Thompson Friction Welding's
E100 extends the use of linear friction welding through its ability to weld an
area nearly twice as large as previously achieved (a surface area of 10,000 mm2).
It also uses sophisticated servo valve control to precisely apply a weld forge
load of more than 100 tons (220,000 lb). These capabilities extend linear
friction welding into automotive and aerospace applications, and have helped
advance friction welding to a point where it is viable for critical
applications such as securing the blades on jet engines.
handling systems and rapid machine open/close features on the E100 cut
production cycle times compared with traditional manual operations, and
recharging of the accumulators takes around 30 sec for the largest and longest
welds, according to Stephen Darnell, regional business manager, Northwest
Europe for Moog.
E100 also allows for welded fabrication of parts that previously needed to be
machined from solid metal, a process that can result in up to 80 percent
material waste. It could "transform how jet engines are manufactured by cutting
production cycle times and dramatically reducing waste of expensive materials
such as titanium," says Darnell.
enable friction welding technology for high accuracy and high frequency
applications, the E100's hydraulic servo system (supplied by Moog) integrates a
closed-loop control system with fast response at high amplitude and advanced
digital control techniques for precise control over the weld process. Servo and
proportional valves typically have a limitation in spool speed and acceleration
which prevents the simultaneous delivery of high amplitude and frequency. For
the E100, Moog valve spools perform three to four times faster than normal.
multiple, digitally controlled servo valves operate at peak flow rates of up to
1,200 gpm and a frequency range of 75 to 100 Hz for large scale welding. Use of
multiple valves improves accuracy when the machine is turned down for smaller,
lower force welds. The hydraulic system delivers more than 2 MW of
instantaneous power needed to drive the system, and seven gas volume
accumulators (105 gal) each produce massive accumulation to provide the high
peak oil flow rates.
friction welding requires a more complex machine and control architecture than
rotary techniques, but has the advantage that pre-formed parts of any shape can
be joined. A principal difference between linear friction welding and rotary
welding is that, in linear friction welding, a moving chuck oscillates
laterally instead of spinning and the two surfaces are in contact at much
velocities. This means the two components being welded need to be kept under
high pressure at all times.
process of pre-form manufacturing by linear friction welding, sometimes known
as solid-base additive manufacture, allows complex shapes to be manufactured
without wasting excess material normally associated with machining from a solid
block, casting or forging, saving both manufacturing time and raw material
costs. Manufactured parts are close to the final shape, so very little final
machining is required to produce a fully functional component.
friction welding involves careful generation of localized heat into the two
materials via friction induced by rubbing surfaces together," says Darnell.
"Regular oscillation of one of the two materials creates friction and, after a
period of time, the materials are chemically joined by applying what is known
as forge pressure which continues until the oscillation stops."
resulting joint, when cooled, has parent metal properties indistinguishable
from either material. The key for Thompson Friction Welding is a level of
precision in all the axes that creates an ability to join dissimilar materials
such as copper and aluminum. "When you consider how the melting points of those
two materials are so different, you get a small insight into just how strong a
step forward has been made," Darnell says.
achieve the machine's technical goals of increased accuracy and frequency, one
key is the precision of the oscillator and its relationship to how a weld is
actually performed. Another factor is that the hand-over, in control terms, to
the forging process had to be extraordinarily precise down to micron-level
of the challenges to enabling this was to ensure that all data coming back from
sensors on the machine was interpreted at the right speed and derived from the
right information. The engineering team also developed a menu of operation
functions in the machine, which allows Thompson's welding experts to pinpoint
the type of recipe they need. This flexibility makes it possible for the
control system to deliver comparable performance whether it is welding very
different or similar materials.
machine uses high-speed, closed-loop EtherCAT fieldbus communications to
control the servo valves, sensors, analog and digital I/O modules, as well as
communications between the Moog real-time controllers and Thompson's control
and monitoring systems. Moog application engineers were able to write a
software control algorithms that permitted a fast loop closure with minimal
overheads. The Moog MSD controller offers very fast processing times, but the
software also had to be written to avoid excessive cycle time in the software
says that the use of EtherCAT communications to all of the valves, coupled with
a special laser etched design of the spool to reduce wear to negligible levels,
were key enablers of the system's high performance capabilities.
you stand near the machine and watch the violent process of linear welding take
place, it's one of the most impressive sights and sounds. And to think that
after millions of full load cycles with huge flows of oil and large valve
excursions, the valves internally are in 'as-new' condition is remarkable,"