machining
Gantry-loaded turning centre gives Portsmouth Aviation a dedicated resource to cope
with its specialised and demanding subcontracting market place.
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Cycle times are important’
says Martin Hepburn ‘but
there are other factors to
take into account in what is
a very competitive subcontract
environment’
PORTSMOUTH Aviation is a 150-employee business
with a long and distinguished history. Founded in 1929,
this privately-owned company has at various times
provided an air ferry service between Portsmouth
Airport and the Isle of Wight; specialised in the repair,
refurbishment and flight testing of war-damaged
aircraft; and designed and built the twin-boomed
Portsmouth Aerocar that flew at the Farnborough air
show in 1948. These days, however, Portsmouth Aviation
is a mechanical and aeronautical engineering company
with strong links to the Ministry of Defence, providing
project management, design and development, and
manufacturing services to the MoD and other blue chip
customers for equipment used on land, sea and air.
It has, for instance, been tasked by a major prime
contractor with manufacturing components for nextgeneration
defence programs as well as supplying the reusable
and transportable containers that hold the
completed kits. When this new equipment enters service,
it will provide the Royal Air Force with a precision allweather
operational capability.
Accreditation to BS EN ISO 9001, Civil Aviation
Authority approval and numerous customer approvals,
among them Thales Air Defence, BAE Systems and
GKN Westland Helicopters, underlines Portsmouth
Aviation’s extensive experience of sub-contracting to
government and prime contractors, both in the UK and
abroad. Its seven acre site in Portsmouth encompasses
every aspect of the manufacturing process and is home to
one of the largest metal treatment and finishing facilities
on the south coast, as well as to a machining, fabrication
and assembly facility housing several CNC machine tools
supplied by Yamazaki Mazak UK.
‘The premise is that if it can be done on site, it will be
done on site,’ says machine shop manager Martin
Hepburn; ‘much of the machining work involves mainly
stainless and other steels in small batches, but the most
46 MWP november 2007
recent purchase, a Mazak Quick Turn Nexus 200-II MS
turning centre installed several months ago, is dedicated
to a high volume contract that will run for three years.
The performance and reliability of the existing Mazak
machines, including a twin-spindle, twin-turret
Multiplex multi-function machine, was a determining
factor in this latest acquisition as was the ease-of-use and
reliability of the Mazatrol conversational CNC.
A former machinist and NC programmer, who is still
actively involved on the shopfloor, Hepburn says the
frequent changeovers involved in the majority of
production at Portsmouth Aviation don’t present any
problems whatsoever. ‘Most of our programming is done
at the machine, and the Mazatrol system has shown itself
to be very quick and easy to program.’
As standard, the Mazak Quick Turn Nexus 200-II MS
is equipped with a 26kW/5000rev/min main spindle
and 7.5 kW/6000rev/min second spindle, with rotary
tools held in any of the 12 positions on the VDI-type
drum turret powered by a 5.5kW spindle motor capable
of 4500rev/min, However, Portsmouth Aviation
specified a number of options that included an
integrated gantry load/unload robot. The GL-100F 16pallet
gantry robot enables unmanned operation to take
place over extended periods of time, with load/unload
times kept to the absolute minimum by positioning
speeds of 140m/min (horizontal) and 70m/min
(vertical).
‘Cycle times are important’ says Hepburn ‘but there are
other factors to take into account in what is a very
competitive sub-contract environment. In this high
volume application we opted for a multi-axis, multitasking
machine capable of running unmanned for long
periods of time and reducing significantly the labour
requirement. We have also made insert life the criterion
that determines the frequency of load/unload and,
therefore, the extent of each period of unmanned
running.
‘We know we can machine 60 components without
risk of falling out of tolerance or suffering an insert
failure. So, after the specified number of workpieces has
been machined, we stop the machine, remove the
finished components, load the next set of workpieces,
change all the tool inserts, enter the tool off-sets, and off
we go again. Although there may still be some cutting
life left in the inserts, and changeover times are longer,
the cost of total insert replacement at each changeover is
negligible over the lifetime of this particular component
when weighed against the productivity benefits of
running the machine unattended and eliminating the
risk of damaging high value-added components.’
www.mazak.com
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