Tool selection and cutting amount determination

The selection of cutting tools and the determination of cutting parameters are important contents in the CNC machining process. It not only affects the machining efficiency of CNC machine tools, but also directly affects the machining quality. The development of CAD/CAM technology makes it possible to directly use CAD design data in CNC machining, especially the connection between a microcomputer and a CNC machine tool, so that the entire process of design, process planning and programming is completed on the computer, generally without output Special process documents.

Nowadays, many CAD/CAM software packages provide automatic programming functions. These softwares generally prompt the relevant issues of process planning in the programming interface, such as tool selection, machining path planning, cutting amount setting, etc. The programmer only needs to set the relevant The parameters can be automatically generated and transferred to the CNC machine tool for processing. Therefore, the selection of tools and the determination of cutting parameters in CNC machining are completed in the state of human-computer interaction, which is in sharp contrast with ordinary machine tool processing. At the same time, programmers must master the basic principles of tool selection and cutting parameters. Fully consider the characteristics of CNC machining when programming. This article discusses the tool selection and cutting parameters that must be faced in NC programming, gives some principles and suggestions, and discusses the issues that should be paid attention to.

1. Types and characteristics of commonly used tools for CNC machining

CNC machining tools must adapt to the high-speed, high-efficiency and high degree of automation characteristics of CNC machine tools. Generally, they should include general-purpose tools, general-purpose connection tool holders and a small number of special-purpose tool holders. The tool holder must be connected to the tool and mounted on the power head of the machine tool, so it has gradually been standardized and serialized. There are many ways to classify CNC tools. According to the tool structure, it can be divided into: ①Integral type; ②Inlaid type, using welding or machine clamp connection, machine clamp type can be divided into two types: non-indexable and indexable; ③Special types, such as composite tools, reduce Vibrating knives, etc. According to the materials used to manufacture the tools, it can be divided into: ① high-speed steel tools; ② carbide tools; ③ diamond tools; ④ tools of other materials, such as cubic boron nitride tools, ceramic tools, etc. From the cutting process, it can be divided into: ① turning tools, including outer circle, inner hole, thread, cutting tools, etc.; ② drilling tools, including drills, reamers, taps, etc.; ③ boring tools; ④ milling tools, etc. . In order to meet the requirements of CNC machine tools for tool durability, stability, easy adjustment, and exchangeability, in recent years, machine-clamped indexable tools have been widely used, reaching 30% to 40% of the entire CNC tools. Metal removal The amount accounts for 80% to 90% of the total.

Compared with the tools used on ordinary machine tools, CNC tools have many different requirements, mainly with the following characteristics:

⑴ Good rigidity (especially rough machining tools), high precision, vibration resistance and small thermal deformation;

⑵Good interchangeability, convenient for quick tool change;

⑶ High life, stable and reliable cutting performance;

⑷The size of the tool is easy to adjust to reduce the tool change adjustment time;

⑸ The tool should be able to reliably break or roll chips to facilitate the removal of chips;

⑹Serialization and standardization to facilitate programming and tool management.

Second, the choice of CNC machining tools

The selection of the tool is carried out under the man-machine interaction state of CNC programming. The correct selection of tools and tool holders should be based on the processing capacity of the machine tool, the properties of the workpiece material, the processing procedure, the cutting amount and other related factors. The general principle of tool selection is: convenient installation and adjustment, good rigidity, high durability and precision. On the premise of meeting the processing requirements, try to choose a shorter tool holder to improve the rigidity of tool processing.

When selecting a tool, the size of the tool must be adapted to the surface size of the workpiece. In production, end mills are often used to process the peripheral contours of flat parts; when milling planes, you should choose carbide blade milling cutters; when processing bosses and grooves, choose high-speed steel end mills; processing rough surfaces or rough machining When drilling holes, you can choose corn milling cutters with carbide inserts; for the processing of some three-dimensional profiles and variable bevel contours, ball end milling cutters, ring milling cutters, tapered milling cutters and disk milling cutters are often used.