外文翻译--刀具补偿原理.pdf

1 刀具补偿原理刀具补偿原理 刀具补偿（又称偏置） ，在 20 世纪 6070 年代的数控加工中没有补偿的概念， 所以编程人员不得不围绕刀具的理论路线和实际路线的相对关系来进行编程，容易 产生错误。补偿的概念出现以后很大地提高了编程的效率。 具有刀具补偿功能，在编制加工程序时，可以按零件实际轮廓编程，加工前测 量实际的刀具半径、长度等，作为刀具补偿参数输入数控系统，可以加工出合乎尺 寸要求的零件轮廓。 刀具补偿功能还可以满足加工工艺等其他一些要求，可以通过逐次改变刀具半 径补偿值大小的办法，调整每次进给量，以达到利用同一程序实现粗、精加工循环。 另外，因刀具磨损、重磨而使刀具尺寸变化时，若仍用原程序，势必造成加工误差， 用刀具长度补偿可以解决这个问题。 刀具补偿分为 2 种： 刀具长度补偿； 刀具半径补偿。 刀具长度补偿； 刀具半径补偿。 文献刀具补偿在数控加工中的应用（工具技术，2OO4年第38卷No7，徐伟， 广东技术师范学院）中提到在数控加工中有4种补偿： 刀具长度补偿； 刀具半径补偿； 夹具补偿； 夹角补偿（G39） 。 刀具长度补偿； 刀具半径补偿； 夹具补偿； 夹角补偿（G39） 。 这四种补偿基本上能解决在加工中因刀具形状而产生的轨迹问题。 1.刀具长度补偿 1.1刀具长度的概念 1.刀具长度补偿 1.1刀具长度的概念 刀具长度是一个很重要的概念。我们在对一个零件编程的时候，首先要指定零 件的编程中心，然后才能建立工件编程坐标系，而此坐标系只是一个工件坐标系， 零点一般在工件上。长度补偿只是和 Z 坐标有关，它不象 X、Y 平面内的编程零点， 因为刀具是由主轴锥孔定位而不改变，对于 Z 坐标的零点就不一样了。每一把刀的 2 长度都是不同的，例如，我们要钻一个深为 50mm 的孔，然后攻丝深为 45mm，分别 用一把长为 250mm 的钻头和一把长为 350mm 的丝锥。先用钻头钻孔深 50mm，此时机 床已经设定工件零点，当换上丝锥攻丝时，如果两把刀都从设定零点开始加工，丝 锥因为比钻头长而攻丝过长，损坏刀具和工件。此时如果设定刀具补偿，把丝锥和 钻头的长度进行补偿，此时机床零点设定之后，即使丝锥和钻头长度不同，因补偿 的存在，在调用丝锥工作时，零点 Z 坐标已经自动向 Z+（或 Z）补偿了丝锥的长度， 保证了加工零点的正确。 1.2刀具长度补偿指令1.2刀具长度补偿指令 通过执行含有 G43（G44）和 H 指令来实现刀具长度补偿，同时我们给出一个 Z 坐标值， 这样刀具在补偿之后移动到离工件表面距离为 Z 的地方。 另外一个指令 G49 是取消 G43（G44）指令的，其实我们不必使用这个指令，因为每把刀具都有自己的 长度补偿，当换刀时，利用 G43（G44）H 指令赋予了自己的刀长补偿而自动取消了 前一把刀具的长度补偿。 G43 表示存储器中补偿量与程序指令的终点坐标值相加，G44 表示相减，取消刀 具长度偏置可用 G49 指令或 H00 指令。程序段 N80 G43 Z56 H05 与中，假如 05 存 储器中值为 16，则表示终点坐标值为 72mm。 1.3刀具长度补偿的两种方式1.3刀具长度补偿的两种方式 (1) 用刀具的实际长度作为刀长的补偿（推荐使用这种方式） 。使用刀长作为补 偿就是使用对刀仪测量刀具的长度，然后把这个数值输入到刀具长度补偿寄存器 中，作为刀长补偿。使用刀具长度作为刀长补偿的理由如下： 首先，使用刀具长度作为刀长补偿，可以避免在不同的工件加工中不断地修 改刀长偏置。 这样一把刀具用在不同的工件上也不用修改刀长偏置。 在这种情况下， 可以按照一定的刀具编号规则，给每一把刀具作档案，用一个小标牌写上每把刀具 的相关参数，包括刀具的长度、半径等资料，事实上许多大型的机械加工型企业对 数控加工设备的刀具管理都采用这种办法。这对于那些专门设有刀具管理部门的公 司来说，就用不着和操作工面对面地告诉刀具的参数了，同时即使因刀库容量原因 把刀具取下来等下次重新装上时，只需根据标牌上的刀长数值作为刀具长度补偿而 不需再进行测量。 其次，使用刀具长度作为刀长补偿，可以让机床一边进行加工运行，一边在 对刀仪上进行其他刀具的长度测量，而不必因为在机床上对刀而占用机床运行时 3 A B C 外轮廓加工外轮廓加工 内轮廓加工 A/ B/ C/ C/ 刀具刀具 刀具刀具 图 3-1B 功能刀具补偿的交叉点和间断点 间，这样可以充分发挥加工中心的效率。这样主轴移动到编程 Z 坐标点时，就是主 轴坐标加上（或减去）刀具长度补偿后的 Z 坐标数值。 （2）利用刀尖在 Z 方向上与编程零点的距离值（有正负之分）作为补偿值。这 种方法适用于机床只有一个人操作而没有足够的时间来利用对刀仪测量刀具的长 度时使用。这样做当用一把刀加工另外的工件时就要重新进行刀长补偿的设置。使 用这种方法进行刀长补偿时，补偿值就是主轴从机床 Z 坐标零点移动到工件编程零 点时的刀尖移动距离，因此此补偿值总是负值而且很大。 2刀具半径补偿 2.1刀具半径补偿概念 2刀具半径补偿 2.1刀具半径补偿概念 在轮廓加工时，刀具中心运动轨迹（刀具中心或金属丝中心的运动轨迹）与被 加工零件的实际轮廓要偏移一定距离，这种偏移称为刀具半径补偿，又称刀具中心 偏移。 如图 3-1 所示，在加工内轮廓时， 刀具中心向工件轮廓的内部偏移一个距离； 而加工外轮廓时，刀具中心向工件的外侧偏移一个距离，这个偏移，就是所谓的刀 具半径补偿。图中，粗实线为工件轮廓，虚线为刀具中心轨迹。本图中的偏移量为 刀具半径值。而在粗加工和半精加工时，偏移量为刀具半径和加工余量之和。 由于数控系统控制的是刀具中心轨迹，因此数控系统要根据输入的零 件轮廓尺寸及刀具半径补偿值计算出刀心轨迹。由此可见，刀具半径补偿在数控加 工有着非常重要的作用，根据刀具补偿指令，数控加工机床可自动进行刀具半径补 4 偿。特别是在手工编程时，刀具半径补偿尤为重要。手工编程时，运用刀具半径补 偿指令，就可以根据零件的轮廓值编程，不需计算刀心轨迹编程，这样就大大减少 了计算量和出错率。虽然利用 CAD/CAM 自动编程，手工计算量小，生成程序的速度 快，但当刀具有少量磨损或加工轮廓尺寸与设计尺寸稍有偏差时或者在粗铣、半精 铣和精铣的各工步加工余量变化时，仍需作适当调整，而运用了刀具半径补偿后， 不需修改刀具尺寸或建模尺寸而重新生成程序，只需要在数控机床上对刀具补偿参 数做适当修改即可。既简化了编程计算，又增加了程序的可读性。 刀具半径补偿有 B 功能（Basic）和 C 功能（Complete）两种补偿形式。由于 B 功能刀具半径补偿只根据本段程序进行刀补计算，不能解决程序段之间的过渡问 题，要求将工件轮廓处理成圆角过渡如图 3-1 所示，因此工件尖角处工艺性不好。 而且编程人员必须事先估计出刀补后可能出现的间断点和交叉点，并进行人为处 理，显然增加编程的难度；而 C 功能刀具半径补偿能自动处理两程序段刀具中心轨 迹的转接，可完全按照工件轮廓来编程，因此现代 CNC 数控机床几乎都采用 C 功能 刀具半径补偿。