How to project / flatten developable surfaces in Fusion ? (Sheet metal errors)

[bernard5BABD]

I have this project of a boat hull, intended to be built using the stich and glue method, so all surfaces are developable.

Problem is, I tried everything I could think of to transform each surface into a sheet metal (thickening then extruding straight on a few centimeters), I always have an error saying that it can't calculate the thickness. Is there any other way to get those parts' shapes on a flat surface, to be able to cut them ?

Thanks for your help and advices,
Bernard

[bernard5BABD]

Yes, I know about the tiny planar face. I tried adding one. I don't have Inventor. I will try the loft flange tool.
Thanks for your help, I had no idea this would be so difficult for Fusion.

[bernard5BABD]

Yes, I know about the tiny planar face, that's what I have been trying to add to the thickened surface before attempting to convert to sheet metal. I did not think about the loft flange tool, I will test it. Thanks for your help, I had no idea this would be so difficult for Fusion.

[TheCADWhisperer]

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@bernard5BABD wrote:

 I did not think about the loft flange tool, I will test it. 

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To have much of any chance of getting this to work in Fusion 360 you will have to use the Fusion 360 Sheet Metal tools to model the geometry (not Convert).

I strongly doubt you will have success in this endeavor without using other Autodesk tools.

In any case - Attach your cleaned up Fusion *.f3d file for diagnosis when you get a chance.

[bernard5BABD]

I just tried the loft flange tool, did not work. Contours have to be on a plane.

[bernard5BABD]

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@TheCADWhisperer wrote:

In any case - Attach your cleaned up Fusion *.f3d file for diagnosis when you get a chance.

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Already done.

[TheCADWhisperer]

Rats, I already shut down for the night.

The last file I saw Attached was Insider version - I did not realize that you had replaced it.

[bernard5BABD]

Have a good night, tomorrow is another day... 😉 I m going to do the same !

[TheCADWhisperer]

First thing I notice is that there are no dimensions on your sketches?

Then I noticed that you used splines in your sketches confounding the issue.

Double confounding I noticed that you used Loft (and not an overbuild trimmed Loft).

I do not think you will be successful with this geometry and in any case I would clean it up some more.

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@bernard5BABD wrote:

Sometimes, it's a good idea to believe what the user says,

rather than questioning his ability to know what he is saying/doing. They ARE developable surfaces...

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After 36 years of experience in this business I have learned to never believe anything other than the actual geometry.  This is most definitely not a developable surface. 

Preferably I could reduce the geometry into parts of tangent trimmed cylindrical surfaces well within the manufacturing process tolerance that represents the spline-based geometry.

If I were modeling this geometry and it had to be a spline-based Loft, I would used a overbuild surface and trim.  I would use Autodesk Inventor Professional rather than Fusion for the task.  

I would use dimensions.

Logical dimensions.

[bernard5BABD]

No, there are no dimensions on the sketches, as I scaled the canvas to the dimensions I wanted, and everything is built on them. 

I have to use splines to follow the original (on canvas) design. If you know of another way, I would be glad to learn a possible alternative.

I don't understand what you mean by "overbuild trimmed loft". If you look at how this was built, I use the horizontal and vertical views to extrude surfaces (horizontal first, then cut from the vertical), then loft are made between the edges of the resulting (once cut) surfaces. Again, if you know a better way to do this, as simply as possible, I am willing to learn.

I use this method to avoid the traditional way, which would be to try to find position and shape of frames, then loft between each frame. Here, frames (not designed yet) would be the result of a simple intersection, instead of spending a lot of time trying to find the right shape. They are not on the original drawing, so this method is, from my point of view, simple and efficient. Now, once again, I would be happy to learn an alternative way to  do the same thing.

PS- I am not sure why you say these are not developable surfaces. They are. Make a section analysis from the stem to the bow, and you will see that, at every point, the side of the hull are perfectly straight lines. If Fusion "see" this as not developable, then Fusion as a problem. Like I alreay said, in real life, this plan is intended to be built using the stich and glue technique, from large sheets of multiply wood. Or we don't have the same definition for "developable".

Ps-bis: I can't afford to have Inventor.

[TheCADWhisperer]

>>Overbuild and Trim Surfaces - click link<< 

These spline curves can surely be built with tangent arc curves that are well within any possible manufacturing tolerance, however, by the time you get the 3D intersection curve it will be a spline.  But for simplicity of editing I would most likely use dimensioned tangent arcs.  I would use logical dimensions in my work.  I am used to measuring things out on the shop floor during construction.  I like dimensions.  Dimensions are some of my best friends. 

[bernard5BABD]

I totally understand what you mean, and I am sure you're right. It's just that I doubt changing this would help to solve the current problem... 🙂

[TheCADWhisperer]

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@bernard5BABD wrote:

PS- I am not sure why you say these are not developable surfaces. 

Ps-bis: I can't afford to have Inventor.

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I am surprised that you cannot see the issue in the Loft surface?

OK, this might be doable in Fusion 360, but more care will be needed in creating high-quality geometry.

In my experience observation is key.  The issue with the Loft (as created) should be obvious (especially after it is pointed out). Try Thicken of that surface - what do you observe?

[bernard5BABD]

I did thicken that surface, more than once, and I did not see anything especially noticeable. What I am supposed to see ?

[TheCADWhisperer]

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@bernard5BABD wrote:

I did thicken that surface, more than once, and I did not see anything especially noticeable. What I am supposed to see ?

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You did not Attach a file here with Thickened surface?

How much were you able to Thicken it?

What do you observe in my image of this Thicken?

https://www.youtube.com/watch?v=1rMxcK_No-A&list=PLp5izJt_zvN0GnwEUFR1zE06nQvDAWxz2&index=1

[bernard5BABD]

I thickened to 18 mm, but I have not been zooming as closely as you show (and it's certainly thickened to more than that). OK, I will look at the video, and use arcs instead of splines. 

[davebYYPCU]

Or we don't have the same definition for "developable".

[TheCADWhisperer]

@bernard5BABD 

How are you making out?

Imagine you took a bed sheet and dropped it smoothly across your geometry.  (Overbuilt surface)

Then you trim the edges.

Now imagine that you could see the individual thread-weave. (Isocurve Analysis)

In your geometry observe how all of the "threads" on the bottom panels in one direction are "pinched" to a point (or close to a point).

(In the top image above.)

In the lower image notice how the "thread weaves" in the side panels are nice evenly spaced 4-sided with no pinching.

This is what you want.

Here is a zoomed in view...

Avoid the "pinching" of material.

I think @TrippyLighting has a good link to a more in-depth Alias reference covering this in detail.

[bernard5BABD]

I started watching your videos, I will modify the design with arcs and dimensions as soon as I get some time to do it.

I think @TrippyLighting has a good link to a more in-depth Alias reference covering this in detail.

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Where is this link ? 
Again, thanks for your help. Even if I believe to have a pretty decent experience with Fusion, I realize there is still a LOT to learn.