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  • 技能培訓|磨削加工基礎:磨床的用途及分類
  • 本站編輯:xghl發布日期:2019-11-27 20:06 瀏覽次數:
什么是磨削加工?磨削加工是借助磨具的切削作用,除去工件表面的多余層,使工件表面質量達到預定要求的加工方法。
 
磨削加工在機械制造中是一種使用非常廣泛的加工方法,它用磨料磨具為工具在磨床上進行切削加工。其加工精度可達IT6~IT4級,表面粗糙度Ra值為1.25~0.01μm。還可完成其它機床難加工的材料,如淬硬鋼、硬質合金、玻璃、陶瓷等加工。
 
磨床加工的工藝范圍很寬,可磨削內外圓柱面和圓錐面、平面、齒輪齒廓面、螺旋面及各種成形面等。隨著磨料磨具的不斷發展,機床結構和性能的不斷改進,以及高速磨削、強力磨削等高效磨削工藝的采用,磨削已逐步擴大到粗加工領域。
 
磨削加工時的運動與所用磨具、工藝方法和工件加工表面形狀的不同而異。對于用砂輪進行加工的磨床,主運動都是砂輪的高速旋轉運動,進給運動的形式取決于加工工件表面的形狀和采用的磨削方法,可以由工件或砂輪分別完成,也可以由兩者共同完成。
 
磨床的種類
磨床的種類很多,可適應加工各種不同表面、不同形狀的工件。主要類型有:外圓磨床、平面磨床、工具磨床、刀具刃具磨床及各種專門化磨床等;還有以柔性砂帶為切削工具的砂帶磨床,以油石和研磨劑等為切削工具的精磨機床。
 
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100唯爾教育正弦精密平口鉗上的裝夾操作視頻截圖
 
M1432A型萬能外圓磨床
 
萬能外圓磨床的工藝范圍較寬,可以磨削內外圓柱面、內外圓錐面、端面等。但其生產效率較低,適用于單件小批生產。
 
image
100唯爾教育M1432A型萬能外圓磨床爆炸圖
 
一.M1432A磨床的組成
 
(1)床身
 
床身1是磨床的基礎部件,用于支承砂輪架5、工作臺3、頭架2、尾架6等部件,并保持它們準確的相對位置和運動精度。床身內部是液壓裝置和縱、橫進給機構等。
 
(2)頭架
 
頭架2由殼體、主軸部件、傳動裝置等組成,用于安裝和夾持工件,并帶動工件轉動。調節變速機構,可改變工件的旋轉速度。
 
(3)工作臺
 
工作臺3分上下兩層。上工作臺可繞下工作臺的心軸在水平面內偏轉±10°左右的角度,以便磨削錐面。下工作臺由機械或液壓傳動,帶動頭架2和尾架6隨其沿床身作縱向進給運動,行程則由撞塊控制。
 
(4)內圓磨具
 
內圓磨具4用于磨削工件的內孔,它的主軸端可安裝內圓砂輪,通過單獨的電動機驅動實現磨削運動。
 
(5)砂輪架
 
砂輪架5用于支承并傳動高速旋轉的砂輪主軸。砂輪架裝在橫向導軌上,操縱橫向進給手輪可實現砂輪的橫向進給運動。當磨削短圓錐面時,砂輪架和頭架可分別繞垂直軸線轉動±30°和+90°(逆時針)的角度。
 
(6)尾架
 
尾架6和頭架2的前頂尖一起,用于支承工件,尾座套筒后端的彈簧,可調節頂尖對工件的軸向壓力。
 
(7)腳踏操縱板
 
用于控制尾架上的液壓頂尖,進行快速裝卸工件。
 
二.其它常見磨床種類:
 
1.內圓磨床
 
內圓磨床主要用于磨削各種內孔(包括圓柱形通孔、盲孔、階梯孔以及圓錐孔、環形溝槽等)和軸的端面。常用砂輪周邊進行磨削,也用砂輪端面進行磨削。
 
image
2.無心外圓磨床
 
在無心外圓磨床上磨削外圓表面,工件不需打中心孔,這樣,既消除了因中心孔偏心而帶來的誤差(即沒有定位誤差),又可使裝卸簡單省時。由于有導輪和托板沿全長支承工件,對一些剛度較差的細長工件也可用較大的切削用量進行磨削,故生產率較高。
 
