1) Include a Draft Angle of 1 ½ to 2 (Depends on Both Size and Complexity)

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 production.

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, and draws.

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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