1. Tool selection
Tool selection is one of the important aspects of the CNC machining process. It not only affects the processing efficiency of the machine tool, but also directly affects the processing quality. When programming, the selection of tools usually takes into account factors such as the machine tool's processing capabilities, process content, and workpiece material. Compared with traditional machining methods, CNC machining has higher requirements on cutting tools. It not only requires high precision, good rigidity, and high durability, but also requires stable dimensions and easy installation and adjustment. This requires using new high-quality materials to manufacture CNC machining tools and optimizing tool parameters.
When selecting a tool, the size of the tool must be compatible with the surface size and shape of the workpiece being processed. In production, end mills are often used to machine the peripheral contours of flat parts. When milling flat surfaces, carbide blade milling cutters should be used; when processing bosses and grooves, high-speed steel end mills should be used; when processing rough surfaces or rough holes, carbide blade milling cutters can be used. When selecting an end mill for processing, it is recommended to select the relevant parameters of the tool based on empirical data. Ball-end milling cutters are often used for curved surface processing. However, when processing flatter curved surfaces, the tool cuts with the ball-end cutting edge, and the cutting conditions are poor, so a ring cutter should be used. In single-piece or small-batch production, in order to replace multi-coordinate machine tools, drum milling cutters or taper milling cutters are often used to process some variable bevel angle parts on aircraft, plus inlaid disc milling cutters, which are suitable for CNC machining of five-axis machine tools. The efficiency of machining some spherical surfaces is nearly ten times higher than that of ball end milling cutters, and good machining accuracy can be obtained.
On the machining center, various tools are installed in the tool magazine, and the tools can be selected and changed at any time according to the program regulations. Therefore, it is necessary to have a set of connecting rods to connect commonly used tools so that standard tools used in drilling, boring, expanding, reaming, milling and other processes can be quickly and accurately installed on the machine tool spindle or tool magazine. As a programmer, you should understand the structural dimensions, adjustment methods, and adjustment range of the tool holders used on machine tools in order to determine the radial and axial dimensions of the tool during programming. At present, my country's machining centers use the TSG tool system, which has two types of tool shanks: straight shank (three specifications) and tapered shank (four specifications), including 16 types of tools for different purposes.
2. Determination of cutting parameters
The cutting amount includes spindle speed (cutting speed), backcut amount, and feed amount. For different processing methods, different cutting parameters need to be selected and programmed into the program table. The principle of reasonable selection of cutting parameters is that during rough machining, productivity is generally improved, but economy and processing costs must also be considered; semi-finishing and finishing machining should be carried out on the premise of ensuring processing quality, while considering cutting efficiency, economy and processing costs. Processing costs. The specific values should be determined based on the machine tool manual, cutting parameter manual, and experience.
