through or deform the sheet. So: clamp cleanly, run over it with the right pressure and feed, then you get a clean, tight weld without penetration.