609 典型零件的數(shù)控編程及加工仿真
609 典型零件的數(shù)控編程及加工仿真,609,典型零件的數(shù)控編程及加工仿真,典型,零件,數(shù)控,編程,加工,仿真
英文資料翻譯
Mechanical Design
NUMERICAL CONTROL
Numerical control 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 work part or job．When the job changes，the program of instructions is changed．The capability to change the program is what makes N／C suitable for low-and medium-volume production．It is much easier to write programs than to make major alterations of the processing equipment．
Number control lather main use to carry on a car to pare towards revolving body spare parts, the Tang pare, drill to pare, the Jiao pare, offend silk etc. process of work preface. General ability auto inside completion outside cylinder noodles, conic surface, surface of sphere, cylinder thread, slot and carry noodles etc. the slice of work preface pare to process.
The host is the topic that the number control lather and include a tool machine body, sign pillar, principal axis and enter etc. is to the organization machine parts. Number control equip, is number control tool machine of core, include hardware and correspond of software, used for an importation numeral turn of spare parts procedure, and completion importation information of saving, the transformation of data, put to repair operation and realization various control function. Drive to equip, he is number control the drive of organization of the tool machine performance parts, include a principal axis to drive unit and enter to the unit, principal axis electrical engineering and enter etc. to electrical engineering. He under the control that number control to equip pass electricity or electricity liquid servo system realization principal axis with enters give drive. When several enter to give allied move, can completion fixed position, straight line, process of flat surface curve and space curve. Assistance equips the index number control tool machine of some necessity of kit parts, in order to assurance number control tool machine of circulate, such as cool off, row scraps, lubricate, illuminate, monitor etc. It include a liquid to press friendly move equip, row scraps equip, exchange work set, number control to turn Taiwan and number control cent degree head. Plait distance and other subsidiary equipments, can use to carry on the procedure of spare parts to draw up outside machine, saving.
Modern number control lather to all have X, Z two stalk of allied move function, knife position and point of a knife arc radius of compensate function, and process fix circulation function.
The number control the structure of lather
1. The number control a lather brief introduction
The number control constitute of lather: Number control system, bed body, principal axis and enter to the system, turn round a knife, operation front-panel and assistance system etc..
(1) The economy number control lather: Adoption step enter electric motor and list slice machine to common the car of the lather pare into to the system carry on reformation behind formation of the simple number control lather. The cost is lower, automation degree and function be all more bad, the car pare to process accuracy also not high, be applicable to request not high of turn round type spare parts of the car pare to process.
The economy number control lather
(2) Common number control lather: Pare to process a request to carry on the structure according to the car specialized design, equipment in general use number control system but formation of number control lather. Number control system function strong, automation degree with process accuracy also more Ago, be applicable to general turn round type spare parts of the car pare to process. This kind of number control lather can control 2 sit a mark stalk in the meantime, namely x stalk and z stalk.
Common number control lather
(3)the car pare to process center: At common number control the foundation of lather up, increment C stalk and motive head, more high class of the tool machine still take a knife database, can control X, Z and C 3 sit mark stalk, allied move control stalk can BE(X, Z),(X, C) or(Z, C).Because increment C stalk and Xian pare a motive head, this kind of number control process of lather function consumedly strengthen, in addition to carry on general the car pare, also can carry on path to pare with stalk toward the Xian, the curved face Xian pare, the center line don't turn round in the spare parts center of bore and path pare toward the drill of bore etc. process.
2. The liquid press card dish and liquid to press a tail
The liquid press card dish is number control a car to pare to process clip tight work piece of importance enclosure, rightness general turn round type spare parts can adoption common the liquid press card dish; To the spare parts be clip hold the part isn't the spare parts of cylinder form, demand adoption appropriation card dish; With the stick anticipate direct process spare parts demand adoption spring coil card dish.
To stalk to the size and the path is to the specific value bigger spare parts of size, demand adoption install press a tail in the liquid up of live top carry on prop up to the spare parts end tip, then can assurance carry on to the spare parts exactitude of process. The tail has a common liquid to press tail and programmable liquid to press a tail.
