In modern manufacturing, numerical control machine tools (CNC) are widely used in various metal processing fields. The processing efficiency and part quality are largely dependent on the selection of cutting parameters. Rational selection of cutting parameters can not only improve production efficiency and extend tool life but also ensure processing accuracy and surface quality. Therefore, mastering the method of selecting cutting parameters for numerical control machine tools is crucial.



I. Basic Concepts of the Three Elements of Cutting



Generally, cutting parameters mainly include three basic elements: cutting speed (Vc), feed rate (f), and cutting depth (ap). These three elements together determine the cutting efficiency and tool load during the processing process.



1. Cutting Speed (Vc): It is the linear velocity of a point on the main cutting edge of the tool relative to the workpiece surface, usually measured in m/min. It directly affects tool wear and processing efficiency.

2. Feed Rate (f): It refers to the distance moved by the tool per revolution or per tooth, in units of mm/r or mm/z. The feed rate affects surface roughness and cutting force.

3. Cutting Depth (ap): It refers to the depth of the tool entering the workpiece during each cutting operation, in units of mm. It determines the amount of material removed per operation.



II. Factors Affecting the Selection of Cutting Parameters



1. Workpiece Material Characteristics

The hardness, strength, and thermal conductivity of different materials (such as carbon steel, alloy steel, cast iron, stainless steel, and aluminum alloys, etc.) are different, and the requirements for cutting speed and feed rate are also different. For example, high-hardness materials require lower cutting speeds, while aluminum alloys allow for higher cutting speeds.



2. Tool material and coating

Common tool materials include high-speed steel, hard alloy, ceramic, cubic boron nitride (CBN), and diamond. Different materials of tools have different thermal resistance, wear resistance, and strength, so the maximum cutting speed and feed rate allowed are also different. For example, hard alloy tools are more suitable for higher cutting speeds than high-speed steel tools.



3. Machine tool performance

The main spindle power, rigidity, and stability of the machine tool determine the maximum cutting force and speed range that can be withstand during the cutting process. When selecting cutting parameters, it is necessary to consider the actual capabilities of the machine tool to avoid overloading or vibration.



4. Processing type and requirements

Rough processing usually aims for high material removal rate, choosing large cutting depth and large feed; while finishing processing pays more attention to surface quality and dimensional accuracy, so higher cutting speed and smaller feed rate should be chosen.



5. Cooling and lubrication conditions

Good cooling can effectively reduce cutting temperature, reduce tool wear, and improve processing quality. Under wet cutting conditions, the cutting speed and feed rate can be appropriately increased.



Three, Methods for selecting cutting parameters



Generally speaking, the following steps can be taken to reasonably select cutting parameters:



1. Refer to the cutting parameter manual or the recommended values by the tool manufacturer: This is the most commonly used method, choosing initial parameters based on material, tool type, and processing type.



2. Calculate according to the empirical formula:

- Cutting speed Vc = π × D × n / 1000 (where D is the workpiece or tool diameter, and n is the spindle speed)

- Spindle speed n = 1000 × Vc / (π × D)



3. Conduct trial cutting verification: According to the initially selected parameters, conduct trial cutting, observe the cutting state, tool wear, surface roughness, and dimensional accuracy, and gradually optimize the parameters.



4. Use CAM software for auxiliary setting: Modern CNC programming software such as Mastercam, SolidCAM, etc., have built-in cutting parameter databases that can automatically recommend reasonable cutting conditions.



Four, Precautions



- Do not blindly pursue high efficiency while neglecting tool life and processing quality.

- Avoid excessively large cutting parameters causing overloading of the machine tool or tool breakage.

- In multi-axis linkage or complex path processing, it is necessary to appropriately reduce the feed rate to prevent the machine tool from lagging in response.

- Continuously adjust parameters according to actual processing feedback to achieve dynamic optimization.



Five, Conclusion



The efficient operation of CNC machine tools is inseparable from the reasonable selection of cutting parameters. This is not only a technique but also an accumulation of experience. Operators should, on the basis of mastering theoretical knowledge, combine practical experience, and flexibly respond to different processing conditions to achieve the goal of high efficiency, high quality, and low cost processing. With the development of intelligent manufacturing and automation, the selection of cutting parameters in the future will be more dependent on data analysis and artificial intelligence-assisted decision-making, bringing higher accuracy and efficiency to the manufacturing industry.