grinding
Raysun has been
granted a UK patent
for its DIATI 50 process to
grind parts such as
titanium turbine and
compressor blades. The
company claims the
process takes half the time
of milling. Platform is a
Hermle C40 5-axis vertical
machining centre
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Engis electroplated
grinding points for titanium
half the time it takes to mill them, furthermore with
improved surface finish.
The platform for the process is a Hermle C40 5-axis
vertical machining centre (in a similar fashion to how
VIPER grinding uses Makino or Bridgeport platforms).
Abrasive specialist Tyrolit is involved in the
development of special grinding wheels featuring
diamonds in an electroplated bond. The process can
grind these difficult alloys at 50mm 3 /mm of wheel
width every second. To counter the traditional
problems of grinding titanium - namely wheel
clogging and surface burning - the process uses high
pressure coolant that is fed into and on the electro
plated wheel at high pressure. Internal delivery is at 30
bar and the coolant is fed into labyrinths within the
wheel (quadrants can be pre-selected) and which exits
through holes in the circumference; while externally,
coolant at a pressure of 80 bar is directed on to the
wheel for flushing and cooling. Much attention has
also been given to effective coolant filtration and fume
extraction.
With wheel speeds from 50 to 150m/sec, the process
can remove a high volume of titanium alloy in a short
space of time. Tests have shown it can finish machine a
titanium alloy compressor blade from the as-forged
condition in a cycle time of just 5 minutes - whereas
milling such detail would take around double this time.
To date, most titanium grinding applications have
occurred in the aerospace sector, typically for nonprecision
processes such as deburring. Engis, for example,
is helping aerospace component manufacturers
overcome some of the significant production challenges
that the increasing use of titanium components have
created. Engis says that because titanium is tough, when
conventional bonded abrasive technology is used for
deburring, not only are the grinding wheels damaged
very quickly but a great deal of heat is generated, causing
the titanium swarf to melt and then re-attach itself to the
component as weld spatter.
56 MWP november 2007
Grinding a TiAl compressor blade using a special
diamond wheel from Tyrolit
In the aerospace sector such spatter, which is easily
detectable to the eye and by touch, is completely
unacceptable and can result in the scrapping of highvalue
components - an undercarriage leg for example
could cost several tens of thousands of pounds - so a
cool grinding solution is essential. Engis diamond
electroplated grinding points provide just such a
solution, as the company’s technical specialist, Mark
Foster, explains: ‘Recent tests at a major aerospace OEM
demonstrated that the grinding points could not be
made to create weld spatter, even when run faster and
harder than the manufacturers’ recommendations - a
very reassuring fact for production managers operating
in real-world conditions.’ Engis diamond electroplated
grinding points and wheels are available in both
natural and synthetic diamond in diameters from 0.5 to
550mm, and can be designed and manufactured to
customers own specifications.
For portable grinding applications there are also
solutions, such as Saint Gobain’s recently introduced
Norton SG Blaze R980 abrasive discs. Each grain
continually fractures during the grinding process along
sub-micron faults in crystalline structures, repeatedly
exposing new sharp cutting edges and hence negating
the problem of clogged grains when processing
titanium.
The difficulties of precision grinding titanium are
plain to see but genuine solutions are not far away. With
increasing commercial pressure on fuel economy the
demand for light, strong materials will continue for the
foreseeable future. To this end, the rewards for a
breakthrough ensure there will be no lack of research
effort in developing an optimised grinding process.
www.raysun.co.uk
www.gkholdings.com
www.tyrolit.co.uk
www.engis.com
www.saint-gobain.com
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