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Quality Control Processes in CNC Machining

Computerized systems and intelligent software are commonplace in CNC machining for operations including programming, loading, producing, and monitoring. This allows for standard tolerances at ±0.005” for metal and ±0.010” for plastics. Some gauges, valves, and other parts must be even more precise tolerances to suit industry needs in the automotive, appliance, medical, and aerospace industries. Are the quality control processes in CNC machining able to be completely computer-driven? We look at some of the processes needed in a high-performance machine shop with a shared responsibility between man and machine for the best quality control.

The first step in quality control is becoming ISO certified, and maintaining or upgrading. ISO 9000 standards ensure quality staff training, and business standards and practices. Often ISO certification results in cost savings due to new efficiencies. This is a great marketing tool to position your company well in the marketplace.


Quality begins with maintenance. Machine downtime is the biggest cost to any manufacturing facility. But scheduled downtime is an investment well worth it. High-performance equipment can provide finishes and tolerances that vary greatly depending on speed, but also heat that causes friction and warp. Keeping machines clear of dirt and debris between jobs is understood. Additional scheduled cleaning of tools and clamps, checking tool and machine wear, controlling airflow, coolant, and lubricants is regular maintenance that will also add to quality production.

Maintenance should also include calibration. Vibration during regular operation, and general weight and jarring of heavy raw material feeds can all affect the calibration of chucks and spindles. Tools will not perform at their peak if the clamping systems are not aligning them in the right position. Re-calibration on a regular schedule allows better quality control.


Processing should always begin with simulation. Using simulation allows programmers to follow the toolpath to identify any potential errors or even better ways to approach fabrication. Once production begins, inspection should occur during the operation, with final measurements and finish inspection at completion.

Adding advanced technologies can improve performance during the operation. Sensors and software can provide constant feedback of information on the machine’s performance. As a bonus, this results in higher run rates and longer tool life. And this data can be used to prevent maintenance problems during production as well as set maintenance scheduling.


People are where the mechanisms and programs translate to the customer. Starting with the initial part of the design or interpreting your client’s design, communication is key to determine the desired outcome. Specific tolerances, if needed, finish, and materials should all be discussed and agreed upon before manufacturing begins. With Covid restrictions, video calls may be what is needed to provide peace of mind to the client through mockups or simulations.

Current trends are resulting in a gap in skilled machinists and operators. A new Apprenticeship Achievement Incentive program was announced by Ontario’s Ministry of Labour, Training and Skills Development this year which can help encourage new hires. 

Skilled machinists and programmers are necessary to translate ideas into geometric, and then, computer design. Quality control here pays close attention to design details and efficient design to provide the best product for the least cost to the client. Read our blog post about 4 Steps for Every Quality Machining Process

Once on the shop floor, the quality inspection may include intelligent software but, most often, relies on the intelligence and experience of machine operators. Communication from the design team is critical for the operator to understand tolerance and finish requirements.

And, of course, maintenance also involves a human intervention to clean, repair, and monitor equipment and tools. Maintenance prevents chatter, heat, debris, and a variety of factors from affecting quality production. This is important to both machine and tool life as well as operator safety, in addition to quality control.

Taking steps to ensure quality control processes in CNC machining produces efficiencies as well as quality production. Running a clean shop with skilled staff and effective processes results in a benefit to the client with superior products. The advantage for the manufacturer includes a good reputation, hiring and maintaining skilled staff, and cost savings through those efficiencies.

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