英文原文On the NC latheCNC machine tool numerical control machine tools (Computer numerical control machine tools) abbreviation, is provided with a program control system of automatic machine tools. The logic control system can deal with the control code or other symbolic instruction specified program, and decoding the digital code, said information carrier, through the numerical control device input. After processing by CNC device control signals, control the machine movements, by drawing the shape and size requirements, will be automatically processed by the parts.Features: CNC machine tool operation and monitoring of all completed in the numerical control unit, it is the brain of CNC machine tools. Compared with the general machine tools, CNC machine tools has the following characteristics:● the processing object adaptability, adapt to the characteristics of mold products such as a single production, provide the appropriate processing method for die and mould manufacturing;● high machining accuracy, proce ssing with stable quality;● can coordinate linkage, processing complex shape parts;● machining parts change, only need to change the program, can save the preparation time of production;● the machine itself high precision, rigidity, can choose the amoun t of processing good, high productivity (3~5 times as common machine);The machine is a high degree of automation, reducing labor intensity;● conducive to the production management modernization. The use of CNC machine tools and the standard code of digital information processing, information transmission, the use of computer control method, has laid the foundation for the integration of computer aided design, manufacturing and management;● on the operators of higher quality, higher demands for the repair of the technical staff;● high reliability.Composition: CNC machine tools in general by the input medium, man-machine interactive equipment, CNC equipment, feed servo drive system, spindle servo drive system, the auxiliary control device, feedback apparatus and adaptive control device etc.. [4] in NC machining, NC milling processing is the most complex, need to solve most problems. NC programming of NC line in addition to CNC milling, cutting, CNC EDM, CNC lathe, CNC grinding, each with its owncharacteristics, servo system is the role of the motion signal is converted into the machine moving parts from the numerical control device of pulse. Concrete has the following parts: the structure of CNC machine tools.Driver: he is driving parts of CNC machine tools, actuator, including spindle drive unit, feeding unit, spindle motor and feed motor. He through the electric or electro-hydraulic servo system to realize the spindle and feed drive under the control of numerical control device. When several feed linkage, can complete the positioning, processing line, plane curve and space curve.The main performance(1) the main dimensions.(2) the spindle system.(3) feed system.(4) tool system.(5) electrical. Including the main motor, servo motor specifications and power etc..(6) cooling system. Including the cooling capacity, cooling pump output.(7) dimensions. Expressed as length * width * height.Development trend of CNC lathe:High speed, precision, complex, intelligent and green is the general trend in the development of CNC machine tool technology, in recent years, made gratifying achievements in practicality and industrialization. Mainly in the:1 machine tool composite technology to further expand with the CNC machine tool technology, composite processing technology matures, including milling - car compound, car milling compound, car - boring - drill - gear cutting compound, composite grinding, forming, composite processing, precision and efficiency of machining is greatly improved. "One machine is a processing factory", "one card, complete processing" concept is being accepted by more people, the development of compound processing machine tool is the trend of diversified.Intelligent technology 2 CNC machine tools have a new breakthrough, in the performance of NC system has been reflected more. Such as: automatically adjust the interference anti-collision function, after the power of workpiece automatically exit safety power-off protection function, machining parts detection and automatic compensation function of learning, high precision machining parts intelligent parameter selection function, process automatic elimination of machine vibration functions into the practical stage, intelligent upgrade the function of machine and quality.The 3 robots enable flexible combination of flexible combination of higher efficiency of robot and the host are widely used, make flexible line more flexible, extending the function, flexible line shorten further, more efficient. Robot and machining center, milling composite machine, grinder, gear processing machine tool, tool grinding machine, electric machine, sawing machine, punching machine, laser cutting machine, water cutting machine etc. various forms of flexible unit and flexible production line has already begun the application.4 precision machining technology has the machining precision of CNC metal cutting machine tools from the yarn in the original (0.01mm) up to micron level (0.001mm), some varieties has reached about 0.05 μ M. Micro cutting and grinding machining of ul tra precision CNC machine tools, precision can reach about 0.05 μ m, shape precision can reach about 0.01 μ M. Special processing precision by using optical, electrical, chemical, energy