Sand-Cast vs. Die-Cast
Recently, the subject of die-casting versus sand-casting
has been a topic of interest in our industry. Since GLM is a leading
manufacturer of aftermarket marine parts, we would like to add to
your marketing and technical knowledge on this subject.
As you may already know, GLM currently
produces both vacuumized sand-cast and die-cast products.
The most interesting example of a GLM die-cast product is the Stringer
upper gear case, while the most interesting example of a GLM vacuumized
sand-cast product is the Alpha One lower gear case.
Whether or not a product is sand-cast or die-cast
is determined by many considerations. One of the main considerations
that GLM uses for any product, that it produces is: can
we improve it? There are many examples of GLM products
that have improved engineering and the Alpha One vacuumized sand-cast
lower case is a perfect example of GLM improved engineering.
The original Alpha OEM case is indeed a die-cast
product. However, due to the fact that this particular product is
the heart of this drive unit and operates below the water line,
GLM wanted to make a more reliable stronger case.
Vacuumized sand-casting makes it possible to cast with more resilient
aluminum alloys which cannot be used in die-casting. This increases
strength and the overall amount of aluminum in the final product.
If you weigh a die-cast Alpha One case and a GLM vacuumized sand-cast
case, you will see that the die-cast case weighs approximately 141/2
lbs. and the GLM case weighs 16 lbs. The extra 11/2 lbs. is simply
due to more aluminum in the GLM case.
The OEM Alpha die-cast case uses A380 aluminum
alloy. This is required due to the die-cast method and it produces
a case that is more susceptible to breakage. We are sure that you
have all seen drive units with broken cavitation plates and/or a
broken skeg. By using the vacuumized sand-cast method, GLM is able
to utilize a much less brittle A356 aluminum alloy. This is the
same alloy used in making many automotive/truck wheels and speaks
for itself in regards to the strength of GLM Alpha One cases. As
a matter of fact, OEM Volvo lower units are also sand-cast for these
exact same reasons.
Additionally, many may think that a die-cast case
is more precise than a vacuumized sand-cast case. In reality, there
is only a slight cosmetic difference on the outside of the case
and the GLM five step finish process compensates for this difference.
The internal tolerances for both die cast and sand cast cases are
all machined after either of the casting processes is complete.
GLM hopes that these casting facts will help you
in marketing our products and also give you the real facts
from the original manufacturer.