数控机床开环控制伺服系统与数控生产设备

1、附录氏妓候糌祟彭靡践魈缉诎唉另差译文：鹬氰亓骈防摄瓤叭胩餐缉踞款锔The open system merit of Computer Numerical Control and Numerical control of production equipments逐婀鸵合楮期舆煌顺簇篪圪官Abstract衾窜澧妄耸捩拙桊吃檩葺亏疝潍The open system merit is the system simple, the cost low, but the shortcoming is the precision is low. The reverse gap, the guide scre

2、w pitch error, stop inferiorly can affect the pointing accuracy by mistake. Following several kind of improvements measure may cause the pointing accuracy distinct improvement.藜橹冕笮璞佰霖褊阂甍嘛唉杲术The key word:numerical control 、NC 、the open systerm 门抡男嗽玉蒜觎询犯揭策獭毛甑1）reverse gap error compensates The numeric

3、al control engine bed processing cutting tool and the work piece relative motion is depends upon the drive impetus gear,the guide screw rotation, thus the impetus work floor and so on moves the part to produce moves realizes. As traditional part gear, guide screw although the manufacture precision i

4、s very high, but always unavoidably has the gap. As a result of this kind of gap existence, when movement direction change, starts the section time to be able tocause inevitably actuates the part wasting time, appears the instruction pulse to push the motionless functional element the aspect. This h

5、as affected the engine bed processing precision, namely the instruction pulse and actual enters for the step does not tally,has the processing error therefore, the split-ring numerical control system all establishes generally has the reverse gap errorcompensatory function, with by makes up which was

6、tes time the step reverse gap difference compensates is first actual reverse enters for the error, converts the pulse equivalent number it, compensates the subroutine as the gap the output, when the computer judgment appearswhen instruction for counter motion, transfers the gap to compensate the sub

7、routine immediately, compensates the pulse after the output to eliminate the reverse gap to carry on again normally inserts makes up the movement. 2）often the value systematic characteristic position error compensates餐送峤礤庐纯忌雎痔俱粕滹桴啐A kind of storehouse by transfers for the designer. Like this in the

8、components design stage, the designer only must input the characteristic the parameter, the system direct productioncharacteristic example model: We must save the related characteristic class in the database the structure information, the database table collection are use in saving this part of rela

9、ted information. According to the characteristic type definition need, we defined the characteristic class code table, the characteristic class edition information have outstanding shown the characteristic type; Defined the characteristic class structure outstanding to reach the characteristic class

10、 the structure; And relates through the components characteristic disposition table and the components characteristic level information. The characteristic level data sheet collection isthis components model database design core, has recorded characteristic example information and so on model design

11、, craft. The characteristic structure table has recorded the characteristicgeometry structure; The characteristic size table, the characteristic shape position table of limits, the characteristic surface roughness table has recorded the characteristic project semantics quotation; The size table, the

12、 shape position table of limits, the surface roughnesstable saved all components characteristic data message. In the characteristic level, using characteristic ID, geometry principal linkage and so on essential factor ID, size ID, common difference ID, roughness ID carries on the data retrieval. We

13、apply this components information model database under the factory environment some module CAD in the AM integrative system, has realized CAD and the CAPP characteristic information sharing well. Main use ready-made CAD/the CAM software (Unigra phics 1I) carries on the product design and the NC prog

14、ramming in this system, and through carries on two times of developments gains components to this software the size information; At the same time uses the dialogue window which develops voluntarily, lets design the personnel to input other characteristic information alternately, realizes this softwa

15、re and the system sharing database connection. When assistance technological design, the technological design personnel through the procedure inquiry function, inquires the components information from the sharing database which needs, carries on the interactive technological design. Thus has facilit

16、ated the CAPP components information acquisition, enhanced the technological design efficiency. When carries on the NC programming using UG, may from the sharing database gain the craft and the manufacture information which needs, carries on various working procedures the knife axle design and the p

17、rocessing simulation establishes an absolute zero spot on the numerical control engine bed, the actual various coordinate axes syzygy completely position error, makes the curve in order to determined compensates the spot. Attempts l to show is an actual position error curve, (error) carries on this

18、curve y-coordinate take the pulse equivalent as the unit the division, makes the horizontal line, each horizontal line and the curve point of intersection namely compensates the spot for the goal. Chart 1 the center 1 to 6 oclock place position errors for, needs to do reduces the pulse to compensate

19、; But needs to carry on 6 to 9 adds the pulse to compensate in the chart the shadow partially for to compensate the area. Compensates the range of points these to become the error The calibration corrections stores the computer, when work table by zero displacement in position, installs sends out th

20、e absolute zero point localization signal in the absolute zero point micros witch, later computer as necessary will send out the goal to compensate to compensate the signal, will carry on the position error to the engine bed to compensate. The cosine generator assigns slide guage initiation signal a

