# Unfold a surface (unloft?) to flat pattern?

• posted

Can someone tell me of a Solidworks built-in capability to pattern a surface from a given model so that a piece of flat material can be cut accordingly and placed over an actual object, form-fitting? The computiong trick I want to perform is to know where to cut out material for folds that must occur in the finished product. A close analogy is cutting fabric so that it could be joined at fold cut-outs and simply slipped over an object, like upholstery. Is this too far out for Solidworks' basic package?

• posted

I was able to do it on a rectangular part. Using surfaces. I would like to try your part. If you could send it to me.

What I did was inserted the origional Part into an assembly and made a new part that contained the surfaces with zero offset. Then I thickened to .001" and ripped the apropriate edges and inserted bends.

Corey Scheich

• posted

Corey,

That is exactly the kind of thing I am trying to do. My model is basically pure curves, so I am sure there are many ways to use your method on this problem, if the rip function will work with no exact corners. Thnx.

• posted

If everything is curves, more than likely, your surfaces are not gaussian surfaces.

Gaussian surfaces are those which can be flattened without any stretching or tearing. Such surfaces include cylinders and cones.

A non-gaussian surface is one which cannot be flattened without stretching or tearing. Think of an orange peel.

Unless you are VERY careful about how you created your surfaces, ensuring that ALL surfaces are either perfectly flat, a perfect cylinder, or a perfect cone, flattening you surface cannot be accomplished with SWX, or almost any other "mainstream" software.

To flatten a non-gaussian surface requires very detailed knowledge of both the mechanical properties of your material AND how it is formed from a flat. There are many programs used in the stamping industry to calculate flats from non-gaussian surfaces. They use FEA and complex analytical calculations to do this. I am not sure if similar packages exist for fabric material sheets. There probably are somewhere if you really need this functionality. It will be expensive, however.

I believe there are some "simple" programs which can flatten non- gaussian surfaces (Rhino, perhaps???). But, AFAIK, they do not factor in material properties or the forming process. I really have no idea how they get it done (some sort of least energy method I would assume), but I would be willing to bet that it is not very accurate in the "real world."

Note: SolidWorks does have a "Lofted Bend" feature in which non-gaussian sheetmetal shapes can be created and unbent. SolidWorks also includes tools to analyze deviations between the bent and flat state. However, the practical use of this tool is limited in many situations. For instance, the lofted bend must be the first feature in a part; you cannot thicken existing surfaces to create a lofted bend; and some others. Plus, like I said in the above paragraph, it does not factor material properties or process in the flattening process. Thus "highly" non-gausian lofted bends can be quite inaccurate. Of course, the closer the surface is to a gaussian surface, the more accurate a lofted bend can become.

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