| Spring 2002 |
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Generating Non-Circular Helixes
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3. Create a projected datum curve. Sketch a projected datum curve using the “follow surf” option across the entire flattened wall. The sketch should be a single straight line starting at one corner of the part at some angle. Instead of an angular dimension, though, create a linear dimension that represents the pitch of the helix. Front, back and vertical end surfaces of the unbent wall must be selected for the projection.
5. Copy the helix into the real part. Use the External Copy Geometry feature to copy the datum curve from the sheet metal part into a new part that will be the spring. (Using the External Copy Geometry feature avoids the use of an assembly.) Copy the curve using the One by One option that wraps around the inside and outside of the sheet metal part.
6. Create a surface between the two sets of curves. Create a blended surface by bounds selecting the outside set of curves as the first curve in the first direction and the inside set of curves as the second curve in the first direction. There is no need to select curves in the second direction. Define control points by selecting corresponding vertices from the curves.
8. Create a swept protrusion. Using the outside edge of the surface as the trajectory, create a swept protrusion to create the solid spring.
Non-circular helixes can be a challenge to make. Using Pro/SHEETMETAL’s capability to unbend and bend back along with the appropriate datum curve type, the solution is straightforward and easy. Bruce Bodnyk is a staff engineer at FCI Electronics. He can be reached by email at bbodnyk@fciconnect.com. |
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1. Create a sheet metal wall. Using Pro/SHEETMETAL, create an extruded wall whose outside dimensions correspond to the shape of the spring. All corners of the wall should have radiuses. The thickness of the wall does not matter.
2. Rip along one of the tangent edges of the wall and unbend the wall. Create an edge rip along one of the tangent edges. Then create an unbend all feature to flatten the part.
4. Perform a bend back. Create a bend back to bend the flattened wall back into shape. The projected datum curve will follow along and be wrapped around the part afterwards.
7.Transform the surface. Transform the surface by the pitch. Pattern the transform the desired number of times and merge all the surfaces together.