但機床調整時間較長,適用于成批及大量生產。
 
此外,無心外圓磨床不能磨削周向不連續的表面(如有鍵槽),也不能保證被磨外圓和內孔的同軸度。
 
image
3.工具磨床
 
工具磨床是對各種特殊復雜工件磨削加工所使用磨床的統稱,主要用于磨削各種切削刀具的刃口,如車刀、銑刀、鉸刀、齒輪刀具、螺紋刀具等。裝上相應的機床附件,可對體積較小的軸類外圓、矩形平面、斜面、溝槽和半球等外形復雜的機具、夾具、模具進行磨削加工。具體包括工具曲線磨床、鉆頭溝槽磨床、拉刀刃磨床、滾刀刃磨床以及花鍵軸磨床、螺紋磨床、活塞環磨床、齒輪磨床等
 
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4.數控磨床
 
數控磨床是利用磨具對工件表面進行磨削加工的機床。數控磨床又有吃到女朋友的胸她叫了、數控無心磨床、數控內外圓磨床、數控立式萬能磨床、數控坐標磨床、數控成形磨床等等
 
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磨削過程
 
磨削加工時以砂輪的高速旋轉作為主運動,與工件低速旋轉和直線移動作為進給運動的一種切削加工。在機械零件加工和機械制造中是常用的加工方法之一,下面為大家分享一下磨削加工的原理和相關知識。
 
磨削過程是由分布在砂輪表面上的大量磨粒以很高的速度旋轉對工件表面進行加工的過程,每一個磨粒就似一把小切削刃。
 
單個磨粒的磨削過程中,切入工件時的作用分為三個階段:
 
(1)滑擦階段。磨粒在工件表面上發生摩擦、擠壓,使工件發生彈性變形。此時磨粒沒起切削作用,稱為滑擦階段。
 
(2)刻劃階段。磨粒在工件表面上刻劃出溝紋,這個階段稱為刻劃階段。
 
(3)切削階段。磨粒前方金厲沿剪切面滑移而成切屑,此階段稱為切削階段。
 
由此可見,一個磨粒的磨削過程使磨削表面經歷了滑擦、刻劃(隆起)和切削三個階
 
段。形成的磨屑常見形態有帶狀、節狀、蝌蚪狀和灰燼等。
 
磨削運動及用量
 
磨削時,一般有四個運動。
 
(1)主運動。砂輪的旋轉運動稱為主運動。主運動速度υc(m/s)是砂輪外圓的線速度,即
 
υc=πd0n0/1000。式中,d0是砂輪直徑(mm);n0是砂輪轉速(r/s)。
 
普通磨削時,主運動速度υc為3035m/s;當υc>45m/s時,稱為高速磨削。
 
(2)進給運動。進給運動有以下三種:
 
1)徑向進給運動。徑向進給運動是砂輪切入工件的運動。徑向進給量fr指工作臺每雙(單)行程內工件相對于砂輪徑向移動的距離,單位為mm/雙行程。當砂輪做連續進給時,單位為mm/s。一般情況下,fr(或ap)=0.050.02mm/雙行程。
 
2)軸向進給運動。軸向進給運動即工件相對于砂輪的軸向運動。軸向進給量是指工件每轉一圈或工作臺每雙行程內工件相對于砂輪的軸向移動距離,單位為mm/r或mm/雙行程。一般情況下,fa(或f)=(0.20.8)B,B為砂輪寬度,單位為mm。
 
3)工件的圓周(或直線)進給運動。工件速度υw是指工件圓周進給運動的線速度,或工作臺(連同工件一起)直線進給的運動速度,單位為m/s。
 
磨削階段
 
磨削時,由于背向力Fp很大,引起工藝系統的彈性變形,使實際磨削深度與磨床刻度盤上所顯示的數值有差別。所以普通磨削的實際磨削過程分為三個階段。
 
(1)初磨階段。當砂輪剛開始接觸工件時,由于工藝系統的彈性變形,實際磨削深度比磨床刻度盤顯示的徑向進給量小。工藝系統剛性越差,初磨階段越長。
 
(2)穩定階段.在穩定階段,當工藝系統的彈性變形到達一定程度后,繼續徑向進給時,實際磨削深度基本上等于徑向進給量。
 
(3)清磨階段。在磨去主要加工余量后,可以減少徑向進給量或完全不進給再磨一段時間。這時,由于工藝系統的彈性變形逐漸恢復,實際磨削深度大于徑向進給量。隨著工件被一層層磨去,實際磨削深度趨近于零,磨削火花逐漸消失。清磨階段主要是為了提高磨削精度和表面質量。
 
關于磨削液:
 
