Castability

Castability is nothing but producing a casting with minimum cost, defects and time. This can be done by the high compatibility between the product requirement and process castability. In this article let us review about the design of castability and some methods of castability analysis.

In this article the three major factors that influence castability are explained in detailed as follows:

• Material Selection.
• Geometry Planning.
• Quality.

Material Selection :
The metals used for casting are characterized by their following casting properties:

• Fluidity.
• Solidification capacity.
• Slag formation.
• Pouring temperature.

Geometry Planning :
Designing the geometry of the product is quite cost effective & it depends upon the complexity of the process. It also depends on the tools used.
Quality :
Quality of the casting product means free of defect or less defect. The casted product should have a desired surface quality, a proper dimension and internal reliability. Radiography and pressure testing are some of the methods by which the quality of a casted product can be tested.

Castability process-friendly design :
A casting design is considered to be friendly if it has the following characteristics:

• Easy to manufacture.
• Lower tooling cost.
• Lower energy requirement.
• Implying faster development.
• Minimal rejections.

In this article let us see about some guidelines, which can improve the castability.

Complexity of the part :
In order to improve the castability the shape Complexity criteria can be explained by 3 Different dimensionless equations:

• Ratio of the part volume to the volume of its bounding box:
  Vc /(abc)
  Vc= part volume
  Vc= part volume
• Ration of surface area of cube of equal volume to the surface area of the cast part:
  6(Vc)2/3/Ac
  Ac= surface area of the cast part.
• Number of features:
  1/(1+nf) ^0.5
  nf = number of features.

Parting Line :
Parting line is also one of the factors that affect the tooling cost. A non-planner parting line must be avoided to have a proper parting.

Cored Features :
The cored holes should posses the following criteria's:

• Minimum diameter.
• Aspect ratio.
• Location in thick sections.
• Distance from edge and neighbor hole.

Filling Characteristics :
The part must be designed in such a way that it reduces the turbulence during filling and to promote complete filling of all sections.

Solidification process :
The Solidification process should have the following characteristics:

• Minimizing isolated hot spots.
• Promoting controlled progressive directional solidification.

The above mentioned are the factors that affects the castability.