I'll soon lose my mind ... yellowish background of rectangle is gone

[ovisopa]

Hello guys,

I start a new thread for this new problem, somehow related to my other daily issues I have with Fusion (Sketch offset of imported DXF - SOLVED / Can't apply draft operation) yesterday I posted about a issue regarding the offset of an imported sketch from a dxf file, I talked to the client and explained this issue I constantly have with those files, and they made some changes to the drawing (made sure or the curves and lines are in the same direction, and they also joined the lines/curves before exporting ).

Now with the new drawing I could do the offset in one operation only, Fusion recognized the entire contour ... BUT .. I faced another problem - an very common problem I have with Fusion, I couldn't apply the draft operation on that contour, it worked only to 15 degree, but I need the draft to be 30 degree, after that angle I got an error "Error: The operation would cause a large topology change.Try adjusting the values or changing the input geometry."

So I already  lost 30 minutes trying to make the 3D model, I started redrawing the sketch in Fusion like you always suggest, I did it with splines, only half of the model and mirrored it, I did the internal offset before mirroring .. everything went good, the model as you can see bellow , but there was something weird, when I selected the edges for extrude, somehow, the original sketch, which was hidden, had influenced my selection, as all the very small 0.005 differences ware not extruded, .. now I still can't do the draft operation, even if the 3D model looks much better, with a continuous curved shape, not an frequently interrupted one

After seeing the new issue I tried to figure out where it comes from and noticed the difference between the original sketch and the new sketch3 that I did in fusion, the original sketch was hidden from the LIGHT BULB icon, but when selecting the lines for extrude I could see some light orange lines, those ware the original sketch, i right click the original sketch and pressed HIDE PROFILE .. and toggle that a few times while checking the lines, but now my new problem is the the background of the new sketch is gone, and I can't extrude it anymore ?

I will start everything from the beginning, with a new file, but please can you tell me if I can somehow regenerate that yellowish background in my sketch so I can do the extrude, on future designs.. ??? 

[TrippyLighting]

Not sure what you are trying to explain with these sketches but see are several suggestions:

1. Use fewer points on your spines and work with the spline handles to get your form.

2. Don't mirror a spline. In Fusion 360 that's a bad idea.

3. It is unlikely that drafting such a thin walled structure will ever work. Draft the outer contour, splint it off, shell it and combine-join it.

4. Of course this cannot be drafted beyond 15 degrees. The inner radii at the bottom of the drafted  structure change collapse beyond 15 degrees. 

[kb9ydn]

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@TrippyLighting wrote:

4. Of course this cannot be drafted beyond 15 degrees. The inner radii at the bottom of the drafted  structure change collapse beyond 15 degrees. 

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The only way you can get a draft angle of 30deg is to lower the extrusion height so the shape doesn't collapse at the top.  It's easier to play with this if you extrude the shape by itself and use the draft angle built into the extrusion (Instead of cutting it out of a block and then applying the draft in a separate step).  With a 30deg draft it seems to extrude ok up to 2.5mm.  Beyond that it gets weird and starts adding strange extra faces, and then above 3mm it either fails completely or produces really messed up geometry.

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