Creating a compound curved surface from spline lines

Rhino Rhino for Windows
1

Hey everyone,

I have Rhino 3.0 and Flamingo but have never learned to use them because, I think, my PC’s memory back then could not handle them well. I do some tabletop CNC machining, and I am faced with a project that, I hope, Rhino can handle (I am mulling upgrading to Rhino 5 and adding CAM software to replace my current setup).

My tiny home business involves creating museum quality (if I might be so bold) model railroad items. The all-time classic diesel, known as an F-unit, was manufactured by EMD, a General Motors subdivision. The nose of the F-unit is formed from compound curves. I am going to attempt to attach a diagram. At the top of the diagram is a side profile of the diesel-electric locomotive. Below is a two-part spline line profile (I do not know correct terminology, please correct me). The top spline line grouping is a plan (top down) view, the bottom spline line grouping is a side view.

Considering the side spline line grouping, the lines are some inches apart. To cut this profile on my CNC mill, I will need to interpolate many, many more cutting lines between those in the drawing. Can Rhino help me blend new spline lines between those in the existing drawing? If so, can you point me to the Rhino tool(s) that will allow me to do that?

(Before I follow any advice forthcoming here, I’m going to have to do some serious Rhino re-education work!)

Thank you much for the help any of you here are able to give to me,

Brian Chapman

Cedar Rapids, Iowa

2

Well, the best way to do this sort of thing is to create a real 3D surface in Rhino that represents the nose of the diesel and then mill that with 3D CAM software. However, from the wording of your post, it seems you might not have 3D CAM.

If that’s the case, I guess you want to create lot of splines in, say, the side view that are at the correct Z level for that view, and them mill them in 2D to create a sort of stepped surface that you can sand to final shape…?

In any case I still think the best will be to use Rhino’s tools to model the nose in 3D until you get it right, using traced contours from the drawing to create the surface as well as check the accuracy of the result. Then if you can’t mill in 3D, you can use the Contour command to create 2D slices of the surface at any interval you want.

Failing that, you can certainly interpolate any of the traced lines using Rhino’s TweenCurves command.

HTH, --Mitch

3

Mitch, a huge help, thank you much for taking time to lend a hand!

I do not have 3D CAM. I’m mulling whether or not to get it now and go through the learning difficulties the software will no doubt impose on me, or go the 2D sliced surface route. If I mill cut in .001" slices, the result is smooth to the touch and requires only the finest sanding.

Again, thanks much,

Brian Chapman
Cedar Rapids, Iowa