At least, that’s the claim by Moog and Thompson Friction Welding. The Linear Friction Welding (LFW) machine, designated the E100, could transform how jet engines are manufactured by cutting production cycle-times and reducing waste of expensive materials such as titanium. It is capable of welding a surface area of 10,000 mm2 (15 in.2), nearly twice as much as previously achieved, and breaks the record of weld forge load at 100 tons. Now, LFW becomes a viable tool for use in the automotive and aerospace industries to produce components such as vehicle flooring and secure the blades on jet engines.
Friction welding technology has not been used before over such a wide operating envelope. Its automatic handling systems and rapid machine open/close features cut production cycle times when compared with traditional manual operations, while recharging of the accumulators takes only around 30 seconds for the largest and longest welds. The machine opens up new possibilities for welded fabrication of parts that previously needed to be machined from solid metal, a process that can result in up to 80% material waste.
Thompson manufactured the E100 at their facility in the United Kingdom. A partnership with Moog garnered the requisite expertise in hydraulics, servo system design, control engineering, and manufacturing.
The challenge was to develop a hydraulic motion control system to drive the machine. The machine weighs 100 tons, is 2.5 m (100 in.) tall, and has a capacity of 100 tons in terms of the amount of force that it can apply to a welded joint. This demanded a suitable hydraulic servo system, which was designed and built by Moog.
Moog’s hydraulic servo system and support for the machine included:
-A closed-loop control system delivering fast response at high amplitude with advanced digital control over the weld process. Normal servo and proportional valves have a limitation of spool speed and acceleration that prevents the simultaneous delivery of high amplitude and frequency. For the E100, Moog valve spools were made to perform three or four times faster than normal. Special precautions were necessary to ensure valve integrity over a large number of welds.
-Multiple digitally controlled servo valves, which together operate at peak flow rates of up to 4,500 lpm (1,200 gpm) and possess a high frequency range of 75 to 100 Hz for large scale welding. Multiple valves also improve accuracy when the machine is turned down for smaller, lower force welds.
-Hydraulic power plant delivering over 2 MW of instantaneous power to drive the system.
-Seven 400 l (105 gal) gas volume accumulators, each producing massive accumulation to provide the high peak oil flow rate ((4,500 lpm) (1,200 gpm)) required for the weld.
This machine is a significant development in light of the unique aspects of LFW. LFW requires more complex machine architecture and control than rotary techniques, but has the advantage that preformed parts of any shape can be joined. Compared to rotary welding, a moving chuck oscillates laterally instead of spinning and the two surfaces are in contact at much higher velocity. This means the two components being welded need to be kept under high pressure at all times.
The benefits of pre-form manufacturing by linear friction welding are numerous. The process, sometimes known as solid-base additive manufacture, allows complex shapes to be manufactured without the wastage of excess material normally associated with machining from solid block, casting or forging, saving both manufacturing time and raw material costs. Manufactured parts are close to the final shape so that very little final machining is required to produce a fully functional component.
Filed Under: Aerospace + defense, Linear motion • slides, Mechanical, Motion control • motor controls