Toolpaths by Type and Use

Before going further, it is helpful to understand how 2D toolpaths are classified in most CAM software. Table 7.1 lists the common 2D toolpaths by type and common use. For example, 2D contour, chamfer, and fillet toolpaths are often accomplished using the 2D Contour menu selection. Of course, where each function is located will be slightly different depending on the CAM product, but this list is appropriate to most modern CAM.

Table 7.1: 2D Toolpaths and Common Uses
Type	Toolpath	Common Uses
Face	Face	Finish face of part.
Face	Island Facing	Finish face with open sides and bosses.
2D Contour	Contour	Loops. Partial loops. Single edges. Stick (single point) fonts. Create dovetail, keyset, or saw cut.
	Chamfer	Create chamfer using tapered mill or center drill. De-burring.
	Fillet	Creating fillet using Corner Round tool.
Pocket	Pocket	Remove excess material. Machining TrueType (outlined) fonts and logos.
Pocket	Slot Mill	Straight slot. Arc slot.
Drill	Drill	Create spot drill, drill, tap, bore or reamed hole.
	Circular Pocket Milling	Making holes greater than .75 in diameter.
	Thread Mill	Create ID threads over .75 in diameter. Create milled OD threads of any size.

It is probably obvious to you now that manufacturing is an exceedingly complex process. Many factors influence every decision and often more than one solution to any problem. Manufacturing is also a win/lose game. Either the part is right (within tolerance) or not. Don't be overwhelmed by the choices for now. Some knowledge and experience will help you settle many of these variables and greatly simplify the job of planning CNC processes.

2D Machining Features Example

Figure 7.5 and Table 7.2 show the operations and machining sequence to CNC mill this part.

Figure 7.5: 2D Machining Features Example

Table 7.2: 2D Features Example
Op.	Toolpath	Notes
1	Face	It is common practice that the first machining operation roughs and finishes to the highest flat surface of the part. Face paths overlap the sides of the loop selected.
2	2D Contour	Machine outside loop.
3	2D Contour	Machine outside of boss.
4	2D Pocket	Use Pocket to rough and finish enclosed loops.
5	Slot Mill	Mill slots.
6	Circular Pocket Mill	Machine the center hole through. You could also use a Drill operation to make this hole, but would center-drill the hole first.
7	Chamfer	Use 2D Contour, Chamfer function and a chamfer tool (or center drill) to make this 45 degree chamfer.
8	Fillet	Use 2D Contour, fillet function and a corner round tool to make this fillet feature.
9	Spot Drill	Spot drill all holes to: Ensure subsequent drill does not wobble and thus is located precisely. Create chamfer for this hole.
10	Drill	Drill to make hole. Do this before the Circular Pocket Mill so the Spot Drill conic still exists.
11	Circular Pocket Mill	Create counterbore.