|
|
原文
Commonly used grinding machine
As a kind of important ultra-precision processing method，the advantage of grinding is high machining accuracy, processing materials range, almost suitable for all kinds of materials processing, grinding can get very high precision and shape accuracy, even can reach the limit, the machining accuracy of grinding device is simple, does not need a lot of the complex mechanical and not demanding equipment precision conditions.
As a super finishing one method, grinding machine is mainly used for the high precision grinding workpiece plane, the surface of cylindrical workpieces both inside and outside, tapered face inside, sphere, thread face and other type surface. Its main types have dise-type grinding machine, shaft type grinding machine, magnetic grinding machine and all kinds of special grinding machine.
Dise-type grinding machine points single plate and double-tray two to double-tray grinding machine used the most common. In double-tray polishing machine, multiple workpiece and into the mill plate, located on the cage between inside, maintain frame and workpiece drives by eccentric or planet of plane parallel movement. The mill rotating, the parallel with the grinding plate can not turn, or with grinding plate under negative spin, and can move to pressure workpiece (pressure adjustable). In addition, with the grinding plate can also turning round pillar rocker to Angle, unloading workpieces. Double-tray grinding machine is mainly used for processing two parallel planes, a plane (two pressure should be increased to the workpiece accessorie), outside YuanZhuMian and sphere (with belt v-shaped slot grinding plate), etc. YuanZhuMian, because the processing and workpiece to both sliding, shall be reasonable choose to keep rolling type and arrangement plane slots Angle. Only a single plate grinding machine, used for grinding plate under the grind workpiece under plane, can make the different shapes and sizes with plate processing, grinding workpiece higher precision. Some grinding machine with the grinding process can be automatic calibration grinding plate institution.
Shaft type grinding machine from positive, negative spin of spindle drive work-piece or inquiry with adjustable grinding ring or abrasive (great) rotation, the structure is simple, used for grinding inside and outside cylindrical planes.
Magnetic grinding machine is by using magnetic force transmission to stainless steel mill for high frequency workpiece needle to rotary motion; But for precision workpiece in the hole and blind Angle, tiny crack rise obvious good polishing grinding remove burr effect.
Special grinding machine by grinding workpiece in accordance with the different, have central hole grinding machine, steel ball grinding machine and gear grinding machine, etc.
In addition, still have a kind of adopting similar centerless grinding principle unconditional grinding machine, used for grinding cylindrical workpieces.
Grinding is by abrasive abrasive effect on surface of workpiece, to trace processing. Grinding workpiece surface dimension accuracy, form and position precision, abrasive tools, such as life and milling efficiency depends largely on whether grinding movement. In order to make the surface of workpiece grinding uniform, from the perspectives of kinematics concludes the following plane grinding best kinematics condition: firstly, workpiece with relative research of plane movement, should guarantee by grinding workpiece surface with different points on relative research are the same or similar grinding track; secondly, grinding motion is provided by the workpiece and the relative movement between developed a realization, different points on the surface of workpiece velocity should as far as possible the grinding the same; thirdly, grinding movement direction should constantly change, grinding grain crisscross changeful, favors the surface roughness of workpiece machining, but should avoid reduced by grinding workpiece surface with different points on the relative research curvature grinding track changes too big, fourthly, grind with or pads working surface shape accuracy will reflect on the surface of workpiece, so the trajectories of workpiece with throughout the inquiry should be distributed homogeneously, favors the surface and uniform worn with research; finally, workpiece with relative research by abrasive removal direction a sports freedom, so that can avoid for grinding machines guidance precision and cause errors.
Grinding basic principle is to use embedded in coating or pressure with the abrasive particles on grind workpiece with and, through research in the relative movement under certain pressure for processing surface finish machining process.
The cylindrical plane grinding process is to use free grits are two plane of cylinder scraping and extrusion process of removing materials to reduce cylindrical height, improve planar degree and reduce the surface roughness purpose. These remove effects through the cylindrical grinding plate with the relative movement in grits role down to perform. Abrasive is the main medium grinding process. The grinding process according to abrasive change can be divided into three stages.
The first stage: the broken free abrasive stage. At the beginning of precision lapping ,initial larger grits cutting, then first participate in a belt of edges and abrasive polyhedron, cutting ability. The role of the pressure, the grits size by crushing make more grits are competing in cutting, then on one hand consumption dimensions and cylinder of processes, this phase residual surfaces grinding efficiency is higher, size, cylindrical surface roughness consumed fast. But this stage time is very short.
