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NC machining tool must adapt to NC machine tool high speed, high efficiency and high degree of automation, general should include general tools, general connection tool and a small number of special tool handles. Tool handles are attached to the tool and mounted on the power head of the machine, so they are gradually standardized and serialized.
There are many methods to classify NC cutting tools.
According to the structure of cutting tools can be divided into: 1 Integral Type; 2 mosaic type, using welding or machine clamp type connection, machine clamp type can be divided into non-indexable and indexable two types; 3 special types, such as compound type cutting tools, damping type cutting tools and so on.
According to the materials used in the manufacture of cutting tools, they can be divided into: 1 high speed steel cutting tools, 2 carbide cutting tools, 3 diamond cutting tools, 4 other material cutting tools, such as cubic Boron nitride cutting tools, ceramic cutting tools, etc. .
From the cutting technology can be divided into: 1 turning tools, sub-circle, bore, thread, cutting tools and so on; 2 drilling tools, including drill, reamer, tap and so on; 3 boring tools; 4 milling tools.
In order to meet the requirements of NC machine tools for durability, stability, easy adjustment and interchangeability, machine clip indexable cutters have been widely used in recent years, reaching 30 ~ 40 of the total number of NC tools and 80 ~ 90 of the total number of metal cutting tools.
Compared with the cutting tools used on common machine tools, CNC cutting tools have many different requirements, mainly having the following characteristics: 1 good rigidity (especially rough cutting tools) , high precision, anti-vibration and small thermal deformation; 2 good interchangeability, convenient for quick tool change; 3 High Life, stable and reliable cutting performance; 4 the size of the tool is easy to adjust to reduce the adjustment time for tool change; 5 the tool should be able to break chips or roll chips reliably to facilitate the removal of chips; 6 serialization, standardization, for easy programming and tool management.
The tool selection is carried out in the human-computer interactive state of NC programming. Tools and handles should be correctly selected according to the machining capacity of the machine, the properties of the workpiece materials, the processing procedures, the cutting parameters and other relevant factors.
The general principles of tool selection are: easy installation and adjustment, good rigidity, durability and high precision. On the premise of meeting the machining requirements, the shorter tool shank is selected as far as possible to improve the rigidity of cutting tool machining. When selecting the cutting tool, the size of the cutting tool should be adapted to the surface size of the workpiece to be processed. In production, the milling cutter is often used to process the peripheral contour of the plane parts; when milling the plane, the carbide insert milling cutter should be selected; when machining the boss and Groove, the high-speed steel end milling cutter should be selected; when machining the surface of the blank or roughing hole, the milling cutter with Carbide Insert can be selected, and the ball-end milling cutter, Ring Milling Cutter, cone milling cutter and disc milling cutter are often used to process some solid surfaces and contour with variable bevel angle.
When machining free-form surface (die) , because the cutting speed of the end of the ball-end cutter is zero, in order to guarantee the machining precision, the top close distance is usually used as the cutting line distance. Flat-head cutter is superior to ball-head cutter in surface quality and cutting efficiency, so as long as it is not over-cut, whether rough or finish machining, flat-head cutter should be preferred.
In addition, the durability and accuracy of the tool have a great relationship with the price of the tool. It must be noted that, in most cases, though the cost of the tool increases, the quality and efficiency of the process will be improved, then the whole processing cost can be greatly reduced.
On the machining center, all kinds of cutting tools are installed on the tool magazine, according to the procedure at any time to select and change the cutter action. Therefore, it is necessary to use the standard tool Shank, so that the standard tools used in drilling, boring, expanding, milling and other processes can be quickly and accurately installed on the machine spindle or tool bank. The programmer should know the structure size, adjustment method and adjustment range of the tool shank used on the machine tool, in order to determine the radial and axial dimensions of the tool when programming. At present, TSG tool system is used in machining center in our country. There are two kinds of tool shanks: straight SHANKS (3 kinds of specifications) and taper shanks (4 kinds of specifications) , including 16 kinds of tool shanks for different purposes.
In the machining process of economical NC machine tools, because the cutting tools are ground, measured and replaced manually, which takes up a long auxiliary time, it is necessary to arrange the order of cutting tools reasonably. Generally, the following principles should be followed: 1 minimize the number of tools; 2 after a tool is clamped, it should complete all the processing steps it can carry out; 3 the rough and finish cutting tools should be used separately, even if they are of the same size; 4 milling first and drilling later, 5 finishing the curved surface first and then finishing the 2D contour, 6 making use of the automatic tool changing function of NC machine as far as possible to improve the production efficiency, etc. .
The principles of reasonable selection of cutting parameters are: In rough machining, productivity should be increased, but economy and processing cost should also be considered; in semi-finishing and finishing, under the premise of ensuring the quality of processing, give consideration to cutting efficiency, economy and processing cost. The specific value should be based on the machine tool instruction, cutting quantity manual, and the combination of experience.
Specific to consider the following factors: 1 Cutting Depth T. In the case of machine tool, workpiece and tool stiffness allowed, t is equal to machining allowance, which is an effective measure to improve productivity. In order to ensure the accuracy of parts processing and Surface roughness, generally should leave a certain margin for finishing. CNC machine finishing allowance can be slightly less than ordinary machine tools. 2 Cutting Width L. Generally L is proportional to the tool diameter D and inversely proportional to the cutting depth. In the machining process of economical NC machine tools, the value range of general L is: L = (0.6 ~ 0.9) d. 3 cutting speed V. Increasing V is also a measure to increase productivity, but V has a close relationship with tool durability. With the increase of V, the tool durability decreases sharply, so the choice of v mainly depends on the tool durability. In addition, the cutting speed also has a great relationship with the processing materials, for example, when milling alloy gang 30CrNi2MoVA with end milling cutter, V can use about 8 M/min, and when milling aluminum alloy with the same end milling cutter, V can choose more than 200 m/min. 4 spindle speed N (R/min). Spindle speed is generally based on the cutting speed V to choose. The formula is: v = ND 1000. CNC machine tool control panel is generally equipped with spindle speed adjustment (rate) switch, can be in the process of spindle speed adjustment. Feed rate, VF. VF shall be based on the machining accuracy and Surface roughness requirements of the parts as well as the cutter。