can reach nanometer level (0.001 μ m). By optimizing the design of ma chine tool structure, machine tool parts of ultra precision machining and precision assembly, using high precision closed loop control and temperature, vibration and other dynamic error compensation technology, improve the geometric accuracy of machine tool processing, reduce the shape of error, surface roughness, and into the submicron, nano super finishing tiThe 5 functional component to improve the performance of functional components are at a high speed, high precision, high power and intelligent direction, and obtain the mature application. A full digital AC servo motor and drive device, high technology content of the electric spindle, linear motor, torque motor, linear motion components with high performance, application of high precision spindle unit and other function parts, greatly improving the technical level of CNC machine tools.The feed drive system of CNC lathe:Effect of feed drive system,The feed drive system of CNC machine tools will be received pulse command issued by the numerical control system, and the amplification and conversion machine movements carry the expected movement.Two, the feeding transmission system requirementsIn order to guarantee the machining accuracy of NC machine tool is high, the feed drive system of transmission accuracy, sensitivity high (fast response), stable work, high stiffness and friction and inertia small, service life, and can remove the transmission gap.Category three, feed drive system1, stepping motor servo systemGenerally used for NC machine tools.2, DC servo motor servo systemPower is stable, but because of the brush, the wear resulting in use need to change. Generally used for middle-grade CNC machine tools.3, AC servo motor servo systemThe application is extremely widespread, mainly used in high-end CNC machine tools.4, the linear motor servo systemNo intermediate transmission chain, high precision, the feed speed, no length limit; but the poor heat dissipation, protection requirements are particularly high, mainly used for high-speed machine.Driving component four, feed system1, the ball screw nut pairNC machining, the rotary motion into linear motion, so the use of screw nut transmission mechanism. NC machine tools are commonly used on the ball screw, as shown in Figure 1-25, it can be a sliding friction into rolling friction, meet the basic requirements of the feed system to reduce friction. The transmission side of high efficiency, small friction, and can eliminate the gap, no reverse air travel; but the manufacturing cost is high, can not lock, size is not too big, generally used for linear feed in small CNC machine tool.2, rotary tableIn order to expand the scope of the process of NC machine tools, CNC machine tools in addition to make linear feed along the X, Y, Z three coordinate axes, often also need a circumferential feed movement around Y or Z axis. Circular feed motion of CNC machine tools in general by the rotary table to realize, for machining center, rotary table has become an indispensable part of.Rotary table of commonly used CNC machine tools in the indexing table and NC rotary table.(1) indexing tableIndexing table can only finish dividing movement, not circular feed, it is in accordance with the instructions in the NC system, when indexing will work together with the workpiece rotation angle. When indexing can also use manual indexing. Provisions of indexing table is generally only rotary angle (such as 90, 60 and 45 degree).(2) NC rotary tableNC rotary table appearance similar to the indexing table, but the internal structure and function is not the same. The main function of the NC rotary table is based on the numerical control devicesends command pulse signal, complete circumferential feed movement, various arc processing and surface processing, it can also be graduation work.3, guideRail is an important part of feed drive system, is one of the basic elements of the structure of machine tool, rigidity, precision and accuracy of NC machine tool which determines to a large extent retention. At present, guide the NC machine tool are sliding rail, rolling guideway and hydrostatic guideway.(1) sliding guideSliding guide rail has the advantages of simple structure, easy manufacture, good stiffness, vibration resistance and high performance, widely used in CNC machine tools, the use of most metal plastic form, known as the plastic guide rail, as shown in figure 1-26.On characteristics of the plastic sliding guide: friction characteristic is good, good wear resistance, stable movement, good manufacturability, low speed.(2) rolling guideRolling guide is placed in the rail surface between the ball, roller or needle roller, roller, the rolling friction instead of sliding surface of the guide rail between wipe.Rolling guide rail and the sliding rail, high sensitivity, small friction coefficient, and the dynamic, static friction coefficient is very small, so the motion is uniform, especially in the low speed movement, the stick-slip phenomenon is not easy to occur; high positioning accuracy, repeatability positioning accuracy is up to 0.2 μ m; traction force is small, wear small, portable in movement; good precision, long service life. But the vibration of rolling guide, high requirements on protection, complicated structure, difficult manufacture, high cost.Automatic tool changer:One, the function of automatic tool changerAutomatic tool changing device can help save the auxiliary time