3. The number control the knife of lather
Number control lather can equipment two kinds of knife:
(1) Appropriation knife from lather produce manufacturer oneself development, haft for use is also appropriation of. This kind of the advantage be that the manufacturing cost is low, but lack in general use.
(2)in general use knife according to certain in general use standard(like VDI, Germany engineer's association) but produce of knife, number control lather production manufacturer can according to number control the function of lather request to carry on a choice allocation.
In general use knife
4. The Xian pare a motive head
Number control lather knife top to install Xian after pare the motive head can consumedly expand number to control process of lather ability. Such as :Make use of the Xian pare a motive head to carry on stalk to drill a hole to pare stalk toward the slot with Xian.
The N／C system consists of the following components：data input，the tape reader with the control unit，feedback devices，and the metal—cutting machine tool or other type of N／C equipment．
Data input，also called “man—to—control link”，may be provided to the machine tool manually，or entirely by automatic means．Manual methods when used as the sole source of input data are restricted to a relatively small number of inputs．Examples of manually operated devices are keyboard dials，pushbuttons，switches，or thumbwheel selectors．These are located on a console near the machine．Dials ale analog devices usually connected to a syn-chro-type resolver or potentiometer．In most cases，pushbuttons，switches，and other similar types of selectors aye digital input devices．Manual input requires that the operator set the controls for each operation．It is a slow and tedious process and is seldom justified except in elementary machining applications or in special cases．
In practically all cases，information is automatically supplied to the control unit and the machine tool by cards，punched tapes，or by magnetic tape．Eight—channel punched paper tape is the most commonly used form of data input for conventional N／C systems．The coded instructions on the tape consist of sections of punched holes called blocks．Each block represents a machine function，a machining operation，or a combination of the two．The entire N／C program on a tape is made up of an accumulation of these successive data blocks．Programs resulting in long tapes all wound on reels like motion-picture film．Programs on relatively short tapes may be continuously repeated by joining the two ends of the tape to form a loop．Once installed，the tape is used again and again without further handling．In this case，the operator simply loads and unloads the parts．Punched tapes ale prepared on type writers with special tape—punching attachments or in tape punching units connected directly to a computer system．Tape production is rarely error-free．Errors may be initially caused by the part programmer，in card punching or compilation，or as a result of physical damage to the tape during handling，etc．Several trial runs are often necessary to remove all errors and produce an acceptable working tape．
While the data on the tape is fed automatically，the actual programming steps ale done manually．Before the coded tape may be prepared，the programmer，often working with a planner or a process engineer, must select the appropriate N／C machine tool，determine the kind of material to be machined，calculate the speeds and feeds，and decide upon the type of tooling needed. The dimensions on the part print are closely examined to determine a suitable zero reference point from which to start the program．A program manuscript is then written which gives coded numerical instructions describing the sequence of operations that the machine tool is required to follow to cut the part to the drawing specifications．
The control unit receives and stores all coded data until a complete block of information has been accumulated．It then interprets the coded instruction and directs the machine tool through the required motions．
The function of the control unit may be better understood by comparing it to the action of a dial telephone，where，as each digit is dialed，it is stored．When the entire number has been dialed，the equipment becomes activated and the call is completed．
Silicon photo diodes，located in the tape reader head on the control unit，detect light as it passes through the holes in the moving tape．The light beams are converted to electrical energy，which is amplified to further strengthen the signal．The signals are then sent to registers in the control unit, where actuation signals are relayed to the machine tool drives．
Some photoelectric devices are capable of reading at rates up to 1000 characters per second．High reading rates are necessary to maintain continuous machine—tool motion；otherwise dwell marks may be generated by the cutter on the part during contouring operations．The reading device must be capable of reading data blocks at a rate faster than the control system can process the data．
A feedback device is a safeguard used on some N／C installations to constantly compensate for errors between the commanded position and the actual location of the moving slides of the machine tool．An N／C machine equipped with this kind of a direct feedback checking device has what is known as a closed-loop system．Positioning control is accomplished by a sensor which，during the actual operation，records the position of the slides and relays this information back to the control unit．Signals thus received ale compared to input signals on the tape，and any discrepancy between them is automatically rectified．
In an alternative system，called an open—loop system，the machine is positioned solely by stepping motor drives in response to commands by a controllers．There are three basic types of NC motions, as follows:
Point-to-point or Positional Control In point-to-point control the machine tool elements (tools, table, etc.) are moved to programmed locations and the machining operations performed after the motions are completed. The path or speed of movement between locations is unimportant; only the coordinates of the end points of the motions are accurately controlled. This type of control is suitable for drill presses and some boring machines, where drilling, tapping, or boring operations must be performed at various locations on the work piece. Straight-Line or Linear Control Straight-Line control systems are able to move the cutting tool parallel to one of the major axes of the machine tool at a controlled rate suitable for machining. It is normally only possible to move in one direction at a time, so angular cuts on the work piece are not possible, consequently, for milling machines, only rectangular configurations can be machined or for lathes only surfaces parallel or perpendicular to the spindle axis can be machined. This type of controlled motion is often referred to as linear control or a half-axis of control. Machines with this form of control are also capable of point-to-point control.
