Constant depth cut from curved surface

[randy_stjohn]

I would like to know how to cut a constant depth channel from the top of a curve surface. In this particular case it is a cut out around a carved guitar top for a binding. The carved top is made from a loft.

Around most of the body the surface is fairly flat where the cut needs to happen so a constant depth can be obtained by a simple extrude. However, by the neck the body curves up and I want the binding channel to curve up with the body.

I have tried to cut the body with the profile of the binding outline and then scale the outer cut part but the bottom of the cut is not flat where the surface is curved.

Any suggestion?

[davebYYPCU]

Sweep the binding profile, along the 3d contour path.  

Might help….

[randy_stjohn]

That's actually a good idea I haven't thought of.  However, it would require me to edit the path in 3D to get it to conform to the surface towards the neck. Either that or project the path onto the surface.

So this is how I think I might do it

1. Take the path that follows the outside of the 3D model

2. Project the path to the surface of the 3D model. (Maybe adjust points as needed).

    Although with the path at the outside edge it might not project to the surface. I might have to make it a bit smaller to "hit" the surface

3. Make a square/rectangle in a plane perpendicular to the path end, height and depth to get the cutout the right size

4. Sweep the square along the path and cut the 3d Model

I will try this and see if there are any errors. 

[laughingcreek]

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@randy_stjohn wrote:......it would require me to edit the path in 3D to get it to conform to the surface towards the neck. Either that or project the path onto the surface....

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the path already exists.  you use the edge of the surface as the path.

[johnsonshiue]

Hi! Another approach is to create an offset surface from the curved faces (in normal direction). Or create a zero-distance offset surface from the curved faces. Then move the offset surface downward (extruding direction).

After the surface is created, Extrude -> Cut -> select the surface as terminating object.

Many thanks!

[randy_stjohn]

@laughingcreek 

That actually looks like it will work. I have not tried this before so I didn't know you could use the edge of a surface for this. Will try it tonight.

[randy_stjohn]

@johnsonshiue 

The problem with this approach is that the surface is not flat. Therefore the offset surface will not be flat at the bottom of the channel but will be curved like the top surface. I want the bottom of the cut to be parallel with the x-y plane. Unless I don't understand some detail about offset surfaces.

[laughingcreek]

another approach attached

[randy_stjohn]

@laughingcreek

Ok, so this does not quite work.  The path from the edge of the surface results in the same issue as just cutting with a loft. If follows the bottom of the body plane and does not account for the rise of the surface next to the neck. I would need to create/project a path onto the body where the carve is.

In addition, it keeps telling me that the new sweep will intersect with itself.

[laughingcreek · Accepted solution]

see attached. sweep with guide surface.  not as clean as the above example with a ruled surface.

[randy_stjohn]

I ended up using a combination of suggestions. Thank everyone for your input. No single Sweep/extrude could I get to work for the whole cut but a combination worked fine.