of CNC machine tools, and meet in an installation completed procedure, step processing requirements.Two, on the requirement of automatic tool changerNumerical control machine tool for automatic tool changer requirement is: tool change quickly, time is short, high repetitive positioning accuracy, tool storage capacity is sufficient, small occupation space, stable and reliable work.Three, change the knife form1, rotary cutter replacementIts structure is similar to the ordinary lathe turret saddle, according to the processing of different objects can be designed into square or six angle form, consists of the NC system sends out the instruction to the rotary cutter.2, the replacement of the spindle head tool changeThe spindle head pre-loaded required tools, in order to machining position, the main motor is switched on, drives the cutter to rotate. The advantage of this method is that eliminates the need for automatic clamping, cutting tool, clamping and cutting tool moving and a series of complex operation, reduce tool change time, improveThe ATC reliability.3, the use of changing toolThe processing required tools are respectively arranged in the standard tool, adjust the size of the machine after certain way add to the knife, the exchange device from the knife and the spindle take knife switch.Four, the tool switching deviceAutomatic tool change device, device for knife library and the main shaft transmission and handling tool for tool exchange device. Tool exchange often have two kinds: mechanical hand tool exchange and by relative motion of knife and machine tool spindle exchange tool (knife to spindle forThe knife or the spindle motion to the knife knife tool change position), the mechanical hand tool change is most common.Five, the knifeThe knife is one of the most important parts in automatic tool changer, have great influence on the overall design of NC machine tool and its capacity, layout and structure.1, the capacity of the tool storageA number of knife inventory cutters, generally depending on the processing requirements. The capacity of small knife, can not meet the processing needs; capacity is too large, will make the knife database size, covers an area of large, tool selection process for a long time, and the knife library utilization rate is low, the structure is too complex, causing great waste. 2, the knife typeGenerally, the chain disc and drum type knife several.Disc cutter tool was circular arrangement, low utilization of space, size is not large but simple structure.Chain magazine compact structure, large capacity, link shape can also be random bed made of various forms and flexible layout, but also will change the cutter location prominent for tool change, widely used.Drum type or lattice type knife, covers an area of small, compact structure, large capacity, but cutter selection, tool movements are complicated, for centralized knife system for FMS.3, tool selectionOften order tool selection and random selection tool two.The order of tool selection is before processing, the processing required tools to process sequence of insert knife knife, order not wrong, processing adjust knife in order. The work piece changes, the need to reset the tool sequence, the operation is simple, and the processing tool with a workpiece can not be repeated use.A knife is the cutting tool has its own code, optional and can be repeatedly used in processing, also do not put in the fixed knife, knife, the knife is convenient.Technology file is the guiding file workers during processing, process scheme is reasonable, not only affect the efficiency of NC machining, and will directly affect the machining quality. Therefore, before NC programming, NC machining process follows the process of certain principles and combined with the characteristics of CNC lathe seriously and develop in detail the good parts.In the CNC lathe processing parts, should according to the principle of dividing process concentrated, in a fixture as far as possible to complete the most or even all of the surface processing. Part positioning, according to the structure of different shapes, usually cylindrical, face or end clamping, and strive to design basis, process reference and programming the unification datum.The main contents are: analysis of NC machining technology of part drawings, clear processing content; determination method, workpiece on lathe the surface processing sequence and tool feed line and cutting tools, fixtures and cutting the amount of choice.Analysis, part drawing processIn the machining process planning of parts, first of all to carry on in-depth analysis to the processing object. For NC turning process should consider the following aspects:1 reading part drawing, analysis of geometric conditions of part contourIn turning process of manual programming, to calculate each node coordinates; in automatic programming, to define the components outline all geometric elements. Therefore, in the analysis of parts should pay attention to:Parts of the map is missing a dimension, the geometric conditions are not sufficient to constitute the part outline, influence;Map location map parts of the ambiguity or dimension is not clear, so that the program can't start;The part drawing geometry given is not reasonable, resulting in mathematical difficulties.The part drawing dimensioning methods should adapt to the characteristics of CNC lathe processing, should size or directly given coordinate dimension with the same standard.2 dimensional accuracy