Seminar :- Various types of surfaces

Made by :- Hitesh sokar(131044119001) Guided by :- Prof. Alpesh joshi

Gujarat Power Engineering &Research Institute, Mehsana

Types of surfaces:-

From CAD/CAM point of view surfaces are as important as curves and solids. We need to have an idea of curves for surface creation. In the same way surfaces form the boundaries of the solids.

The surfaces entities are of two types:-

1. Analytic surfaces

2. Synthetic surfaces

1. Analytic surfaces Surface entities which are defined by the analytic equation are

knows as analytic surface.

The various type of analytic surfaces, used in surface modeling are discussed below:

1) Plane surface 2)Ruled surfaces 3) Tabulated surface 4) Surface of revolution

1) Plane Surface This is the simplest surface, requires 3 non-

coincidental points to define an infinite plane. The plane surface can be used to generate cross sectional views by intersecting a surface or solid model with it.

2) Ruled (lofted) Surface This is a linear surface. It interpolates linearly

between two boundary curves that define the surface. Boundary curves can be any wire frame entity. The surface is ideal to represent surfaces that do not have any twists or kinks.

3) Tabulated Surface This is a surface generated by translating a

planar curve a given distance along a specified direction. The plane of the curve is perpendicular to the axis of the generated cylinder.

4) Surface of Revolution This is an axisymmetric surface that can

model axisymmetric objects. It is generated by rotating a planar wire frame entity in space about the axis of symmetry of a given angle.

2. Synthetic surfaces The surface entities are defined by the set of

data point are known as synthetic surfaces. The synthetic surfaces are needed when a

surface is represented by a collection of data points. The synthetic surface are represented by the polynomial.

The various types of synthetic surfaces, used in surface modeling are:-

1)Hermite bi-cubic surface 2) Bezier surface3)B-spline surface 4) Coons

surface(patch)5) Fillet surface 6) Offset surface

1)Hermite bi-cubic surface This 3-D surface is generated by interpolation

of 4 endpoints. Bi-linear surfaces are very useful in finite element analysis. A mechanical structure is discretized into elements, which are generated by interpolating 4 node points to form a 2-D solid element.

2) Bezier surface This is a synthetic surface similar to the Bezier

curve and is obtained by transformation of a Bezier curve. It permits twists and kinks in the surface. The surface does not pass through all the data points. It is synthetic surface which is approximated by the given data point.

3) B-Spline surface This is a synthetic surface and does not pass

through all data points. The surface is capable of giving very smooth contours, and can be reshaped with local controls

4) Coons surface(patch) Coons patch or surface is generated by the

interpolation of 4 edge curves as shown

5) Fillet surface Fillet surface is a blend of two surfaces which

intersect each other. If required, a fillet of specified radius may be provided at the intersection of two surfaces.

6) Offset surface An existing surfaces can be offset to create

new surface. The offset surface is identical in shape with the existing surface, but may have the different dimensions.

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