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Rhino is easy!

First, check out these examples from the Rhino 3d site, and see just what this software is capable of creating. Before you really begin to sweat, please remember that it is very doubtful that you'll ever need to machine a dinosaur! Instead, see here how easy it is to create a simple part. Five basic steps is all it takes!

 
Step 1: Create a Curve

The general flow for most useful CAD/CAM models is from curve, to surface, and finally, to solid.

Here, we generate a curve, not much different from something you'd do with MS Paint. There are no surfaces, and certainly no solids. The individual portions of the curve are selected and joined into a single curve.

There is yet no Z-axis component.

Step 2: Turn the 2D Curve into a 3D model

To do this, the curve is extruded. As a portion of the extrusion command, we specify the model be capped, which means that the upper and lower surfaces are generated as part of the extrusion process.

The display here is portrayed as a wireframe model. We could, if we so chose, display it (and work upon it) as a shaded, X-rayed, or even a basically rendered model. But the wireframe display is easier to work upon at this stage, as we can select curve segments and other parts of the model which would be otherwise hidden.

What we have created here is called a polysurface; an enclosed solid composed of a number of joined, individual surfaces.

Thus, very quickly, we went from a 2D curve to a true 3D model.

Step 3: Fillet, chamfer, basic edge-dressing.

Once the basic 3D form is created, it can be extensively modified. Here, I have filleted the upper surface edges with a single command using a specified radius.

The Perspective view is very useful. You can rotate and zoom to your heart's content.

Step 4: Huge power with Boolean solid operations.

Now it gets cool. By creating another solid, in this case a cylinder, and positioning it that they are conjoined in some fashion, we can do one of the following:

Boolean Union - Join the two 3d solids into a single solid

Boolean Intersection - Only those portions of the solid common to both are retained. For me, this is the least used of the boolean solids options.

Boolean difference - The "Big One". Keep one solid, remove the other, leaving behind its imprint. To visualize, think of the more complex lower shape here being made of clay, and the cylinder is made of aluminum, pressed into place into the clay. The cylinder is then removed...

Step 5: Ready for CAM

... and we are left with the boolean difference. BDiff is used to pocket, drill holes, any number of hugely powerful functions.

Now wasn't that easy?? This handful of commands will create any large number of useful 3d models for CAM. This 3d solid can now be read by Visual Mill, and the necessary toolpaths generated.

What was I so scared of? I have no idea. This model took perhaps 4 minutes to create.