MACHINE TOOLS
rigidity and reduce vibration. It uses
Mori Seiki’s DCG (Driven at the Centre of
Gravity) technology, which incorporates
two ball screws on both the Y and Z axis,
aligned to drive the machine table
through its centre of gravity.
Conventional machines only use one
ball screw. This creates forces that are
out of balance, thus vibration, as the
machine finds its next position.
The low levels of vibration inherent
with DCG enable the machine to cut
faster than conventional machines,
improving the accuracy and surface
finish.
Rigidity is at the heart of the
machine’s design. Its massive castings
provide solidity while its box-in-box
construction makes it compact. Mori
Seiki carries out both static and dynamic
analysis of its machine components to
check and optimise performance under
live cutting conditions.
Additionally, to secure the supply of
high-quality castings, the company has
taken a 33 per cent share in the Japanese
Watanabe Steelworks. The company says
with the growth in the Chinese economy,
much of the casting manufacturers’
capacity will be taken up with domestic
demand, making it difficult for users of
Chinese castings to meet delivery and
quality targets.
The NMV5000 features an octagonal
ram supporting the direct drive spindle.
The symmetry of the octagonal guides
cancels out the effects of heat distortion
associated with square guides, ensuring
that the centre of the spindle is unaffected
and benefits from improved rigidity.
Both the spindle and the rotary table
use direct drive motors, thus eliminating
backlash associated with more
traditional geared systems.
In the event of a collision on the
machine worm drive, parts can become
damaged, introducing further inaccura-
cies and vibrations into the system.
Combining these features enables the
machine to cut a cone shape using all five
axes simultaneously to achieve a
roundness of 3.11nm, compared with
20-30nm on the previous model.
The Hardinge Group designs and
manufactures CNC machining centres,
grinding machines, lathes, collets, chucks
and indexing fixtures, and has
manufacturing operations in North
America, Europe and Asia. It distributes
machines to all the big industrialised
countries.
In recent years it has acquired
many other machine tool builders,
including Kellenberger, Bridgeport,
Hauser, Tripet and Tschudin.
The Hardinge XR 500 HSC (formerly
Bridgeport’s HSC 500), is a high-speed
vertical machining centre ideally
suited to the machining of graphite and
copper electrodes.
The XR 500 HSC machines have a
rigid cast iron portal construction and
are equipped with high-speed, heavy-
duty HSK E32 40,000rpm spindles. The
spindles have ceramic bearings, which
generate less heat than conventional
bearings.
These, and thermally-controlled
With the growth in the Chinese economy, much
of the casting manufacturers’ capacity will
be taken up with domestic demand
refrigerated cooling jackets, help
reduce thermal distortion and improve
part accuracy and repeatability — even
during long and unattended machining
operations.
The machine’s linear guides, fast
acceleration/deceleration (0.85g) and
15m/min feeds and quick-change tool
changer help increase work throughput
and reduce part cycle times.
The machines are also supplied with
the Heidenhain iTNC 530 control,
which provides short block processing
times (0.5 milliseconds).
The machine’s productivity can be
60 the EnGIneeR 15–28 SEPTEMBER 2008
further enhanced by incorporating a
range of optional automation
features, including automated pallet
changing systems.
Market-leading precision tool and
die-making specialist Lasercomb Dies
has recently invested in two HSC 500
high-speed machining centres from
Hardinge-Bridgeport to machine brass
embossing dies for applying Braille text
onto pharmaceutical packaging.
The high-speed spindle is
ideal for the small diameter tooling
required. It maintains the surface
speed necessary to cut the embossing
dies cleanly and accurately, while
meeting the tight lead time of two to
three days demanded by the customer.
‘Of equal importance in our
machine tool decision-making process
was the after-sales and service back-
up,’ said Alistair Baxter, sales director
at Lasercomb Dies.
‘We operate in a demanding
and pressurised manufacturing
environment.
‘Machine downtime is not an
option for us so we need to know not
only that the machine tool is reliable,
but that if repairs or parts are required
they can be carried out and delivered
immediately.
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