creating a sheet metal part from intersection of two curves in different planes

david_george815

Hi all,

I am trying to create a sheet metal part from the intersection of two curves in different planes

In the document below I have a simple example. I would prefer that the curves were actual curves rather than line segments ie: that the discretization of the curves into line segments is eliminated.

At it stands, the closest that I get is to create a bunch of individual 3D lines, then Fill the surface on each triangle - which is a tedious process.

Please feel free to modify the document to illustrate.

Thanks in advance!

https://cad.onshape.com/documents/b7f25f33096994535163af2c/w/a3d8d8942d33d46fe7d165db/e/23ba952b10f96d63802dbfd2?renderMode=0&uiState=679e7a49bbe9085c60556b95

martin_kopplow

It is hard to understand what your intent is.

Please read about sheet metal parts in the learning section. Your model has several issues that make the geometry you created unsuitable for a sheet metal part:

• The bends of your triangles touch at the edges, which wouldn't allow bends to be created (bends have a width > zero).
• Even if you used curves, the resulting surface would be warped, which would require a pressed/stamped part rather than a bent sheet metal part.
• You have no curves, they are rather a collection of lines. No wonder you get no curved surface.

Parts like this can certainly be created in Onshape, but this not a mesh modeler. I'm curious: Why have you not used curves?

MDesign

@martin_kopplow there are bends. They are super tiny. This is zoomed in as far as possible.

glen_dewsbury

This sample has a lot less features to accomplish the task. The 3D lines are not needed. Sheet metal/thicken works. It does leave some odd cut backs because of how the tool works.

It's a start at least.

https://cad.onshape.com/documents/7d76b3c88da24f84094246aa/w/d41a0deece74aebb6a74a8ea/e/719b9a3c95a5232bcba03edf

martin_kopplow

@MDesign woah, that was really thin; I din't even see that.

If it really had to be made out of bent triangular segments (really?), I'd probably approach it this style, introducing two more planes to get rid off the sharp cornes before I make it a sheet model, maintaining the planar faces the tool requires. Then, everything should go smoothly:

https://cad.onshape.com/documents/7d5ba82fd481e948ad0029f3/w/a0c6da39a4afcd745cd53ebd/e/f9e0b5bc6c246e81d443aea0?renderMode=0&uiState=679fba258f780f042c3219dd

I exaggerated the thickness quite some so it comes visible. But in reality, if it was to be such an odd shape from such a thin sheet, I'd just tell the shop to fit some manually and shave off the excess. It is always hard to discuss things without even knowing the rough context.

david_george815

Hi all,

Thanks for the feedback. I have tried to use curves, but have been limited by the Sheet Metal model indicating only certain types of faces can be used as inputs for this (cylinders, planar faces). The use of the triangles is just me trying to approximate the curves, while meeting the restrictions of the Sheet Metal model. I would prefer to not have the triangles at all and simply create a surface between two curves - but then I cant use that surface in the Sheet Metal model.

The weird artifacts at the joints are of no concern at this point as I am still just trying to figure out the best approach.

I've added a second method using loft as glen_d suggested - but the loft is not a permitted surface for the SMM. The only reason that glen_d's works is, I believe, because it is still using line segments (ie planar surfaces)

Ultimately I will be using canvas to create the part (effectively an awning) so need a flat pattern that I can cut to. Hence bend radius can be considered very small.

Thanks again and I appreciate your responses.

glen_dewsbury

As a fabric awing it should be good enough to use the flatten surface tool. You'll have to export as DXF since that's all the tool allows. Just insert the DXF into a sketch after that can be dimensioned in a drawing. Almost forgot about this tool since I haven't used it since it was added a month or 2 ago.

awning

david_george815

oh - I was unaware of the 'Flatten surfaces' function. I'll check that out!

Thanks