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What is Friction Stir Welding?
Friction Stir Welding is a revolutionary technique that was developed by The Weld Institute (TWI) in Cambridge, England, in 1991. In friction stir welding (FSW) a cylindrical, shouldered tool with a profiled probe is rotated and slowly plunged into the joint line between two pieces of sheet or plate material, which are butted together. The parts are clamped onto a backing bar in a manner that prevents the abutting joint faces from being forced apart. Frictional heat is then generated between the wear resistant welding tool and the material of the work-pieces. This heat causes the work pieces to soften without reaching the melting point and allows traversing of the tool to the trailing edge of the tool probe and is forged by the intimate contact of the tool shoulder and the pin profile. It leaves a solid bond between the two pieces. The process can be regarded as a solid phase key-hole welding technique since a hole to accommodate the probe is generated, then filled dur-ing the welding sequence.

Why Friction Stir Welding?
The advantages of Friction Stir Welding result from its being a solid-state process, in which the joining occurs without fusion of the metal alloys to be welded. The absence of melting eliminates many of the problems normally associated with conventional metal welding such as fumes, spatter, porosity, solidification cracking, and shrinkage. FSW technology produces welds that are stronger and more durable than other techniques, and it can be done faster, resulting in less cost. The process is uniquely suited to join materials, such as aluminum alloys that are difficult to fusion weld. These include the 2000 and 7000 series aluminum alloys and the 2195 aluminum-lithium alloy, used on the external fuel tank of the NASA Space Shuttle. Friction Stir Welding can use existing and readily available machine tool technology. The process is also suitable for automation and adaptable for robot use. Additional advantages include:

• Non-consumable tool
• One tool can typically be used for up to 100mof weld length on 6000 series aluminum alloys
• No filler wire
• No gas shielding for welding aluminum
• No welder certification required
• Some tolerance to imperfect weld preparations – thin oxide layers can be accepted
• No grinding, brushing, or pickling required in mass production

GTC Capabilities
General Tool Company has been at the forefront of FSW technology delivering on its promise to achieve applied production success. General Tool Company has designs, engineers, and manufactures the Accustir™ line of Friction Stir Weld machines. GTC also has the capability to custom design FSW machines to meet your specific industry needs. If you require an immediate solution to meet your customer’s needs, GTC can help. GTC holds a license from TWI to perform friction stir welding, and we can adapt our own in-house machine to fit your specifications. We can deliver a successful, cost effective solution to out pace your competition. General Tool Company provides a comprehensive set of support services including in-house testing and on-site installation of FSW machines to ensure the highest standards of quality are met.

FSW in Action
General Tool Company has a longstanding history of successfully and efficiently building special machines to create parts and assemblies that must meet exacting specifica-tions. GTC successfully engi-neered and built its first friction stir weld machine to weld amplifier frame assembly units for the National Ignition Facility (the world’s most powerful laser system) designed on behalf of Lawrence Livermore National Laboratory. The National Ignition Facility contains the world’s largest laser, a research tool that will allow scientists to recreate on Earth conditions at the center of the Sun. Those conditions of high temperatures and pressures will spark nuclear fusion ignition and energy gain for the first time in a laboratory. The resulting data will help the Energy Department maintain the safety and reliability of the nation’s nuclear weapon stockpile without underground testing. NIF will also perform important research in fusion energy development, basic science, and astrophysics. General Tool Company manufactured Frame Assembly Units that house the flash lamp and laser slab cassettes used during the main laser amplifier stages. After they are at full power (500 trillion watts) and energy, NIF’s 192 laser beams will be directed to a small fusion target. The FAU’s provide both structural support and precise positioning of the cassettes. A total of 171 Frame Assembly Units were manufactured: 122 units measure 52” x 59” x 96” and 49 units measuring 52” x 89” x 96”.

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