Machining Methods

Selection Of Tools Suitable For CNC Machining

Selection Of Tools Suitable For CNC MachiningSelection Of Tools Suitable For CNC Machining

It is important to choose the right CNC tool when programming. The general requirements for CNC tools are easy installation and adjustment, excellent rigidity, high accuracy, and excellent durability. Based on this, a comprehensive consideration of the cutting performance of the workpiece material, the processing power of the machine tool, and the types of CNC machining processes. Cutting quantities and many factors related to the working range of machine tools and numerical controls

1. Factors that influence the choice of CNC tools

Key factors are considered when choosing a tool type and specification.

(1) Nature of production

The production characteristic here is the batch size of parts that mainly considers the influence of machining costs on tool selection. For example, the use of special tools in mass production may be cost effective. For small lot production, the selection of standard tools is more suitable.

(2) Model

Complete CNC machine tool used in this step, tool type (drill, lathe or milling tool) selection of effect. Highly productive tools such as high speed cutting tools and large feed turning tools are acceptable provided that the workpiece system and tool system are rigid.

3) CNC machining plan

Different types of tools can be used in different CNC machining solutions. For example, hole machining can be done with a drill and reamer, or with a drill and boring tool.

(4) Work size and shape

The size and shape of the workpiece also influences the choice of tool type and specifications. For example, special surfaces are machined with special tools.

(5) Processed surface roughness

The surface roughness of the machined surface affects the structural shape of the tool and the amount of cutting. For example, rough tooth milling cutters can be used for rough machining, but fine milling cutters are best for finish milling.

(6) Machining accuracy

Machining accuracy affects the type and shape of finishing tools. For example, the final machining of a hole can be processed by drilling, reaming, or drilling, depending on the accuracy of the hole.

(7) Work material

The geographic material will determine the choice of tool material and the geometry of the cut part. Tool material is related to the machining accuracy of the workpiece and the hardness of the material.

2. CNC tool performance requirements

CNC machine tools are characterized by high machining accuracy, high machining efficiency, centralized machining process and low component clamping time, which imposes higher requirements on the CNC tools used.

In terms of tool performance, CNC tools must be higher than those used in regular machine tools.
When choosing a CNC tool, the first choice is to use a standard tool first. You can use a variety of high-performance composite tools and special special tools as needed. When choosing a standard CNC tool, it should be combined with the actual situation as much as possible, choosing various advanced tools such as indexable tools, carbide tools, ceramic tools.

When choosing a CNC machine tool, you should also consider the following:

  • (1) CNC tool types:specifications and accuracy levels must be able to meet machining requirements, and the tool material must be compatible with the workpiece material.
  • (2) Good cutting performance:To accommodate rough machining of difficult-to-machine materials and the large backing and high feed rates of tools during machining, the tool must be able to withstand high-speed and strong cutting. At the same time, batches of the same tool must be stable in terms of cutting performance and tool life in order to achieve tool change according to tool life or to manage tool life with a CNC system.
  • (3) High accuracy:To meet the high precision of CNC machining and the requirements of automatic tool change, the tools must be high precision. For example, integrated end mills have radial dimensional accuracy up to 0.005 mm.
  • (4) High reliability:You need to prevent accidental damage to the tool and potential defects in CNC machining. This affects the smooth progress of processing. The tool and the accessories associated with it must have excellent reliability and strong adaptability.
  • (5) High durability:Whether roughing or finishing, CNC machine tools should be more durable than those used in traditional machine tools. To minimize the number of replacement or grinding tools and tool settings, thereby improving the processing efficiency and quality assurance process of CNC machine tools.
  • (6) Good tip crushing tip removal performance:In CNC machining, chips and chips are not processed manually as in ordinary machine tools. Chips wrap around tools and workpieces, tend to damage tools, scratch machined surfaces, and can even cause injuries and equipment accidents. Tools are required to have better chip removal and chip removal performance as they affect the quality of the machine and the safe operation of the machine tool.

3. How to select a tool

Tool selection is one of the important contents in the CNC machining process, which not only affects the machining efficiency of machine tools, but also directly affects the machining quality of parts. This is because the spindle speed and range of CNC machine tools are much higher than those of ordinary machine tools, and the spindle output is large. Therefore, compared to traditional machining methods, higher requirements are placed on CNC machining tools, including high precision, high strength, good stiffness, high durability, stable size, and convenient installation and adjustment. .. This requires a reasonable structure of the tool, standardization of geometric parameters, and serialization. CNC tools are one of the prerequisites for improving machining efficiency. The choice depends on the shape of the part being machined, the condition of the material, the stiffness of the fixture, and the tool selected for the machine.

The following points should be considered:

(1) Select a tool according to the cutting performance of the part material.

For turning and milling high-strength steel, titanium alloys and stainless steel parts, we recommend choosing a wear-resistant throw-away carbide tool.

(2) Select a tool according to the machining stage of the part.

That is, the roughing step is primarily to remove margins, and you should choose a tool that is stiffer and less accurate. During the semi-finishing and finishing stages, durable and precision tools must be selected to ensure the machining accuracy and product quality of the parts. The tools used in the roughing stage have the lowest precision and the tools used in the finishing stage have the highest precision. If you select the same tool for roughing and finishing, we recommend that you select the tool excluded from finishing for roughing. Since most finish tool wear conditions are slight wear on the blades, the coating wears and repairs light, and continuous use affects the finish’s processing quality, but with less impact on roughing.

(3) Tool and shape parameters are selected according to the characteristics of the machining area.

If the structure of the part allows it, use a tool with a large diameter and a small aspect ratio. The central cutting edge of thin, ultra-thin parts must have a centripetal angle sufficient to reduce the cutting forces of tools and cutting parts. When machining parts such as aluminum and copper, you should choose an end mill with a slightly larger front corner.

When selecting a tool, match the size of the tool to the surface size of the workpiece to be machined. In manufacturing, the outer contours of flat parts are often machined by end mills. When milling flat surfaces, you must select a cemented carbide insert mill. Choose high speed steel end mills when machining bosses and grooves. When machining the surface of a blank or roughening holes, you can choose a cone milling cutter with a carbide insert. Ball end mill cutters, ring milling cutters, conical milling cutters and disc milling cutters are often used for machining some 3D and variable angle contours.

In free-form surface machining, the cutting speed at the tip of the ball-end tool is zero. Ball end mills are suitable for finishing curved surfaces because the cutting pitch is generally small to ensure machining accuracy.
End mills are far superior to ball end mills in terms of both surface quality and processing efficiency. Therefore, if you need to prevent parts from being cut when roughing or semi-finishing the surface, choose an end mill. In addition, the durability and accuracy of the tool is highly dependent on the price of the tool and should be noted.

In most cases, choosing the right tool will increase the cost of the tool, but it will improve processing quality and efficiency, which can significantly reduce the overall processing cost.

In machining centers, all tools are pre-installed in the tool magazine and the corresponding tool changes are performed by tool selection and tool change commands in the NC program. Standard shanks for machine tool system specifications must be selected so that the CNC machine tool can be quickly and accurately mounted on the machine tool spindle or returned to the tool magazine. The programmer understands the structural size, adjustment method, and adjustment range of the tool holder used in the machine tool, the radial and axial dimensions of the tool are determined during programming, and the tools are properly ordered.

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