CAD to CAM to CNC: Part Three — From a Simple 2D Drawing to 3D Design
In previous posts, I drew the basic 2D curved shape for the BARN Workbench vise chop using CAD software. Because I was still at the beginning stage of the project, I also designed and built a jig that holds the blank stock during machining on a CNC. Now that the basics are out of the way, it’s time for the fun part: Turning a simple 2D shape into a 3D vise chop.
Here’s the 2D shape we started with.
Now, let’s take that 2D shape and use it to create a 3D object. One way to do this is a process that’s almost universal amongst 3D CAD programs. We’ll use the extrude function to turn the 2D lines into a 3D form. Essentially, as you’re pulling the lines up to a chosen height, a surface is formed along your lines. When you’re done, you have a 3D object. In our case, I extruded to the height of the blank vise chop, 2.75”. Voila! Instant 3D. Extrusion may be simple CAD process, but it’s one that’s particularly useful for woodworkers. Furniture makers in particular, will use it often.
Above is the extrusion of the vise chop. Yes, it works, but from a designer’s perspective, it’s thick, flat and pretty clunky. We need to taper and soften that top surface a bit — something we can do with our 3D tools.
I’d like to create a 3D surface that curves on all sides. First, from the front view, I’ll draw a tapering curve from the top (left side) to the bottom (right side) of the vise using a single curved line. The peak of the curve is at the centerline of the vise screw’s location.
Again, thinking in 3D, I do the same from the right view where I can see the bottom and top of the chop. In this view, the vise is symmetrical, and that makes it easy. So, I draw a smooth taper from the center out to one side of the chop and mirror a copy of it over to the other side. Note: As in previous drawings, I’m using center construction lines as a visual aid to keep everything lined up.
Taking a bit of a short cut in my explanation, I make copies of the sides and end lines and connect them together at their end points. Above is what the four curved lines look like from a perspective view. Now, using a surface creation CAD tool (Sweep 2 Rails, in Rhino3D) I use the four lines to create a sweeping, curved 3D surface.
Now, we have a base 3D vise chop shape to work with, it’s time for patterns and textures. We’ll show some of the techniques I used to create them in future posts. Now, the real fun begins!