forming & fabrication
Building a nuclear
submarine is a
complicated
business - not least
when it comes to
the sheet metal
components. The
confined space and
curved walls of the
interior mean that many items, such as lockers, bunks,
kitchen equipment and ducting for heating and ventilation
have to be made as one-offs to fit the space available.
Astute choice for BAe Systems
Contracts to supply
submarine fittings
pose special challenges to
sheet metal specialists in
terms of productivity and
flexibility
read more about
forming & fabrication
at www.mwponline.com
New Products
and Services
■ Rofin Star Pulse for
laser welding
Rofin-Baasel
http://tinyurl.com/3cfwt2
■ Elumatec at MACH
2008
Elumatec
http://tinyurl.com/2pjg2t
Case Studies
■ Arc welding by robot
for seat frame
Motoman
http://tinyurl.com/3xpcnu
THE BAE Systems shipyard at Barrow has launched
HMS Astute, the first of a new class of nuclear-powered
hunter-killer submarines for the Royal Navy, and is now
building the next two boats, with a fourth on order. An
LVD Global 20 CNC punch press provides the capability
and flexibility to ensure that the sheet metal requirements
for these vessels are met in a timely and cost-effective way.
Colin Taylor, Outfit Manufacturing Manager at the
Devonshire Dock Hall in the Barrow yard, runs the sheet
metal shop and explains the complexities: ‘There are
around 8,000 different bits of equipment on every
submarine to be fabricated from sheet metal - as well as
1000 metres of heating and ventilation ductwork. For items
such as lockers we have to design and manufacture units of
the right size and shape to fit into the available space. It isn’t
like a surface ship where you can use standard units. It’s the
same on the ducting. Whereas on a normal contract you
would expect long straight runs, on a submarine every
ventilation spool is different.’
Even where a number of similar components are needed
they can’t be scheduled to be made together. Everything
must be delivered ‘JIT’ for installation as the boat is
constructed - deck by deck and module by module. ‘You
have to make what they need when they need it. We make a
wide diversity of parts and use a lot of different materials -
aluminium, stainless steels, mild steel and galvanised steel -
in thicknesses up to 3mm on steel and 6mm on
aluminium. And while somebody making PC cabinets or
washing machines is making thousands of the same part,
we might make a single locker in mild steel, then run half
a sheet of aluminium and then move on to something else.
It can literally be one-off after one-off after one-off. And
although we try to plan like with like, we may change the
material on the machine eight times a day.’
These requirements drove the decision to replace an old
punch press with the LVD Global. The one at Barrow is a
20-tonne hydraulic, thick-turret machine with thirty tool
stations. Tool capacity is expanded via multi-tools in two of
the three rotary stations. These hold eight and three tools
each, and each tool can be individually rotated. Overall, this
66 MWP january 2008
gives a total of 39 tools in the turret at any one time, of
which twelve are fully indexable.
‘Around 80% of what we produce in the sheet metal
shop goes through the punch press so it has to be very
productive and very flexible. We were doing massive
numbers of tool changes on our old machine because of the
variety of materials. Now we have a bigger turret with
more tools so we have been able to optimise the tooling
configuration for the type of work. For example, we have
some common tools duplicated around the turret, but set
up with different die clearances for different materials.
This new flexibility means that we only have to change the
turret configuration a couple of times a day.’
The Global has allowed BAe Systems to use new
manufacturing and design strategies. Form-working, in
particular, has allowed it to reduce secondary ops and
assembly time. ‘We aren’t a first generation user going
from making a locker by hand to using CNC. We are going
from one CNC process to a more sophisticated one. Now
we want to explore how we can refine our designs to really
use the machine’s capabilities.’ At its simplest level this
means using a centre-dot marking tool to identify every
part with a unique product number - previously this was
done by hand using a marker pen.
At a more sophisticated level, the use of semi-shear tool
allows parts to be snapped together without rivets, and a
hinge-making tool can form the hinge from the sheet -
whereas before the hinges were also riveted on. ‘We have
made a lot of modifications to the locker doors, for
example,’ says Taylor. ‘We used to rivet the outer and inner
skins of the door together; now the semi-shear tool means
we can just snap the parts together. And with the hingemaking
tool, the only secondary operation required is to
slide the hinge-pin into place. We are saving time by not
using rivets.’ By taking out manual second ops the standard
manufacturing time for a finished locker has been cut
from eight hours to five hours. ‘And if we have to we can
manufacture a locker from start to finish in about 2 1/2
hours rather than the seven hours it would have taken us.’
www.lvdgroup.com
To view a Ceros magazine you need to have JavaScript enabled in your browser and have the flash player 8 or higher installed. To install the latest flash player, click the icon above, install the flash plugin and then click here to refresh this page.