这时要求建立刀具半径补偿程序段的后续至少两个程序段必须有指 定补偿平面的位移指令（G00、G01，G02、G03 等） ，否则无法建立正确的刀具补偿。 2.2刀具半径补偿指令2.2刀具半径补偿指令 根据 ISO 规定，当刀具中心轨迹在程序规定的前进方向的右边时称为右刀补， 用 G42 表示；反之称为左刀补，用 G41 表示。 G41 是刀具左补偿指令（左刀补） ，即顺着刀具前进方向看(假定工件不动)，刀 具中心轨迹位于工件轮廓的左边，称左刀补。如图 3.2(a)所示。 G42 是刀具右补偿指令（右刀补） ，即顺着刀具前进方向看(假定工件不动)，刀 具中心轨迹位于工件轮廓的右边，称右刀补。如图 3.2(b)所示。 G40 是为取消刀具半径补偿指令。使用该指令后，41、42 指令无效。 图 3-2刀具半径的左右补偿 (a) 外轮廓补 偿 (b) 内轮廓补 偿 5 在使用 G41、G42 进行半径补偿时应采取以下步骤： （1）设置刀具半径补偿值：程序启动前，在刀具补偿参数区内设置补偿值。 （2）刀补的建立：刀具从起刀点接近工件，刀具中心轨迹的终点不在下一个程 序段指定的轮廓起点，而是在法线方向上偏移一个刀具补偿的距离。在该 段程序中，动作指令只能用 G00 或 G01。 （3）刀补进行：在刀具补偿进行期间，刀具中心轨迹始终偏离编程轨迹一个刀 具半径的偏移值。在此状态下，G00、G01、G02、G03 都可以使用。 （4）刀补的取消：在刀具撤离工件、返回原点的过程中取消刀补。此时只能用 G00、G01。 2.3功能刀具半径补偿2.3功能刀具半径补偿 对直线而言，刀具补偿后的轨迹是与原直线平行的直线，只需要计算出刀具中 心轨迹的起点和终点坐标值。 如图 3-3 所示，被加工直线段的起点在坐标原点，终点坐标为A。假定上一程 序段加工完后，刀具中心在O点坐标已知。刀具半径为 r，现要计算刀具右补偿 后直线段OA的终点坐标A。设刀具补偿矢量AA的投影坐标为,则 XXX YYY xOAA AK 22 sin Y Xrr XY 22 cos X Yrr XY 22 rX YY XY 22 rY XX XY 6 对于圆弧而言，刀具补偿后的刀具中心轨迹是一个与圆弧同心的一段圆弧。只 需计算刀补后圆弧的起点坐标和终点坐标值。如图 3-4 所示，被加工圆弧的圆心坐 标在坐标原点O，圆弧半径为R，圆弧起点A，终点B，刀具半径为r。 假定上一个程序段加工结束后刀具中心为A，其坐标已知。那么圆弧刀具半 径补偿计算的目的，就是计算出刀具中心轨迹的终点坐标B。设BB在两个坐标 上的投影为,XY ，则 以图 3-1 的加工外轮廓为例，采用 B 功能刀具半径补偿方法，加工完第一个程 序段，刀具中心落在B /、点上，而第二个程序段的起点为 A /，两个程序段之间出现 了断点，只有刀具中心走一个从B /、至 A /的附加程序，即在两个间断点之间增加一 个半径为刀具半径的过渡圆弧B1B2，才能正确加工出整个零件轮廓。 可见，B 刀补采用了读一段，算一段，再走一段的控制方法， ，无法预计到由于 刀具半径所造成的下一段加工轨迹对本程序段加工轨迹的影响，相邻两程序段的刀 y O x X y K A(X,Y) r Y A(X,Y) B(Xb,Yb) A(Xa,Ya) X K x B（Xb,Yb） Y O O R K A(Xa,Ya) r 图 3-3 直线刀具补偿图 3-4 圆弧刀具补偿 / bb XXX bb YYY BOxB BK cos sin b b X Xrr R Y Yrr R b bb b bb rX XX R rY YY R 7 具中心轨迹之间可能出现间断点或交叉点。为解决下一段加工轨迹对本段加工轨迹 的影响，在计算本程序段轨迹后，提前将下一段程序读入，然后根据它们之间转接 的具体情况，再对本段的轨迹作适当修正，得到本段正确加工轨迹，这就是 C 功能 刀具补偿。C 功能刀补更为完善，这种方法能根据相邻轮廓段的信息自动处理两个 程序段刀具中心轨迹的转换，并自动在转接点处插入过渡圆弧或直线从而避免刀具 干涉和断点情况。 2.4功能刀具半径补偿2.4功能刀具半径补偿 目前，通常的 CNC 系统中，实际所能控制的轮廓只有直线和圆弧，相应的有如 下转接线形：直线与直线转接、直线与圆弧转接、圆弧与圆弧转接、圆弧与直线转 接。 根据两段轨迹的矢量夹角和刀具补偿方向的不同，有以下几种转接过渡方式： 缩短型、伸长型、插入型。 3夹具偏置补偿（坐标系偏置）3夹具偏置补偿（坐标系偏置） 正如刀具长度补偿和半径补偿一样， 让编程者可以不用考虑刀具的长短和大小， 夹具偏置可以让编程者不考虑工件夹具的位置而使用夹具偏置。当一台加工中心在 加工小的工件时，工装上一次可以装夹几个工件，编程者不用考虑每一个工件在编 程时的坐标零点，而只需按照各自的编程零点进行编程，然后使用夹具偏置来移动 机床在每一个工件上的编程零点。夹具偏置是使用夹具偏置指令 G54G59 来执行 的。还有一种方法就是使用 G92 指令设定坐标系。当一个工件加工完成之后，加工 下一个工件时使用 G92 来重新设定新的工件坐标系。 4 夹角补偿4 夹角补偿 加工中两平面相交为夹角，可能产生超程过切现象，导致加工误差的产生，此 时可采用夹角补偿(G39)来解决。使用夹角补偿(G39)指令时需注意，本指令为非模 态指令，只在本程序段内有效，而且只能在G41或G42指令后才能使用，该指令主要 用于加工中心和数控铣床。 以上是数控加工中的四种补偿方式，给我们的编程和加工带来很大的方便，能 大大地提高生产效率和产品合格率。 8 9 Cutter Compensation Principle The cutter compensation (calls bias), in the 20th century 60 the 70ss numerical control processing compensation concept, Therefore the programmers can not but revolve cutting tools theory route and the actual routes relative relations carry on the programming, easy to make the mistake. The compensation concept will appear later very greatly raised the programming efficiency. Has the cutter compensation function, when establishment processing program, may according to the components real profile