浮動夾頭工藝及夾具設計
浮動夾頭工藝及夾具設計,浮動,夾頭,工藝,夾具,設計
外文資料翻譯
NC and CNC
數控技術
The History of NC and CNC Development
數字控制與計算機數字控制的發(fā)展歷史
Numerical Control (NC) is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for the tool movements. The NC concept was proposed in the late 1940s by John Parsons of Traverse City, Michigan. Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.
數字控制是按照含有機床(刀具)運動信息程序所指定的順序自動執(zhí)行操作的加工過程。數控這一概念是由密歇根洲特拉華城的約翰·帕森于20世紀四十年代后期提出的。為了在工件上加工光滑的輪廓，帕森提出了一種自動的機床控制方式，它能夠引導銑床刀具加工出一種“過軸曲線”。
In 1949, The U.S. Air Force awarded Parsons a contract to develop a new type of machine tool that would be able to speed up production methods. Parsons commissioned the Massachusetts Institute of Technology (M.I.T.) to develop a practical implementation of his concept. Scientists and engineers at M.I.T. built a control system for a two-axis milling machine that used a perforated paper tape as the input media. In a short period of time, all major machine tool manufacturers were producing some machines with NC, but it was not until the late 1970s that computer-based NC became widely used. NC matured as an automation technology when inexpensive and powerful microprocessors replaced hard-wire logic-making computer-based NC systems.
1949年，美國空軍與帕森簽署了合同，要求開發(fā)一種能夠提高生產率的新型機床。帕森委托麻省理工學院(MIT)來開發(fā)一種新概念機床，麻省理工學院的科學家和工程師研制出了一種用穿孔紙帶作為輸入媒介的二軸聯(lián)動銑床控制系統(tǒng)。在較短時間內，當時所有主要的機床生產商都生產了一些數控機床，但直到20世紀七十年代后期，基于計算機的數字控制才被得到廣泛的使用。只有價格低廉且功能強大的微處理芯片代替了計算機數控系統(tǒng)中的硬連線邏輯發(fā)生器后，NC才真正成為一門自動化技術。
When Numerical Control is performed under computer supervision, it is called Computer Numerical Control (CNC). Computers are the control units of CNC machines, they are built in or linked to the machines via communications channels. When a programmer input some information in the program by tape and so on, the computer calculates all necessary data to get the job done.
當數控機床在計算機監(jiān)控下工作時，它就被稱為計算機數控機床(CNC)。計算機是CNC機床的控制單元，它們內嵌于數控機床或者通過通訊渠道與數控機床聯(lián)接，當程序員編程時，通過紙帶或磁盤將一些信息輸入，計算機將對一些必要的數據進行計算的完成工作。
On the first Numerically Controlled (NC) machines were controlled by tape, and
because of that, the NC systems were known as tape-controlled machines. They were able to control a single operation entered into the machine by punched or magnetic tape. There was no possibility of editing the program on the machine. To change the program, a new tape had to be made.
由于第一臺數控機床的數據是由紙帶控制的，因此數控系統(tǒng)被稱為紙帶控制機床。它們只能控制由輸入到機床內的紙帶或磁帶所規(guī)定的單一操作，輸入到機床內的程序是不能被編輯的，要改變程序必須重做新紙帶。
Today's systems have computers to control data; they are called Computer Numerically Controlled (CNC) machines. For both NC and CNC systems, work principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile
當今的系統(tǒng)都由計算機來控制數據，因而稱之為計算機數控機床(簡稱CNC機床)。NC和CNC系統(tǒng)兩者的工作原理一樣，僅僅控制執(zhí)行的方式不同。新型的數控系統(tǒng)通常速度更快、功率更大、功能更齊全。
The Applications of NC/CNC
數字控制與計算機數字控制的應用
Since its introduction, NC technology has found many applications, including lathes and turning Centers, milling machines and machining centers , punches , electrical discharg machines(EDM) Flame cutters,grinders,and inspection equipment. the most complex CNC machine tools are the turning center,shown in Fig.4-1(Amodern turning center with a ten-station turret that accepts quick-chang tools.Each tool can be positioned in Seconds with the press of a button).And the machine center shown in Fig.4-2(Vertical machining center,the tool magazine is on the machine.the control panel on the right can be swiveled by the operator)and Fig.4-3(horizontal machining center,equipped with an automatic tool changer .tool magazines can store 200 ctting tools.
