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.
