CNC Milling/MachiningA cutting process in which material is removed from a block by a rotating tool
CNC Milling Overview
In CNC milling the cutting tool is moved in all three dimensions to achieve the desired part shape. The cutting tool usually rotates about an axis that is perpendicular to the table that holds the material to be cut. A milling machine looks somewhat like a drill press at first glance. A cutting tool protrudes down from a rotating spindle. A block of material is placed on a moving table below the cutter. While the cutting tool turns, a computer controls the vertical (Z axis) motion of the cutter and the horizontal (X and Y axis) motion of the block of material. The cutter is guided to move through the material, removing portions to create shapes. Additionally, the material can be turned to various orientations in the middle of the process and cutting tools of various shapes can be used. Material is usually removed by both the end and the side of the cutting tool. Some common cutter shapes include:
- Flat end mill (used for most milling) – creates walls with straight 90 degree edges and sharp corners at the bottom of recesses
- Chamfer end mill – creates 45 degree bevels on the top edge of a wall or recess
- Grooving end mill – creates rectangular grooves in side walls
- Ball mill – creates rounded edges at the bottom edge of a recess
- Rounding end mill – creates rounded edges at the top edge
- Angle end mill – creates walls at angles other than 90 degrees and (not shown) a conventional drill
CNC milling has several advantages over other manufacturing processes. It is cost effective for short runs. Complex shapes and high dimensional tolerances are possible. Smooth finishes can be achieved. CNC milling can produce almost any 2D or 3D shape provided that the rotating cutting tools can reach the material to be removed. Examples of CNC milled parts include: engine components, mold tooling, complex mechanisms, enclosures, etc. Although tooling is mainly software, custom jig tooling is often required for work holding. Cost reduction options include reducing the amount of material removed, limiting complexity, avoiding intricate features and making shapes that are easy to hold.
CNC milling can process most rigid materials including most metals: Aluminum, Stainless Steel, Copper, Steel, Brass, Titanium, Sterling Silver, Bronze, etc., as well as hard plastics and other materials such as Nylon, Acetyl, Poly carbonate, Polystyrene, Acrylic, Fiberglass, Carbon fiber, Teflon, ABS, PVC, etc.