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When choosing the type and specification of the tool, the main factors are considered:
(1) Nature of production The nature of production here refers to the batch size of parts, mainly considering the influence on the tool selection from the processing cost. For example, the use of special tools in mass production may be cost-effective, while in single or small batch production, the choice of standard tools is more suitable.
(2) Machine type The effect of the CNC machine used to complete the process on the selected tool type (drill, turning or milling). High productivity tools such as high speed cutting tools and large feed turning tools are allowed under the condition that the workpiece system and the tool system are rigid.
(3) CNC machining scheme Different CNC machining schemes can use different types of tools. For example, the machining of holes can be done with drills and reamers, or with drills and boring tools.
(4) Size and shape of the workpiece The size and shape of the workpiece also affect the choice of tool type and specification. For example, special surfaces should be processed with special tools.
(5) Machining surface roughness The surface roughness of the machining affects the shape and cutting amount of the tool. For example, rough rough milling cutters can be used for rough roughing, and fine-tooth milling cutters are preferred for finishing milling.
(6) Machining accuracy Machining accuracy affects the type and shape of the finishing tool. For example, the final machining of the hole can be processed by drilling, reaming, reaming or boring according to the accuracy of the hole.
(7) Workpiece material The workpiece material will determine the choice of the tool material and the geometry of the cutting part. The tool material is related to the machining accuracy of the workpiece and the material hardness.
2. Understand the performance requirements of CNC tools:
Because CNC machine tools have the characteristics of high machining precision, high machining efficiency, concentrated machining process and few parts clamping times, higher requirements are imposed on the CNC tools used. In terms of tool performance, CNC tools should be higher than those used in ordinary machine tools.
When selecting a CNC tool, the first choice is to use the standard tool first. If necessary, you can use a variety of high-efficiency compound tools and special special tools. When selecting a standard CNC tool, it should be combined with the actual situation, as far as possible to choose a variety of advanced tools, such as indexable tools, solid carbide tools, ceramic tools.
When choosing a CNC machine tool, you should also consider the following aspects:
(1) The type, specification and accuracy level of the CNC tool should be able to meet the machining requirements, and the tool material should be compatible with the workpiece material.
(2) Good cutting performance. In order to adapt to the tool's large backing and high feed rate during roughing or machining of difficult-to-machine materials, the tool should be able to withstand high-speed cutting and powerful cutting. At the same time, the same batch of tools must be stable in terms of cutting performance and tool life in order to achieve tool change according to tool life or to manage tool life by CNC system.
(3) High precision. In order to meet the requirements of high precision and automatic tool change of CNC machining, the tool must have high precision, such as the radial size accuracy of the integral end mill up to 0.005mm.
(4) High reliability. It is necessary to ensure that the tool will not be accidentally damaged and potential defects in the CNC machining, which will affect the smooth progress of the machining. It is required that the tool and the accessories combined with it must have good reliability and strong adaptability.
(5) High durability. CNC machining tools, whether in roughing or finishing, should have higher durability than ordinary machine tools, in order to minimize the number of replacement or grinding tools and tooling, thus improving the machining efficiency of CNC machine tools. And guarantee the quality of processing.
(6) Good chip breaking and chip discharging performance. In CNC machining, chip breaking and chip removal are not handled manually by ordinary machine tools. Chips are easily entangled on tools and workpieces, which can damage the tool and scratch the machined surface, and even cause injury and equipment accidents. Affects the quality of the machine and the safe operation of the machine tool, so the tool is required to have better chip breaking and chip removal performance.
3. Master the selection method of the tool:
The choice of tool is one of the important contents in the CNC machining process, which not only affects the machining efficiency of the machine tool, but also directly affects the machining quality of the part. Because the spindle speed and range of CNC machine tools are much higher than ordinary machine tools, and the spindle output power is large, compared with the traditional machining methods, higher requirements are imposed on CNC machining tools, including high precision, high strength and rigidity. Good, durable, and required dimensional stability, easy installation and adjustment. This requires reasonable structure of the tool, standardization of geometric parameters, and serialization. CNC tooling is one of the prerequisites for improving machining efficiency. Its choice depends on the geometry of the part being machined, the material state, the rigidity of the tool and the tool selected by the machine tool. The following aspects should be considered:
(1) Select the tool according to the cutting performance of the part material. For cars or milled high-strength steels, titanium alloys, and stainless steel parts, it is recommended to select indexable carbide tools with good wear resistance.
(2) Select the tool according to the machining stage of the part. That is, the roughing stage is mainly to remove the margin. The tool with better rigidity and lower precision should be selected. The semi-finishing and finishing stages should be used to ensure the machining accuracy and product quality of the parts. The durability should be high and the precision should be selected. For high tools, the tools used in the roughing phase have the lowest precision and the tools used in the finishing phase have the highest precision. If the same tool is selected for roughing and finishing, it is recommended to use the finishing tool to eliminate the roughing tool, because the tool wear condition of the finishing process is mostly the slight wear of the blade, the coating wear and light, and the use will affect the finishing. Processing quality, but less impact on roughing.
(3) Select the tool and geometry parameters according to the characteristics of the machining area. Large diameter and long diameter ratio tools should be used when the structure of the part is allowed; the end mill edge of the thin-walled and ultra-thin wall parts should have sufficient centripetal Angle to reduce the cutting of the tool and the cutting part. force. When processing parts such as aluminum and copper, you should select an end mill with a slightly larger front corner and the number of teeth should not exceed 4 teeth.
When selecting a tool, the size of the tool should be adapted to the surface size of the workpiece being machined. In the production, the peripheral contour of the plane parts is often processed by an end mill; when milling the plane, the cemented carbide insert milling cutter should be selected; when the bosses and grooves are machined, the high-speed steel end mill is selected; the surface of the blank is machined or roughed. For the hole, the corn milling cutter with the carbide insert can be selected; for the machining of some three-dimensional and variable bevel contours, ball-end milling cutters, ring milling cutters, conical milling cutters and disc milling cutters are often used.
In the free-form surface machining, since the cutting speed of the end of the ball-end tool is zero, in order to ensure the machining accuracy, the cutting pitch is generally small, so the ball-end milling cutter is suitable for the finishing of the curved surface. The end mill is far superior to the ball end mill in both surface quality and machining efficiency. Therefore, when roughing and semi-finishing the surface, try to select the end while ensuring that the part is not cut. Milling cutter. In addition, the durability and accuracy of the tool are highly dependent on the tool price. It must be noted that in most cases, the choice of a good tool increases the tool cost, but the resulting processing quality and processing efficiency increase. , can make the entire processing cost greatly reduced.
In the machining center, all the tools are pre-installed in the tool magazine, and the corresponding tool change is performed by the tool selection and tool change commands of the NC program. The corresponding standard shank for the machine tool system specification must be selected so that the CNC machining tool can be quickly and accurately mounted to the machine spindle or returned to the tool magazine. The programmer should be able to understand the structure size, adjustment method and adjustment range of the tool holder used in the machine tool to ensure that the radial and axial dimensions of the tool are determined during programming, and the order of the tools is arranged reasonably.
Through careful consideration, careful understanding, mastering the method, we can choose the CNC tool that we are satisfied with.
How to buy a satisfactory CNC tool?
1. Consider the factors that affect the selection of CNC tools: