1 NC machining technology
Division of NC machining processes Parts are machined on NC machine tools, and the processes are relatively concentrated. All processes should be completed in one clamping as far as possible. There are two common principles for process division.
The principle of ensuring accuracy
Numerical control machining has the conditions of centralized working procedures. Rough machining and finish machining are often completed in one clamping to ensure the machining accuracy of parts. When thermal deformation and cutting force deformation have great influence on the machining accuracy of parts, rough machining and finish machining should be carried out respectively.
The principle of improving production efficiency
In NC machining, in order to reduce the number of tool changes and save the time of tool change, all parts that need to be processed with the same knife should be processed, and then other parts should be processed with another knife. At the same time, the idle stroke should be reduced as much as possible, and when machining multiple parts of the workpiece with the same knife, the machining parts should be reached by the shortest route. In actual production, NC machining is often divided into working procedures according to NC tools or machining surfaces.
2 Selection of turning tool position
In NC machining, NC program should describe the trajectory of NC tool relative to workpiece. In NC turning, the formation of the workpiece surface depends on the position and shape of the envelope of the moving tool, but in programming, it is only necessary to draw the trajectory of a selected point on the NC tool system.
The cutter location of NC tool is the point selected on NC tool during programming to represent the position of NC tool, and the machining trajectory described in the program is the movement trajectory of this point.
2. What problems should be paid attention to when choosing NC tools?
(1) Select the cutting tool according to the cutting performance of the part material.
If turning or milling high-strength steel, titanium alloy and stainless steel parts, it is recommended to choose indexable cemented carbide tools with good wear resistance. (2) Select the cutter according to the processing stage of the parts.
That is to say, in the rough machining stage, tools with better rigidity and lower precision should be selected, while in the semi-finish machining and finish machining stage, tools with higher durability and precision should be selected to ensure the machining precision and product quality of parts, with the lowest precision in the rough machining stage and the highest precision in the finish machining stage. If the same tool is used for rough machining and finishing, it is recommended to choose the tool eliminated by finishing for rough machining, because most of the edges of the tools eliminated by finishing are slightly worn and the coating is worn and polished. Continued use will affect the machining quality of finishing, but it has little effect on rough machining.
(3) Choose cutting tools and geometric parameters according to the characteristics of the machining area. When the structure of parts allows, tools with large diameter and small aspect ratio should be selected; The end edge of the over-center milling cutter used for cutting thin-walled and ultra-thin-walled parts should have enough centripetal angle to reduce the cutting force of the cutter and cutting parts.
When processing parts made of soft materials such as aluminum and copper, end mills with slightly larger rake angle should be selected, with no more than four teeth. .
3. What kind of knowledge does CNC tool have?
Basic knowledge of NC tool technology
Numerical control tool is a tool used for cutting in mechanical manufacturing, also known as cutting tool. Broadly speaking, cutting tools include both cutting tools and abrasives. At the same time, "CNC tool" includes not only cutting blades, but also accessories such as arbor and handle!
According to the tool structure, it can be divided into:
Integral type: the cutter is integrated, made of blank and not separated;
Welding type: connected by welding, divided into cutter head and cutter bar;
Machine clip type: machine clip type can be divided into two types: non-indexable and indexable; Usually, CNC tools are machine-clamped!
Special types: such as compound cutter, damping cutter, etc.
According to the materials used to make the tool, it can be divided into:
High speed steel cutter;
Carbide cutter;
Diamond cutter;
Other material tools, such as cubic boron nitride tools, ceramic tools, etc.
From the cutting process can be divided into
Turning tools, such as excircle, inner hole, thread, cutting and grooving tools;
Drilling tools, including drills, reamers, taps, etc.
Drilling tools;
Milling tools, etc.
The development of cutting tools plays an important role in the history of human progress. As early as the 28th century BC to the 20th century BC, brass cones, copper cones, drills, knives and other copper tools appeared in China. In the late Warring States period (3rd century BC), due to mastering carburizing technology, a copper cutter was made. At that time, drills and saws had some similarities with modern flat drills and saws.
