How is cutting time calculated?

Cutting time equals the total cutting toolpath length divided by the feed rate. If a part has 40 inches of cuts at 20 inches per minute, the cutting time is 2 minutes. The tool sums all cutting moves you enter.

Why include rapid traverse time?

Rapids are non-cutting moves between features and to and from tool-change positions. On long programs the rapid time adds up, so dividing total rapid distance by the rapid rate keeps the estimate honest for scheduling and quoting.

How long is a tool change?

It varies by machine. A fast carousel changer may take 2 to 4 seconds, while older or umbrella changers can take 6 to 10 seconds. Enter your machine's measured time per change and multiply by the number of changes in the program.

Is this estimate accurate enough to quote from?

It is a solid rough estimate based on programmed motion. Real cycle time can run longer due to feed-rate overrides, acceleration and deceleration on short moves, and dwell or probing. Add a small contingency for quoting.

Does it account for acceleration and deceleration?

No. The model assumes moves run at the programmed feed and rapid rates. On parts with many short, sharp moves the machine never reaches full speed, so add 5 to 15 percent for accel and decel losses on complex programs.

What is the CNC Machining Cycle Time Estimator?

Estimates total CNC cycle time from cutting toolpath length, feed rate, rapid traverse distance, tool-change count, and dwell time. Sums cut time plus non-cut (rapid and tool change) time into a total per part to help quote jobs and schedule machine hours. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

CNC Machining Cycle Time Estimator

Name: CNC Machining Cycle Time Estimator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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A quick, defensible cycle-time number is the backbone of any machining quote and of realistic machine scheduling. This estimator sums the time a CNC actually spends moving: cutting at feed, rapid traversing, changing tools, and dwelling. It does not need a postprocessor or simulation, only a few figures you can read off the program or the slicer.

How it works

Time is distance over speed for each motion type, plus fixed times for tool changes and dwells:

cut time     = cutting path length / feed rate
rapid time   = rapid distance / rapid rate
change time  = number of tool changes × seconds per change
dwell time   = total programmed dwell
total cycle  = cut + rapid + change + dwell

Feed and rapid rates are typically in inches (or mm) per minute, so lengths in inches (or mm) give minutes directly. Tool-change and dwell times are added in seconds and converted.

Worked example

Consider a turned part with multiple diameters:

Cutting path: 60 in total (roughing and finishing passes combined) at a feed rate of 25 IPM
Rapid traverse: 30 in of positioning moves at 400 IPM
Tool changes: 5 tools (turning insert, grooving, threading, boring, chamfering) at 4 seconds each
Dwell: 2 seconds total for spindle settle and thread relief

cut time     = 60 / 25          = 2.400 min
rapid time   = 30 / 400         = 0.075 min
change time  = (5 × 4) / 60    = 0.333 min
dwell time   = 2 / 60          = 0.033 min
total cycle  = 2.841 min ≈ 2 min 51 s

Multiply by your machine’s fully-loaded hourly rate (machine depreciation, labour, overheads) to get cost per part, and by order quantity for total run time and scheduling impact.

Where estimates diverge from real cycle time

The model assumes every cutting move runs at the programmed feed rate and every rapid at the programmed rapid rate. In practice several factors lengthen real cycle time:

Short moves with direction changes — On parts with many small features, the servo axes cannot accelerate to the commanded speed before the move ends. This is the most common cause of real cycle times running 10 to 25% over the estimate. The effect is proportional to feature density and inversely proportional to move length.

Feed-rate overrides — Operators often run at 80 to 90% of programmed speed, especially on first articles. The estimate assumes 100%; if your shop runs overrides, multiply the cut time by the typical override factor.

Soft-limits and look-ahead — Some controllers reduce speed when approaching tight interior corners to protect the machine or hold tolerance. High-precision mold and die work often has intentionally reduced feed rates in specific areas.

Spindle spin-up and orientation — Machining centres with spindle orientation before tool change, or turning centres with live tooling that needs to spin up, add a few seconds per change not captured by the ATC time alone.

Probing and in-process gauging — If your program includes on-machine measurement cycles, add those times separately. Probing a feature can take 5 to 15 seconds per feature.

Tips for quoting and scheduling

Add a contingency margin to the estimate before quoting: 10% for straightforward parts, 15 to 20% for complex geometry or first-time programs. Use the per-part time multiplied by order quantity as your scheduling block, adding setup time as a separate fixed entry because it does not scale with quantity. Re-measure the actual cycle on the first production run and update your quoting data — real measured times from your own machines are far more reliable than estimates for repeat work.