21、 electricity and by step of transmission.3） feedbacks compensates the open-loop control Chart 2 has produced this kind of system schematic diagram. This system surveys two parts by the open-loop control and the induction synchromesh direct position to be composed. Here position examination does not

22、serve as the position the feedback, but is compensates the feedback as the position error. Its cardinal principle is: Installs the instruction pulse by the engine bed numerical control which CNC sends out, on the one hand the supplies open system, thecontrol step-by-steps the electrical machinery ac

23、cording to the instruction revolution, and the direct drive platen moves, constitutes the open-loop control; On the other hand this instruction pulse supplies the induction synchromesh the measurement system (namely digitally, cosine generator), as position demand signal a by. The work in the warnin

24、g way induction synchromesh this time not only is the position sensor, also is the comparator, it by, The cosine generator assigns slide guage initiation signal a electricity and by step of transmission.4） conclusions Under the CIMS environment the technology which develops unceasingly based on char

25、acteristic components information modeling, how enhances the components order of complexity which the characteristic design can complete; How causes question and so on request which the characteristic design adoption trick recognition, the characteristic semantics transforms also to wait for the peo

26、ple to solve. This article introduced the characteristic technology in the components information modeling application, describes this components data model database realization with emphasis; Establishes the components information database system may satisfy the CIMS system well to the letter. Nume

27、rical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job. When the

28、 job changes, the program of instructions is changed. The capability to change the program is what makes NC suitable for low-and medium-volume production. It is much easier to write new programs than to make major alterations of the processing equipment.从暴瓿蜩蕴识鹂娴霰蟪嫘霖励羲Basic components of NC 瓣铫赚苋泺堵琳意蠲

29、高母稗甑昱A numerical control system consists of the following three basic components:裙瘥筒稻扛拭薛浊焦癀溧忮丰笄Program of instructions诂羟叫五冕踵饲筮祢荨帜吲秧喝Machine control unit撞钝澉误联纱槐贡橘圳竦偎咚韦Processing equipment喂笋坩愫虽辩便幄僧粜潇郜诗苡The general relationship among the three components is illustrated in Fig.2.1. The program is fed in

30、to the control unit, which directs the processing equipment accordingly.疣环蕹兵腼报轻护畦貌腹拇聆砀The program of instructions is the detailed step-by-step commands that direct the processing equipment. In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktab

31、le on which the part is fixtured. More advanced instructions include selection of spindle speeds, cutting tool, and other function. The most common medium in use over the last several decades has been 1-in. -wide punched tape. Because of the widespread use of the punched tape, NC is sometimes called

32、 “tape control”. However, this is a misnomer in modern usage of numerical control. Coming into use more recently have been magnetic tape cassettes and floppy diskettes.偌辆臭呓怛姜箕迢辆掣氵薜芬皤The machine control unit (MCU) consists of the electronics and control hardware that read and interpret the program of

33、 instruction and convert it into mechanical actions of the machine tool or other processing equipment.即锎钨玩毹萘此鹞昔饿腔秕裟扫The processing equipment is the third basic component of an NC system. It is the component that performs useful work. In the most common example of numerical control, one that performs

34、 machining operations, the processing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.锌旦殆菏阏劝诮钡赐殿褐澍姹平TYPES OF CONTROL SYSTEMS鞒蘖蜩娌洪锭睿黑蛇痹罗搿速铽There are two basic types of control systems in numerical control: point-to-point and contouring. In the p

35、oint-to-point system, also called positioning, each axis of the machine is driven separately by leadscrews and, depending on the type of operation, at different velocities. The machine moves initially at maximum velocity in order to reduce nonproductive time but decelerates as the tool reaches its n

36、umerically defined position. Thus in an potation such as drilling or punching, the positioning and cutting take place sequentially. After the hole is drilled or punched, the tool retracts, moves rapidly to another position, and repeats the operation. The path followed from one position to another is

37、 important in only one respect: The time required should be minimized for efficiency. Point-to-point systems are used mainly in drilling, punching, and straight milling operations.琵蠛莺桥魅佬姗蒯檑褓铩啕纬铬In the contouring system, also known as the continuous path system, positioning and cutting operations are

38、 both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. The contouring system is used on lathes, milling machines, grinders, welding machinery, and machining

39、 centers.吠园筚熠削烈肇肮茳梅锌武蝮长Movement along the path, or interpolation, occurs incrementally, by one of several basic methods. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tool wear during machining

40、, can be made in the NC program.般欷喇鬃墓晡辫抓规渐致蹇霭滹There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring-type NC system. They include:寝额亳讷荒刂嘀余蟓飓购碜酆衡Linear interpolation睾迥盐祗鄄爝艰骺浪浇

41、笤苯毕氨Circular interpolation员诈斥酌蛞裣端漏龀屏滥城崆飙Helical interpolation猁三课堇絮柙鄹恭颈畎猪逼焰錾Parabolic interpolation植铺掩髋啁诖甑驹糊阍财除轧阑Cubic interpolation次彀珠凭俎粗啊宰皓槊噗腾魇痱Each of these interpolation procedures permits the programmer (or operator) to generate machine instructions for linear or curvilinear paths, using a relat

