CNC Router Essentials. Randy Johnson

3.9. The diameters of the roughing and finishing bits depend on the size and detail of your project.

      Image 3.5: A CNC can make many types of cuts, but these four are the most commonly used ones. In the world of CNC, these cuts are also referred to as toolpaths.

      Image 3.6: The Pocket Toolpath typically uses a straight bit of some type to cut the recessed area.

      Pocket cut

      Profile cut

      3-D carving

      V-carving

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      CNC Router Essentials

       Toolpath Essentials : 3

      Profile cuts can be used to cut partly or completely through your work, Image 3.10. Think of it as a saw blade or dado blade that makes a cut partially or completely through the material. It is commonly used to separate the part from the surrounding material or to create grooves and slots.

      With these four types of CNC cuts, you can create a variety unique projects. Yet, we've only scratched the surface of what can be done with these cuts, as there are many other ways they can be used to enhance your CNC projects.

      Cutting direction

      Climb cuing with a handheld router or router table (moving in the same direction the router bit is spinning) can be dangerous since the bit can grab the material and

      Image 3.7: The V-Carve/Engraving Toolpath uses a V-bit to create decorative incised carving. It works equally well on text and non-text line designs.

      Image 3.9: A spiral ballnose bit is used to complete the finishing pass on a 3-D carving. Small-diameter ballnose bits taper up to the diameter of the shank to provide added strength to the cutting flutes.

      Image 3.8: Most 3-D carvings are cut in two steps. The first step is the roughing toolpath, which is often done with a straight or spiral bit to quickly remove the majority of the material.

      8CNC Router Essentials

      3 : Toolpath Essentials

      cause you to lose control of the tool. With a CNC, this is not a concern, Image 3.11, and you can reap the primary benefit of climb cuing, which is that it reduces grain chipping when cuing solid wood. Conventional cuing is commonly used for other materials or as a finishing pass aer climb cuing. Sometimes determining the best cuing direction requires running a test cut and then examining both sides of the cut and choosing the one with the best edge quality. Whichever cuing direction you use, the goal is a smooth edge that’s best for your project. On projects with exposed edges, you can expect to do about the same amount of sanding as you would when using a handheld router or router table.

      Offset and raster

      Achieving a smooth surface at the boom of a pocket cut can be a challenge. First, make sure you are using a bit designed for boom cuing in your material. Generally, this will be some a type of end mill bit. Then give some thought to the pocket clearing direction for the cut. Two common ones include offset and raster, Image 3.12. Think of offset cuing as a spiral motion, and raster as a straight-line motion. Raster can be set up to cut in the X or Y direction or at an angle. Think about machining a piece of wood. You typically get the best cut quality by going with the grain, or at an angle. So, when you’re concerned about the quality of the finished cut, seing the raster cut parallel to the

      Image 3.10: The Profile Toolpath is used to cut around a shape or on a line. Any bit can be used with a Profile Toolpath, although a straight bit works best when cutting out around a project.

      Image 3.11: As a general practice, use climb cutting for solid wood and conventional cutting for other materials, but run some tests to determine which feed direction produces the best edge quality for your particular material and bit. Sometimes a combination of the two feed directions is used to produce the desired results.

      Conventional Cut