Complex surface patch that won't complete

[nicolas_noakes]

I am trying to patch the area on a guitar neck which is shown in my screenshot below, similarly to the patch on the opposite side which is already done.

If it helps, my design method is based on a tutorial by Austin Shaner.

From the best of my diagnosis, it seems that the point I have marked with a red arrow is the problem because if I isolate it by bypassing it with a straight line between two other nodes on the perimeter, then the patch tool works. But I can't find any problems with that point so I don't know why it won't patch when it is included.

I have attached the model for reference. Thanks to anyone who can help!

[nicolas_noakes]

Well folks, that was yesterday that most of it would patch except if that one corner (marked in the first post) was included. Today it won't try to patch at all, whatever parts of the area I exclude!

[jhackney1972]

You will need to attach your model is anyone on the Forum can attempt to help.

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.

[nicolas_noakes]

Thanks for pointing out that the file is not attached. I did originally attach it.

[TrippyLighting]

I encountered a similar problem with another guitar neck a few months ago, which I was able to patch after some trial and error. I posted it on the Fusion Slack channel, and some work is going on to improve the behavior.

However, this one is not budging in my attempts so far. I've added this to the thread on the Slack channel.

[nicolas_noakes]

Thanks for trying TrippyLighting - if we could just have a way to identify where the problem is or what is causing it to fail.

[jhackney1972]

You have quite a few breaks in your projected sketches.  I traced over them to find the problems, it is close but you may want to check behind me.  Also the surface indicated below, I am now sure you wanted this one, if not, it is the last in the timeline.  Model attached.

[TrippyLighting]

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@jhackney1972 wrote:

You have quite a few breaks in your projected sketches. 

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Can you please highlight were you see those breaks?

In my own designs I almost never work with projected curves or intersection curves. I work with the edges of trimmed surfaces, which is a much more robust workflow then relying on some of Fusions inadequate sketch projection functionality.

Even when trying that, I was not able to complete the patch. We need to get to the bottom of this, otherwise we never get these ancient bugs fixed!

[TrippyLighting]

I've been able to work around the issue (just did not see it the last time I tried) and the way I did this exactly highlight the issue I reported to the Fusion team.

I'll have to create a screencast later to explain this. "Breaks in projected sketches" are not the reason this did not work the first time, or why @jhackney1972 was able to create the patch. Still, I do not ever work with intersection curves for other reasons.

[nicolas_noakes]

Hello again and thanks for your help so far,

Sorry, I've been preoccupied recently. 

Yes, I have noticed that projected lines and intersection curves are quite unreliable. Would working with trimmed surfaces still allow a design to be parametric?

[TrippyLighting · Accepted solution]

Ha, I had actually created a screencast, but never posted it here.

Intersection curves are not unreliable; they just often exhibit curvature problems. Those might not matter for the project at hand, which is likely going to be CNC milled and then sanded.

We're not creating a large glossy Automotive Class A surface 😉 

[nicolas_noakes]

Just watched your screencast now...

There's a lot of useful info and tips in there, thanks. 

Something I would like to add about the design, is that on the side that does work, I have replaced the vertical line (originally a projected line like the rest of the sketch) with an ordinary line. Before this, it too did not patch.

Also, in your screencast you call the patch tool a "last resort", and I can kind of see what you mean. Is there another way I could create such a surface?

[TrippyLighting]

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@nicolas_noakes wrote:

Also, in your screencast you call the patch tool a "last resort", and I can kind of see what you mean. Is there another way I could create such a surface?

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Not in Fusion. 

[SaeedHamza · Accepted solution]

Here is one way to do it. I've done it with the timeline turned off, but you don't have to do the same.

In this video, you'll see that I've created an aproximation of the spline, which is not perfectly identical, although using some API scripts, I can create a perfect copy of it, but I've tried doing it using only Fusion 360 tools.

I hope it helps.

[TrippyLighting]

@SaeedHamza These extra splines help to create the patch, but the edges of the patch will not be smooth. I explain why in my screencast.

[SaeedHamza]

@TrippyLighting yes you're right, the tangency option for the patch selected edges only shows up when selecting a brep edge and not a spline, and to get as much tangency options for patch edges as possible, you'll need to leave the curved-tangent parts of the model as the last part to create (as a bridge between the nick and the head of the guitar).

In my method, I only counted on the edges that were already modeled in the file, where I should have created the head and then created a patch with all selections for the patch command being brep edges.

I still believe that the spline fix I did is needed since some edges curvetures were messed up, but I should have done the above before directly creating the patch.

[TrippyLighting]

You should really watch my screen cast 😉