Uncurling an object, flattening an object

Hello, I have an STL file with complex topography and curved shape. My goal is to simplify it for CMC cutting of the profile in steel sheet. I want to reduce the complexity of the topography for real (smoothing with loss of data) and flatten it without compressing so that once cut out of steel, I can reshape it to approximate the original shape (minus surface details).

If SketchUp cannot do this, is there a program that can?

Many Thanks,


If the surface is not conformal it can’t be flattened without distortion by any means, SketchUp or otherwise.

Hopefully I am understanding what you are saying (I am not one of you folks, I am a biologist who does metalsmithing as a hobby). I don’t mind distortion of the surface features, in fact, I want them to be totally smoothed except for profile edges. If it ends up being the average thickness orthogonal to the idealized curved shape all across the idealized, uniform thickness shape, I am good with that (again, I don’t care about the surface topography). I would then want to flatten the shape not by compression in one dimension, but by “uncurling” it (hopefully, I am making sense; the opposite of taking a rectangular panel and joining the two ends to make a tube). Once “uncurled”, it will provide the silhouette with simple enough descriptive features to send to cutting machine. The resultant silhouette piece can then be forged into shape (recurved, some surface features approximated). Does this change your response, or is it all just a no go from the get go?

I have 2 different issue, one is the surface topography is too complex, the CMC machine can’t handle that amount of date. The second issue is that the object is curved. So, 2 different problems, really.

I think before you worry about unfolding that object you might want to look at a simpler model to get an understanding of what needs to happen. Keep in mind that the .stl is made up of a whole bunch of triangles. In order to unfold the triangles they all have to be rotated into the same plane. There is an extension in the Extension Warehouse called Unwrap and Flatten. My guess is if it will work, it will at least take a very long time.


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Thank you! Will give it a try.

As @DaveR told you, first simplify your model. Maybe Skimp can do this, not sure…

Actually I was suggesting that he try it with a simpler modeler to see what happens.

For example:

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You’re quite right!

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Thanks @DaveR , this example clearly illustrates the notion of conformality. The original shape can’t be flattened onto a plane without either distorting the individual faces badly or introducing all those slits between sections. It’s a classic problem that all global map makers face. Each mapping projection tries to preserve just some limited set of properties, such as area, direction relative to north, etc. but none can map all of them perfectly onto a plane.