For the first part of a series on Autodesk Inventor Surface Creation, I will look at the different types of surface connection that are available.
Inventor can create some very nice quality surface data, with all that is required from the user being an understanding of how to choose from the options.
To begin with any of the features can be used to create a surface, simply by selecting the surface option. What this creates is a surface, which depending on the feature type and sketch can be either open or closed. Another way to create a surface would be to create a solid and then delete a face to leave an open surface.
Another method would be to create a patch surface. This uses a closed loop of either edges or curves to create a surface. The real power of this feature is that each curve can have a condition placed on it. These conditions are very important when creating surfaces. The three options are;
Free – no condition, the surface is simply attached to the curve/edge.
Tangent – the surface is at a tangent to the selected surface.
Smooth (G2) – the surface has a G2 continuity to the selected surface.
So what are the differences in a nut shell between the quality of connection between the two surfaces.
A free connection has no connection other than the location, so it’s like a sharp corner.
A tangent connection (see image left) is getting better and as the name suggests the new surface is at a tangent to the selected. This connection looks more pleasing, but with polished or shiny surfaces a distinct line can be seen where the point of tangency occurs. Although superior to a free connection it is still not really good enough for consumer type product design.
The best connection is the G2 or smooth type (see image right). To understand why we must look at the point of connection, with a tangent joint, the new surface may be tangential, but at the point of connection the radius of the two surfaces are different. For example, a flat face with a fillet on it has a fixed radius on the fillet, but the radius of a flat plane is infinite. A G2 or smooth connection has the same curvature value for both surfaces at the connection.
This goes to show that Inventor is more than capable of creating high quality G2 surfaces, and as such is a great tool for industrial design of consumer goods. It’s just about using the correct connection type and understanding how to apply it.
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