Solid Modeling and CAD/CAM
The backbone of various CAD/CAM programs is the solid modeling technique which helps in amending the speed and accuracy of several tasks in casting development. This technique implements economical manufacture of products with intricate geometry to near net shape. Any basic segments having complex curved surfaces, blends between sculptured surfaces, intricately shaped pockets, meandered holes aside characteristics like steps, ribs, slots and bosses can be produced. In a single casting, usually many geometric elements or features can be economically combined together otherwise it requires assembly or joining of multiple parts.

The most common approaches used in solid modeling are :

Extrusion or sweep: This approach comprises sketching of a cross section on a plane and stretching it through a curved or straight path. According to the path, you can have solids of revolution and straight extruded figures. The cross section can also have inner loops bulging to hollow shapes. The distance can also be provided for having straight extrusion.



Constructive Solid Geometry: This approach makes use of various boolean operations like intersection, union, difference on pairs of simpler models to construct the desired shape. To initiate the modeling, this technique is provided with a inbuilt library containing solid primitives like torus, cube, cylinder, sphere, cone and many more. Any selected figure is instantiated by specifying the values of its location, orientation and dimensions. The model which is created finally is combined with other primitives or solids to eventually get the required shape of the component. At last, the models are represented in a CSG tree that shows the primitives and steps used for making the model.



Parametric modeling: Some of the recent systems use this kind of modeling technique. In this technique, the user can specify relationships between geometric elements. Standard shapes of casting and tooling features can be covered in terms of few selected parameters. The proper shape is automatically constructed by giving the parameter values which are involved.

Other special techniques: This comprises analytical surfaces, lofting and shelling. Analytical surfaces are helpful for defining curved surfaces, lofting includes defining number of cross sections and further joining them using an analytical surface. For creating an offset surface, shelling is used.

Including experience as well as training, designer must have the deciding strategy in regards to a particular modeling technique which needs least number of steps. It may happen in some cases that after retracing the steps during modeling, designer has to take a different approach to complete the shape. Even an experienced designer, sometimes take many days for creating the model of a complex casting. In general, most of the castings require a combination of all techniques.

Read More On Solid Modeling: Model Exchange Formats
Read More On Solid Modeling: Model Verification and Application Requirements