Continuous Path or Contouring Control In continuous path control the motions of two or more of the machine axes are controlled simultaneously, so that the position and velocity of the can be tool are changed continuously. In this way curves and surfaces can be machined at a controlled feed rate. It is the function of the interpolator in the controller to determine the increments of the individual controlled axes of the machines necessary to produce the desired motion. This type of control is referred to as continuous control or a full axis of control.
Some terminology concerning controlled motions for NC machines has been introduced. For example, some machines are referred to as four-or five-or even six-axis machines. For a vertical milling machine three axes of control are fairly obvious, these being the usual X, Y, Z coordinate directions. A fourth or fifth axis of control would imply some form of rotary table to index the work piece or possibly to provide angular motion of the work head. Thus, in NC terminology an axis of control is any controlled motion of the machine elements (spindles, tables, etc). A further complication is use of the term half-axis of control; for example, many milling machines are referred to as 2.5-axis machine. This means that continuous control is possible for two motions (axes) and only linear control is possible for the third axis. Applied to vertical milling machines, 2.5axis control means contouring in the X, Y plane and linear motion only in the Z direction. With these machines three-dimensional objects have to be machined with water lines around the surface at different heights. With an alternative terminology the same machine could be called a 2CL machine (C for continuous, L for linear control). Thus, a milling machine with continuous control in the X, Y, Z directions could be termed be a three-axis machine or a 3c machine, similarly, lathes is usually two axis or 2C machines. The degree of work precision depends almost entirely upon the accuracy of the lead screw and the rigidity of the machine structure．