requirementsAnalysis of the pattern of parts size precision requirements, to determine whether achieve the turning process, and determine the process method to control the dimension precision.In the analysis process, but also can convert some dimensions such as size, incremental and absolute size and dimension chain calculation. In the use of NC lathe turning parts, average value of components often required size and maximum and minimum limit of size size as the basis of programming.3 shape and position accuracy requirementsPattern of parts tolerance of shape and location given is important foundation to ensure the parts precision. When machining parts, to determine the location reference and measurement reference according to the requirements, can also carry out some technical processing according to the special needs of CNC lathe parts, in order to control effectively the shape and position accuracy.4 requirements of surface roughnessSurface roughness is an important requirement of micro precision parts of the surface, but also the reasonable selection of NC lathe, cutting tools and cutting the amount determined on the basis of.5 material and heat treatment requirementsThe part drawing on material and heat treatment given requirements, is the choice of cutter, CNC lathe, cutting the amount determined on the basis of model.Determination of two and fixture, clamping scheme selectionDivision 1.(1) according to the tool used by the process division can improve machining efficiency.(2) can keep the NC lathe machining according to the rough, finishing process division adopted this approach accuracy.The 2 part is determined and the fixture clamping scheme selectionThe CNC lathe parts mounting method is the same with the ordinary lathe, universal fixture should try to choose the existing clamping, and attention should be paid to reduce clamping times, as far as possible in one clamping parts can put all to processing surface processing. Datum location should be coincident with the design reference, in order to reduce the positioning error effect on the dimensional accuracy.CNC lathe with chuck with three jaws to clamp workpiece; shaft parts can also be used to support the tailstock center. Due to the NC lathe spindle speed is very high, for the convenience of the workpiece clamping, the use of hydraulic high-speed power chuck, because it is in the production plant has passed the strict balanced, with a high speed (the speed limit is 4000 ~ 6000rpm), high clamping force (the maximum force is 2000 ~ 8000N), high precision, convenient adjusting claw, a through hole long service life, etc.. By adjusting the pressure of oil cylinder, which can change the clamping force, the special needs of holding various thin-walled workpiece deformation and easy to meet.Deformation of slender shaft processing to reduce stress, improve the machining accuracy, as well as in processing the shaft with hole workpiece inner hole, the hydraulic automatic centering central frame, the centering precision can reach 0.03 mm.Three, determine the processing order and feed routeDetermination of 1 processing sequenceIn the process of NC machine tool, as the processing object is complicated, especially the shape and position of the myriads of changes curve, with the influence of different materials, different from that of the bulk and other factors, in the formulation of the processing sequence of specific parts, should make a concrete analysis and distinction, flexible processing. Only in this way, can the processing order of the rational, so as to achieve excellent quality, high efficiency and low cost objective.(1) the coarse to fineIn order to improve production efficiency and ensure the precision parts processing quality, in the cutting process, should arrange the roughing process, in a relatively short period of time, the finishing before machining allowance amount of removed, at the same time as much as possible to meet the precision machining allowance uniformity requirements.When the roughing process arrangement is finished, and then arrange the semi-finish machining and finish machining for the knife after the. Among them, arrange the semi-finishing aims, when after the rough machining allowance of uniformity can not meet the precision requirement, canarrange the semi-finish machining as a transitional process, in order to make the finishing allowance is small and uniform.In the arrangement of a knife or blade finish machining process of the part, the final contour should be the last knife and continuous processing. At this time, the cutting tool and cutter location to consider appropriate, try not to arrange the cut and cut out or tool change and pause in a continuous contour, so as to avoid sudden changes of cutting force caused by elastic deformation, resulting in smooth connection defects, surface scratch shape mutation or retention tool mark profile.(2) to nearly far after processing, reduce air travel timeHere said the far and near, is according to the processing site relative to the size of the knife point distance. In general, especially in the rough, usually arranged from near the site of the first processing tool, tool bit far from site after processing, in order to shorten tool moving distance, reduce air travel time. For turning, the first after the far past helps maintain the rough orsemi-finished parts of the rigid, improve the cutting condition.