Second stage: the grits particular and Mosaic stage. Due to the effects of stress fluctuation grinding plate and cylinder interaction constantly rolling mill grain, make the coarse grinding grain gradually broken into fine grits and size to converge, then the highest grinding efficiency, time also the longest. With the continuously detailed, all kinds of abrasive is also relatively stable stage elements, at this stage of the geometry precision ball improved and basically reaches corresponding requirements, the surface quality gradually enhance, roughness decline. This phase is gangqiu stability processing phases.
The third stage: grits passivation and grinds light phase. In this phase abrasive most refined for o. apms m the following three fine grits, grits by the shape of the original sharp geometry without sharp edges into the sleek sphere, grinding speed greatly reduced. Passivation of grits only to micro powder cylindrical plane more trace grinding, polishing quantity Grinding quantity is about from 0.2 to 0.3 microns per hour .This stage cylindrical surface roughness further reduce and eventually reach the standard.
Generally speaking, there are four main grind track: (1) linear grinding trajectory. This method is applicable to the steps of long and narrow plane workpiece grinding can obtain higher geometry precision, but not easily get smaller surface roughness. (2) swing linear grinding trajectory. Can achieve good straightness. (3) spiral grinding trajectory. Mainly used for discs shape or cylindrical workpieces grinding, flat end can gain a high flatness and smaller surface roughness. (4) "8" glyph grinding trajectory. Suitable for flat class overhauled and small plane workpiece of grinding workpiece, can make mutual grinding plane media contact and has even developed evenly wear.
In the production practice, grinding is a kind of common finishing craft, grinding method unceasing progress and renewal, to adapt to the different processing requirements of various literature material reports, there are many methods of grinding, polishing, abrasive flow injection of ultrasonic machining, electrochemical polishing, chemical polishing, magnetic abrasive grinding, liquid abrasive grinding etc exterior smooth the whole processing technology. The most commonly used and application most is a mechanical polishing, its characteristic is can obtain higher dimension precision, shape accuracy and low surface roughness, but requires the operator has high level of technology and experience, machining efficiency low, labor intensive, processing quality not easy to control, the surface residual stress is big, surface residual grits can also affect surface quality.
Magnetic abrasive law is through magnetic polarity will magnetic abrasive surface processing, suction pressure in surface processing and between the poles for millimeter clearance, can be in magnetic abrasive machining gap arrange them along the field, forming elastic magnetic brush and pressure on the surface of workpiece attached. Rotating magnetic field or rotating product, make magnetic brush and relative motion processing, thus pure polisher a surface. The characteristics of magnetic grinding is that no matter how the surface processing, you should just make poles shape and processing surface shape can be generally anastomose,it can accurate grinding a fine curved surface of workpiece surface, and magnetic abrasive act applies to grind cutting and grinding process is usually to competent complex shape parts surface smooth processing.
Grinding machine adopts stepless speed regulation control system, can be easily adjusted adheasine grind various parts of grinding speed. Using electricity - gas proportional valve close-loop feedback grinding machine pressure control, can independence regulation pressure device. Slow falling installed in the up-tray to prevent the crash of brittleness slice. Through a time relay and a grinding counter, can press processing requirements accurately Settings and control of milling time and grinding lap. Work can be adjusted pressure mode, achieve grinding set time or lap will automatically stop alarm prompt, realize half automation.
Grinding machine variable speed control method, grinding has three stages, namely beginning, formal stage and end stage, beginning abrasive acc rotation, the official stage abrasive constant speed rotating, end stage abrasive slow down, whose character is, rotating grinding beginning in grinding speed, artificially controlled by slow from zero to acceleration of fast speed increases, when the abrasive ascended to the formal grinding speed, acceleration the half of the changes occur a inflection point, control the acceleration of grinding speed by slowly by almost to the maximum speed is reduced, until the grinding tools to formally, the acceleration of speed grinding speed reduced to zero.
Use the characteristic of a solid abrasive abrasive, according to the relative movement between grinding workpiece track density distribution, a reasonable design abrasive abrasive density distribution on, in order to make abrasive that occur in the grinding process does not affect the abrasive wear face type, thereby significantly improve the precision of the surface type precision.