With this system．there is no self-correcting action or feedback of information to the control unit．In the event of an unexpected malfunction，the control unit continues to put out pulses of electrical current．If，for example，the table on a N／C milling machine were suddenly to become overloaded，no response would be sent back to the controller．Because stepping motors are not sensitive to load variations，many N／C systems are designed to permit the motors to stall when the resisting torque exceeds the motor torque．Other systems are in use，however，which in spite of the possibility of damage to the machine structure or to the mechanical system，ale designed with special high—torque stepping motors．In this case，the motors have sufficient capacity to “overpower’’ the system in the event of almost any contingency．
數(shù)控
數(shù)控是可編程自動化技術(shù)的一種形式，通過數(shù)字、字母和其他符號來控制加工設(shè)備。數(shù)字、字母和符號用適當(dāng)?shù)母袷骄幋a為一個特定工件定義指令程序。當(dāng)工件改變時，指令程序就改變。這種改變程序的能力使數(shù)控適合于中、小批量生產(chǎn)，寫一段新程序遠(yuǎn)比對加工設(shè)備做大的改動容易得多。
數(shù)控車床主要用來對旋轉(zhuǎn)體零件進(jìn)行車削、鏜削、鉆削、鉸削、攻絲等工序的加工。一般能自動完成內(nèi)外圓柱面、圓錐面、球面、圓柱螺紋、槽及端面等工序的切削加工。
主機(jī)是數(shù)控車床的主題，包括機(jī)床身、立柱、主軸、進(jìn)給機(jī)構(gòu)等機(jī)械部件。數(shù)控裝置，是數(shù)控機(jī)床的核心，包括硬件以及相應(yīng)的軟件，用于輸入數(shù)字化的零件程序，并完成輸入信息的存儲、數(shù)據(jù)的變換、插補(bǔ)運算以及實現(xiàn)各種控制功能。驅(qū)動裝置，他是數(shù)控機(jī)床執(zhí)行機(jī)構(gòu)的驅(qū)動部件，包括主軸驅(qū)動單元、進(jìn)給單元、主軸電機(jī)及進(jìn)給電機(jī)等。他在數(shù)控裝置的控制下通過電氣或電液伺服系統(tǒng)實現(xiàn)主軸和進(jìn)給驅(qū)動。當(dāng)幾個進(jìn)給聯(lián)動時，可以完成定位、直線、平面曲線和空間曲線的加工。輔助裝置，指數(shù)控機(jī)床的一些必要的配套部件，用以保證數(shù)控機(jī)床的運行，如冷卻、排屑、潤滑、照明、監(jiān)測等。它包括液壓和氣動裝置、排屑裝置、交換工作臺、數(shù)控轉(zhuǎn)臺和數(shù)控分度頭。編程及其他附屬設(shè)備，可用來在機(jī)外進(jìn)行零件的程序編制、存儲等。
現(xiàn)代數(shù)控車床都具有X、Z兩軸的聯(lián)動功能、刀具位置和刀尖圓弧半徑的補(bǔ)償功能、以及加工固定循環(huán)功能。
數(shù)控車床的結(jié)構(gòu)
1.數(shù)控車床簡介
