Spherical shaped sheetmetal

[emil.rindell]

Hi,

Does anyone know or have a smart idea to create a spherical shaped sheet metal? If this is even possible.

 

 

The shape should look something like this:

 

[Cary OConnor]

I'm not sure it can unfold. The only thing I can think of is a loft shape but it would end up sort of like a conic. So I don't think it is really possible with the current IronCAD Sheet Metal.

[Josh]

Current IC sheet metal unfolding only supports "Developable" surfaces, which means anything that does not need to be stretched or compressed to unfold. The way I understand this is that basically anything sheet metal can only bend on one direction at a time. A useful way to physically interpret this is with a piece of paper, if you can make something with a piece of paper, then it's a developable surface (broadly). Paper does not allow much compression or stretching, so it's a useful representation. You can do a square to round transition with paper, and also twists etc without needing to crease the paper.

If you try to fold a sphere out of paper, you will need to crease/fold the paper, it won't be possible as one smooth piece, because a sphere is not a developable surface. But if you take something flexible, like balloon rubber, then you can make a sphere by stretching the material.

Look up "Cut out sphere from paper" on Google and you'll see what's needed if you want to keep it developable.

So IronCAD operates on the assumption that sheet metal cannot stretch. However in the real world sheet metal can stretch, especially when using a press.
It's worth noting that I think IronCAD's method is still correct, because if you need to include "stretching" then you have to account for the properties of different materials and thicknesses, basically how stretchy they are, otherwise the unfold will be wrong if the stretchiness is not accurate. So doing this would make sheet metal calculations much more complicated.

However it would be VERY useful in future for IronCAD to have the ability to unfold non-developable surfaces with some sort of assigned stretch value. Rhino can do this. Instead of part of sheet metal, I think this would need to be a separate tool "Unfold Non-Developable Surfaces" where you told the system the type of material you were using, and then it would use the properties of that material to produce a correct(ish) unfold. I think having some ability to do this would be very valuable, especially for boat hull design and car panel design. It could also be used for fabrics on sofas, car seats etc.

Even if it is only accurate to within a few mm or so, the tolerance can be quite high and it would still be very useful tool to have.

[HDEAR]

On 2/2/2021 at 3:20 PM, Josh said:

Current IC sheet metal unfolding only supports "Developable" surfaces, which means anything that does not need to be stretched or compressed to unfold. The way I understand this is that basically anything sheet metal can only bend on one direction at a time. A useful way to physically interpret this is with a piece of paper, if you can make something with a piece of paper, then it's a developable surface (broadly). Paper does not allow much compression or stretching, so it's a useful representation. You can do a square to round transition with paper, and also twists etc without needing to crease the paper.

If you try to fold a sphere out of paper, you will need to crease/fold the paper, it won't be possible as one smooth piece, because a sphere is not a developable surface. But if you take something flexible, like balloon rubber, then you can make a sphere by stretching the material.

Look up "Cut out sphere from paper" on Google and you'll see what's needed if you want to keep it developable.

So IronCAD operates on the assumption that sheet metal cannot stretch. However in the real world sheet metal can stretch, especially when using a press.
It's worth noting that I think IronCAD's method is still correct, because if you need to include "stretching" then you have to account for the properties of different materials and thicknesses, basically how stretchy they are, otherwise the unfold will be wrong if the stretchiness is not accurate. So doing this would make sheet metal calculations much more complicated.

However it would be VERY useful in future for IronCAD to have the ability to unfold non-developable surfaces with some sort of assigned stretch value. Rhino can do this. Instead of part of sheet metal, I think this would need to be a separate tool "Unfold Non-Developable Surfaces" where you told the system the type of material you were using, and then it would use the properties of that material to produce a correct(ish) unfold. I think having some ability to do this would be very valuable, especially for boat hull design and car panel design. It could also be used for fabrics on sofas, car seats etc.

Even if it is only accurate to within a few mm or so, the tolerance can be quite high and it would still be very useful tool to have.

+1

[emil.rindell]

Thanks all of you for your answers:)