Facing

Facing is often the first machining operation. It is used to cut away excess material and finish the highest flat face of the part. Depending on how much stock is removed, several roughing cuts may be required. A smaller finish pass ensures a flat surface and good surface finish.

Use a face mill when possible for all but the smallest part. The large diameter of facing mills and multiple carbide insert cutting edges provide for very high material removal rates.

High speed loop transitions between cut passes produce a fluid tool motion that place less stress and wear on the CNC machine.

Figure 5: 2D Facing Toolpath

Rules for Facing:

• Because face mills do not plunge well, start the tool path far enough away from the part so the tool does not plunge into the stock material.
• Be aware that saw cut stock can vary considerably in thickness from one part to another: as much as 10 mm or more. When planning roughing passes, be sure to account for the worst case stock material – maximum height and add additional roughing passes as needed. It is better to have a “air cut” or two with the shortest stock than to have the tool engage too much material for the highest which could cause the tool to break or the part to be pushed out of the vise or fixture.