數(shù)控車床的組成：數(shù)控系統(tǒng)、床身、主軸、進(jìn)給系統(tǒng)、回轉(zhuǎn)刀架、操作面板和輔助系統(tǒng)等。
(1)經(jīng)濟(jì)型數(shù)控車床：采用步進(jìn)電動機(jī)和單片機(jī)對普通車床的車削進(jìn)給系統(tǒng)進(jìn)行改造后形成的簡易型數(shù)控車床。成本較低，自動化程度和功能都比較差，車削加工精度也不高，適用于要求不高的回轉(zhuǎn)類零件的車削加工。
經(jīng)濟(jì)型數(shù)控車床
(2)普通數(shù)控車床：根據(jù)車削加工要求在結(jié)構(gòu)上進(jìn)行專門設(shè)計，配備通用數(shù)控系統(tǒng)而形成的數(shù)控車床。數(shù)控系統(tǒng)功能強(qiáng)，自動化程度和加工精度也比較高，適用于一般回轉(zhuǎn)類零件的車削加工。這種數(shù)控車床可同時控制兩個坐標(biāo)軸，即x軸和z軸。
普通數(shù)控車床
(3)車削加工中心：在普通數(shù)控車床的基礎(chǔ)上，增加了C軸和動力頭，更高級的機(jī)床還帶有刀庫，可控制X、Z和C三個坐標(biāo)軸，聯(lián)動控制軸可以是(X、Z)、(X、C)或(Z、C)。由于增加了C軸和銑削動力頭，這種數(shù)控車床的加工功能大大增強(qiáng)，除可以進(jìn)行一般車削外，還可以進(jìn)行徑向和軸向銑削、曲面銑削、中心線不在零件回轉(zhuǎn)中心的孔和徑向孔的鉆削等加工。
2.液壓卡盤和液壓尾架
液壓卡盤是數(shù)控車削加工時夾緊工件的重要附件，對一般回轉(zhuǎn)類零件可采用普通液壓卡盤；對零件被夾持部位不是圓柱形的零件，則需要采用專用卡盤；用棒料直接加工零件時需要采用彈簧卡盤。
對軸向尺寸和徑向尺寸的比值較大的零件，需要采用安裝在液壓尾架上的活頂尖對零件尾端進(jìn)行支撐，才能保證對零件進(jìn)行正確的加工。尾架有普通液壓尾架和可編程液壓尾架。
3.數(shù)控車床的刀架
數(shù)控車床可以配備兩種刀架：
(1)專用刀架 由車床生產(chǎn)廠商自己開發(fā)，所使用的刀柄也是專用的。這種刀架的優(yōu)點是制造成本低，但缺乏通用性。
(2)通用刀架 根據(jù)一定的通用標(biāo)準(zhǔn)(如VDI，德國工程師協(xié)會)而生產(chǎn)的刀架，數(shù)控車床生產(chǎn)廠商可以根據(jù)數(shù)控車床的功能要求進(jìn)行選擇配置。
4.銑削動力頭
數(shù)控車床刀架上安裝銑削動力頭后可以大大擴(kuò)展數(shù)控車床的加工能力。如：利用銑削動力頭進(jìn)行軸向鉆孔和銑削軸向槽。
數(shù)控系統(tǒng)由下列組件組成：數(shù)據(jù)輸入裝置，帶控制單元的磁帶閱讀機(jī)，反饋裝置和切削機(jī)床或其他形式的數(shù)控設(shè)備。
數(shù)據(jù)輸人裝置，也稱“人機(jī)聯(lián)系裝置”，可用人工或全自動方法向機(jī)床提供數(shù)據(jù)。人工方法作為輸人數(shù)據(jù)唯一方法時，只限于少量輸入。人工輸入裝置有鍵盤，撥號盤，按鈕，開關(guān)或撥輪選擇開關(guān)，這些都位于機(jī)床附近的一個控制臺上。撥號盤通常連到一個同步解析器或電位計的模擬裝置上。在大多數(shù)情況下，按鈕、開關(guān)和其他類似的旋鈕是數(shù)據(jù)輸入元件。人工輸入需要操作者控制每個操作，這是一個既慢又單調(diào)的過程，除了簡單加工場合或特殊情況，已很少使用。
幾乎所有情況下，信息都是通過卡片、穿孔紙帶或磁帶自動提供給控制單元。在傳統(tǒng)的數(shù)控系統(tǒng)中，八信道穿孔紙帶是最常用的數(shù)據(jù)輸入形式，紙帶上的編碼指令由一系列稱為程序塊的穿孔組成。每一個程序塊代表一種加工功能、一種操作或兩者的組合。紙帶上的整個數(shù)控程序由這些連續(xù)數(shù)據(jù)單元連接而成。帶有程序的長帶子像電影膠片一樣繞在盤子上，相對較短的帶子上的程序可通過將紙帶兩端連接形成一個循環(huán)而連續(xù)不斷地重復(fù)使用。帶子一旦安裝好，就可反復(fù)使用而無需進(jìn)一步處理。此時，操作者只是簡單地上、下工件。穿孔紙帶是在帶有特制穿孔附件的打字機(jī)或直接連到計算機(jī)上的紙帶穿孔裝置上做成的。紙帶制造很少不出錯，錯誤可能由編程、卡片穿孔或編碼、紙帶穿孔時的物理損害等形成。通常，必須要試走幾次來排除錯誤，才能得到一個可用的工作紙帶。