However, in the late18th century, with the development of steam engines and other machines, cutting tools developed rapidly. 1783, René of France first made a milling cutter. 1792, taps and dies made in Maudslay, UK. The earliest document about the invention of twist drill was recorded in 1822, but it was not produced as a commodity until 1864.
At that time, the cutting tool was integral high-carbon tool steel, and the allowable cutting speed was about 5 meters per minute. 1868, the alloy tool steel containing tungsten was specially made in Muscher, England. 1898, American Taylor and White invented high-speed steel. 1923, Germany Schroeder invented cemented carbide.
When alloy tool steel is used, the cutting speed of the tool is increased to about 8m/min, which is more than doubled when high speed steel is used, and more than doubled when cemented carbide is used, and the surface quality and dimensional accuracy of the machined workpiece are also greatly improved.
Due to the high price of high speed steel and cemented carbide, the cutting tool adopts welding and mechanical clamping structure. From 1949 to 1950, the United States began to use indexable inserts on turning tools, and soon it was applied to milling cutters and other tools. 1938, Germany's Degussai Company obtained a patent for ceramic tools. 1972, General Electric Company produced polycrystalline synthetic diamond and polycrystalline cubic boron nitride blades. These non-metallic tool materials can make the tool cut at a higher speed.
1969, sandvik Iron and Steel Works, Sweden obtained the patent for producing titanium carbide coated cemented carbide blades by chemical vapor deposition. From 65438 to 0972, Bonsa and Ragulin in the United States developed the physical vapor deposition method, which coated a hard layer of titanium carbide or titanium nitride on the surface of cemented carbide or high-speed steel tools. The surface coating method combines the high strength and toughness of the matrix material with the high hardness and wear resistance of the surface layer, thus making this composite material have better cutting performance.
According to the form of the machined surface of the workpiece, tools can be divided into five categories. Tools for processing various external surfaces, including turning tools, planers, milling cutters, broaches and files on the external surfaces; Hole processing tools, including drills, reamers, boring tools, reamers and broaches for inner surfaces; Thread processing tools, including taps, dies, automatic thread cutting heads, thread turning tools and thread milling cutters; Gear machining tools, including hob, gear shaper cutter, gear shaving cutter, bevel gear machining tool, etc. Cutting tools, including sawtooth circular saw, band saw, bow saw, cutting turning tool and saw blade milling cutter, etc. In addition, there are combined cutters.
4. How to choose a good CNC tool?
Hello, CNC tools are used for machining in mechanical manufacturing. When choosing a good tool, it should be noted that: (1) Choose the tool according to the cutting performance of the part material. For example, turning or milling high-strength steel, titanium alloy and stainless steel parts, it is suggested to choose indexable cemented carbide tools with good wear resistance. (2) Select the cutter according to the processing stage of the parts. That is to say, in the rough machining stage, the focus is on removing the allowance, and the tool with good rigidity and low precision should be selected. Semi-finishing and finishing mainly focus on ensuring the machining accuracy and product quality of parts, and tools with high durability and precision should be selected. The precision of tools used in rough machining is the lowest, and the precision of tools used in finish machining is the highest. If the same tool is selected for rough machining and finish machining, it is recommended to choose the tool eliminated by finish machining, because most of the tools eliminated by finish machining are slightly worn at the edges and the coating is worn and polished, which will affect the quality of finish machining, but the continuous use will affect the quality of finish machining.
5. What are the commonly used tools in NC machining?
Turning tool is the most widely used tool in metal cutting.
It can be used for machining excircle, end face, thread and inner hole on lathe, and also for slotting and cutting. Turning tools can be divided into integral turning tools, welding assembly turning tools and mechanical clamping blade turning tools.
Turning tools for mechanical clamping blades can be divided into machine tool turning tools and indexable turning tools. Mechanical clamping lathe tool has stable cutting performance, and workers do not need to sharpen the knife, so it is more and more used in modern production.