programming, before the processing, survey the actual cutting tool radius, the length and so on, as the cutter compensation parameter input numerical control system, may process conforms with the size request the components outline. The cutter compensation function may also satisfy the processing craft and so on other requests, may through change the cutting tool radius compensation value size gradually the means that the adjustment each time to feed quantity, achieves the use identical procedure to realize, the precision work circulation thickly. Moreover, when because of the tool wear, the grind causes the tool dimension change, if still used the original procedure, will create the processing error inevitably, may solve his problem with the cutting tool length compensation. The cutter compensation divides into 2 kinds: cutting tool length compensation; cutting tool radius compensation. The literature Cutter compensation in Numerical control Processings Application (tool technology, 2OO4 year 38th volume No7, Xu is great, Guangdong technology Normal school) mentioned that has 4 kind of compensations in the numerical control processing: cutting tool length compensation; cutting tool radius compensation; 10 jig compensation; included angle compensation (G39). These four kind of compensations basically can solve in the processing the path question which produces because of the cutting tool shape. 1.cutting tool length compensation 1.1cutting tool length concept The cutting tool length is a very important concept. We in programs to components, must first assign the components the programming center, then can establish the work piece programming coordinate system, but this coordinate system is only a work piece coordinate system, zero generallyon work piece. The length compensation is only and the Z coordinate related, it does not look like in X, Y plane the programming zero spot, because the cutting tool is by the main axial cone hole localization, but does not change, is dissimilar regarding Z coordinates zero. Each knifes length is different, for example, we must drill a depth are the 50mm holes, then attacks the silk depth is 45mm, respectively uses a length is the 250mm drill bit nd a length is the 350mm screw tap. Uses the drill bit to drill depth of hole 50mm first, this time the engine bed already established the work piece zero spot, when exchanges the screw tap attacks the silk, if two knives both from suppose the zeroing to start to process, because the screw tap the ratiorills the head length to attack the silk to be excessively long, damages the cutting tool and the work piece. This time if the hypothesis cutter compensation, arries on the screw tap and drill bits length the compensation, after this time engine bed zero hypothesis, even if the screw tap and the drill bit length are different, because compensates existence, when transfer screw tap work, zero selected the Z coordinate to be already automatic to Z+ (or Z) has compensated the screw tap length, has guaranteed a processing zero correctness. 