NEAR NET
SHAPE
A simple Near Net Shape (NNS) fabrication process using Electron
Beam Welding to manufacture critical parts from plate that have traditionally
been made by casting is
outlined below:
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For a number of critical components made from
castings the number of approved foundries is limited and there
is often a very stringent approval route required for both
the product and the process.
Also because the minimum melt quantity may be
10-15 tonnes
and the castings are typically less than
2 tonnes in weight
the process can be very inefficient. With expensive patterns,
long lead times and a large inventory of handed components
an alternative production route was developed. |
Solution
Electron beam welding
of machined blanks has been demonstrated to be very cost
effective alternative to
casting.
EB welding produces very high quality components
with very short lead times and since the parts to be welded
are
oxy-fuel cut from blanks the process is a very efficient
use of material. Changes to produce left and right-handed “castings” can
be very quickly made by simple programme changes.
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Blanks are produced using oxy-fuel cutting using a CNC programmer
to produce the
rough shape.
Oxy-fuel cut blanks cut from plate prior to machining 
Blanks are then machined to simple shapes prior to EB welding and
finally machined after rigorous inspection.
• High integrity
• Short lead times
• Design flexibility
• Application to other materials and industries
Copyright TWI Ltd. 2004 Photographs and illustrations reproduced
by permission.
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