Figure 5. 1300 mm, 180 kg Bronze Propeller
»
this technology is limited by its speed and the size
of component it can accurately manufacture. In
contrast, the processes being developed at Cranfield
are designed for high deposition rates.
To put this difference into context, the Cranfield
centre is currently targeting a deposition rate of 10
kg/hr, compared with a typical 0.1kg/hr using laser
+ powder methods, which can also potentially carry
the risk of the material not being fully consolidated
if fusion has not occurred between grains. Additive
arc + wire systems are also capable of producing parts
several metres in size and simplify the process of
producing single piece linear intersections.
The Damen Shipyards Group entered a cooperative
consortium with RAMLAB, Promarin, Autodesk and
Bureau Veritas to develop first class approved marine
propellers.
The early work terminated in the production of the
world’s first WAAM manufactured propeller in 2017
[Ref: 8]. It is based on a Promarin design typically
found on a Damen Stan Tug type 1606 [Figure 5].
10 TUBE NEWS June 2019
Cost of Equipment
Powder deposition technology requires a substantial
metal enclosure within which all the operating
system including laser (or electron beam) heat
source, computer numerical control equipment and
powder dispensing. A typical cost of a production
system is $750,000. Wire deposition is undertaken
with standard arc welding equipment coupled with a
5-axis articulated robot costing a total of $120,000.
[Ref: 9]
Cost of Consumables
Only a limited number of metallic alloy systems are
currently available for additive manufacturing using
powders principally Ti-6Al-4V, some stainless steels,
Inconel 625/718, and Al-Si-10Mg. The cost for many
stainless steels is in the region of $400/kg. Few
problems remain when it comes to fusion welding
and consequently an extensive variety of wire
electrodes is available, most of which can be used
for arc deposition. Because of the quantity of wire
manufactured the cost is not high. Typically, stainless
steel filler wire is readily available for $30/kg.