The basic principle of CNC machine tool selection and cutting amount determination!

Tool selection and cutting amount determination in CNC machining are completed in the state of human-machine 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 amount determination. Taking full account of the characteristics of CNC machining, it is possible to correctly choose the cutting tools and cutting parameters. CNC machining tools must adapt to the characteristics of high-speed, high-efficiency, and high degree of automation of CNC machine tools. Generally, they should include general-purpose tools, general-purpose connection tool holders and a small number of special 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.

1. The structure of CNC machine tools

1. Integral;

2. Inlaid type, welded or machine-clamped connection, machine-clamped type can be divided into two types: non-indexable and indexable;

3. Special types, such as compound cutters, shock-absorbing cutters, etc.

Second, the materials used to make the knives

1. High-speed steel tools;

2. Carbide cutting tools;

3. Diamond tools;

4. Cutting tools of other materials, such as cubic boron nitride cutting tools, ceramic cutting tools, etc.

Three, the classification of cutting technology

1. Turning tools, including outer circle, inner hole, thread, cutting tool, etc.;

2. Drilling tools, including drills, reamers, taps, etc.;

3. Boring tool;

4. Milling tools, etc.

Fourth, in order to meet the requirements of CNC machine tools for durability, stability, easy adjustment, and exchangeability, in recent years, machine-clamped indexable tools have been widely used, and the number has reached 30% to 40% of the entire CNC tools. The amount of metal removal accounts for 80% to 90% of the total.

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

2. Good interchangeability, convenient for quick tool change;

3. High life, stable and reliable cutting performance;

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

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

6. Serialization and standardization to facilitate programming and tool management.

Five, the choice of 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 high 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 to be processed. In production, end mills are often used to process the peripheral contours of plane parts; when milling planes, carbide blade milling cutters should be selected; when processing bosses and grooves, high-speed steel end mills should be selected; rough surface 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 disc milling cutters are often used.

In the free-form surface (mold) processing, since the end cutting speed of the ball-end tool is zero, to ensure the machining accuracy, the cutting line spacing generally adopts the top-end close pitch, so the ball end is often used for the finishing of the curved surface. The flat-end tool is superior to the ball-end tool in terms of surface processing quality and cutting efficiency. Therefore, as long as it is guaranteed not to cut, whether it is roughing or finishing of curved surfaces, flat-end tools should be preferred. In addition, the durability and accuracy of the tool have a great relationship with the price of the tool. It must be noted that in most cases, the selected tool increases the tool cost, but the resulting increase in processing quality and processing efficiency , You can greatly reduce the overall processing cost.

On the machining center, various tools are installed in the tool magazine, and the tool selection and tool change actions are carried out at any time according to the program regulations. Therefore, standard tool holders must be used so that standard tools used in drilling, boring, expanding, milling and other processes can be quickly and accurately installed on the spindle or tool magazine of the machine tool. The programmer should understand the structure size, adjustment method and adjustment range of the tool holder used on the machine tool in order to determine the radial and axial dimensions of the tool during programming.

Six, the arrangement of knives should follow the principles

In the machining process of economical CNC machine tools, since the sharpening, measurement and replacement of tools are mostly performed manually, which takes a long time to assist, it is necessary to arrange the order of the tools in a reasonable manner. Generally, the following principles should be followed:

1. Minimize the number of tools;

2. After a tool is clamped, all processing steps that it can carry out should be completed;

3. The rough and finishing tools should be used separately, even if they are tools of the same size;