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1.3.6 B-Spline representation

The description and modelling of sculptured faces is a crucible of modem CAD system. The description of the faces is different. For example a planar face can be represented in many different ways: using an analytical eąuation, a parametric eąuation, a normal vector and a point on the surface, etc. In addition, a closed 3D boundary which lies on the surface is needed to define the face. In conventional CAD Systems, the use of faces is usually restricted to the ąuadrics like cones, cylinders, spheres, etc. The modem CAD Systems use a variety of formats to represent sculptured faces. One of the most common is the B-Spline representation. It is a category of surfaces employing parametric polynomials.

The B-Spline surface is a collection of B-Spline curves, i.e. the tensor product of two curves defined by two parameters. The surface is defined as the set of points obtained by evaluating of an eąuation.

CAD systems most often offer the possibility to assemble the solid parts already detailed into an assembly. Subseąuent kinematics or dynamie analysis is sometimes possible. Links with Finite Element Method packages also exist, sometimes even associative, i.e. the features on the CAD side and FEM side are the same. Some CAD systems offer a programming interface in order to allow customers to develop their own applications. Some CAD systems offer catalogues of standard components which can be incorporated in the design.

1.4 CAPP - Computer Aided Process Planning

The Computer aided process planning (CAPP) represents the implemented methodology of process planning in the software package. The CAPP includes all process planning activities needful to realise of the design of the process plan. The CAPP system has to solve the planning activities such as selection of machining operations, selection of machinę and cutting tools etc.

The CAPP is concemed with the preparation of a route sheet for the engineering drawing. The part must be interpreted in terms of manufacturing process to be used. The route sheet is a listing of the seąuence of operations. Closely related to the process planning are the functions of determining appropriate cutting conditions for the machining operations and setting the time standards for the operations.

The CAPP is often a heart of the CA systems in the engineering enterprise. Input for the CAPP system is output from the CAD system. Output from the CAPP system is at the same time especially the input for the CAM system. One can often to meet the integrated the CAD/CAPP and the CAPP/CAM.

Figurę.E: CAPP