Tooling in CNC machining

In CNC machining, the selection of tools and the cutting amount of clear belongs to the quite important content, it will not only on the CNC machine tool machining efficiency output impact, and will also have a direct impact on the machining quality. CAD / CAM technology has developed, so that in CNC machining can be directly with the help of CAD design data, especially microcomputer connected to the CNC machine, so that the whole design, process planning and programming process are reached on the computer, usually do not need to show the special process documents. Planning and programming process are reached on the computer, usually do not need to show the special process documents. Nowadays, many CAD / CAM software packages with automatic programming capabilities, these software is often in the programming interface to remind the process of planning related issues, such as tool selection, machining path planning, cutting dosage to determine, etc., as long as the programmer set up the relevant parameters, can automatically generate NC procedures and transfer to the CNC machine to complete the processing. Therefore, CNC machining tool selection and cutting amount of determination, is reached under the condition of human-computer interaction, which constitutes a stark contrast with the Pusha Zhentong machine tool processing, but also requires programmers to grasp the tool selection and cutting amount of determination of the basic guidelines, in programming the time to fully take into account the characteristics of CNC machining. This article for CNC programming must face the problem of tool selection and cutting amount to determine the discussion, gives some principles and recommendations, and should pay attention to the problem was discussed. First, CNC machining, the existence of common types of tools and their characteristics is what it is, CNC machining tools have to adapt to CNC machine tools with high speed, high efficiency and high degree of automation of such characteristics, generally speaking, should cover the general-purpose tools, universal connection shanks and a small number of special shanks, shanks have to be coupled with the tool and mounted on the machine tool power head so that the case, so it has been gradually standardised and series of development, CNC tooling, CNC tooling, CNC tooling and cutting tools. Series development, the classification of CNC tools exist in a variety of ways, according to the structure of the tool can be divided into these, one for the whole type, the second is inlaid, inlaid with welded or clamped connection, clamped can be divided into non-inverted and can be indexed in two ways, and the third is a special type of special type, such as composite tools, vibration-damping tools and so on. By virtue of the manufacturing requirements, according to the account of Jieyin County, the priority focus on the internal construction of cutting tools used in the material can be divided into: ① high-speed steel cutting tools; ② carbide cutting tools; ③ diamond cutting tools; ④ other materials cutting tools, such as cubic boron nitride cutting tools, ceramic cutting tools, and so on. From the cutting process can be divided into: ① turning tools, divided into cylindrical, bore, threading, cutting tools and many other types; ② drilling tools, covering drills, reaming off the complementary city shifting cutter, taps, etc.; ③ boring tools; ④ milling tools and so on. In recent years, machine-clamped indexable tools, access to a wide range of applications, the number of CNC tools accounted for 30 to 40 per cent of the total amount of metal removal accounted for eighty to ninety per cent of the total amount of the purpose of adapting to the CNC machine tool for the tool durability, stability, easy to adjust, be able to replace and other aspects of the requirements. CNC tools and ordinary machine tools used, the placement of the tool in comparison, there are many different requirements, mainly with the following characteristics:, good rigidity (especially roughing tools), high precision, vibration and thermal deformation of a small;, interchangeability is excellent, always including the use of myriad of open-ended words, easy and fast replacement of the tool;, long service life, cutting performance is stable, trustworthy;, the tool The size of the tool is easy to adjust, thus reducing the time needed to change the tool adjustment;, the tool should be able to cell super-negative home egg selection of goods reliably chip breakage or chip roll, which is conducive to the smooth elimination of chips Huanfeng root iron YangBiHuaJiaoxing dissolution;, series, standardised, in order to facilitate the compilation of mine in the package process and tool management. Second, CNC machining in order to detect the selection of low-grain cutting tools, tool selection is in the CNC programming under the state of human-computer interaction, need to be based on the machine tool's machining capacity, the performance of the workpiece material, machining process, cutting dosage, as well as other relevant factors to the correct selection of tools and shanks, the tool selection of the general principle is to install and adjust the convenience of good rigidity, durability and high precision, to meet the machining requirements of the Under the premise of meeting the processing requirements, as far as possible to choose a shorter shank, in order to improve the rigidity of the tool processing, the selection of tools, to let the size of the tool and the surface size of the workpiece to be machined to match. In the production chain, for plane parts to be processed when the peripheral contour, often used end milling cutter; and when milling plane operation, should pick carbide insert milling cutter; if the processing of convex, groove, then we must choose high-speed steel end milling cutter; in the processing of blank surface or roughing hole, you can choose to insert carbide insert corn milling cutter; for some three-dimensional surface and variable For some three-dimensional profile and variable angle contour profile processing, often use ball milling cutter, ring milling cutter, taper milling cutter and disc milling cutter. In the process of free-form surface machining, given that the cutting speed