Castability Guidelines and Checks

Castability has certain limitations and guidelines based on the experiences and the problems which have come across during the manufacturing process. In this article let us see about some of the problems which are caused during the casting process, and the solutions for the problem.

Castability guidelines: Guidelines for parting and undercuts design:
For example, during the casting process if the cast is made up of non planar parting line, then the tooling process is quite difficult. It accomplices higher cost and even the accuracy of the final product is not up to the mark. So the solution for this type of problem is that it is always better to have a flat parting in-between the mold segments or else the part design can be modified.

Let us see another example, where the parting design has the undercuts, they need cores, which in turn results in high tooling cost. Even for this the solution is same as the above, which needs a flat parting between the mold segments.

Guidelines for cores : One can come across the following two problems in the core design. While designing the core size of a cast, if the hole diameter is made very small, it leads to the formation of hot spots and core material fusion, if the small hole is surrounded by heavy sections. There are 3 ways to suppress this problem. They are:

• The heavy section round the core can be reduced.
• The hole can be eliminated by drilling
• The diameter of the hole can be increased.

The next one would be- if the hole length is large, it leads to poor dimensional quality and can also lead to core failure. This problem can be solved either by increasing the hole diameter or an additional support can be provided.

Guidelines for solidification and feeding designs : During the solidification design process if the thickness of the largest section to the smallest section is very high, then it leads to the production of hot spots. So it is always better to make sections with uniform thickness

In the feeding process, the volume of the feeder should not be higher than the original feed volume. If it happens so then we need to connect more than one casting, to the same feeder, or we can change a feeder with small feeding aid.

Guidelines for mold filling and gating : If the casting sections are very thin and long, it leads to incomplete filling of the sections. So to avoid this problem we need to have thick casting sections or the length of the section should be reduced.

During the gating process if the gate size is more than the cast portion, then it may lead to fettling problem. So always connect the gates to the thicker sections of the casting.

Guidelines for mold filling and gating : If the casting sections are very thin and long, it leads to incomplete filling of the sections. So to avoid this problem we need to have thick casting sections or the length of the section should be reduced.

During the gating process if the gate size is more than the cast portion, then it may lead to fettling problem. So always connect the gates to the thicker sections of the casting.

Castability Checks : The casting features needs frequent health checks based on the geometry of the casting features. Casting features are explained below in detail.

• Base features. They comprise of rectangular, spherical, cylindrical, torus etc.
• Tooling features. They comprise of parting line, core, ingate, feeder, feed aid, undercuts etc.
• Form Features. They comprise of slot, boss, rib, hole, pocket etc.
• Feature modifier. They comprise of chamfer, fillet, taper etc.

Proper information's about the dimensions, informations, location and orientation of the parent, child, neighbour, similar etc is needed for a proper casting to be made.