| The first high power density welding
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| | evacuated to the operating vacuum level
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| systems were electron beam. The
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| | in a matter of seconds rather than
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| generation of a high power electron beam
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| | minutes. Many automotive and other parts
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| in a vacuum environment, accelerating
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| | i.e. flywheels, transmission planet
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| this stream of electrons via high voltage
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| | carriers, catalytic converters, hydraulic
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| applied between the cathode and anode,
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| | pistons, hacksaw blades, band saw blades,
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| and then electromagnetically focusing
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| | commutator blanks, torque converters, and
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| that total power to a very small spot on
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| | spark plugs etc. have been produced on a
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| the piece to be welded. The power density
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| | production basis with "Soft Vacuum"
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| (power per unit area) was so intense that
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| | electron beam welding equipment. With
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| it immediately vaporized the metal being
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| | some of these systems a unique dial feed
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| welded, which then solidified behind the
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| | table with a sliding vacuum seal was
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| progression of the weld as the aligned
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| | incorporated which allowed the part to be
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| weld joint of the part was being moved at
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| | pre-evacuated in the station before the
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| a constant velocity under the focused
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| | weld station. This set up, totally
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| beam. The welding parameters were power,
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| | eliminated the vacuum pump down time from
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| speed, and focus which provided the weld
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| | the machine cycle time. Production rates
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| penetration and weld properties desired.
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| | up to 3,000 parts per hour have been
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| The characteristics of an electron beam
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| | achieved using this welding technique.
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| weld are excellent because the welding
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| | With the advent of higher power lasers
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| takes place in a vacuum environment and
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| | many of the applications that were
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| oxidation of the weld area is not a
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| | accomplished by electron beam are now
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| problem since any significant oxygen is
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| | being processed by laser systems.
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| absent.
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| | However, many of the close tolerance high
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| Other considerations which detract from
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| | value aircraft engine and aerospace
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| electron beam welding are that the part
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| | components that require deep penetrating
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| or the electron beam gun has to be
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| | non contaminated welds are still being
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| manipulated in a large vacuum chamber in
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| | processed by electron beam. The laser is
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| order for the part to be welded. These
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| | also a much more versatile tool. The
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| large vacuum chambers require large
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| | various wave lengths available with
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| mechanical and oil vapor diffusion pumps
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| | lasers can offer some very selective
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| to draw down the vacuum to the high
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| | results depending on the interaction of
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| vacuum operating level required. Pump
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| | that wavelength with the material being
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| down times can be 20 minutes to a few
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| | processed. For instants, a Nd:YAG laser
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| hours for large systems. In the case of
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| | with a wavelength 1,060 nm can weld a
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| welding the large titanium wing box for
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| | clear piece of plastic to an opaque piece
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| the Grumman F15 Fighter the vacuum
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| | of plastic by passing directly through
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| chamber was extremely large and the
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| | the clear piece without affecting it and
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| vacuum pumps were also large and
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| | then impinging on the opaque piece
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| numerous.
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| | heating and melting its surface and
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| A second consideration is the fact that
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| | effectively producing a leak-tight weld
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| electron beam welders produce intense
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| | at the interface of the two materials.
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| X-Rays. The high voltage electron beam
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| | Pulsed Nd:YAG lasers are used for
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| welders (150,000 volts) with stationary
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| | intricate highly controlled low
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| electron beam guns produced the highest
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| | penetration welding. This would be the
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| penetrating X-Rays and thus the vacuum
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| | welding of heart pacemakers, heart
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| chambers and guns had to be lined with 1
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| | valves, medical instruments, orthopedic
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| 8" thick lead. The lower voltage (60,000
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| | implants, small hermetically sealed
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| volts) movable gun systems had to use 1
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| | electronic enclosures, spot welding razor
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| inch thick steel in the construction of
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| | blades, jewelry welding applications etc.
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| the vacuum chamber to attenuate the
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| | These lasers produce high energy pulses
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| X-Rays. Both types of electron beam
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| | of short duration so a seam weld needs to
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| welders had to use thick leaded glass for
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| | be produced by overlapping these pulses
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| the viewing ports.
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| | approximately 75%.
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| The next iteration of electron beam
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| | High Power CO2 Lasers have been used for
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| welders where called non-vacuum welders.
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| | numerous welding applications, many of
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| With this process the electron beam was
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| | which have replaced electron beam welding
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| generated in a small high vacuum chamber
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| | for the same applications. However, the
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| around the electron beam gun only and the
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| | future for narrow deep penetrating
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| electron beam was passed through a small
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| | electron beam type welds will fall to the
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| pressure differential orifice into normal
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| | new High Power Fiber Lasers. These lasers
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| atmospheric pressure. The electron beam
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| | are extremely efficient, have a long
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| immediately collided with air molecules
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| | expected solid state pumping diode
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| and dispersed rapidly. The weld joint
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| | lifetimes of over 100,000 hours, are
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| needed to be extremely close to the exit
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| | virtually maintenance free, and can
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| orifice (1/8" to 3/8") or the electron
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| | deliver this laser power through a small
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| beam spot diameter was too large to do
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| | flexible fiber optic cable. Manufacturers
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| any effective work. Even at a close
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| | can use robots to manipulate the fiber
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| distance from the exit orifice the weld
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| | optic delivery system to weld a wide
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| characteristics lost the deep depth to
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| | variety of large production parts or
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| width ratios associated with high vacuum
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| | incorporate it into high speed automated
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| electron beam welding. The exit orifices
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| | production lines.
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| were expensive and eroded fairly quickly.
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| | The laser beam quality of the fiber laser
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| The non-vacuum electron beam welder was
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| | (ability to focus to the smallest spot
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| also a large X-Ray producer and any
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| | diameter) is superior to other high power
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| automation or production material
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| | lasers and provides faster welding speeds
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| handling equipment had to be baffled and
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| | for a given power level or increased
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| placed in a lead room. Several electron
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| | production rates. Also because of the
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| beam in air systems were produced but
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| | better beam quality the stand-off
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| this technology did not last long.
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| | distances of the focusing optics to the
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| Electron Beam Welding then progressed
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| | work piece can be extended to two to four
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| into the production welding environment
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| | feet for some applications. Great strides
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| with the advent of "Soft-Vacuum" electron
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| | in the number of new laser welding
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| beam welding. With this technology the
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| | applications can be expected in the near
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| electron beam is generated in a small
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| | future. The high power fiber laser can be
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| high vacuum chamber, directed through a
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| | an expensive commodity but should be able
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| small pressure differential orifice and
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| | to greatly increase productivity and
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| into a partial vacuum generated by only
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| | equipment up time and easily justify
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| mechanical displacement vacuum pumps. The
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| | their cost. Remember; automation, robots,
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| electron beam still maintains its deep
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| | and reliable lasers level the playing
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| penetrating narrow weld characteristics,
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| | field with low labor costs when competing
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| while a smaller vacuum chamber closely
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| | on the world stage.
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| sized to the parts to be welded, can be
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