Here are some concepts and techniques that have proved helpful in designing 3D surfaces.
· Design first, edit last. Put all the surfaces in place first, then trim and fillet the surfaces together to create the final shape and boundaries.
· Use quality source curves. Quality curves have as much detail as possible designed into the curves before the curves are used to make surfaces. Curves are much simpler to design and edit. With parametric modeling active, changes to your source curves propagate automatically into the surface.
· Build as much detail into a single surface as possible. It’s easier to split and reduce surfaces than to merge and combine them. Similarly, machining with isoline operations uses one surface at a time and filleting and trimming work with two surfaces at a time so the more detail the better.
· Learn which surface methods are approximate and which are exact. Approximate methods are not better or worse than exact methods, but have more degrees of freedom in filling in the space between input curves or surfaces. Other surface methods are conditional. They are exact to what they do, but when used with approximate surfaces, the resulting surface is still approximate.
· Approximate: surface intersection, trim, untrim, fillet, lofting, merge, modify, offset (Another key is any operation that includes a tolerance setting. That is a flag that the source material is being approximated.)
· Exact: extrude, surface of revolution, sweep, ruled, sphere, cylinder, flat, from a feature
· Conditional: split, region, reverse, coons, cap. Coons is neither approximate nor exact, but a mathematical definition of how four boundary curves describe a surface. Learn which dialog boxes give you the option to modify-in-place or create a new object.
· Learn when and how to use the option to modify-in-place or create a new object. Both methods have their uses. Modifying an object in place breaks the parametric link for which constructor was used for the original object and prohibit parametric modeling from updating an object in the future. This limits you to further modification operations only. Creating new objects can result in excessive clutter on the screen.
· Don't use self-intersecting curves or surfaces. Curves and surfaces with that characteristic are not viable for predictable editing, construction or machining.