# How to make Curved Surface for CNC cut

Hello everybody, I have this surface in the picture below and I wanna unroll? it for CNC cut. any body knows what should i do in rhino or grasshopper ?
if you wanna rhino model i will upload.
thanks in advance

Test.3dm (234.1 KB)

Yes. Upload please; better than guessing, right?

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Of course. File attached.

Your surface has double-curvature which you can evaluate by using Analyze>Surface>Curvature analysis Gaussian Auto-Range

Also see Min and Max radius.

The UnrollSrf command flattens a surface or polysurface with curvature in one direction to a planar surface. Look at: https://docs.mcneel.com/rhino/6/help/en-us/index.htm#commands/unrollsrf.htm?Highlight=unroll

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thank you . i worked with this tools but the had no good result for my model. any other solution?

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Your object has double curvature so it will not unroll or flatten without distorting. That is due to the geometry of the shape, and is not a limitation of Rhino.

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I could be wrong, but I vaguely remember the Unroll, Smash and Squish do similar things but depends on how many directions of curvature.

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yes. what is your suggestion. do you know any other softwares to do this ?

You can â€śrationalizeâ€ť the surface, means re-assemble it from developable stripes. But without knowing anything about the project it is hard to say if it makes senseâ€¦

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It is impossible to flatten a surface with double curvature without distortion. That is how both the physics and mathematics works.

It is the same reason part of a sphere cannot be flattened without distortion.

Splitting the surface into strips and modifying each strip so that it is developable will result in gaps between edges of the strips.

@m.khalili9093 If your design is to be cut from a flat piece of material and then formed into the desired shape you need to either use a forming method which stretches the material, or change your design.

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Yes there is a flat material and then after cutting the holes ,it will formed in plan. but i didnâ€™t understand what you said at the end? sorry for terrible Englishâ€¦
you mean the whole surface can not get cut at a time .?

Yes. Unless the material can be stretched or shrunken. It is the same problem as making part of a sphere from flat material.

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It depends on the material and the available fabrication methods. Can you tell us a bit more about that?

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@davidcockey @Jess The complete design is like this picture. they wanna cut this on a plate and then form it in order to have planner curve. does it make sense?

Not really but in general everything is possible. It is just a question if they can afford it.
What is it? A facade, simple ironwork or mirror-polished stainless steel, self-carrying?

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I didnâ€™t design it but it is going to be an element like a sign for some where in the city.

unfortunately designer didnâ€™t think about specifically about fabrication.

thank you @Fred_C thank you so much i didnâ€™t know about this tool.

Youâ€™re welcome. A quick look shows longest dimension about 3.5 meters. Perhaps consider individual cut elements, shaped/bent and connected/welded. If you can provide more info maybe someone can offer suggestions. Good luck.

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