Looking at the intricate geometrical designs of a metal item is simply amazing. But one is seldom inclined to give it a second thought. So much effort, labor and thought go into making a superbly designed metal product. Metal cast designs are now prepared via computer programs. Various CAD/CAM programs aim to come up with the perfect geometric design including a flexible solid mold for all metal products. In addition to beauty, this is also a means to ensure full-proof speed and accuracy in the process of casting. There is no room for error.The Beginning :
The process of cast modeling starts with the journey of casting features. In technical jargon, the process of casting features is defined as the economical method of visualizing, shaping, molding and developing an intricate geometrical feature to a coarse feature fitting. The primary advantage of the feature casting process is the complete eradication of excess machinery and labor in assembly lines for purposes of joining separate metal features to create one geometric metal design. In the long run, this also helps a foundry or corporate venture improve its rate of productivity and profitability. The process enables the creation of complex curved surfaces.
It also helps in the creation of joints and transitioning surfaces called 'blends' between sculptured surfaces. Casting process enables the design and development of intricately shaped pockets with meandering holes. Features of bosses, slots, steps and ribs can also be successfully produced. The casting feature process also enables the conjunction of two or more metal geometrically designed parts into a single metal object. The process of casting revolves around the twin components of tooling and base features.Components :
There are three components i.e. the base and local features including the tooling process. The former refers to the overall shape of the casting. It is usually expressed in minute volume shapes that are equipped to completely close the casting. This enables the removal of small boss shaped projections. These shapes generally involve a rectangular block, cylinder, sphere, hemisphere, torus, spiral, L-bracket including a wheel.
The latter component of local feature is generally a depression shaped in the form of a hole, pocket or slot. In other cases, it can also be in the form of a protrusion such as a boss or a rib designed on the base surface feature.
The final component of the casting process is tooling and the modification method. This usually includes features of pattern, mold, core box, undercut, parting line, core support, ingate, runner, sprue, feeder, feeder neck and various feed aids -- chill, insulation and exothermic in nature. The modification method can be viewed as a method of connectivity wherein two distinct features are solidly connected such as such as connecting taper, chamfer, fillet and wall between two holes. The feature modifier also stands for a minor modification to the standard shape of a single feature using draft, chamfer or a fillet.Approaches to solid modeling :
Next in line come the modeling techniques, which involve extrusion of a 2D section and constructive solid geometry. Another popular modeling approach being deployed today is the features-based modeling.
The modeling method of extrusion centers around the method of sketching a cross-section on a plane. In addition, the technique also refers to a method of sweeping it or dragging it gently in a straight or curved path. The resulting cross-section design usually has inner loops leading to hollow shapes. It is possible to have positive, negative and even circular extrusion provided the distance of dragging is already set.Constructive solid geometry :
This method is based on the concepts of union, intersection and difference on pairs of simpler models to develop the desired shape. The concept of difference can be used to create shapes of cube, cylinder, sphere, cone and torus. Consequently, these diverse shapes are used to produce and formulate different models. The modeling technique, as a whole, is initiated by supplying the values of the different shape dimensions, location and orientation. In the end, the model created by this method is combined with the model created by the extrusion technique to come up with an integrated solid design.
Designing of metal products is a complicated business requiring skill and expertise. Nowadays, parametric modeling, analytical modeling and features based modeling are also used extensively. These modeling techniques are based on principles of shelling and lofting. Computers and Internet networks are used to geometrically design a certain metal with desired thickness and shape specifications.
The future of casting is presumed to become a web- based collaborative efforts whereby engineers and technicians communicate about different feature designs and tooling processes.