Tool selection is one of the key elements in CNC machining technology, which not only affects the machining efficiency of the machine tool, but also has a direct impact on the processing quality of the parts. For CNC tools, the overall requirements are convenient installation and adjustment, good rigidity, high precision, and strong durability. On this basis, it is also necessary to comprehensively consider the cutting characteristics of the workpiece material, the processing capacity of the machine tool, the type of CNC machining process, the amount of cutting, and many factors related to the working range of the machine tool and the CNC device.

          Factors affecting CNC tool selection

When choosing the type and specification of the tool, it is important to consider the influence of the following factors:

1.Production nature：The nature of production here refers to the batch size of the part, mainly from the perspective of machining costs, considering the impact on tool selection. For example, it may be more cost-effective to use special tools for mass production; For single piece or small batch production, it is more appropriate to choose standard tools.

2.Machine type：The CNC machine used to complete the process can have an impact on the choice of tool type, such as drilling, turning or milling. On the premise of ensuring good rigidity of the workpiece system and tool system, high-productivity tools such as high-speed cutting turning tools and high-feed turning tools can be used.

3.CNC machining solution：Different types of tools can be selected for different CNC machining schemes. For example, holes can be machined with drills and reaming drills, as well as with drills and boring tools. 

1. The size and shape of the workpiece

The size and shape characteristics of the workpiece will also affect the choice of tool type and specification. For example, special tools are required for special surfaces.

2. Processing surface roughness

The roughness of the machining surface affects the structural shape of the tool and the amount of cutting. Taking blank rough milling as an example, coarse tooth milling cutters can be selected; And when performing finishing operations, it is best to use fine-tooth milling cutters.

3. Processing accuracy

Machining accuracy can affect the type of finishing tool and the shape of the structure. For example, in the final processing of the hole, according to the accuracy requirements of the hole, tools such as drills, reaming drills, reamers or boring cutters can be selected for processing.

4. Workpiece material

The workpiece material determines the choice of tool material and the geometric parameters of the cutting part. The tool material is closely related to the machining accuracy of the workpiece, the hardness of the material and other factors.

Performance requirements of CNC tools

In view of the characteristics of CNC machine tools such as high machining accuracy, high processing efficiency, centralized processing processes and small number of parts clamping, more stringent requirements are put forward for the CNC tools used. From the perspective of tool performance, CNC tools should be better than the tools used in ordinary machine tools. When selecting CNC tools, standard tools should be given priority first, and all kinds of efficient compound tools and special special tools should be selected only when necessary. When choosing standard CNC tools, it is necessary to combine the actual situation and choose a variety of advanced tools as much as possible, such as indexable tools, integral carbide tools, ceramic tools, etc. When choosing CNC machine tool machining tools, the following aspects need to be considered:

1.The type, specification and accuracy level of the CNC tool should be able to meet the processing needs, and the tool material should be suitable for the workpiece material.

2. Good cutting performance. In order to enable the tool to be large in rough machining or machining difficult-to-machine materialsThe amount of knife eating on the backand high feed rate, the tool should have the ability to withstand high-speed cutting and powerful cutting. At the same time, the same batch of tools must be stable in terms of cutting performance and tool life, so as to realize tool replacement according to tool life or manage tool life by CNC system.

1、High precision

In order to meet the requirements of CNC machining high precision and automatic tool change, the tool needs to have high precision. For example, some integral end mills have a high standard of radial dimensional accuracy.

2. High reliability

In order to ensure the smooth CNC machining process and avoid accidental damage to the tool and potential defects affecting the machining, it is required that the tool and its combination accessories must have good reliability and strong adaptability.

3. High durability

The tools used in CNC machining, whether rough or finished, should have higher durability than the tools used in ordinary machine tool machining. This can minimize the number of times of replacing or regrinding tools and tool setting, thereby improving the processing efficiency of CNC machine tools and ensuring the quality of machining.

4. Good chip breaking and chip removal performance

In CNC machining, chip breaking and chip removal cannot be handled manually in time like ordinary machine tool processing. If chips are wrapped around the tool and workpiece, it will damage the tool, scratch the machined surface of the workpiece, and may even cause injury and equipment accidents, affecting the machining quality and the safe operation of the machine tool. Therefore, the tool is required to have excellent chip breaking and chip removal performance.

Method of selecting knives

Because the spindle speed and range of CNC machine tools far exceed those of ordinary machine tools, and the spindle output power is larger, compared with traditional machining methods, higher requirements are put forward for CNC machining tools, covering high precision, high strength, good rigidity, high durability, as well as stable dimensions, easy installation and adjustment. This prompts the tool to have a reasonable structure, standardized geometric parameters and serialization. CNC tools are one of the key factors to improve machining efficiency, and their selection depends on the geometry of the part being machined, the state of the material, the fixture, and the rigidity of the tool selected by the machine tool. The following aspects should be considered:

1. According to the material of the partCutting performance of tool selection:

For example, when machining or milling high-strength steel, titanium alloy, and stainless steel parts, it is recommended to use indexable carbide tools with better wear resistance.

2、Tool selection according to the machining stage of the part:

The roughing stage is mainly to remove the allowance, and the tool with good rigidity and low precision should be selected. The semi-finishing and finishing stages are mainly to ensure the processing accuracy and product quality of parts, and tools with high durability and high precision should be selected. Typically, the tools used in the roughing stage have the lowest accuracy, while those used in the finishing stage have the highest accuracy. If the same tool is used for roughing and finishing, it is recommended to use the tool eliminated by finishing during roughing, because most of the wear of the tool eliminated by finishing is slightly worn on the edge, and the coating is worn and polished.

3) Select the tool and determine the geometric parameters according to the characteristics of the machining area. Under the premise that the part structure allows, a tool with a large diameter and a small length-to-diameter ratio should be selected; When cutting thin-walled, ultra-thin pendulum parts, the end edge of the over-center mill needs to have sufficient centripetal angle to reduce the cutting force between the tool and the cutting part. When processing parts of softer materials such as aluminum and copper, choose an end mill with a slightly larger rake angle, and the number of teeth should not exceed 4 teeth.