Correct selection and programming skills of cuttin

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At present, many CAD/CAM software packages provide automatic programming function. These software usually prompt the related problems of process planning in the programming interface, such as tool selection, machining path planning, cutting parameter setting, etc. as long as the programmers set the relevant parameters, they can automatically generate NC programs and transmit them to the NC machine tool to complete processing

therefore, the tool selection and cutting in NC machining also made Bian Xinchao, who was directly immersed in the experiment of polylactic acid materials in Changchun Institute of chemistry at that time, see the opportunity that the determination of dosage is completed in the state of human-computer interaction, which is in sharp contrast with ordinary machine tool machining. At the same time, programmers must master the tool. Nel regent, deputy general manager of DPCA technology and head of the headquarters of the technology center, Preside over the basic principles of selecting and determining the cutting parameters in the technical exchange meeting, fully consider the characteristics of NC machining when programming, and be able to correctly select the cutting tools and cutting parameters

2. Types and characteristics of commonly used tools for digital animal processing

NC machining tools must adapt to the characteristics of high-speed, high efficiency and high degree of automation of NC machine tools, generally including general-purpose tools, general-purpose connecting tool handles and a small number of special tool handles. The tool handle should be connected with the tool and installed on the power head of the machine tool, so it has been gradually standardized and serialized

2.1 there are many methods for the classification of NC tools

a. according to the tool structure, it can be divided into

(1) integral type

(2) inlay type, which adopts welding or machine clamp connection. Machine clamp type can be divided into non transposable and transposable

(3) special types, such as compound cutting tools, shock absorbing cutting tools, etc

b. according to the materials used to manufacture cutting tools, it can be divided into:

(1) high speed steel cutting tools

(2) cemented carbide tools

(3) diamond tools

(4) tools made of other materials, such as cubic boron nitride tools, ceramic tools, etc

c. in terms of cutting technology, it can be divided into:

(1) turning tools, including excircles, inner holes, threads, cutting tools, etc

(2) drilling tools, including drill bits, reamers, taps, etc

(3) boring tool

(4) milling tools, etc

in order to meet the requirements of CNC machine tools for tool durability, stability, easy adjustment, replaceability, etc., machine clamp indexable tools have been widely used in recent years, reaching 30-40% of the total CNC tools in terms of quantity, and the amount of metal removal accounts for 80-90% of the total

2.2 compared with the tools used in ordinary machine tools, CNC tools have many different requirements, mainly with the following characteristics:

(1) good rigidity (especially rough machining tools), high precision, low vibration resistance and thermal deformation; Good interchangeability, convenient for quick tool change

(2) high service life, stable and reliable cutting performance

(3) the size of the tool is easy to adjust to reduce the adjustment time of tool change

(4) the tool should be able to reliably break or curl chips, so as to facilitate the removal of chips

(5) serialization and standardization to facilitate programming and tool management

3. selection of NC machining tools

the selection of tools is carried out in the human-computer interaction state of NC programming. The cutting tool and tool handle should be selected correctly according to the processing capacity of the machine tool, the performance of the workpiece material department, the cutting amount of the machining process and other relevant factors. The general principle of tool selection is: convenient installation and adjustment, good rigidity, high durability and precision. On the premise of meeting the processing requirements, try to choose a shorter tool handle to improve the rigidity of tool processing

(1) when selecting a tool, make the size of the tool adapt to the surface size of the workpiece being processed. In production, end mills are often used to process the peripheral contour of plane parts; When milling the plane, the carbide blade milling cutter should be selected, and when machining the boss and groove, the high-speed steel end milling cutter should be selected; When processing the rough surface or rough machining holes, the corn milling cutter with cemented carbide blade can be selected; Ball end milling cutter, ring milling cutter, conical milling cutter and disc milling cutter are often used for machining some three-dimensional surfaces and variable angle contours

(2) when machining free-form surfaces (molds), because the end cutting speed of the ball head tool is zero, in order to ensure the machining accuracy, the cutting line spacing generally adopts the top dense distance, so the ball head is often used for surface finishing. Flat end tools are superior to ball end tools in terms of surface processing quality and cutting efficiency. Therefore, as long as the premise of not cutting is guaranteed, flat end tools should be preferred in both rough and finish machining of curved surfaces. In addition, the durability and accuracy of tools have a great relationship with the price of tools. It must be noted that in most cases, the selection of good tools increases the cost of tools, but the resulting improvement in processing quality and efficiency can greatly reduce the overall processing cost

(3) on the machining center, various tools are installed on the tool magazine respectively, and the tool selection and pressing actions are carried out at any time according to the program regulations. Therefore, it is necessary to use standard tool holders so that the standard tools used in drilling, boring, expanding, milling and other processes can be quickly and accurately installed on the machine tool spindle or tool magazine. Programmers should understand the structural size, adjustment method and adjustment range of the tool handle used on the machine tool, so as to determine the radial and axial size of the tool during programming. At present, China's machining centers adopt TSG tool system, and its tool shanks include straight shanks (3 specifications) and taper shanks (4 specifications), including 16 tool shanks for different purposes

(4) in the processing process of economic NC machine tools, because the grinding, measurement and replacement of tools are mostly carried out manually, taking up a long auxiliary time, it is necessary to arrange the arrangement order of tools reasonably. Generally, the following principles should be followed: ① try to reduce the number of cutting tools; ② After a tool is clamped, all machining steps it can carry out shall be completed; Rough and finish machining tools should be used separately, even if they are of the same size and specification; ④ Milling before drilling; ⑤ Finish the surface first, and then realize the reduction of packaging materials and two-dimensional contour finishing; ⑥ If possible, the automatic tool change function of CNC machine tools should be used as much as possible to improve production efficiency

4. determination of cutting parameters in the machining process

the principle of reasonable selection of cutting parameters is: during rough machining, generally, it is mainly to improve productivity, but economy and processing cost should also be considered; In semi finishing and finishing, cutting efficiency, economy and processing cost should be considered on the premise of ensuring processing quality. The specific value should be determined according to the machine tool manual, cutting parameter manual and experience

Due to lack of experience and no reference to relevant data

the following factors should be considered:

(1) cutting depth AP. When the rigidity of machine tool, workpiece and tool allows, AP is equal to machining allowance, which is an effective measure to improve productivity. In order to ensure the machining accuracy and surface roughness of parts, a certain allowance should be left for finishing machining. The finishing allowance of CNC machine tools can be slightly smaller than that of ordinary machine tools

cutting width L. Generally, l is directly proportional to the tool diameter D and inversely proportional to the cutting depth. In the processing process of economical NC machine tools, the value range of L is generally l= (0.6 ~ 0.9) d

(2) cutting speed v. Increasing V is also a measure to improve productivity, but V is closely related to 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 is also closely related to the processing materials. For example, when milling diamond 30crni2mova with an end mill, V can be about 8m/min; When milling aluminum alloy with the same end milling cutter, V can be more than 200m/min

spindle speed n (r/min). The spindle speed is generally selected according to the cutting speed v. The calculation formula is: v=pnd/1000. The control panel of the NC machine tool is generally equipped with a spindle speed adjustment (magnification) switch, which can adjust the spindle speed by an integral multiple during the processing process

(3) feed speed VF. VF shall be selected according to the machining accuracy and surface roughness requirements of parts and the materials of cutting tools and workpieces. The increase of VF can also improve production efficiency. When the requirement of machined surface roughness is low, VF can be larger. During processing, VF can also be manually adjusted through the repair switch on the machine tool control panel, but the maximum feed speed is limited by the equipment stiffness and the performance of the feed system

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