Why estimating job time matters for sign and CNC routing work
A CAM program reports toolpath length easily enough, but that number alone does not tell you how long a job will actually take on the machine, since plunge moves, tool changes, and rapid travel all add time that a simple path-length figure ignores. Quoting a sign or carving job off toolpath length alone tends to under-estimate the real cycle time once plunges are factored in.
How the number is calculated
Estimated job time equals the total toolpath length divided by the feed rate, which gives the cutting time, plus the number of plunges multiplied by the time per plunge. Each plunge adds a fixed chunk of time since the machine typically slows down or dwells briefly at the start of a cut, and that adds up quickly on jobs with many short strokes, like lettering or detailed carving with lots of individual letter starts.
Practical tips
Pull the toolpath length and plunge count directly from your CAM software rather than estimating them, since both numbers are usually reported automatically in the toolpath simulation. For jobs with unusually high plunge counts relative to path length, such as dense text or fine detail carving, plunge time can end up being a larger share of the total job time than the actual cutting, so do not assume path length alone predicts cycle time.