3611 臥式組合鉆床設(shè)計(jì),臥式,組合,鉆床,設(shè)計(jì) N/C Machine Tool ElementsN/C machine tool elements consist of dimensioning systems, control systems, servomechanisms and open-or close-loop systems. It is important to understand each element prior to actual programming of a numerically controlled part.The team measuring system in N/C refers to the method a machine tool uses to move a part from a reference point to a target point. A target point may be a certain location for drilling a slot, or other machining operation. The two measuring systems used on N/C machines are the absolute and incremental. The absolute (also called coordinate) measuring system uses a fixed reference point (origin). It is on this point that all positional information is based. In other words, all the locations to which a part will be moved must be given dimensions relating to that original fixed reference point. The incremental measuring system (also called delta) has a floating coordinating system. With the inference point each time the part is moved .Notice that with this system, each new location bases its values in X and Y from the preceding location. One disadvantage to this system is that any errors made will be repeated throughout the entire program, if not detected and corrected.There are two types of control systems commonly used on N/C equipment: point-to-point and continuous path. A point-to-point controlled N/C machine tool, sometimes referred to as a positioning control type, has the capability of moving only along a straight line. However, when two axes are programmed simultaneously with equal values a 45°angle will be generated .Point-to-point systems are generally found on drilling and simple milling machine where hole location and straight milling jobs are performed. Point-to-point systems can be utilized to generate arcs and angles by programming the machine to move in a series of small steps. Using this technique, however, the actual path machined is slightly different from the cutting path specified.Machine tools that have the capability of moving simultaneously in two or more axes are classified as continuous-path or contouring. These machines are used for machining arcs, radii, circles, and angles of any size in two or three dimensions. Continuous-path machines are more expensive than point-to-point systems and generally require a computer to aid programming when machining complex contours.N/C servomechanisms are devices used for producing accurate movement of a table or slide along an axis. Two types of servos are commonly used on N/C equipment: electric stepping motors and hydraulic motors. Stepping motor servos are frequently used on less expensive N/C equipment. These motors are generally high-torque power servos and mounted directly to a lead screw of a table or tool slide. Most stepping motors are actuated by magnetic pulses from the stator and rotor assemblies. The net result of this action is that one rotation of the motor shaft produces 200 steps. Connecting the motor shaft to a 10-pitch lead screw allows 0.0005-in, movements to be made (1/200×1/10=0.0005 in.).Hydraulic servos produce a fluid pressure that flows through gears or pistons to effect shaft rotation. Mechanical motion of lead screws and slides is accomplished through various valves and controls from these hydraulic motors. Hydraulic servos produce more torque than