Here’s the breakdown of how to estimate CNC job time manually:

1. Find Total Cutting Length: In your CAM (Computer-Aided Manufacturing) software, simulate the toolpath. The software will typically report the total length of all cutting moves. This is your primary input.
2. Determine Total Cutting Distance: If your job requires multiple passes to reach the final depth, multiply the cutting length by the number of passes.
   Total Distance = Cutting Length × Number of Passes
3. Calculate Pure Cutting Time: Divide the total cutting distance by your machine's feed rate (the speed at which it cuts). This gives you the time in minutes.
   Cutting Time (min) = Total Distance / Feed Rate (in/min)
4. Estimate Rapid Traverse Time: This is the time the machine spends moving quickly between cutting paths (not cutting). Your CAM software may estimate this, or you can use a reasonable guess based on experience (e.g., 60-180 seconds for a moderately complex job).
5. Combine for Total Time: Add the cutting time and the traverse time (converted to minutes) to get your final estimate.

• Feed Rate: The velocity at which the cutting tool moves through the material. Measured in inches per minute (in/min) or millimeters per minute (mm/min).
• Toolpath: The programmed path that the cutting tool follows to machine a part.
• Pass: A single cutting move along a toolpath at a specific depth. Multiple passes are often used to cut through thick material.
• Rapid Traverse: A high-speed, non-cutting movement of the CNC machine to reposition the tool for the next cut.
• CAM (Computer-Aided Manufacturing): Software used to generate toolpaths and G-code for a CNC machine based on a CAD model.
• G-Code: The programming language that tells a CNC machine how to move.

"Your CAM software's time estimate is a good starting point, but it's often optimistic. It doesn't always account for the machine's true acceleration and deceleration rates. I always add a 'fudge factor' of 10-15% to the CAM estimate to account for these real-world physics and for any unexpected pauses or tool checks." - Experienced CNC Machinist

"The biggest time-saver in most jobs isn't cranking up the feed rate. It's optimizing your toolpaths. Reduce unnecessary rapid moves, use adaptive clearing strategies where possible, and minimize the number of tool changes required. A few minutes of CAM optimization can save hours of machine time on a large job."

Example 1: Engraving a Nameplate
Total cutting length is 500 inches with a V-bit. You use a single pass at 60 in/min. Rapid moves are minimal, maybe 30 seconds total.
Cutting Time: `(500 inches * 1 pass) / 60 in/min = 8.33` minutes.
Total Time: `8.33 min + (30 sec / 60) = 8.83` minutes, or about 8m 50s.

Example 2: Cutting Plywood Cabinet Sides
Total toolpath length is 2000 inches. You need to cut through 0.75" plywood, so you use 4 passes. Feed rate is 180 in/min. Traverse time is significant, around 120 seconds.
Cutting Time: `(2000 inches * 4 passes) / 180 in/min = 44.44` minutes.
Total Time: `44.44 min + (120 sec / 60) = 46.44` minutes, or about 46m 26s.

• Forgetting Multiple Passes: A very common error is to calculate time based on the 2D length of the toolpath, forgetting to multiply it by the number of depth passes.
• Ignoring Rapid Moves: On complex jobs with many separate parts or pockets, the time spent on rapid traverses can be significant. Ignoring it will lead to a major underestimation.
• Using Unrealistic Feed Rates: Don't use the maximum feed rate your machine is capable of. The actual feed rate depends on the material, the tool, and the depth of cut. Be realistic.
• Not Factoring in Tool Changes: If your job requires manual or automatic tool changes, this can add several minutes to the total time. This calculator doesn't account for that, so you must add it mentally.

• Quoting Jobs for Clients: Quickly provide an estimate of machine time to price a project accurately.
• Production Planning: Schedule machine time and plan workflow for multiple jobs.
• Optimizing Toolpaths: Compare the estimated time of different cutting strategies in CAM to find the most efficient one.
• Hobbyist Project Management: Get a good idea of how long you'll need to be in the workshop to complete a project.