bowl with transitions

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endgrainguy
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bowl with transitions

Post by endgrainguy »

bowl with problems.crv3d
(1.9 MiB) Downloaded 52 times
bowl with problems.crv3d[/attachment]
bowl with problems.crv3d
(1.9 MiB) Downloaded 52 times
I'm trying to model an elliptical bowl with near vertical walls at its center, and more typical gracefully curved walls at its ends, with a gradual transition between them. Is this best accomplished using two rail sweep? If so, how are the vectors for rails and weeps configured? My efforts were frustrating, and I ended up making an assymetric (left- to-right) bowl, cutting it in half and mirroring the resulting component to form a symmetric bowl, but it seems wrong still, and when I go to toolpath it, there's a double-ling (halving actually) disconnect with the stated model height in componant tree(2.5"), and the model height shown in the 3d set-up (1.25). I don't do a whole lot of 3d work, and I'm pretty confused here.... Thanks!
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endgrainguy
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Re: bowl with transitions

Post by endgrainguy »

For a quick visual clarification of what I'm looking for (sort of)Here's a jpeg of the preview of this interior shape. I'd prefer the curved walls at the ends to extend a ways down towards the middle before becoming nearly vertical.
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preview.jpg
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endgrainguy
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Re: bowl with transitions

Post by endgrainguy »

Well no one seemed too interested in straightening out my muddle, but a night's sleep did the trick. I have about what I want now. Starting with half bowl vectors and many more nodes and sweeps gave me a half bowl that doubled nicely with componant mirror function. Sorry for posting before I'd exhausted my own resources!
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preview2.jpg
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SteveNelson46
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Re: bowl with transitions

Post by SteveNelson46 »

Have you tried using the create shape tool instead of the 2 rail sweep. Then play with the scaling options.
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Inverted Dome.png
Inverted Dome2.png
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endgrainguy
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Re: bowl with transitions

Post by endgrainguy »

Yes I considered that, and I understand how "create shape" works, I think,but I don't see how that strategy would allow creation of a bowl that had near vertical sides in its middle, transitioning to the shape "create shape" tool makes for its ends.

I am not thrilled with the faceted look towards the ends of the shape I produced using two rail sweep, and If I had sufficient mastery over 2RS I think I might be able to combine the 2 strategies, using the create shape bowl for the ends of the bowl, and the 2rs bowl for its middle. I tried doing that, and this jpeg shows the result (for the left hand side of the bowl). If the abrupt transition area could be made a gradual shift that would be the ideal thing. Anyone out there understand this well enough to suggest the key to this?
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preview3.jpg
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martin54
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Re: bowl with transitions

Post by martin54 »

I am sure someone will chip in, sometimes it can take a while depending on the question & who is about, no point me offering any help because my 3D modeling skills are almost non existant :oops: :oops: You are probably miles ahead of me all ready :lol: :lol:

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dealguy11
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Re: bowl with transitions

Post by dealguy11 »

Here's one way to do it with a 2-rail sweep. Draw 2 oval vectors and a sweep vector as shown. Create the sweep with "Scale cross sections with width" turned OFF and "Fill Center of closed vector rails" turned ON. In this case, I created a zero plane and set its height to the same as the sweep vector to provide a good transition at the top. Pay attention to the combine modes in the first picture. There are other ways to do this that will work as well, but this works.
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Oval Sweep Vectors.JPG
Oval Sweep.JPG
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com

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dealguy11
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Re: bowl with transitions

Post by dealguy11 »

One further note - you can play with the rails and sweep vectors to get an even more dramatic transition. In this example, the center rail is a circle .01" in diameter. I used 2 different sweep vectors. The bottom vector connects the points on the north/south of the circle/oval, and the top vector connects the east/west points. This results in a much sharper transition between the side and the bottom. Also, since I lengthened the original vector, it results in a continuous curve to the bottom of the component.
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Oval sweep vectors 2.JPG
Oval Sweep 2.JPG
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com

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FixitMike
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Re: bowl with transitions

Post by FixitMike »

It can be done with the fluting toolpath using a series of closely spaced horizontal vectors. I've drawn the inner vectors at .05" spacing, and the outer vectors at .025" spacing to reduce ridges along the long sides.
Note that the cutout will be larger than the area covered by the vectors, as the vectors determine the path of the center of the bit.
This will work in VCarve as well as Aspire.
Capture.JPG
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endgrainguy
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Re: bowl with transitions

Post by endgrainguy »

Thanks so much! I thought I remembered once seeing something done with closed vectors inside each other. This is exactly what I'm trying to create, and the method is so simple and elegant, --and gives me a better understanding of 2 rail sweep's abilities. The fluting method is brilliant too, but won't work in this case as I have other things to be added that will get in the way, -but I'm always interested in ways to create 3d shape that don't require a 3d model, or at least don't require typical 3d machining.

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