of the end of the ball-end tool is zero, so in order to protect the machining accuracy, the cutting line distance is generally made quite close, so the ball-end is often used for surface finishing. And flathead tools in surface processing, its quality is better than the ball tool, in cutting efficiency is also obvious advantages, so as long as the premise of ensuring that does not occur under the preconditions of overcutting, no matter for surface roughing, or surface finishing process, should give priority to choose to use the flathead tool. At the same time, the tool has the degree of durability and precision, and the price of the tool itself has a great correlation between the relationship must be paid attention to it is worth noting that in the vast majority of cases, selecting and choosing the quality of the tool despite the increase in spending will increase the cost of the tool a, but the resulting result of the triggered by the improvement in the quality of the processing and machining efficiency can make the entire machining process cost significantly reduced. The cost of the entire processing process can be significantly reduced. In the machining centre environment, a variety of different types of tools are installed in the tool magazine, and according to the pre-set requirements of the program, there is always the possibility of selecting and changing tools at any time. Therefore, standard shanks must be used in order to allow the standard tools used in drilling, boring, expanding, milling and other processes to be quickly and accurately mounted on the machine spindle or in the tool magazine. Programmers need to know the size of the structure of the machine tool shanks used on the machine, the adjustment method and the scope of adjustment, to determine the radial and axial dimensions of the tool at the time of programming. Today's machining centres are equipped with the TSG tooling system, which includes both straight (three sizes) and tapered (four sizes) shanks, with a total of 16 different shanks for different applications. In economical CNC machining, tool sharpening is carried out manually by hand, tool measurement is carried out manually by hand, and tool replacement is also done manually by hand, and these take up a long auxiliary time, so the order of tool arrangement must be arranged reasonably. Generally follow these principles: first, try to reduce the number of tools; second, a tool clamped, it should be done after it can carry out all the machining parts; third, roughing and finishing tools should be used separately, even if the size of the same specifications of the tool; fourth, the first milling and then drilling; fifth, the first surface finishing, and then do the two-dimensional contour finishing; sixth, in the feasible case, should be the maximum Sixth, where feasible, should maximise the use of CNC machine tools, automatic tool change function, in order to improve productivity. Third, CNC machining cutting to determine the amount of reasonable choice of cutting has its principles, roughing time, usually to improve productivity as the main consideration, but also take into account the economy and processing costs; semi-finishing and finishing time, should be under the premise of ensuring the quality of machining, taking into account the cutting efficiency, economy and processing costs. Specific values need to be based on machine instructions, cutting manual, and combined with experience to determine. (1) depth of cut t. In the case of machine tools, workpiece and tool rigidity allows, t is equal to the machining allowance, which is an effective measure to improve productivity. In order to ensure the accuracy of parts processing and surface roughness, usually to leave a certain amount of margin to do finishing, CNC machine tools will be slightly smaller than ordinary machine tools finishing margin. Then look at the cutting width L, generally speaking, L and tool diameter d into a positive correlation with the depth of cut into an inverse correlation, in the economic CNC machining, usually the value of L category is: L = (0.6 ~ 0.9) d. In addition to the cutting speed v, enhance v is also an initiative to improve productivity, however, v and the correlation of tool durability is quite close, as v increases, tool durability will be sharply reduced, so the selection of v depends mainly on the tool durability. The selection of v depends mainly on tool durability. And, the cutting speed and processing material there is a great correlation, for example, when the use of end milling cutter to milling alloy just when, v can be used about 8m/min; However, the use of the same end milling cutter milling aluminium alloy, v can be selected more than 200m/min. (4) Spindle speed n (r/min). Spindle speed is usually based on the cutting speed v to finalise. Calculation formula is as follows: where, d is the tool or workpiece diameter (mm). The control panel of the CNC machine tool is generally equipped with a spindle speed trimming (multiplier) switch, which enables the spindle speed to be adjusted by an integer multiple during the machining process. (5) feed speed vF. vF should be selected in accordance with the requirements of parts machining accuracy, surface roughness requirements, as well as tool materials and workpiece materials. vF increase can enhance productivity. When the machining surface roughness requirements low, not high, vF can be selected more large. During the machining process, vF can be manually adjusted by the trim switch on the machine control panel, but the maximum feed rate is limited by the rigidity of the equipment and the performance of the feed system. With the widespread use of CNC machine tools in production, CNC programming has become one of the key issues in CNC machining. CNC programming, in the state of human-computer interaction, to instantly select the tool, but also to determine the amount of cutting. Therefore, the programmer must be familiar with the tool selection method, and to know the cutting amount to determine the principle, so as to ensure the quality of parts processing, but also to ensure that the machining efficiency, give full play to the advantages of CNC machine tools, and thus improve the economic efficiency of enterprises to enhance the level of production.