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Solidworks CAD Modeling ("Sheet metal" Tools)

#1
I am not sure if anyone else uses Solidworks for their model designs but I am lucky enough to be able to use the full version. I figured I would give some insight into the main tool I use and what it can and can not do to speed up build designs. Feedback or experiences are welcomed!

The Good: So I have access to Solidworks and I have been using the "sheet metal" tools to design my F-117 model. What is nice about them is that there is a fold and unfold tool that enables me to see how the flat cutout patterns of my foam designs look actively as I build the plane in 3 dimensions. You can also work backwards and draw what you think the pattern should be and tell the program to fold it to see what it is going to look like.

The Bad: The problem with the "sheet metal" tool is that it is designed to account for materials elasticity or ability to stretch when bent. This makes accounting for A, B and C style bends almost impossible. Foam board doesn't act the same way as metal as it has a layer of un-stretchable paper on its surface. So what happens when you ignore that fact is that your flat patterns are only accurate if all the inside corners of the bends are "closed" as in not cut. If you look at the images below. You can see that the bends along the top are curved. The curved length is actually "stretched" because the program thinks the material is elastic, which technically it is. When it flattens the pattern it will actually shrink that length to make the two surfaces flush. this is bad because when you cut it out in reality and attempt to cut and fold, you end up being short material. However, if you were to cut out the curved section instead of the inside, you would have the correct amount of material. Problem with that is that you end up with the second to last image below. Looks actually cool but it wouldn't hold together unless I filled the gaps with beads of glue and that is a bit much.

The Ugly: So how do we fix this? There are two ways I have found to be able to account for some of the difficulties of the tool. Both take a bit of time either initially when your designing, or at the end when you are ready to prototype. A third technically involves toying around with the tools "bend allowances" and pattern manipulations but that is too much of a headache honestly.
1) Faster Designing: The bend lines in the flat patterns are placed at the exact center of the bend. So you can account for the missing material by cutting the bend line and adding space equivalent to the style of bend. Takes a bit more math but you save a metric S-ton of time to begin with by using the sheet metal tool anyway instead of 2D drawing and manually placing and validating folds. Plus once you do the math for a particular style of bend, its the same no matter what model you work on.
2) Higher Accuracy Prototypes: You can attempt to model the A, B and C cuts into the model. This would require designing backwards from the flat pattern instead of from the 3D model first. If you know where your cuts will be, you can remove the material and apply bends that have the tiniest of gaps but are accurate to what the design will be in reality. This takes a little bit more time than just modeling and accounting for the tool limitations but your patterns will be more accurate from the get go. The key is making sure your bends are applied with a gap that allows for the program to be able to actually bend appropriately. Otherwise you may end up with bends that are too tight and requires more material.

F-117 FliteHawk Prototype 3 (Updated model):
Colored View.png Rear View Mount.png

Sheet Metal Tool Example Bend:
Bend example.png

Fuselage Folded Model:
Fuse-Core.png

Fuselage Flat Pattern Model:
Fuse-Core-Flat.png

Open Cut Bends (Original prototype 1not the updated one from above):
196795_8a01fb8b4756445b494cecc98c397001.jpeg

Much better results if done right (Prototype 2, doesn't have the extended mini power-pod intakes):
198287_2e5b614616b9913b9f6d6b047bc6b528.jpeg
 

GMalatrasi

Active member
#3
I believe there's an option to change the bend axis, the point where the stretch is zero which is normally set to 33% of the material thickness.
If you set it to 0 or 100% it will behave like foam board.
 

jhitesma

Some guy in the desert
Mentor
#6
I used SolidEdge at university. Really miss it. Too bad it is so expensive. I really like the quick method
There is one cheap way to get legal access to SolidWorks. Join EAA. You get a personal license to solidworks free as part of your membership ( as well as access to a whole BUNCH of science/aviation museums across the US) Pretty good deal $40 a year.
 

Mad_Mechanic

Well-known member
#9
Nice to see another SolidWorks operator here on the forum!

I'm a mechanical engineer with about 8 years of SolidWorks experience. Love the program, but I was wondering about the same issue of bend allowance with the sheet metal package and foamboard.