1.2cutting tool length compensation instruction Includes G43 through the execution (G44) and the H instruction realizes the cutting tool length compensation, simultaneously we give a Z coordinate figure, such cutting tool after compensation moves to leaves the work piece surface distance is the Z place. Other instruction G49 is cancels G43 (G44) the instruction, 11 actually we do not need to use this instruction, because has every time the cutting tool own length compensation, when trades the knife, (G44) the H instruction entrusted with the own knife long compensation using G43 to cancel the preceding cutting tools length compensation automatically. G43 expressed that in the memory compensates the quantity and program directive end point coordinate figure adding together, G44 expresses the cancellation, cancels the cutting tool length bias available G49 instruction or the H00 instruction. Segment N80 G43 Z56 H05 and, if in 05 memories the value is 16, then the expression end point coordinate figure is 72mm. 1.3cutting tool length compensation two ways (1)uses cutting tools virtual length (recommendation to use this way) as the knife long compensation. Uses the knife long is uses the tool setting gauge as the compensation to survey cutting tools length, then inputs this value to the cutting tool length compensation register, takes the knife long compensation. The use cutting tool length the reason which long compensates as the knife is as follows: First, uses the cutting tool length to take the knife long compensation, may avoid in the different work piece processing repairing unceasingly cuts again the long bias. This kind of cutting tool uses on the different work piece does not need to repair cuts again the long bias. In this case, may defer to certain cutting tool serial number rule, makes the file for each cutting tool, inscribes with a small product label every time cutting tools related parameter, including material and so on cutting tools length, radius, many large-scale machine-finishing enterprises uses this means in fact to the numerical control processing equipments cutting tool management. This was equipped with the cutting tool Control sections company specially regarding these, had no need with the operator face-to-face to tell the cutting tool the parameter, when even if simultaneously the knife storage capacity quantity reason took down the cutting tool and so on will install next time, only need act according to the product label the knife long value as the cutting tool length compensation not to again carry on the survey. Next, uses the cutting tool length to take the knife long compensation, may let one side the engine bed carry on the processing movement, at the same time carries on other 12 cutting tools linear measure on the tool setting