cnc milling machine
Milling cutter for CNC milling machine
XK7126 Vertical cnc milling machine
The selection of tools and the determination of cutting amount in CNC milling machine processing are completed under the state of human-machine interaction. It requires programmers to master the basic principles of tool selection and cutting amount determination, fully consider the characteristics of CNC processing when programming, and correctly select cutting tools and cutting amount. CNC processing technology covers a wide range. In terms of application, the characteristics and difficulties of its processing technology still lie in how to correctly select CNC machine tool tools at high speed and high efficiency to compile CNC processing processes and programs that meet the technical requirements of products. CNC processing can greatly shorten the manufacturing cycle of products and effectively solve the processing of complex, precise, single-piece small batch, and variable-shaped parts in mechanical products.
2. CNC milling machine tool selection
1. Characteristics and types of tools
There are many types of CNC milling machine processing tools. In order to adapt to the characteristics of high speed, high efficiency and high degree of automation of CNC machine tools, the tools used are developing in the direction of standardization, generalization and modularization, and are mainly divided into two categories: milling tools and hole processing tools. In order to meet the requirements of high efficiency and special milling, various special-purpose special tools have been developed.
1) Toolholder structure
The toolholder structure of CNC milling machine tools can be divided into two types: modular and integral. The modular tool system is a more advanced tool system, and each toolholder can be assembled through various serialized modules. Different assembly schemes can be adopted for different processing parts and machine tools to obtain a variety of toolholder series, thereby improving the adaptability and utilization rate of the toolholder. The working part of the integral toolholder for clamping the tool is integrated with the handle for installation and positioning on the machine tool. This toolholder has poor adaptability to the change of machine tools and parts. In order to adapt to the change of parts and machine tools, users must reserve toolholders of various specifications, so the utilization rate of the toolholder is low. The matching cone surface of the CNC milling machine toolholder and the spindle hole adopts a 7:24 tapered handle, and adopts a corresponding type of pull nail to combine with the machine tool spindle. The tapered handle has the characteristics of non-self-locking and convenient tool change. The commonly used specifications of toolholders are No. 40, No. 45 and No. 50. At present, the most widely used ones in my country are IS07388-1983, MAS403-1982, ANSI/ASME 135.50-1985, etc. When choosing, the toolholder specifications should be considered to be compatible with the machine tool spindle and manipulator. JT: Indicates the use of the international standard IS07388 taper shank for machining center machine tools (with manipulator clamping groove); the following number is the corresponding ISO taper number. BT: Indicates the use of the Japanese standard MAS403 taper shank for machining center machine tools (with manipulator clamping groove); the following number is the corresponding ISO taper number. For high-speed cutting, HSK series toolholders are generally used.
In order to improve processing efficiency, high-efficiency tools and toolholders should be selected as much as possible. Choose a strong milling chuck handle with high clamping accuracy. It can be used to clamp straight shank tools. Because the clamping deformation of the circlip itself is small, the self-locking property is good, and the clamping force is large, it can be used for strong milling processing; it can also be used for high-precision milling and reaming processing, and can also clamp hole-type tools through a connecting rod.
Choose a spring chuck handle, the elastic deformation of the circlip is 1mm, and it is mainly used to clamp small-sized milling cutters, such as drills, milling cutters, reamers, taps, etc. Choose a modular tool system because of its high positioning accuracy, convenient loading and unloading, good connection rigidity, and good vibration resistance. It is currently a more commonly used type. It consists of a shank, an intermediate connecting rod, and a working head. Choose a double-edged boring tool handle for rough boring, which can not only improve processing efficiency, but also help reduce cutting vibration; for typical workpieces with large batches and complex processing, composite tools should be used as much as possible. Although composite tools and tool holders are relatively expensive, the use of composite tools on CNC machine tools can concentrate the process, merge multiple processes into one process, and complete them with one tool, which is conducive to reducing processing time and tool change times, and significantly improving production efficiency.
2) Classification of CNC milling machine tools
There are many ways to classify CNC milling machine tools. According to the tool structure, they can be divided into:
①Integral type
②Inlaid type, connected by welding or machine clamping, and machine clamping can be divided into indexable and non-indexable types
③Special types, such as composite tools, shock-absorbing tools, etc.
According to the materials used to manufacture the tools, they can be divided into:
①High-speed steel tools
②Carbide tools: Carbide is classified according to the international standard ISO, and all grades are divided into six categories marked with colors, represented by the letters P, M, K, N, S, and H. P is used to process steel parts with long chips; M is used to process stainless steel parts; K is used to process cast iron parts with short chips; N is used to process non-ferrous materials with short chips; S is used to process difficult-to-process materials and H is used to process hard materials. Coated carbide tools are divided into two types: chemical vapor deposition CVD and physical vapor deposition PVD⑧ Diamond tools ④ Ceramic blade materials such as silicon nitride ceramic Si3N4, cubic boron nitride CBN
From the cutting process, they can be divided into: milling tools (face milling cutters, end milling cutters, round nose cutters, ball head milling cutters, taper milling cutters) hole processing tools (twist drills, reamers, boring cutters, taps, etc.).
In order to meet the requirements of CNC machine tools for tool durability, easy adjustment, stability, and replaceability, machine clamping indexable tools are widely used, accounting for 40%-50% of the entire CNC tools, and the amount of metal removal accounts for 80% to 90% of the total.
2. Selection of CNC machining tools·
The general principle of tool selection: easy installation and adjustment, good reliability, good rigidity, durability and high precision. Under the premise of meeting the processing requirements, try to choose tools with shorter shanks to enhance the rigidity of processing.
1) Select the tool according to the surface size of the workpiece
When selecting the tool, the size of the tool should be adapted to the surface size of the workpiece. In production, end mills are often used to process the contours around flat parts; carbide blade milling cutters should be selected for milling planes. When processing bosses and grooves, high-speed steel end mills are selected; when processing the surface of the blank or rough processing of holes, corn milling cutters with carbide blades can be selected; for the processing of some three-dimensional surfaces and variable bevel contours, disc milling cutters, round nose cutters, and flat cutters are selected for rough processing, and ball-end milling cutters, annular milling cutters, and tapered milling cutters are selected for fine processing.
2) Select the tool according to the surface shape of the workpiece
When processing molds, since the cutting speed of the end of the ball-end tool is zero, in order to ensure the processing accuracy, the cutting line spacing generally adopts the top close spacing, so the ball-end milling cutter is often used for the fine processing of curved surfaces. Flat-end tools are superior to ball-end tools in terms of surface processing quality and cutting efficiency. Therefore, as long as overcutting is guaranteed, flat-end tools should be preferred for both rough and fine processing of curved surfaces. In addition, the durability and precision of the tool are closely related to the price of the tool. It must be noted that in most cases, although the selection of good tools increases the tool cost, the improvement in processing quality and processing efficiency brought about by this can greatly reduce the overall processing cost.
3) Reasonable arrangement of tool arrangement sequence
In the processing process of economical CNC machine tools, since the wear, measurement and replacement of tools are mostly done manually, which takes up a long auxiliary time, the arrangement sequence of tools must be arranged reasonably. Generally, the following principles should be followed:
① The process is concentrated and clamped once, and the same tool can complete all the processing steps it performs;
② The tools for rough and fine processing should be used separately;
③ First face and then hole;
④ First perform surface finishing, then perform two-dimensional contour finishing;
⑤ Reasonably use the automatic tool change function of CNC machine tools to improve production efficiency;
⑥ Minimize the number of tools.
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