42、ively few input parameters. The interpolation module in the MCU performs the calculations and directs the tool along the path.室瞳竽臀粪癍瘩嬖帛獍冀蓉旦筮Linear interpolation is the most basic and is used when a straight-line path is to be generated in continuous-path NC. Two-axis and three-axis linear interpolat

43、ion routines are sometimes distinguished in practice, but conceptually they are the same. The program is required to specify the beginning point and end point of the straight line, and the feed rate that is to be followed along the straight line. The interpolator computes the feed rates for each of

44、the two (or three) axes in order to achieve the specified feed rate.丌榛蜒趴肜淹芡圣集蹦接轾擐慧Linear interpolation for creating a circular path would be quite inappropriate because the programmer would be required to specify the line segments and their respective end points that are to be used to approximate th

45、e circle. Circular interpolation schemes have been developed that permit the programming of a path consisting of a circular arc by specifying the following parameters of the arc: the coordinates of its end points, the coordinates of its center, its radius, and the direction of the cutter along the a

46、rc. The tool path that is created consists of a series of straight-line segments, but the segments are calculated by the interpolation module rather than the programmer. The cutter is directed to move along each line segment one by one in order to generate the smooth circular path. A limitation of c

47、ircular interpolation is that the plane in which the circular arc exists must be a plane defined by two axes of the NC system.辋叹姓狂攫钕胴馐捌卜蕙员虏肿Helical interpolation combines the circular interpolation scheme for two axes described above with linear movement of a third axis. This permits the definition

48、of a helical path in three-dimensional space.觎蝗掏黍燧被鬼蘼菩恃墼粲桂釉Parabolic and cubic interpolation routines are used to provide approximations of free-form curves using higher-order equations. They generally require considerable computational power and are not as common as linear and circular interpolatio

49、n. Their applications are concentrated in the automobile industry for fabricating dies for car body panels styled with free-form designs that cannot accurately and conveniently be approximated by combining linear and circular interpolations.帕沌捱螓草徵艨泛锑栉娟歪鲳生PROGRAMMING FOR NC鞋岷尚糅勒沈艉芡未季洽嵛槊恂A program for

50、 numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation, machining being the most commonly used process. Programming for NC may be done by an internal programming department, on the shop floor, or purchased from an outside source. Also, prog

51、ramming may be done manually or with computer assistance.档啃鄙啕瑞桥撇回讪腿磐桃菖筹The program contains instructions and commands. Geometric instructions pertain to relative movements between the tool and the workpiece. Processing instructions pertain to spindle speeds, feeds, tools, and so on. Travel instructi

52、ons pertain to the type of interpolation and slow or rapid movements of the tool or worktable. Switching commands pertain to on/off position for coolant supplies, spindle rotation, direction of spindle rotation, tool changes, workpiece feeding, clamping, and so on.胶淌蕲璋晌峄苹胳螗保量汤孩运1 Manual Programming

53、Manual part programming consists of first calculating dimensional relationships of the tool, workpiece, and work table, based on the engineering drawings of the part, and manufacturing operations to be performed and their sequence. A program sheet is then prepared, which consists of the necessary in

54、formation to carry out the operation, such as cutting tools, spindle speeds, feeds, depth of cut, cutting fluids, power, and tool or workpiece ally a paper tape is first prepared for trying out and debugging the program. Depending on how often it is to be used, the tape may be made of more durable M

55、ylar.醺娟俺荇朱径相内萋亡檑却喂琳Manual programming can be done by someone knowledgeable about the particular process and able to understand, read, and change part programs. Because they are familiar with machine tools and process capabilities, skilled machinists can do manual programming with some training in pr

56、ogramming. However, the work is tedious, time consuming, and uneconomical-and is used mostly in simple point-to-point applications.骸睡己庚鲕骗妖癸栏逼糈邰陉祓2 Computer-Aided Programming Computer-aided part programming involves special symbolic programming languages that determine the coordinate points of corner

57、s, edges, and surfaces of the part. Programming language is the means of communicating with the computer and involves the use of symbolic characters. The programmer describes the component to be processed in this language, and the computer converts it to commands for the NC machine. Several language

58、s having various features and applications are commercially available. The first language that used English-like statements was developed in the late 1950s and is called APT (for Automatically Programmed Tools). This language, in its various expanded forms, is still the most widely used for both poi

59、nt-to-point and continuous-path programming.媚吊何酰朝胗溏枭凼婉蝰鹛匀焙Computer-aided part programming has the following significant advantages over manual methods:爪捩盈媳塍邱惘沾陶醢礞浜筚棋 Use of relatively easy to use symbolic language豹栲嵯乐潜案谓壕瞍喇伧跷刃辑Reduced programming time. Programming is capable of accommodating a large amount of data concerning machine characteristics and process variables, such as power, speeds,