Generally speaking, hole machining tools can be divided into two categories: one is tools for machining holes with solid materials, such as twist drills, center drills, deep hole drills, etc. The other is a tool that reprocesses the existing holes in the workpiece, such as reamer, reamer, boring tool, etc. Milling cutter is a kind of widely used multi-edge rotary cutter, and there are many kinds.
It is divided into: 1) for machining planes, such as cylindrical plane milling cutter and end milling cutter; 2) Used for machining grooves, such as end milling cutter, T milling cutter and angle milling cutter; 3) Used for machining molding surfaces, such as convex-concave semi-circular milling cutters and milling cutters for machining other complicated molding surfaces. Generally, milling productivity is high and surface roughness is high.
6. Knowledge of CNC tools
1 CNC machining process CNC machining process division of labor Machining parts on CNC machine tools, the processes are relatively concentrated, and all processes are completed in one clamping as far as possible. There are two common principles of process division.
The principle of ensuring accuracy NC machining has the condition of centralized working procedures. Rough machining and finish machining are often completed in one clamping to ensure the machining accuracy of parts. When thermal deformation and cutting force deformation have great influence on the machining accuracy of parts, rough machining and finish machining should be carried out respectively. The principle of improving production efficiency in NC machining, in order to reduce tool changing times and save tool changing time, all parts that need to be processed with the same knife should be processed, and then other parts should be processed with another knife.
At the same time, the idle stroke should be reduced as much as possible, and when machining multiple parts of the workpiece with the same knife, the machining parts should be reached by the shortest route. In actual production, NC machining is often divided into working procedures according to NC tools or machining surfaces.
2 Selection of turning tool position In NC machining, the NC program should describe the trajectory of the NC tool relative to the workpiece. In NC turning, the formation of the workpiece surface depends on the position and shape of the envelope of the moving tool, but in programming, it is only necessary to draw the trajectory of a selected point on the NC tool system.
The cutter location of NC tool is the point selected on NC tool during programming to represent the position of NC tool, and the machining trajectory described in the program is the movement trajectory of this point.
7. What are the main materials of CNC tools?
Because parts work in high temperature, high pressure, high speed and corrosive fluid media, more and more difficult-to-machine materials are used, and the automation level of cutting and the requirements for machining accuracy are getting higher and higher. In order to adapt to this situation, the development direction of cutting tools will be to develop and apply new cutting tool materials. Further develop the vapor deposition coating technology of tools, and deposit a layer with higher hardness on the matrix with high toughness and high strength to better solve the contradiction between hardness and strength of tool materials; Further develop the structure of the rotary cutting machine; Improve tool manufacturing accuracy, reduce product quality differences, and optimize tool use. Tool materials can be roughly divided into the following categories: high-speed steel, cemented carbide, cermet, ceramics, polycrystalline cubic boron nitride and polycrystalline diamond. Ceramics are mainly mentioned here. They were used in cutting tools earlier than cemented carbide, but they developed slowly because of their brittleness. However, since 1970s, they have developed rapidly. There are two main types of ceramic tool materials.
8. I want to know what are the machining characteristics of CNC tools?
Hello, the height of blade and handle is universal, standardized and serialized.
Rationality of durability and economic life index of blades or cutters. Standardization and typification of geometric parameters and cutting parameters of tools or blades.
The material and cutting parameters of the blade or cutter should match the processing material. The cutting tool should have high accuracy, including the shape accuracy of the cutting tool, the position accuracy of the blade and the tool holder relative to the spindle of the machine tool, the indexing accuracy of the blade and the tool holder, and the repeatability accuracy of assembly and disassembly.
The strength, rigidity and wear resistance of the handle should be high. The mounting weight of the tool holder or tool system is limited.
The cutting position and direction of the blade and handle are necessary. The positioning datum of blade and handle and the automatic tool changing system should be optimized.
The tools used in CNC machine tools should meet the requirements of convenient installation and adjustment, good rigidity, high precision and good durability.