數控技術自創(chuàng)立以來就得到了廣泛的應用，包括車床和車削中心、銑床和加工中心、沖床、電火花(EDM)加工機床、線切割機床、磨床以及測試檢測裝置等。最復雜的計算機數控機床是車削中心，圖4—1所示一個具有十轉位的刀架能進行快速換刀的現(xiàn)代車削中心，立式加工中心如圖4—2所示(刀具庫在機床的左邊。右邊的控制面板可由操作者通過轉臂轉動)，以及臥式加工中心，通過按下按鈕每把刀可在數秒鐘內定位。如圖4—3所示(配有自動換刀系統(tǒng)。刀具庫儲備有200把切削工具)。
When preparing a progam for a particular operation ,the prommer must select all cutting data using recommendations for conventional machining .this includes proper
Selection of cutting speeds,feedrate,tools and tool geometry,and so on.when the programmer has chosen all of the necessary information properly,the operator loads the programme into the machine and presses a button to start the cutting crycle .the CNC machine moves automatically from one maching operation to another , changing the cutting tols and applying the coolent.in a surprisingly short time ,the workpiece is
Machined according to the highest quality stangards. But that is not all.no matter how big the work series is,all of the parts will be almost identical in size and surface finishing. At this time of advanced technology,with its high demands for surface finishing and tolerances of components in,for example ,aerospace,nuclear,and medical equipment manufacturing,only CNC machines provide successful results.
當為某項操作編程時，程序員必須選擇傳統(tǒng)的加工切削數據推薦值。這些切削數據包括切削速度、進給率、刀具和刀具幾何形狀等。當程序員正確選擇所有必要信息后，操作人員將程序載入機床并按下按鈕，切削循環(huán)就開始。
Numerical 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. The instructions are provided by either of the two binary coded decimal systems: the Electronic Industries Association (EIA) code, or the American Standard Code for Information Interchange (ASCII). ASCII-coded machine control units will not accept . EIA coded instructions and vice versa. Increasingly, however, control units are being made to accept instructions in either code. 121Automation operation by NC is readily adaptable to the
operation of all metalworking machines. Lathes, milling machines, drill presses, boring machines, grinding machines, turret punches, flame or wire-cutting and welding machines, and even pipe benders are available with numerical controls.
數控技術是一種利用程序實現(xiàn)自動控制的技術，加工制造設備采用數控技術后能由數字、字符和符號等進行控制。這些數字、字符和符號等被編碼成按一定格式定義的指令程序用于一個特定的加工或工件，這些指令可以采用兩種二進制編碼的數字系統(tǒng)中的任意一種進行定義，這兩種二進制編碼數字系統(tǒng)分別為電工協(xié)會代碼(EIA)和美國標準信息交換代碼(ASCII)。一般來說，ASCII編碼的機床控制系統(tǒng)不能接受EIA編碼的指令，反之亦然。當然，這樣的問題已經逐漸得到解決。數控加工制造目前已經廣泛地應用于幾乎所有的金屬加工機床：車床，銑床，鉆床，鏜床，磨床，回轉沖床，電火化，線切割和焊接機床，甚至彎管機也采用數控加工技術。
Basic Components of NC
數控技術的基本組成
A numerical control system consists of the following three basic components:
一個數控系統(tǒng)主要由以下3個部分組成：
(1) Program instructions
(1)程序指令
(2) Machine control unit
(2)加工控制單元
(3) Processing equipment
(3)制造裝備
The program instructions are the detailed step by step commands that direct the processing equipment. [31In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixtured. More advanced instructions include selection of spindle speeds, cutting tools, and other functions.
程序指令是由一條一條的詳細指令所組成，制造裝備按要求執(zhí)行這些指令。最常用的指令有：可以按要求使機床刀具主軸位于工作臺上的具體位置，工作臺是用于固定加工零件的，許多更高級的指令還包括用于主軸速度的選擇、刀具速度的選擇及其他一些功能。
The machine control unit (MCU) consists of the electronics and control hardware that reads and interprets the program of instructions and convert it into mechanical actions of the machine tool or other processing equipment.
