Unfolding 3d Solids

[Anonymous]

I import 3d sheet metal part solids in AutoCAD, and I want unfolding it.

I tried got the 3d solid object entity and property , but I don't know which one can help me unfolding the 3d solid.

Does anyone have any idea on how can I unfold solids using Lisp or visual lisp?

[dgorsman]

Not directly possible with LISP.  And while you could bootstrap it with some dotNET-defined LISP functions, the complexity will still be significant.  Do you already have the math/algorithms for doing this?

[stevor]

One way to get some info, is to explode a copy of the 3DSolid. Search 'explode 3d solid autolisp.'

[Anonymous]

Hi dgorsman, stevor

I only understand Lisp and Visual Lisp , I can't use dotNET....

I tried a math/algorithms, like this：

1. copy a 3d solid and explode the solid, got all region and surface

2. used two main region and get the solid thickness

3. erase region with equal thickness, leaving only a continuous surface

4. rotate and move all region to same plane, and add KFactor between region

But I don't know how to determine which region should be connected which region

because steel solids are variety, especially fold not one side.......

kindly help me out.

Thanks

[wkmvrij]

I completely agree with dgorsman about the unexpected complexity of this problem. First it would seem wise to study the arithmatic sid of this like in 

https://mathspace.co/learn/world-of-maths/early-geometry/nets-of-simple-solids-33774/unfolding-a-3d-...

Then there is the aspect of material thickness. Starting with a flat piece of material the neutral line in the material ( the part of the thickness that stresses versus the part that compresses)  is not exactly in the middle of the of the thickness. Add to that the production method: Will the part be stamped in a mold or free bent on press brake. 

Furthermore the shape of the product: Does it contain other shapes than just flat planes .

The list goes on and on. Best advice : go search for an established program. There are good ones out there. Why design a nail? Go buy one!

[brianyUL99V]

You are on the right path. Everything I’m about to say applies to air bending with a .030” radius top punch.
Most Sheet Metal shops/ brake operators do not use K factor as it only applies to large radius bends, and is still a guess. Each material type (ferrous/nonferrous) has a bend deduction. For ferrous we use 100% material thickness, for nonferrous 80%. Using .125” material for both. Assuming your Zee brake shape was 1”x1”x1” OD/Outside Diameter you would get the following length flat patterns by adding up from edge to bend to bend to edge:

Ferrous/Steel=.875+.75”+.875”=2.5”

Nonferrous/Aluminum=.9”+.8”+.9”= 2.6”

a lookup function using a table could easily perform this while allowing variables.