Future as people are becoming more demanding to improve product performance, grinding machining accuracy and processing with its high quality, which has attracted the attention of people. Therefore, ultra-precision will be more conspicuous in the future.
译文
常用球磨机
研磨是超精密加工中一种重要加工方法，其优点是加工精度高，加工材料范围广，几乎适合于各种材料的加工，研磨加工可以得到很高的尺寸精度和形状精度，甚至可以达到加工精度的极限，研磨装置简单，不需要大量复杂的机械并且不苛求设备的精度条件。
作为超精加工的一种方法，球磨机主要用于研磨工件中的高精度平面、内外圆柱面、圆锥面、球面、螺纹面和其他型面。其主要类型有圆盘式球磨机、转轴式球磨机、磁力球磨机和各种专用球磨机。
圆盘式球磨机分单盘和双盘两种，以双盘球磨机应用最为普通。在双盘球磨机上，多个工件同时放入位于上、下研磨盘之间的保持架内，保持架和工件由偏心或行星机构带动作平面平行运动。下研磨盘旋转，与之平行的上研磨盘可以不转，或与下研磨盘反向旋转，并可上下移动以压紧工件（压力可调）。此外，上研磨盘还可随摇臂绕立柱转动一角度，以便装卸工件。双盘球磨机主要用于加工两平行面、一个平面(需增加压紧工件的附件)、外圆柱面和球面（采用带V形槽的研磨盘）等。加工外圆柱面时,因工件既要滑动又要滚动，须合理选择保持架孔槽型式和排列角度。单盘球磨机只有一个下研磨盘，用于研磨工件的下平面，可使形状和尺寸各异的工件同盘加工，研磨精度较高。有些球磨机还带有能在研磨过程中自动校正研磨盘的机构。
转轴式球磨机由正、反向旋转的主轴带动工件或研具（可调式研磨环或研磨棒）旋转，结构比较简单，用于研磨内、外圆柱面。
磁力球磨机是通过采用磁场力量传导至不锈钢磨针使工件作高频率旋转运动；可对精密工件内孔、死角、细小夹缝起到明显较好的抛光研磨去除毛刺的效果。
专用球磨机依被研磨工件的不同，有中心孔球磨机、钢球球磨机和齿轮球磨机等。
此外，还有一种采用类似无心磨削原理的无心球磨机，用于研磨圆柱形工件。
研磨是磨具通过磨料作用于工件表面，进行微量加工的过程 。研磨工件表面的尺寸精度、形位精度、研磨工具的寿命及研磨效率等，在很大程度上取决于研磨运动。为使工件表面研磨均匀，从运动学角度归纳出如下的平面研磨最佳运动学条件：(1)工件相对研具作平面运动，应保证工件被研磨表面上各点相对研具均有相同或相近的研磨轨迹；(2)研磨运动是由工件与研具之间的相对运动实现的，工件表面上各点的研磨运动速度应尽可能相同；(3)研磨运动方向应不断变化，研磨纹路交错多变，以利于工件加工表面粗糙度的降低，但应尽量避免工件被研磨表面上各点相对研具的研磨轨迹曲率变化过大；(4)研具或抛光盘工作表面的形状精度会反映到工件表面上，所以工件的运动轨迹应遍及整个研具表面并且分布均匀，以利于研具的均匀磨损；(5)工件相对研具在被研磨材料的去除方向上具有运动自由度，这样可以避免因球磨机械的导向精度不高而引起误差。
研磨基本原理是利用涂敷或压嵌在研具上的磨料颗粒，通过研具与工件在一定压力下的相对运动对加工表面进行的精整加工的过程。
圆柱面的研磨加工过程就是利用游离磨粒对圆柱两平面进行刮削和挤压去除材料的过程，达到减小圆柱高度，提高平面度和降低表面粗糙度的目的。这些去除作用要通过柱面与研磨盘的相对运动在磨粒的作用下来完成。磨料是研磨加工的主要介质。整个研磨过程根据磨料的变化可分为三个阶段。
