FOCUS ON WELDING
MAKING A STIR
A new‘ self-fixturing’ friction stir technique from PNNL could open the door to wider friction stir welding operations in general manufacturing.
“ A breakthrough from the Pacific Northwest National Laboratory( PNNL) in the USA could increase the use of friction stir welding on commercial assembly lines.”
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spinning tool plunges into two pieces of metal, rotating at a high rate of speed. As the tool begins to move, it softens and mixes the metal, creating a powerful weld— one that can securely join similar and dissimilar materials( particularly metals and alloys) without rivets, fasteners or adhesive. This advanced manufacturing technique, called friction stir welding, requires only a fraction of the energy required by conventional techniques but is not used on many assembly lines today.
Why? Because friction stir welding exerts tremendous force( up to 5,000 pounds) and something needs to capture that force. Currently, the process requires a rigid, perfectly shaped anvil underneath the material being welded. For many assembly lines, that requirement is tough to meet.
“ When the friction stir tool heats the material, it exerts a massive amount of force that we need to constrain to ensure a precise and secure weld,” said Mitch Blocher, a mechanical engineer at the U. S. Department of Energy’ s( DoE’ s) Pacific Northwest National Laboratory
( PNNL).“ For
Image: TWB Company, LLC.
Oliver Peckham,
Pacific Northwest National Laboratory( PNNL), USA.
A friction stir-welded car door made possible by PNNL’ s advanced manufacturing research.
Four robotic arms with self-fixturing friction stir attachments are rendered alongside a partially built car. PNNL’ s development of self-fixturing friction stir welding could enable applications on assembly lines like the one illustrated here.
Rendered image: Mitch Blocher, Pacific Northwest National Laboratory.
basically the entire history of friction stir, the way you do that is by putting a rigid anvil underneath the material.”
Now, a breakthrough at PNNL could free friction stir from those constraints— and open the door for increased use of the advanced manufacturing technique on commercial assembly lines.
Overcoming the barriers
Here’ s the rub … currently, friction stir welding is not widely applicable on most assembly lines.
“ There is some friction stir welding that is done in vehicle manufacturing,” said Piyush Upadhyay, senior materials scientist at PNNL.“ But typically, it is limited to two flat sheets welded on top of a rigid anvil.”
A case in point: ten years ago, PNNL worked with several companies— including General Motors— to apply friction stir welding in the production of car doors. The process involved welding flat sheets before stamping them into the 3-D shape of a car door.
However, that approach does not work for larger, more complex car parts that cannot simply be stamped into shape: for instance, roof rails and the metal frames that surround the doors.
“ If you want to friction stir weld anything that isn’ t flat, you’ re going to need an anvil in the shape of that part,” Upadhyay explained.“ If you’ re welding a roof rail, you’ ll need a roof railshaped anvil. For a real-world assembly line, that’ s too cumbersome...”
Many components manufactured for vehicles still rely on spot welding and adhesives for joining. The PNNL team knew that if it could design a new, more manoeuvrable fixturing system for friction stir welding, manufacturers could produce those same components with lighter materials, stronger welds and lower energy costs.
62 | ismr. net | ISMR November 2025