磨削加工能獲得很高尺寸精度和較低的表面粗糙度。磨削時,磨削速度高發熱量大,磨削溫度可高達800~1000℃,甚至更高,容易引起工件表面燒傷和由于熱應力的作用產生表面裂紋及工件變形,砂輪磨損鈍化,磨粒脫落,而且磨屑和砂輪粉末易飛濺,落到零件表面而影響加工精度和表面粗糙度,加工韌性和塑性材料時,磨屑嵌塞在砂輪工作面上的空隙處或磨屑與加工金屬熔結在砂輪表面上,會使砂輪失去磨削能力,因此,為了降低磨削溫度,沖洗掉磨屑和砂輪末,提高磨削比和工件表面質量,必須采用冷卻性能和清洗性能良好、并有一定潤滑性能和防銹性能的切削液。
What is grinding? Grinding is a machining method to remove the redundant layer on the surface of the workpiece and make the surface quality of the workpiece reach the predetermined requirements by means of the cutting action of the abrasive tool.
 
 
 
Grinding is a widely used machining method in mechanical manufacturing. It USES abrasive tools as tools for cutting on the grinder. Its machining accuracy can reach IT6 ~ IT4, and the surface roughness Ra value is 1.25 ~ 0.01 m. It can also be used to finish other difficult materials, such as hardened steel, hard alloy, glass, ceramics and so on.
 
 
 
The grinding machine has a wide processing range, which can grind cylindrical surface, cone surface, plane, gear tooth profile surface, spiral surface and various forming surface, etc. With the continuous development of abrasives, the continuous improvement of machine structure and performance, as well as the adoption of high speed grinding, power grinding and other efficient grinding technology, grinding has been gradually expanded to the rough machining field.
 
 
 
The movement during grinding varies with the grinding tools used, the process and the shape of the workpiece surface. For a grinding machine processed with a grinding wheel, the main movement is the high-speed rotating movement of the grinding wheel. The form of feed movement depends on the shape of the surface of the workpiece and the grinding method adopted. It can be completed by the workpiece or the grinding wheel respectively, or both.
 
 
 
Type of grinder
 
 
 
There are many kinds of grinding machines, which can be used to process the workpiece with different surface and shape. The main types are: cylindrical grinder, surface grinder, tool grinder, cutting tool grinder and various specialized grinder, etc. There are also sand belt grinder with flexible belt as cutting tool, and fine grinding machine with whetstone and abrasive as cutting tool.
 
 
 
The image
 
100 video screenshot of mounting operation on sinusoidal precision flat jaw pliers
 
 
 
M1432A universal cylindrical grinder
 
 
 
Universal cylindrical grinding machine has a wide range of technology, which can grind inner and outer cylindrical surface, inner and outer cone surface, end surface, etc. But its production efficiency is low, suitable for single small batch production.
 
 
 
The image
 
Explosion diagram of 100 vell education M1432A universal cylindrical grinder
 
 
 
I. composition of M1432A grinder
 
 
 
(1) the bed
 
 
 
The bed 1 is the basic part of the grinder, which is used to support grinding wheel frame 5, table 3, head frame 2, tail frame 6 and other parts, and keep their accurate relative position and motion accuracy. Inside the bed is a hydraulic device and vertical, horizontal feed mechanism.
 
 
 
(2) the head
 
 
 
Head frame 2 is composed of shell, spindle parts, driving device, etc., used for mounting and clamping the workpiece, and driving the workpiece to rotate. Adjust the variable speed mechanism to change the rotating speed of the workpiece.
 
 
 
(3) working table
 
 
 
The working table is divided into two layers. The upper table can be rotated around the mandrel of the lower table at an Angle of ±10° in the horizontal plane for grinding the cone surface. The lower table is driven by mechanical or hydraulic, driving the head frame 2 and tail frame 6 to make longitudinal feeding movement along the bed body, and the travel is controlled by the collision block.
 
 
 
(4) internal round abrasives
 
 
 
Inner round grinding tool 4 is used for grinding the inner hole of the workpiece. The spindle end of the inner round grinding wheel can be installed to realize the grinding movement driven by a separate motor.
 
 
 
(5) grinding wheel rack
 
 
 
Grinding wheel rack 5 is used to support and drive the grinding wheel spindle with high speed rotation. The grinding wheel rack is mounted on the transverse guide rail and the operation of the transverse feeding hand wheel can realize the transverse feeding movement of the grinding wheel. When grinding the short cone surface, the grinding wheel holder and the head stand can rotate ±30° and +90° (counterclockwise) angles around the vertical axis, respectively.
 
 
 
(6) tail stock
 
 
 
The front center of tailstock 6 and headstock 2 is used to support the workpiece, and the spring at the rear end of tailstock sleeve can adjust the axial pressure of the center on the workpiece.
 