(3) and crossOn both the inner surface (inner type cavity), and outer surface of machined parts, the processing sequence arrangement, should be done before and after surface rough machining, inner and outer surface finishing. Must not be parts of a portion of the surface (the inner or outer surface) after machining, processing and other surface (inner or outer surface).(4) surface of first principlesSurface is used as a fine benchmark priority should be processed, because the surface of locating datum is more precise, clamping error is smaller. For example, shaft parts processing, always first machining center hole, and then to the center hole for precision machining surface and surface.The principle is not immutable and frozen, for some special cases, you need to take a flexible scheme.Determination of processing feed line 2The feed line is the tool relative to the workpiece in the whole movement process, it not only includes the steps of content, but also reflect the step sequence. One of the feed line is the basis of programming.Determine the processing route must keep the size precision and surface quality of machining parts, then consider the numerical calculation is simple, knife route as short as possible, higher efficiency. Because of the feed line finishing is basically along the contour sequence, therefore the determination of feed line focus is to determine the feed line rough machining and air travel. The following will analyze:(1) the relationship between processing route and machining allowanceIn the CNC lathe is not to popularize the use of conditions, the general should be a roughcast margin too much, especially with forging, casting hard layer cushion placed in ordinary lathe. If must use NC lathe machining, should pay attention to the flexible program. The first cutting processing must arrange some subroutine to margin too much site.(2) the tool cut, cut outThe processing of CNC machine tools, to arrange the tool cut, cut out the route, the tangent direction to make the tool along the outline of the cut, cut out.(3) to determine the shortest route for emptyDetermine the shortest tool path, in addition to rely on a lot of practical experience, should be good at analysis, if necessary, supplemented by some simple calculations.(4) determine the cutting feed shortestCutting feed route is short, can effectively improve the production efficiency, reduce the tool wear. In the cutting feed route arrangement the rough or semi-finished, it shall also take into account to be rigid and processing parts processing technology requirements, do not care for this and lose that.Four, to determine the cutting parametersCNC programming, the programmer must determine the cutting parameters of each process, and instructions in the form of written procedures. Cutting parameters including spindle speed, depth of cut and feed speed. For the different processing methods, selection of cutting parameters for different needs. Principle of selection of cutting parameters is: to ensure the accuracy and surface roughness of the parts processing, give full play to the tool cutting performance, guarantee a reasonable tool life and give full play to the performance of the machine tool, to maximize the productivity, reduce the cost of.To determine the 1 spindle speed(1) determine the spindle speed of light carSpindle speed should be based on the allowable cutting speed and workpiece diameter selection, the calculation formula is as followsN=1000v/ (d)Type V -- the cutting speed (M / min), determined by the tool life.N -- the spindle speed (R / min);D -- or the diameter of cutter and workpiece diameter (mm).Spindle speed calculation n finally depends on the machine specifications selecting machine or close to the speed of.(2) the car threaded spindle speedIn thread cutting, the lathe spindle speed will be thread pitch (or lead) factors affecting size, driving motor movements frequency characteristics and thread interpolation operation speed, the different NC systems, recommended the spindle speed range of different options. Spindle speed as most ordinary lathe CNC system recommended threading:N ≤ 1200/p-KType P -- pitch or lead the thread (mm);K -- the insurance factor, usually taken as 80;N -- the spindle speed, rpm.To determine the 2 feed speedThe feed velocity is an important parameter in the CNC machine tool cutting, mainly according to the machining accuracy and surface roughness value selection of parts and tool, workpiece material properties. The maximum speed limit by the performance of machine tool stiffness and feed system.To determine the feed speed is the principle:(1) when the workpiece quality requirements can be guaranteed, in order to improve the production efficiency, can choose the higher feed rate. 100 ~ 200mm / min range selection.(2) in cutting, machining deep hole or processing of high-speed steel cutting tool, should choose a lower feeding rate, generally in the 20 ~ 50mm / min range selection.(3) when processing high precision and surface roughness values is small, the feed rate should be smaller, the range of 20~50mm/min selection.(4) the tool to air travel, especially to zero distance, can be set to the highest feed speed setting of the machine tool CNC system.To determine the depth of the 3The cutting depth was decided according to machine tool, workpiece and cutting tool rigidity, stiffness in the permit conditions, should as far as possible back an amount equal to the machining allowance of the workpiece, thus reducing the feeding times, improve production efficiency. 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