第一阶段：游离磨料的破碎阶段。精研初期较大的磨粒首先参与切削，这时磨料多呈带棱角的多面体，切削能力强。在压力的作用下，尺寸大的磨粒被破碎使更多的磨粒得以参加切削，这时圆柱体一方面消耗尺寸及上工序的残留表面，这个阶段磨削效率较高，尺寸消耗快，圆柱表面粗糙。但该阶段时间很短。
第二阶段：磨粒细化和镶嵌阶段。由于压力的作用上下研磨盘和圆柱体相互作用不断地辗压磨粒，使粗磨粒逐渐破碎为细磨粒且大小趋于一致，这时磨削效率达到最高，时间也最长。随着磨料的不断细化，各种要素也处于相对稳定阶段，在这个阶段钢球的几何精度得以改善并基本达到相应的要求，表面质量逐渐提高，粗糙度下降。这个阶段是钢球的稳定加工阶段。
第三阶段：磨粒钝化和研光阶段。在这个阶段磨料绝大部分细化为O．3µm以下的微细磨粒，磨粒的形状也由原来锐利的几何体变为无锐棱的圆滑球体，磨削速度大大降低。钝化了的磨粒微粉对圆柱面只能进行更微量的研磨，研磨量大约0．2～O．3／µm／h。此阶段圆柱表面粗糙度值进一步降低，最终达到标准要求。
一般来讲，研磨轨迹主要有4种：（1）直线研磨运动轨迹。此种方法适用于台阶的狭长平面工件研磨，可获得较高的几何精度，但不易获得较小的表面粗糙度。（2）摆动式直线研磨运动轨迹。可以获得较好的平直度。（3）螺旋形研磨运动轨迹。主要用于圆片形或圆柱形工件端平面研磨，能获得较高的平面度和较小的表面粗糙度。（4）“8”字形研磨运动轨迹。适用于平板类工件的修整和小平面工件的研磨，能使相互研磨的平面介质均匀接触，并且研具均匀地磨损。
在生产实践中，研磨是一种常用的精加工工艺，研磨的方法不断进步和更新，为适应不同的加工要求，各种文献资料报道的研磨方法有多种，有超声波抛光、磨料流喷射加工、电解研磨、化学抛光、磁性磨料研磨、液体磨料研磨等表面光整加工技术。 最常用的并且应用最多的是机械研磨，其特点是可获得较高的尺寸精度、形状精度和较低的表面粗糙度，但要求操作者有很高的技术水平和经验，加工效率低，劳动强度大，加工质量不易控制，表面残余应力大，表面残留磨粒还会影响表面质量。
磁性研磨法是通过磁场的磁极将磁性磨料吸压在加工件表面，加工件表面与磁极之间可以有数毫米的间隙，磁性磨料在加工间隙中沿磁力线整齐排列， 形成弹性磁刷，并压附在工件表面!旋转磁场或旋转加工件，使磁刷与加工件产生相对运动，从而精磨工件表面。磁研磨加工的特点是，不管加工件表面形状如何，只要使磁极形状与加工表面形状大体吻合，就可精磨有曲面的工件表面，因而磁研磨法适用于通常研削和研磨加工难以胜任的复杂形状零件表面的光滑加工。
球磨机采用无级调速系统控制，可轻易调整出适合研磨各种部件的研磨速bocuo度。采用电—气比例阀闭环反馈球磨机压力控制，可独立调控压力装置。上盘设置缓降功能，有效的防止薄脆工件的破碎。通过一个时间继电器和一个研磨计数器，可按加工要求准确设置和控制研磨时间和研磨圈数。工作时可调整压力模式，达到研磨设定的时间或圈速时就会自动停机报警提示，实现半自动化操作。
球磨机变速控制方法，研磨加工有三个阶段，即开始阶段、正式阶段和结束阶段，开始阶段磨具升速旋转，正式阶段磨具恒速旋转，结束阶段磨具降速旋转，其特征在于，在研磨加工开始阶段，人为控制磨具转速的加速度从零由慢到快地增大，当磨具转速升到正式研磨速度的一半时，加速度的变化出现一个拐点，控制磨具转速的加速度由最大值由快到慢地减小，直到磨具转速达到正式的研磨速度，磨具转速的加速度降为零。
利用固着磨料研磨的这一特点，根据工件磨具间的相对运动轨迹密度分布，合理地设计磨具上磨料密度分布，以使磨具在研磨过程中所出现的磨损不影响磨具面型精度，从而显著提高工件的面型精度。
今后随着人们对产品性能的要求日益提高，研磨加工以其加工精度和加工质量高而越来越受到了人们的关注。因此,超精密研磨等技术的研究,今后将更引人注目。