gauge, but does not need because of takes the engine bed running time on the engine bed to the knife, like this may display the machining center fully the efficiency. Such main axle moves to when programs the Z fiducial mark, after is the main axle coordinate adds on (or subtracts) the cutting tool length compensation Z coordinate value. (2)uses the knife point (to have the positive and negative division) in the Z direction with the programming zero distance value to take the compensation value. This method is suitable in the engine bed has a person to operate, but does not have the enough time to survey time cutting tools length using the tool setting gauge uses. Does this, when processes other work piece with a knife must carry on the knife long compensation the establishment. Uses when this method carries on the knife long compensation, the compensation value is the main axle from the engine bed Z coordinate zero spot moves to the work piece programming zero hour knife point migration distance, therefore this compensation value negative value moreover is very always big. 2cutting tool radius compensation 2.1cutting tool radius compensation concept When contour machining, the cutting tool central motion path (cutting tool center or tinsel centers path) with is processed the components the real profile to displace certain distance, this kind of displacement is called the cutting tool radius compensation, also calls the cutting tool off-centering. As shown in Figure 3-1, when processing outline, the cutting tool center displaces a distance to the work piece outlines interior; But outside processes time the outline, the cutting tool center displaces a distance to the work piece flank, this displacement, is the so-called cutting tool radius compensation. In the chart, the thick line is the work piece outline, the dashed line is the cutting tool center path. In this chart displacement quantity for cutting tool radius value. But of when rough machining and semi-finishing, displacement quantity sum of for cutting tool radius and the machining allowance. 13 A B C A/ B/ C/ C/ What because numerical control systems control is the cutting tool center path, therefore the numerical control system must calculates the knife heart path according to the input components overall size and the cutting tool radius compensation value. Thus it can be seen, the cutting tool radius compensation has the very vital role in the numerical control processing, according to the cutter compensation instruction, the numerical control processing engine bed may carry on the cutting tool radius compensation automatically. Specially when manual programming, cutting tool radius compensation especially important. When manual programming, using the cutting tool radius compensation instruction, may act according to the components the outline value programming, cannot calculate the knife heart path programming, like this greatly