加工控制單元(MCU)包括一些用于閱讀和解釋程序指令并將其轉換為機床刀具或其他制造裝備的機械動作的電子和控制硬件。
The processing equipment is the component that performs metal process. In the most common example of numerical control, it is used to perform machining operations. The process-ing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.
制造裝備是一種進行金屬加工的數控技術裝備，在常用的數控技術領域中，制造裝備用于進行機械制造。制造裝備包括工作臺、主軸、電機及控制驅動單元。
Types of NC
數控技術的類型
There are two basic types of numerical control systems: point to point and contouring.
數控技術系統(tǒng)主要有兩種類型：點對點數控系統(tǒng)和輪廓線數控系統(tǒng)。
Point to point control system, also called positioning, is simpler than contouring control system. Its primary purpose is to move a tool or workpiece from one programmed point to another. Usually the machine function, such as a drilling operation, is also activated at each point by command from the NC program. Point to point systems are suitable for hole machining operations such as drilling, countersinking, couterbofing, reaming, boring and tapping. Hole punching machines, spotwelding machines, and assembly machines also use point to point NC systems.
點對點數控系統(tǒng)也稱為位置數控系統(tǒng)，比輪廓線數控系統(tǒng)簡單，其主要的原理是移動刀具或工件從一個程序控制點到另一一個控制點，通常像鉆床這樣的加工功能，每個點幫司以通過NC程序中的指令進行控制。點對點數控系統(tǒng)適用于像鉆孔、沉孔加工、沉孔鏜孔、鉸孔和攻絲等。其他沖孔機床、點焊機和裝配機床等也都采用點對點數控系統(tǒng)。
Contouring system, also known as the continuous path system, positioning and cutting operations are 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,incrementally, by one of several basic methods. 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 linear interpolation,circular interpolation, helical interpolation, parabolic interpolation and cubic interpolation. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tools wear during machining, can be made in the NC .
輪廓線數控系統(tǒng)也稱為輪廓線路徑數控系統(tǒng)，定位和切割操作都是以不同的速度沿著控制的路徑進行的。由于刀具沿路徑進行切削，因此刀具的運動和速度的精確控制和同步性能是非常重要的。輪廓線數控系統(tǒng)經常應用于車床、銑床、磨床、焊接機床和加工中心中。刀具沿著路徑的運動，或稱為插補逐漸出現(xiàn)了幾個不同的方法。有許多類型的插補方法用于處理輪廓線數控系統(tǒng)中生成光滑的輪廓線時遇到的各種問題。幾種比較常用的方法有線性插補，圓形插補，螺旋形插補、拋物線插補和立方插補等，在所有的插補方法中，路徑控制是以刀具的旋轉中心為標準，對于不同類型、不同直徑的刀具，加工過程中的不同刀具磨削量在數控程序中獲得不同的補償。
Programming for NC
數控系統(tǒng)的編程
A program for 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, programming may be done manually or with computer assistance.
一個數控系統(tǒng)(NC)的程序包括使數控(NC)機床進行操作和加工的一系列指令。數控程序可以由數控機床內部的程序庫開發(fā)生成，也可以從外面采購獲得。另外，程序可以通過手工編寫，也可以進行計算機輔助編程。
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 instructions 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. The first NC programming language was developed by MIT developmental work on NC programming systems in the late 1950s and called APT(Automatically Programmed Tools).
