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How to Estimate CNC Machining Time

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Calculating the cycle time on a CNC, or computer numerical controlled, machine can help you maximize its efficiency. By looking at times through simulations, you can get the best estimates, but by comparing the part with others you have cut in the past you can also get an estimate without the assumptions the program may make for you. Using a more complicated method such as actual, real-world tool movements may be the most accurate way to get the correct cycle time.

After you have programmed the cycle in a CAM, or computer-aided manufacturing, program, simulate the process. The CAM program can quickly simulate all of the processes and estimate the length of the cycle. It also accounts for tool changes, and more sophisticated programs will allow you to enter the model of CNC you will be using.

Run a simulation at the control if you have programmed the part at the machine rather than in a CAM program. CNC controls allow you to simulate the program. This is useful for two reasons - it will let you know of errors in the program and give you an estimate of cycle time.

Compare the part you are cutting with a similar operation. If the new part has more complicated cuts, you can assume it will take longer than the cycle of the original part. You also can look at the print and the final sizes to estimate cycle times. If there is a high amount of roughing, it may take longer since roughing passes are usually about half as fast as finishing cuts.

Look at the amount of tool changes in the program. This will affect the time of the cycle. If there are 10 or more tool changes, the cycle will be longer than if it only uses one tool. It takes time for the machine to put one tool back in the turret and grab another.

Use the feed rates and the number of passes in the program to calculate the time it will take. If the roughing pass is running at 2 inches per minute and the part is 6 inches in size, the section will take 12 minutes. Estimate the other passes, including the finishing cuts. Add that and estimate about 30 seconds per tool change to get an estimate of total time.


Christian Mullen is a graduate from the University of Central Florida with a bachelor's degree in finance. He has written content articles online since 2009, specializing in financial topics. A professional musician, Mullen also has expert knowledge of the music industry and all of its facets.

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