reduced the computation load and the error ratio. Although using the CAD/CAM automatic programming, the manual computation load is small, generating routines speed is quick, but when the cutting tool has the few attrition or the processing overall size and the design size have the deviation slightly or in the rough milling, half fine mill and time the fine mill various labor step machining allowance change, must make the appropriate readjustment, but after having utilized the cutting tool radius compensation, cannot revise the tool dimension or the modelling size, but the generating routine, only needs on the numerically-controlled machine tool to make the suitable revision again to the cutter compensation parameter then. Both simplified the programming computation, and increased the procedure readability. Cutting tool In contour machining Cutting tool Figure 3-1 B function cutter compensation intersection and point of discontinuity Outside contour machining 14 The cutting tool radius compensation has the B function (Basic) and the C function (Complete) two kind of compensation forms. Because the B function cutting tool radius compensation only acts according to this section of procedures to carry on the knife to make up the computation, cannot solve between the segment transition problem, requests 3-1 work piece outline processing full circle angle transition as shown in Figure, therefore the work piece acute angle place technology capability is not good. Moreover the programmers must estimate beforehand after the knife makes up, possibly appears the point of discontinuity and the intersection, and carry on artificial processing, obviously increases the programming the difficulty; But the C function cutting tool radius compensation can the automatic reduction two segment cutting tool center paths transfer, be possible to defer to the work piece outline to program completely, therefore the modern CNC numerically-controlled machine tool nearly uses the C function cutting tool radiuscompensation.Bynowrequestedtheestablishmentcuttingtoolradius compensation segment the following two segments to have at least assigns the compensation plane the shift order (G00, G01, G02, G03 and so on), otherwise is unable to establish the correct cutter compensation. 2.2cutting tool radius compensation instruction Stipulated according to ISO, when cutting tool center path stipulated in the procedure direction of advance right side when is called the right knife to make up, indicated with G42; Otherwise is called the left knife to make up, indicated with G41. G41 is the cutting tool left compensation instruction (left knife makes up), namely is suitable the cutting tool direction of advance to look that (hypothesis work piece motionless), the cutting tool center path located at the work piece outlines left side, said that the left knife makes up.As shown in Figure 3.2(a). G42 is the cutting tool right comp