The selection of cutting tools is one of the important contents in CNC machining technology, which not only affects the machining efficiency of the machine tool, but also directly affects the machining quality of the parts.
Due to the fact that the spindle speed and range of CNC machine tools are much higher than ordinary machine tools, and the spindle output power is larger, compared to traditional machining methods, higher requirements are put forward for CNC machining tools, including high precision, high strength, good rigidity, high durability, stable size, and convenient installation and adjustment. This requires a reasonable structure of the cutting tool, standardization of geometric parameters, and serialization. CNC cutting tools are one of the prerequisites for improving machining efficiency, and their selection depends on the geometric shape of the processed parts, material status, fixture, and the rigidity of the tool used in the machine tool.
The selection of cutting tools for CNC machine tools should consider the following aspects:
(1) Select the cutting tool based on the cutting performance of the part material. For turning or milling high-strength steel, titanium alloy, and stainless steel parts, it is recommended to choose indexable hard metal cutting tools with good wear resistance.
(2) Select the cutting tool based on the processing stage of the part. In the rough machining stage, the main focus is on removing excess, and tools with good rigidity and low accuracy should be selected. In the semi precision and precision machining stages, tools with high durability and accuracy should be selected to ensure the machining accuracy and product quality of the parts. The precision of the tools used in the rough machining stage is low, while the precision of the tools used in the precision machining stage is high. If the same tool is selected for rough and precision machining, it is recommended to use the tool that has been eliminated from precision machining during rough machining, because the wear of the eliminated tool in precision machining is mostly slight wear on the edge, and the coating is worn and polished. Continued use will affect the machining quality of precision machining, but the impact on rough machining is relatively small.
(3) Select tools and geometric parameters based on the characteristics of the processing area. When the structure of the parts allows, tools with large diameter and small aspect ratio should be selected; The end edge of the over center milling cutter for cutting thin-walled and ultra-thin wall parts should have sufficient centripetal angle to reduce the cutting force on the tool and cutting area. When processing soft material parts such as aluminum and copper, a slightly larger rake angle end milling cutter should be selected, and the number of teeth should not exceed 4.
When selecting a tool, it is important to ensure that the size of the tool matches the surface size of the workpiece being processed. In production, the processing of the contour around flat parts often uses end mills; When milling flat surfaces, a hard alloy blade milling cutter should be selected; When processing bosses and grooves, choose high-speed steel end mills; When processing rough surfaces or rough holes, corn milling cutters with carbide blades can be selected; Ball end milling cutters, circular milling cutters, conical milling cutters, and disc milling cutters are often used for the processing of some three-dimensional surfaces and variable bevel contour shapes.
When machining free form surfaces, due to the zero cutting speed at the end of the ball end tool, in order to ensure machining accuracy, the cutting line spacing is generally very small. Therefore, ball end milling cutters are suitable for precision machining of surfaces. And the end milling cutter is far superior to the ball end milling cutter in both surface processing quality and processing efficiency. Therefore, while ensuring that the parts are not cut, it is recommended to choose the end milling cutter as much as possible when rough machining and semi precision machining curved surfaces. In addition, the durability and accuracy of cutting tools are greatly related to tool prices. It must be noted that in most cases, selecting a good tool increases tool costs, but the resulting improvement in processing quality and efficiency can greatly reduce the entire processing cost.
On the machining center, all cutting tools are pre installed in the tool library, and corresponding tool change actions are carried out through the tool selection and tool change instructions of the CNC program. It is necessary to select corresponding standard tool handles that are suitable for the specifications of the machine tool system, so that CNC machining tools can be quickly and accurately installed on the machine tool spindle or returned to the tool library. Programmers should be able to understand the structural dimensions, adjustment methods, and adjustment range of the tool handle used in the machine tool, in order to ensure that the radial and axial dimensions of the tools are determined during programming and the arrangement order of the tools is reasonably arranged.
Cutting tools are only one of the important contents in the CNC machining process. In addition, CNC machining also involves a series of links such as pattern analysis, process division, machining equipment, work cards and measuring tools, fixtures, and the development of optimized machining programs. How to solve quality problems with processed products? The problem may arise at any intermediate stage.