雖然紙帶上的數(shù)據(jù)是自動進(jìn)給的，但實際編程卻是手工完成的，在編碼紙帶做好前，編程者經(jīng)常要和一個計劃人員或工藝工程師一起工作，選擇合適的數(shù)控機(jī)床，決定加工材料，計算切削速度和進(jìn)給速度，決定所需刀具類型，仔細(xì)閱讀零件圖上尺寸，定下合適的程序開始的零參考點，然后寫出程序清單，其上記載有描述加工順序的編碼數(shù)控指令，機(jī)床按順序加工工件到圖樣要求。控制單元接受和儲存編碼數(shù)據(jù)，直至形成一個完整的信息程序塊，然后解釋數(shù)控指令，并引導(dǎo)機(jī)床得到所需運動。
為更好理解控制單元的作用，可將它與撥號電話進(jìn)行比較，即每撥一個數(shù)字，就儲存一個，當(dāng)整個數(shù)字撥好后，電話就被激活，也就完成了呼叫。
裝在控制單元里的紙帶閱讀機(jī)，通過其內(nèi)的硅光二極管，檢測到穿過移動紙帶上的孔漏過的光線，將光束轉(zhuǎn)變成電能，并通過放大來進(jìn)一步加強(qiáng)信號，然后將信號送到控制單元里的寄存器，由它將動作信號傳到機(jī)床驅(qū)動裝置。
有些光電裝置能以高達(dá)每秒1000個字節(jié)的速度閱讀，這對保持機(jī)床連續(xù)動作是必須的，否則，在輪廓加工時，刀具可能在工件上產(chǎn)生劃痕。閱讀裝置必須要能以比控制系統(tǒng)處理數(shù)據(jù)更快的速度來閱讀數(shù)據(jù)程序塊。
反饋裝置是用在一些數(shù)控設(shè)備上的安全裝置，它可連續(xù)補(bǔ)償控制位置與機(jī)床運動滑臺的實際位置之間的誤差。裝有這種直接反饋檢查裝置的數(shù)控機(jī)床有一個閉環(huán)系統(tǒng)裝置。位置控制通過傳感器實現(xiàn)，在實際工作時，記錄下滑臺的位置，并將這些信息送回控制單元。接受到的信號與紙帶輸入的信號相比較，它們之間的任何偏差都可得到糾正。
在另一個稱為開環(huán)的系統(tǒng)中，機(jī)床僅由響應(yīng)控制器命令的步進(jìn)電動機(jī)驅(qū)動定位，工件的精度幾乎完全取決于絲杠的精度和機(jī)床結(jié)構(gòu)的剛度。有幾個理由可以說明步進(jìn)電機(jī)是一個自動化申請的非常有用的驅(qū)動裝置。對于一件事物，它被不連續(xù)直流電壓脈沖驅(qū)使,是來自數(shù)傳計算機(jī)和其他的自動化的非常方便的輸出控制系統(tǒng)。當(dāng)多數(shù)是索引或其他的自動化申請所必備者的時候，步進(jìn)電機(jī)對運行一個精確的有角進(jìn)步也是理想的。因為控制系統(tǒng)不需要監(jiān)聽就提供特定的輸出指令而且期待系統(tǒng)適當(dāng)?shù)胤磻?yīng)的公開- 環(huán)操作造成一個回應(yīng)環(huán)，步進(jìn)電機(jī)是理想的。 一些工業(yè)的機(jī)械手使用高抬腿運步的馬乘汽車駕駛員，而且步進(jìn)電機(jī)是有用的在數(shù)字受約束的工作母機(jī)中。 這些申請的大部分是公開- 環(huán) ,但是雇用回應(yīng)環(huán)檢測受到驅(qū)策的成份位置是可能的。 環(huán)的一個分析者把真實的位置與需要的位置作比較，而且不同是考慮過的錯誤。 那然后駕駛員能發(fā)行對步進(jìn)電機(jī)的電脈沖，直到錯誤被減少對準(zhǔn)零位。在這個系統(tǒng)中，沒有信息反饋到控制單元的自矯正過程。出現(xiàn)誤動作時，控制單元繼續(xù)發(fā)出電脈沖。比如，一臺數(shù)控銑床的工作臺突然過載，阻力矩超過電機(jī)轉(zhuǎn)矩時，將沒有響應(yīng)信號送回到控制器。因為，步進(jìn)電機(jī)對載荷變化不敏感，所以許多數(shù)控系統(tǒng)設(shè)計允許電機(jī)停轉(zhuǎn)。然而，盡管有可能損壞機(jī)床結(jié)構(gòu)或機(jī)械傳動系統(tǒng)，也有使用帶有特高轉(zhuǎn)矩步進(jìn)電機(jī)的其他系統(tǒng)，此時，電動機(jī)有足夠能力來應(yīng)付系統(tǒng)中任何偶然事故。
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