What is a toolpath?

The reference point is typically the tool tip or tool centre; in 4- and 5-axis work the orientation of the tool axis is part of the path as well. It includes the cutting moves, the approach and retract, the linking moves between cuts and the rapids. In CAM the programmer chooses a strategy, such as clearing a pocket in layers, contouring or a constant-engagement path, and the package computes the path from it.

What does a toolpath depend on?

The shape of the path depends on the geometry, the tool, the cutting data and the strategy. An internal corner radius limits the cutter diameter; a small radius calls for a smaller cutter and often a rest-machining pass. When finishing with a ball-nose cutter, the stepover and the ball radius together set the height of the cusps between passes. On a flat surface the cusp height is h ≈ ae² / (8 × R), with ae the stepover and R the ball radius, both in mm; on a curved surface the cusp height departs from that. It is an estimate from geometry, not a measured roughness. How closely the path follows the shape also depends on the CAM tolerance: it sets how finely freeform surfaces, and any arcs not output as circular moves, are broken into short straight segments.

How does a toolpath work in practice?

Cutting path length divided by feed gives the cutting time at the programmed feed; rapids add their time at the rapid traverse rate. In tight corners the machine often cannot reach that feed because of acceleration and the control's look-ahead, so the real time can be longer. Two programmers can produce two paths for the same pocket that are both sound and still differ by minutes. An estimate made without CAM approximates the paths rather than calculating them, and that is a large part of the uncertainty in machining time. A time from CAM usually arrives only after the quote.

What is a toolpath often confused with?

A toolpath is not the NC program: the path is the movement, the program is the code the control executes, produced by the postprocessor. Nor is a toolpath the same as an operation in the process plan: one operation, such as milling a pocket, often needs several paths for roughing, rest material and finishing.