In CAD, a surface is an infinitely thin feature used to define complex shapes (think the curvy front end of a sports car). In fact, surface design is generally what gives most consumer products their aesthetic appeal.

How can designers create a manufacturable model when there’s no mass? Typically, you use tools and various editing techniques to thicken or otherwise create the solid model from the surface. Here is what you should know to master working with surfaces:

1. How to effectively copy and paste surfaces

Copying and pasting a surface creates an overlay copy of the surface which you can then manipulate. You can select any surface or surface set (e.g., quilt or solid) to copy and paste. Surface set types include the following:

• Single – Press CTRL to select multiple surfaces
• Solid surfaces
• Intent surfaces
• Surface/boundary
• Loop
• Exclude – You can exclude individual surfaces from sets by pressing CTRL and de-selecting them.

   

2. Create a surface quilt by offsetting a value from another quilt or solid surface

The offset surface remains dependent on the original surface. In addition to specifying the offset distance, you can flip the direction the surface is offset. When offsetting surfaces, the following options are available:

• Fit type – Enables you to specify how the surface is offset. Options include:
  • Normal to Surface – Offsets the surface normal to the reference surface or quilt.
  • Automatic Fit – Automatically determines a coordinate system and offsets the surface along its axes as necessary to create the offset approximately in shape to the original. This fit type is useful in cases where the Normal to Surface fit type fails.
  • Controlled Fit – Enables you to select a coordinate system, and manually control whether the surface is translated in the X, Y, and Z axes.
• Create side surface – Creates additional surfaces between the offset surface and the original surface. Note that these surfaces are not merged with the other offset surfaces.
• Special handling – The Special Handling dialog box can appear if the offset fails; this typically occurs when the offset exceeds the radius value of the surface. The Special Handling dialog box provides you with the option of excluding failing surfaces from the offset operation. There is also an option for Approximate Offset within the Special Handling dialog box. This option enables the system to offset what it can and approximate the surface for areas it cannot offset. In addition, you have the option to leave the approximate offset surface attached or unattached from the original.

3. Offset surfaces with the expand and draft features

When creating an offset surface with the expand option, you must specify the surface quilt to be offset and the sketch that is to be expanded. The original surface is literally offset, so an expansion is seen on one side, and a depression is created on the other side. You can also offset with Draft Feature. This option is similar to the Offset Expand option, except it adds in the capability of the draft angle. You can flip the offset direction and also specify a draft angle for the expanded surface.

4. How to thicken quilts

With the Thicken tool, you can offset a selected quit to create or remove material. The following basic controls are available:

• Add material – Fills the thickened quilt with solid material. Use the Fill with solid material option to add material.
• Remove material – Removes material from inside the thickened quilt. Use the Remove material option to remove material from existing solid geometry.
• Thickness Value – Specifies how much the surface is thickened.
• Flip Direction – Enables you to flip the thickness direction to be on either side of the quilt, or center it around both sides of the quilt. Use the Center Thickness Direction option to flip the direction.

5. Solidify quilts to add material

You can use the Solidify tool to add solid material to a model, based on a surface quilt. Select the Fill with solid option in the dashboard. To solidify a surface quilt to add material, it must define an enclosed volume, for example either an enclosed quilt or an open quilt bounded by existing solid material.