Recently, I was teaching an Inventor Sheet Metal Modeling class for a customer and they had an odd part that gave them fits when they tried to model it. The idea of the part was they would bend two flanges on either side of the part, put the part in a press break and bend one end up at an angle, then bend the other end down at an angle.
I can see why it gave them grief. Inventor cannot calculate when the material stretches, or compresses, in more than one direction. Nathan, one of my co-workers was assisting with the class, and between the two of us, we were able to create a workflow that would give them models that would represent the formed part and the flat pattern on a drawing.
The biggest issue on this part is the four regions where the side flanges get bent either up or down. Nathan said that, if we left those regions off the Sheet Metal model, we should get a flat pattern. I said that I have turned sheet metal models into iParts, just so I could suppress features that prevented models from flattening.
So we created the model without the four corners that would prevent the model from flattening. That gave us a flat pattern. I was then able to edit the flat pattern to fill in the gaps, so our flat pattern was a rectangle, and not an odd shape. I attempted my technique of adding features and creating an iPart to suppress those features on one version to preserve the flat pattern. In this case, the flat pattern still failed.
Then Nathan shared that he will sometimes derive a sheet metal model into another file for similar edits. So we created a new standard part, then derived our bracket into that model. We were then able to add Sweep or Loft features to represent the corners that were missing in the other model. A benefit of deriving the sheet metal model into the standard part is that changes to the sheet metal model will then be pushed to the standard part version of the model.
Here is a video of the workflow from beginning to end.
This topic got me thinking of common Sheet Metal questions. I often get questions about how to bend/flatten bar and pipes. There is actually a standard part modeling command called Bend Part. It is kind of hidden in the interface, but it has been around for a pretty long time. The idea, is that the user draws a bend line in a sketch. For bar or pipe, you have to create the sketch on a plane tangent to the tube. After that, it is just a matter of setting the right options for the Bend Part feature. If you need a flat pattern of the bar or pipe, you can convert your model to an iPart and suppress the Bend Part feature on one member of the iPart family.
Here is a video I created that shows how to use Bend Part to bend a pipe.
