The tool selection and cutting amount determination in […]
The tool selection and cutting amount determination in CNC machining are done in the state of human-machine interaction, which is in sharp contrast to ordinary machine tool processing, and also requires programmers to master the basic principles of tool selection and cutting amount determination. Fully considering the characteristics of CNC machining, the cutting tool and cutting amount can be selected correctly. CNC machining tools must be adapted 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 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 been gradually standardized and serialized. There are many ways to classify CNC tools.
First, the structure of CNC machine tool
2. Mosaic type, using welding or machine clamp connection, machine clamp type can be divided into non-indexable and indexable;
3. Special types, such as compound cutters, shock-absorbing cutters, etc.
Second, the materials used to make the tool
1. High-speed steel cutter;
2. Carbide cutting tools;
3. Diamond cutter;
4. Tools of other materials, such as cubic boron nitride tools, ceramic tools, etc.
Third, the classification of cutting technology
1. Turning tools, divided into outer circle, inner hole, thread, cutting tool, etc .;
2. Drilling tools, including drill bits, reamers, taps, etc .;
3. Boring tool;
4. Milling tools, etc.
In order to meet the requirements of CNC machine tools for tool durability, stability, easy adjustment, and exchangeability, machine-clamped indexable tools have been widely used in recent years, and the number has reached 30% to 40% of the entire CNC tool. The volume accounts for 80% to 90% of the total.
Fourth, the characteristics of CNC tools
1.Good rigidity (especially rough machining tools), high precision, low vibration resistance and 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 time for tool change adjustment;
5. The tool should be able to break or curl chips reliably to facilitate the removal of chips;
6. Serialization and standardization to facilitate programming and tool management.
Fifth, the choice of tools
The selection of cutting tools is carried out in the state of human-computer interaction of NC programming. The tools and tool holders should be correctly selected according to the processing capacity of the machine tool, the performance of the workpiece material, the processing procedure, the cutting amount and other related factors. The general principle of tool selection is: easy installation and adjustment, good rigidity, high durability and precision. Under the premise of meeting the processing requirements, try to choose a shorter tool holder to improve the rigidity of the tool processing. When selecting a tool, the size of the tool should 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 flat parts; when milling planes, carbide insert mills should be selected; when machining 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 varying bevel contour shapes, ball head milling cutters, ring milling cutters, cone milling cutters and disc milling cutters are often used.
In the processing of freeform surfaces (molds), the cutting speed of the end of the ball head tool is zero. Therefore, in order to ensure the machining accuracy, the cutting line spacing is generally close to the tip, so the ball head is often used for the finishing of the curved surface. The flat-end cutter is superior to the ball-end cutter in terms of surface processing quality and cutting efficiency. Therefore, as long as the surface is not cut, whether it is rough or precision machining of the curved surface, the flat-head cutter 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, although the choice of a good tool increases the cost of the tool, the resulting processing quality and efficiency increase , You can greatly reduce the entire processing cost.
On the machining center, various tools are installed on the tool magazine, and the tool selection and tool change are performed at any time according to the program. Therefore, a standard tool holder must be used in order to quickly and accurately install the standard tool for drilling, boring, expanding, milling and other processes on the machine tool spindle or tool magazine. The programmer should understand the structure size, adjustment method and adjustment range of the tool holder used on the machine tool, so as to determine the radial and axial dimensions of the tool during programming.