數控程序包括一系列指令系統(tǒng)和命令系統(tǒng)。幾何類指令用于定義刀具和工件之間的相對位置和運動：加工類指令用于定義主軸轉速、進給、刀具轉速等：傳送類指令用于定義刀具或工作臺的運動速度和插補的類型等；開關類指令用于冷卻液供給、主軸旋轉、主軸旋轉方向選擇、換刀、工件進給、夾具等的開關。第一個用于數控編程的數控編程語言是20世紀50年代由麻省理工學院數控編程系統(tǒng)開發(fā)小組專家開發(fā)的，并被命名為自動編程工具(APT)。
DNC and CNC
直接數字控制(DNC)和計算機數字控制(CNC)
The development of numerical control was a significant achievement in batch and job shop manufacturing, from both a technological and a commercial viewpoint. There have been two enhancements and extensions of NC technology, including:
數控技術的發(fā)展在批量生產和車間生產加工中，不管是在技術上還是在商業(yè)上都獲得了巨大的成功。目前，已經有兩種數控技術系統(tǒng)得到了發(fā)展，分別是：
(1) Direct numerical control
(1)直接數字控制(DNC)。
(2) Computer numerical control
(2)計算機數字控制(CNC)。
Direct numerical control can be defined as a manufacturing system in which a number of machines are controlled by a computer through direct connection and in real time. The tape reader is omitted in DNC, thus relieving the system of its least reliable component. Instead of using the tape reader, the part program is transmitted to the machine tool directly from the computer memory. In principle, one computer can be used to control more than 100 separate machines. (One commercial DNC system during the 1970s boasted a control capability of up to 256 machine tools.) The DNC computer is designed to provide instructions to each machine tool on demand. When the machine needs control commands, they are communicated to it immediately.
直接數字控制(DNC)可以被定義為這樣一個生產制造系統(tǒng)，該制造系統(tǒng)有許多臺加工機床，而相互之間由一臺計算機采用直接連接，進行實時控制。這樣，在傳統(tǒng)的數字控制技術中采用的磁帶閱讀器在直接數字控制中被取消，從而保證了系統(tǒng)的可靠性。不使用磁帶閱讀器，被加工的零件程序就從計算機的存儲器中直接傳送到進行加工的刀具上。從原理上講，一臺計算機可以控制多達100臺加工機床，(在20世紀70年代一個商業(yè)使用的DNC系統(tǒng)宣稱可以控制多達256個機床刀具)。直接數字控制計算機用于按要求提供加工指令給每個進行加工的刀具上，當機床需要控制指令時，計算機就可以馬上將指令傳送到機床上。
Since the introduction of DNC, there have been dramatic advances in computer
technology. The physical size and cost of a digital computer has been significantly reduced at the same time that its computational capabilities have been substantially increased. In numerical control, the result of these advances has been that the large hard-wired MCUs of conventionalNC have been replaced by control units based on the digital computer. Initially, minicomputers were utilized in the early 1970s. As further miniaturization occurred in computers, minicomputers were replaced by today's microcomputers.
隨著直接數字控制(DNC)技術和計算機技術的飛速發(fā)展，數字式計算機的尺寸和價格的大幅度的降低，數字式計算機的計算能力的大大提高，大量傳統(tǒng)的以硬件線路為基礎的加工控制單元被以數字計算機為基礎的數字控制單元所替代。最初在20世紀70年代使用了小型計算機。后來，隨著計算機的進一步小型化，早期的小型計算機逐漸被現(xiàn)在的微型計算機所取代。
Computer numerical control is an NC system using dedicated microcomputer as the machine control unit. Because a digital computer is used in both CNC and DNC, it is appropriate to distinguish between the two types of system. There are three principal differences:
計算機數控(CNC)使用專用的微型計算機作為加工控制單元。因為數字計算機都用于計算機數控(CNC)和直接數控(DNC)，所以應該注意兩者之間的區(qū)別，可以從3個方面來加以區(qū)分。
1) DNC computers distribute instructional data to, and collect data from, a large number of machines. CNC computers control only one machine, or a small number of machines.
(1) DNC計算機是將指令數據發(fā)送到許多機床去或從許多機床中收集數據，而CNC計算機每次只控制一臺或幾臺機床。
(2) DNC computers occupy a location that is typically remote from the machines
under their control. CNC computer are located very near their machine tools.
(2) DNC計算機一般位于距機床一定距離的位置，而CNC計算機一般都位于距機床較近的位置。
(3) DNC software is developed not only to control individual pieces of production equipment, but also to serve as part of a management information system in the manufacturing sector of the firm. CNC software is developed to augment the capabilities of a particular machine Tool.
(3) DNC計算機開發(fā)的軟件不僅可以用于控制單件生產，而且可以用于一個企業(yè)制造部門的管理信息系統(tǒng)，而CNC計算機開發(fā)的軟件一般只用于某個特殊加工的工具。
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