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Quality Inspection of CNC Machining: 6 Most Important Aspects, by Vincent Hua

Quality control is essential in all industries, whether for parts, processes, products, equipment, or machines. Manufacturers are increasingly choosing CNC machining over conventional machining due to the numerous benefits offered, including- higher productivity and better process efficiency. But still, quality inspections remain a critical aspect of the manufacturing process. Quality control and inspections need to be performed at various stages of the machining process.

Additionally, quality assurance, which is distinct from quality control, is another crucial element of the manufacturing process. It requires the manufacturer to establish quality inspection procedures to be performed at regular intervals by authorized personnel - often CNC operators. It also requires a way for them to report inspection results using appropriate supporting documentation. So, quality assurance is the establishment of protocols and documents, whereas quality control is the application of the same on a regular or as-needed basis.

Here we talk about the significance of such quality inspections and the procedures utilized for CNC machining.

3 Modes of Quality Inspection for CNC Machining

1. Test for Machine Tool Accuracy

Check the machine tool's calibration and motion accuracy in this phase. Other aspects to consider are the spindle orientation, bracket, axis, etc. All physical components must be in proper relationship with one another. The column of a vertical machining center, for instance, must be perpendicular to its bed. Also, it's crucial to examine the linear axis.

2. Part or Product Assessment

Check the part's dimensions and positioning in this phase. It encompasses inspecting variables like orientation, surface finish, and contour. Also, check geometric and dimensional tolerances based on the specifications or purposes.

3. Process Control and Monitoring

Monitor the procedures at each level to prevent process-related inefficiencies, which may result in faulty, malfunctioning products or unwanted production bottlenecks. The product life cycle is divided into stages, beginning with conception. The designing, feasibility analysis, evaluation, prototype manufacturing phase, testing, bulk production, etc., follow. All tiers are involved in the quality inspection here.

Vital Parameters to Check During CNC Machining Quality Inspection

The objective of rapid prototyping must be accomplished when using a CNC machine to make a specific component. We need to check that the system is competent in generating the desired products and prototypes. When examining CNC machines for performance, reliability & quality, consider the following metrics:

● Strive for precise geometric and dimensional tolerances and ensure that the machines can achieve the mandated accuracy levels while leaving a minimal margin of error.

● Inspect the CNC machine's spindles.

● Verify that the devices are precisely calibrated. Else, their accuracy will deteriorate with time.

● Keep track of the outcomes of the inspection for reference in the future.

● To achieve credibility, consider ISO certification levels.

● If the intention is to outsource this position, ensure that the service suppliers are reliable and create a consistent communication channel.

● If someone is renting or buying this equipment for their business, make sure to evaluate all of the characteristics and get a warranty.

Top 6 Ways to Conduct Quality Control Inspection for CNC Machining

1. Effective Communication

Prompt communication with clients is essential, either throughout the manufacturing process or after shipping prototypes, because buyers and consumers have specific requirements for the product's characteristics and functionality.

2. Understanding the Product’s Design

The engineer must thoroughly evaluate the design of the finalized product's CAD model, comprehend the client's product specs and demands, and double-check every aspect before manufacturing. We should process the parts using the most cost-effective approach, regulate the variables in the complete CNC machining operation, and verify that the requirements are fulfilled.

3. Service and Product

Designs and standards, production routers, procurement paperwork, and inspection & testing protocols specify the monitoring and testing procedures for all precision products.

4. Purchase Product Verification

The receiving inspector visually inspects all procured merchandise. Technical quality control (QC) examinations are also performed on authorized products.

5. Inspection of the Process

Process inspection takes the shape of first product inspection and operator examination to ensure quality and timely delivery of finished orders.

6. Final Inspection

CNC machined products get subjected to a final quality control check. Firstly, it is verified that all stated and ongoing inspections got accomplished. The subsequent inspections and testing are then performed to conclude the evidence of product compliance. All inspection and testing findings need to be documented, and only products that have cleared the final inspection procedure get packaged and dispatched.

Also, it's critical to understand that the type of CNC machining equipment used to make prototypes and manufacturing parts has an influential impact on the quality of the parts produced. For instance, a 4-axis CNC vertical milling machine is typically more advanced than a 2 or 3-axis CNC machine. It provides improved dimensional accuracy and surface finish and can create complicated contours and shapes.


Quality inspection is critical in the CNC machining processes to verify that the manufactured products comply with the requirements and standards of industries, enterprises, and clients. Furthermore, rigorous quality control inspection of CNC equipment will prevent product defects, control the risks, assure supreme performance, dimensional accuracy, and quality, conserve resources, keep costs down, and enhance effectiveness. It benefits both producers and end-consumers.

About the Author:

Vincent Hua

Vincent Hua is the Marketing Manager at TSINFA. He is passionate about helping people understand high-end and complex manufacturing processes. Besides writing and contributing his insights, Vincent is very keen on technological innovation that helps build highly precise and stable CNC Machinery.

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Awesome post! Very informative

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