Over the last ten years Multi-Wing has gained experience in
designing and manufacturing one-piece moulded impellers. A one-piece
moulded impeller is an attractive economical alternative to the
standard, modular Multi-Wing system when production volume is high.
A one-piece solution is, however, not only cost beneficial, but also
advantageous when it comes to performance and noise level as it
enables us to design the impeller specifically for the desirable
duty point as well as reaching the low noise criteria for the
specific application.
The development of the one-piece moulded impeller is a standardized
process. It is a process with a high degree of expertise,
flexibility and reliability. It doesn't require big investments, but
only a little commitment.
The latest knowledge of impeller profiling to minimize noise levels
is used when developing a one-piece moulded impeller as well as it
is with our standard, modular system. Thus sickle shaped impeller
blade profiles are used today in order to minimize noise
contribution at blade frequency by having a curved leading and
trailing edge.
When it comes to one-piece moulded impellers, there is an additional
way of reducing the noise level. The vortex generated between the
tip of the impeller and the shroud is a significant noise source;
however, as the diameter of the one-piece moulded impeller is given,
it is possible to make a ring around the impeller, eliminating the
problem of tip clearance, and enabling us to make a moulded
aerodynamic inlet to the impeller.
The R&D process when making a one-piece moulded impeller starts by
using our in-house facilities for rapid moulding of prototypes. Our
rapid prototyping machine makes it possible to design an exact scale
model of the project overnight from a 3D file based on customer
performance data and geometric requirements. The next step is to
test the model in our wind tunnel so that it matches the desirable
duty point. When the right
performance is achieved, and the mounting details are configured,
the model is ready for the further tooling process.
Over the last five years Multi-Wing has achieved reliable
sub-suppliers of moulding tools in Asia. Here we have found a high
level of engineering skills and fast process times at a far lower
price level when compared to Europe. Looking at “critical volumes”,
the development within tool manufacturing has meant that the amounts
are lower. When we earlier looked at a break-even volume of maybe
8-10000 units per year, a one-piece moulded impeller is now
attractive from any volume around 4000 units.
The moulding tool is finally placed at the most rational place
depending on the geographical location of the OEM manufacturer and
the Multi-Wing outlets.
