Provide Flat Patterns to Manufacturing (Avatech Tricks Tutorial)

9 Apr, 2007 By: Bill Graham

Simulate square-to-round transitions in sheet metal.

When trying to create square-to-round transitions in sheet metal, we need to consider how Inventor processes sheet-metal parts. Inventor's Unfolder tool is designed to deal with parts that can be handled by a brake press. Brake presses handle single bends along a linear axis. Therefore, to properly unfold a pattern, we must break the part down into a series of bends.

Approximate a Round Shape
Begin your design by choosing the proper number of sides to approximate a round shape. The larger number of sides you select, the closer the sheet metal will approach a circular shape. I'll begin by using an octagon to represent a circle.

To begin, draw an octagon to approximate a circle.

Create the Square End
Offset a plane the desired height of your square transition and create the square end for your sheet-metal part. Note that the square end must have exactly the same number of sides as your round end. Each corresponding face must be parallel between the round face and square end.

Set the rectangular and circular approximations.

Loft the Sketches
Now you can loft the two sketches to create the framework for your sheet-metal part. After the loft is complete, fillet the edges to finalize the outer shape of your sheet-metal part. The fillet radius should be BendRadius+Thickness.

Loft the two sketches and fillet the edges.

Shell the Part
You've created the outside profile for your sheet-metal part. To create the inside members, shell the part to a thickness equal to the thickness parameter for a sheet-metal part.

Next, shell the part to a thickness equal to the thickness parameter.

Create a Split and Flat Pattern
To finish the conversion to a sheet-metal part, you need a small split in the sheet metal to allow for unfolding. Use a small extrusion cut to create this split.

Split the part so it can be unfolded.

The final step in the process is to create a flat pattern to send for manufacturing.

Your flat pattern of the sheet-metal part is ready to be sent to manufacturing.

Sheet Metal Made Easy
Approximating your shapes through the use of polygons helps simplify the process of creating square-to-round transitions in sheet metal. Remember the greater the number of sides you have, the better the approximation will be.

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