Flattening Curved Surfaces

[dtompkins93]

Hi, I've got this design for a curved hood vent that I have made a couple of times now.

Each time I do, the sizes change a bit, and I haven't found a reliable way to draw this such that it doesn't break when I change the dimensions. Most of it I can handle, but the tough part is the curved skins.

I can (sometimes) convert them to sheet metal and create a flat pattern. But then I want to be able to nest all three pieces on to one sheet and cut together. However, inside the flat pattern, options are limited. I can export a dxf, but that seems to flatten the geometry, and I lose the mitered edges where the skins come together. Which is of course the main information I need.

I have been doing each part as its own setup in Manufacturing and running them individually. I was hoping to find a more reliable way to flatten these parts out so I can manipulate them with the rest of the design. Flat pattern seems to take you into a instance where the rest of the design is inaccessible. If anybody has found a better way to handle things like this, I would appreciate any insight. Thanks.

[jhackney1972]

Please attach your model.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

[Warmingup1953]

So I gather this joinery not metal working? 

[TheCADWhisperer]

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@dtompkins93 wrote:

… and I lose the mitered edges where the skins come together. 

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Sheet metal edges are cut perpendicular to the flat.

What material are you using?

What manufacturing process/machine are you using to cut mitered edges?

[HughesTooling]

In the manufacture workspace. Create the manufacture models then edit the manufacture model and click on Components in the top toolbar and you can enable the flat patterns. Then just hide the unbent versions and arrange the flat patterns for machining. You could do this manually using joints or use Arrange from the modify menu.

[dtompkins93]

I should have been clearer, this is all built with wood. The skins will be made out of .25" MDF (the pictures below show one made with .25" ply that was then stained). I do a stepped cut along the edge with a cnc router to approximate the miter, and sand the rest of the way. 

It actually ends up making a pretty nice seam.

I have attached the file I am working on (a different one from above), hopefully that will clear things up. (It's not the cleanest drawing, I am still working out the best way to handle compound curves like this effectively. If anybody has any tips on that, ways I might be making things too hard, etc, I would appreciate it as well.)

@HughesTooling I don't seem to have the component manager, that seems quite handy. Is that a part of the manage extension perhaps?

[HughesTooling]

No it's in the manufacture workspace. 

Just use Create Manufacture models.

Then edit and you have independent copies you can modify for manufacture and access to the component manager.

[dtompkins93]

Am I missing something? I don't seem to have that button, I am in the manufacturing model.

I have one manufacturing model, and three flat patterns, but I don't see this components button in any view.

[HughesTooling]

Not sure if it is part of an add in option. Seem to think it didn't show when I first edited the manufacture model but clicking on the Surface workspace then back to Solid made it show up.

Mark

[Warmingup1953]

The Skins as you describe them are I guess one part of your question as they are a separate Nest onto a different board than the structure. Is your current method to flat pattern a Sheetmetal body version of the cladding and you simply trace those lines with a 91 Degree V- Cutter? Are you reliably getting the .dxf you need this way for the skins?

[dtompkins93]

@HughesTooling Weird, I will have to do some searching for that.

@Warmingup1953 I actually dont use a V-Cutter. After creating the flat pattern, within manufacturing, I do a series of arcs, stepping down and over around maybe .01", achieving something like this:

It was the only way I could think of to be able to cut that angle. Already being a compound curve makes it tricky, and once you unfold it, that edge becomes a pretty nonuniform thing. Might be overkill on the edge of a .25" piece of MDF, but we had one we needed to do out of .5", and it did make a difference there. And the cut time is really not bad at all, the slowest part for me right now is dealing with these skins. 

[TrippyLighting]

Do you consider this resolved ?

For example, I don't see anyone addressing the modeling improvements that would stop things from breaking when parameters are changed.

[dtompkins93]

Not really unfortunately. I mean, maybe there just isn't a better way to do this than how I am. I know Inventor could handle something like this a lot easier, I just wanted to simplify my process in Fusion. But what I am doing now does work, and I will keep playing with it and hopefully figure some more tricks out along the way. I wonder if I could do the math myself, and just use parameters to create the flat shapes I need, but I imagine that would be no easy feat. In any case, I understand if this can't be resolved here, and if this post should marked as closed or whatever the case may be. Thanks to everyone for the input so far, it's given me a lead or two at least.

[TrippyLighting]

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@dtompkins93 wrote:

Not really unfortunately. I mean, maybe there just isn't a better way to do this than how I am. 

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I've read through this thread and I yet have to figure out what exactly this is.

You mentioned in your first post:

" Each time I do, the sizes change a bit, and I haven't found a reliable way to draw this such that it doesn't break when I change the dimensions. Most of it I can handle, but the tough part is the curved skins"

Without a model with predictable behavior upon parameter changes, you won't get anywhere! So lets start with that. Agreed ?  

[Warmingup1953]

Provided the skins are perpendicular a 91-degree cutter (the extra 1 degree so the glue can squeeze out) will do a great job there...one pass in 1/4" so that may be a worthwhile investment. Because your Sheet metal Body has mitered edges you can reliably save the flat pattern as a simple dxf so a new sketch from the Unfold will work well

[dtompkins93]

@Warmingup1953 How do i know that the surfaces are perpendicular? It seems to me that even if they are when curved, as soon as I flatten them out, the edge won't necessarily be 90 degrees along the whole edge. Or maybe I am not thinking about that correctly.

@TrippyLighting Fair enough, I haven't been very clear. I think that is because I have multiple questions about a project like this, and I am forcing to much into this one thread. My main question is about getting all three skins into the same manufacturing model so I can program them all at the same time. The DXF's would work except for my above concern about the angle not being consistent. The rest of my issues about parameter changes breaking etc., are something I can work with. I was just wondering if anybody might have a tip or two about any obvious mistakes I might be making that could be causing more timeline breaks than necessary.

[davebYYPCU]

Nowhere in the thread, have you nominated a range of sizes for the parameter changes that break the model.  

Is it the skin thickness?  (0.25 > 0.5)

Is it physical footprint?  

Changing the frame member counts?

[dtompkins93]

I mean, all of the above really. I could list out all the things that were breaking, but I didn't want to derail too much from the main issue here, which again is the nesting of the flattened skins.

But yes, going to a thicker skin sometimes breaks the lofted surface I use to split the skins. Changing the overall dimensions (width, height etc) will often break the relations between the vertical members and where they cut out to mate with the horizontal members inside (especially the circles I place at the corners for dogbones). Changing the frame member counts generally requires a bit of redrawing as well. Time consuming, but not as bad as making another file where I nest the DXF's of my flat patterns, and then using work offsets in the original file to program a separate file per skin on the same sheet (again because I have to program each one in it's own flat pattern, as the DXF's don't contain all of the 3D data I need, just the outlines). Especially when I am making a hood like above where I also have to do this process for the curved Batton pieces (at least the ones that miter together in the corners).

[davebYYPCU]

I wasn't able to break the surface Loft, but the Split Body using them does break the model.

Try unchecking the extend surface option, worked here for me to restore stability.

Might help....

[dtompkins93]

Oh, interesting. I will try that, thanks.