1) Include a Draft Angle of 1 ½ to 2 (Depends on Both Size
This is the required draft angle in order to successfully remove
the casting for the design. This is often an overlooked aspect
of cast design, but it can be critical information when
designing the casting.
Increasing the draft and utilizing it in your design will allow
for greater castability and reduce your tooling/component costs.
This will be due to increased metal flow and ease of tooling
2) Avoid Sharp Corners
The use of sharp corners can lead to many problems with a cast
component. One of the main issues this will lead to is local
structural weakness. The weakness can be due to several factors
associated with sharp corners such as shrinkage, cracks, tears,
The solution to these problems can be found by created round
corners, or fillets. These will allow for the greater stability
provided by the pattern (or mold) during the sand casting
process. This strength is derived from the uniform radii and
thickness connected with the now rounded corner.
3) Know Your Junctions
Another major factor when during the design phase of a project
is to examine which junction will be the best solution. For
example, the X, V, Y and X-T junctions will create added stress
and structural weakness caused by poor metal flow and cooling at
these junctions. T or L junctions are the most often preferred
and structural sound. Another solution can be found by keeping
the radii equal to the section thickness. This will take into
consideration design, casting, and stress factors.
4) Avoid Overly Thick Walls
Avoiding unnecessary thick walls to avoid a major threat to all
castings, improper flow and cooling of liquids. These benefits
include greater metal flow rate, which in turn will avoid
problems caused by cooling issues. Improper cooling of metal in
cast component can lead to sags and structural weakness (just to
name a few).
5) Maintain Uniform Cross-Sections
If cross-section uniformity is not achievable, then a gradual
cross-section change will ease castability. A common
recommendation is to have a transition radius that is 1/3 of the
thicker section and blend in the radius with a 15° slope towards
the thinner walled section. This will increase the fluidity and
cooling of liquid metal through into the pattern/mold.
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