I decided to help a fellow out on GrabCAD, and just ‘whip up’ a quick M13 ammunition clip. Whip up and quick were so far from being true. I killed a lot of valuable time messing with this, but I learned quite a few things along the way.
I was given the original plans to work from, and that was great. They even included the flat pattern. I tried Sheet metal, then tried in only solid modeling, and then back again. Hands down there is no better way to get accurate results than with the original flat pattern. So I decided Sheet metal was the best starting point.
Deriving a single Inventor Part from an Assembly
I broke the part into sections, modeling the axial rolled sections separate. Then assembled them together and derived the result to do the pressed transitions. Why derived? Because the references were just hell in the assembly environment, and deriving a single part from an assembly is so flexible and nice.
Sheet Metal Parts don’t do workarounds well
For reasons that are unknown to me yet, Sheet metal Part files don’t like to do certain things that standard part file should be able to do when referencing. No matter where I was, the Sheet Metal parts and subsequently reverted Sheet Metal parts would not reference the transitioning edges well. Something about the rolled (Fold Command) edges were seen differently by Inventor. I was not willing to give up, but I was running out of answers, and was about to drop back and start over.
Then I tried something and went so fast I was angry. Angry because I had lost hour upon hour of fighting it.
Wanna know what got it done fast?
Autodesk Fusion, Unbiased and Powerful
Relief holes were drilled where the 3D machine forming takes place, and this was the worst modeling dilemma. Fusion and the G2 Smooth transitions in the Loft command worked well.
How did I get the G2 transitions to blend so well and maintain the initial integrity of the original shape?
I left a hint of the original surface curves on the parts to be transitioned so that the smoothing would have no choice but to begin its shape in the same manner. The G2 took right to them. Seamless result.
Fusion Doesn’t Read Sketch Geometry, but it does Surfaces.
Why does this matter? I needed the transitions to be accurate, and needed more help than just a smoothed Loft would give. I needed another cross section sketch I originally had. However Fusion wouldn’t read that in. It just dumps it.
So, I made a surface from the sketch (won’t work all the time). Fusion will bring those in. Nice.
Finish up Later
Now all I have to do is get the last tab on there and its done.
I had monkeyed with this so much that Inventor was not happy with anything I did to get the parts back in from Fusion. Inevitably I saved as SAT files, and brought them in fine. I’ll get the tab positioned and do the last transition back in Fusion, then I can deliver it to its rightful owner.