stepping motors. However, they are more expensive and very noisy. Larger N/C machines use hydraulic servos.N/C machines that use an open-loop system contain no-feedback signal to ensure that a machine axis has traveled the required distance. That is, if the input received was to move a particular table 1.000 in, the servo unit generally moves the table 1.000 in. There is no means for comparing the actual table movement with the input signal, however. The only assurance that has actually moved 1.000 in is the reliability of the servo system used. Open- loop systems are, of course, less expensive than close-loop systems. A close-loop system compares the actual output (the table movement of 1.000 in.) with the input signal and compensates for errors. A feedback unit actually compares the amount the table has been moved with the input signal. Some feedback units on close-loop systems are transducers, electrical or magnetic scales, and synchros. Close-loop systems greatly increase the reliability of N/C machines. 數(shù)控機(jī)床的組成部分?jǐn)?shù)控機(jī)床的組成部分包括測量系統(tǒng)，控制系統(tǒng)，伺服系統(tǒng)及開環(huán)或閉環(huán)系統(tǒng)，在對數(shù)控零件進(jìn)行程序設(shè)計(jì)之前，了解各組成部分是重要的。數(shù)控中，測量系統(tǒng)這一術(shù)語指的是機(jī)床將一個(gè)零件從基準(zhǔn)點(diǎn)移動到目標(biāo)點(diǎn)的方法。目標(biāo)點(diǎn)可以是鉆一個(gè)孔，銑一個(gè)槽或其它加工操作的一個(gè)確定的位置。用于數(shù)控機(jī)床的兩種測量系統(tǒng)是絕對測量系統(tǒng)和增量測量系統(tǒng)。絕對測量系統(tǒng)（亦稱坐標(biāo)測量系統(tǒng)）采用固定基準(zhǔn)點(diǎn)（原點(diǎn)） ，所有位置信息正是以這一點(diǎn)為基準(zhǔn)。換句話說，必須給出一個(gè)零件運(yùn)動的所有位置相對于原始固定基準(zhǔn)點(diǎn)的尺寸關(guān)系。增量測量系統(tǒng)有一個(gè)移動的坐標(biāo)系統(tǒng)。運(yùn)用增量系統(tǒng)時(shí)，零件每移動一次，機(jī)床就建立一個(gè)新的原點(diǎn)（基準(zhǔn)點(diǎn)） 。注意，使用這個(gè)系統(tǒng)時(shí)，每個(gè)新的位置在 X 和 Y 軸上的值都是建立在前一個(gè)位置之上的。這種系統(tǒng)的一個(gè)缺點(diǎn)是，如果產(chǎn)生的任何錯誤沒有被發(fā)現(xiàn)與校正，則錯誤會在整個(gè)過程中反復(fù)存在。用于數(shù)控設(shè)備的控制系統(tǒng)通常有兩類，即點(diǎn)位控制系統(tǒng)和連續(xù)控制系統(tǒng)。點(diǎn)位控制數(shù)控機(jī)床（有時(shí)稱為位置控制型數(shù)控機(jī)床）只有沿直線運(yùn)動的能力。然而，當(dāng)沿兩軸以等值同時(shí)編程時(shí)，會形成 45°斜線。點(diǎn)位控制系統(tǒng)常用于需確定孔位的鉆床和需進(jìn)行直線銑削加工的簡單銑床上。點(diǎn)位控制系統(tǒng)可通過程序控制機(jī)床，以一系列小步運(yùn)動形成弧線和斜線。然而，用這種方法時(shí)，實(shí)際加工軌跡與規(guī)定的切削軌跡略有不同。具有在兩個(gè)或多個(gè)坐標(biāo)軸方向同時(shí)運(yùn)動的能力的機(jī)床，歸屬連續(xù)軌跡控制或輪廓類機(jī)床。這些機(jī)床用于加工兩維或三維空間中各種不同大小的弧形，圓角圓及斜角。連續(xù)軌跡控制的數(shù)控機(jī)床比點(diǎn)位控制的機(jī)床貴得多，在加工復(fù)雜輪廓時(shí)，一般需要計(jì)算機(jī)輔助程序設(shè)計(jì)。數(shù)控伺服機(jī)構(gòu)是使工作臺或滑座沿坐標(biāo)軸準(zhǔn)確運(yùn)動的裝置。用于數(shù)控設(shè)備的伺服機(jī)構(gòu)通常有兩種：步進(jìn)電機(jī)和液壓馬達(dá)。步進(jìn)電機(jī)伺服機(jī)構(gòu)常用于不太貴重的數(shù)控設(shè)備上。這些電機(jī)通常是大轉(zhuǎn)矩的伺服機(jī)構(gòu)，直接安裝在工作臺或刀座的絲杠上。大多數(shù)步進(jìn)電機(jī)是來自定子和轉(zhuǎn)子組件的磁力脈沖驅(qū)動的，這種作用的結(jié)果是電機(jī)軸轉(zhuǎn)一轉(zhuǎn)產(chǎn)生 200 步距。把電機(jī)軸接在 10 扣/英寸的絲杠上，每步能產(chǎn)生 0.0005 英寸的移動（1/200×1/10=0.0005 英寸） 。液壓伺服馬達(dá)使壓力液體流過齒輪或柱塞，從而使軸轉(zhuǎn)動。絲杠和滑座的機(jī)械運(yùn)動是通過各種閥和液壓馬達(dá)的控制來實(shí)現(xiàn)的。液壓伺服馬達(dá)產(chǎn)生比步進(jìn)電機(jī)更大的轉(zhuǎn)矩，但比步進(jìn)電機(jī)貴，且噪音很大。大多數(shù)大型數(shù)控機(jī)床使用液壓伺服機(jī)構(gòu)。使用開環(huán)系統(tǒng)的數(shù)控機(jī)床，沒有反饋信號來確保機(jī)床的坐標(biāo)軸是否運(yùn)動了所需的距離。即，如果接收的輸入信號是使一特定坐標(biāo)軸移動 1.000 英寸，伺服裝置通常使工作臺運(yùn)動 1.000 英寸，但無法將工作臺的實(shí)際運(yùn)動與輸入信號加以比較。使工作臺實(shí)際了 1.000 英寸的唯一保證是所用的伺服機(jī)構(gòu)的準(zhǔn)確性。當(dāng)然，開環(huán)系統(tǒng)比閉環(huán)系統(tǒng)便宜。閉環(huán)系統(tǒng)能將實(shí)際輸出（工作臺一英寸的運(yùn)動量）與輸入信號加以比較，并對任何誤差進(jìn)行補(bǔ)償。反饋裝置真實(shí)地將工作臺已運(yùn)動的量與輸入信號進(jìn)行了比較。用于閉環(huán)系統(tǒng)的一些反饋裝置是傳感器，電尺或磁尺以及同步器。閉環(huán)系統(tǒng)大大增加了數(shù)控機(jī)床的準(zhǔn)確性。