4 Replies Latest reply on Jan 30, 2008 9:28 PM by Kevin Quigley

    Offset feature from curved surface

    Christopher Thompson
      I have curved face on a solid part which I would like to offset ~ .040 inches (w/draft) to create a pocket normal to the original surface as a cut. What is the SW equivalent feature to the Pro-E Offset Feature referenced below?

      My best guess in SolidWorks is to use a split line (projection from plane) onto a curved surface, then use a thicken cut (surface). Is this the best option, or is a better option available in SolidWorks?

      Pro-E examples: http://www.mcadcentral.com/pro...ts.asp?TID=30179&PN=6

      About the Offset Feature (Pro/Engineer)

      You can use the Offset tool to create a new feature by offsetting either a surface or a curve with a constant or variable distance. You can then use offset surfaces to build up geometry or to create patterned geometry, or you can use offset curves to build up a set of curves that you can then use to build a surface. Various options are available from within the Offset tool, such as adding drafts to offset surfaces and offsetting curves within a surface.

      You can create the following types of Offset features using the Offset tool:

      Standard - Offsets a single quilt, surface, or solid face.

      Expand - Creates a continuous volume between the selected faces of a closed quilt or solid sketch or, when using the Sketched region option, of an open quilt or solid surface.

      With Draft - Offsets the region of the quilt or surface that is included inside a sketch, and drafts the side surfaces. You can also create straight or tangent side surface profiles with this option.

      Replace - Replaces a solid face with a quilt or datum plane.
      Curve - Offsets a curve or the one-sided edge of a surface in a specified direction.


      You can also open the Expand dashboard by selecting multiple surfaces and clicking Edit > Offset. If you select solid surfaces and closed quilt surfaces, the default Expand area type is Whole Surface. If you select open quilt surfaces, the default Expand area type is Sketched Region.

      If Sketched Region is selected, you can click Define on the Options slide-up panel and use the Sketch dialog box. After defining an internal sketch, click EDIT (With Draft) to open the Sketch dialog box so you can edit the internal sketch. You can also use Define Internal Sketch and Edit Internal Sketch from the shortcut menu.

      If you are using a surface set as a reference and you want to modify it, click Details on the References slide-up panel and use the Surface Sets dialog box.
        • Offset feature from curved surface
          Kelvin Lamport
          Have you tried the Wrap feature?
            • Offset feature from curved surface
              Christopher Thompson
              The face is composed of a curved surface tangent to a flat surface. If I use the Wrap feature, it works only on the curved surface with no draft angle on the sides. I had to create the draft feature separately. If the curved and flat surface are joined, the Wrap feature will not work.

              Using the Projected split line, and a thicken cut (curved & flat surface knitted together) creates the pocket, although I do not know if this is the best technique. I noticed some features create larger file size or effect performance in SolidWorks. Some have suggested to use surfaces as sparing as possible until SW is optimized for surface modeling.
              • Offset feature from curved surface
                Charles Culp
                Split Line
                Surface Offset (with an offset of 0)
                then Insert>Cut>Thicken
                then Insert>Features>Draft

                Is the method that I would use (very similar to what you). I do not know of a one step method to do this. Another method that would yield similar results would be to:
                offset surface (offset in, the depth of the cut)
                then create a 3d Sketch of the boundary (use split line & spline on surface as req'd) and have a "normal" line
                then "extrude-cut" with the end constraint as the offset surface. you can set the draft in the extrude-cut.

                This second method would provide a draft in the cut-extrude feature, but would only extrude in a linear direction, not normal to the face.

                *Edit: Also, you can check out this page for a neat "trick" from Mike Wilson: http://www.mikejwilson.com/sol...olidworks_files-04.htm
              • Offset feature from curved surface
                Kevin Quigley
                Depends what you are after. Normally when I do this kind of stuff I need to ensure that the cut or boss has draft so effectively what you are doing is extruding the pocket or boss to the surface then cutting it away a specified distance from the main surface.

                The problem with using solids to do this is that you cannot draft from a curved face so you. Doing a cut extrude from a sketch plane will draft from that plane not from the actual surface. The only way (I can see) of doing this is to draft from a split line, so what I will do is extrude a solid from the main sketch plane, and create a split line with the intersection of the extrude and the surface, then "attempt" to draft from the split line. For simple stuff this works but for complex splits it never or rarely works. Once this is done, subtract the extrude to create the drafted pocket.

                This is one area where SW could do with some extra functionality - drafting from non planar faces.