 
 
(7) pedal control board
 
 
 
It is used to control the hydraulic center of the tailstock for fast loading and unloading.
 
 
 
Ii. Other common grinder types:
 
 
 
1. Internal grinder
 
 
 
Internal grinder is mainly used for grinding various internal holes (including cylindrical through hole, blind hole, step hole, conical hole, ring groove, etc.) and shaft end face. Grinding is carried out on the periphery of the common grinding wheel and the end face of the grinding wheel.
 
 
 
The image
 
2. Centerless cylindrical grinder
 
 
 
Grinding the cylindrical surface on the centerless cylindrical grinder, the workpiece does not need to make the center hole, so, not only to eliminate the error caused by the center hole eccentricity (that is, there is no positioning error), and can make loading and unloading simple and save time. As a result of the guide wheel and support plate along the full length of the supporting workpiece, some of the stiffness of the slender workpiece can also be used for grinding larger cutting parameters, so the productivity is higher.
 
 
 
But the machine adjustment time is longer, suitable for batch and mass production.
 
 
 
In addition, centerless external cylindrical grinders cannot grind a surface with a circumferential discontinuity (such as a keyway), nor can they guarantee the coaxiality of the external and internal holes being ground.
 
 
 
The image
 
3. Tool grinder
 
 
 
Tool grinding machine is a general name for the grinding machine used in the grinding of various special and complex workpieces. It is mainly used for grinding the cutting edge of various cutting tools, such as turning tool, milling cutter, reamer, gear tool, thread tool, etc. Install the corresponding machine tool accessories, can be small size of the shaft class outer circle, rectangular plane, bevel, groove and hemisphere and other complicated shape of the machine, fixture, mold grinding. It includes tool curve grinder, bit groove grinder, broach grinder, hob grinder, spline shaft grinder, thread grinder, piston ring grinder, gear grinder and so on
 
 
 
The image
 
4. CNC grinder
 
 
 
CNC grinder is a machine tool that grinds the surface of the workpiece. CNC grinder and CNC surface grinder, CNC centerless grinder, CNC internal and external cylindrical grinder, CNC vertical universal grinder, CNC coordinate grinder, CNC shape grinder and so on
 
 
 
The image
 
The grinding process
 
 
 
In the process of grinding, the high-speed rotation of the grinding wheel is the main movement, and the low-speed rotation and linear movement of the workpiece are the feed movement. In mechanical parts processing and mechanical manufacturing is one of the most commonly used processing methods, the following for everyone to share the principle of grinding and related knowledge.
 
 
 
The grinding process is a process in which a large number of grinding grains distributed on the surface of the grinding wheel rotate on the surface of the workpiece at a high speed. Each grinding grain is like a small cutting edge.
 
 
 
In the grinding process of a single grinding particle, the role of cutting into the workpiece is divided into three stages:
 
 
 
(1) slip and rub phase. Friction and extrusion occur on the surface of the workpiece, resulting in elastic deformation of the workpiece. At this point, the abrasive particles do not play a cutting role, known as the sliding phase.
 
 
 
(2) marking stage. The grinding grains carve grooves on the surface of the workpiece. This stage is called the engraving stage.
 
 
 
(3) cutting stage. In front of the grain, the gold slippage along the shear surface to form the chip. This stage is called the cutting stage.
 
 
 
It can be seen that the grinding process of a grinding particle makes the grinding surface go through three steps: slip, scratch (uplift) and cutting
 
 
 
Segment. The common forms of debris are banding, node, tadpole and ash.
 
 
 
Grinding movement and amount
 
 
 
In grinding, there are generally four movements.
 
 
 
(1) main motion. The rotating motion of the grinding wheel is called main motion. Main movement speed nu c (m/s) is a cylindrical grinding wheel linear velocity, namely
 
 
 
Nu c = PI d0n0/1000. Where, d0 is the diameter of the grinding wheel (mm); N0 is the grinding wheel speed (r/s).
 
 
 
The ordinary grinding, main movement speed nu c for 3035 m/s; When nu c > 45 m/s, known as the high speed grinding.
 
 
 
(2) feed motion. There are three types of feed movements:
 
 
 
1) radial feed movement. Radial feed movement is the movement of the grinding wheel cutting into the workpiece. Radial feed fr refers to the radial movement distance of the workpiece relative to the grinding wheel within each double (single) stroke of the table, in mm/ double stroke. When the grinding wheel makes continuous feed, the unit is mm/s. In general, fr (or ap) =0.050.02mm/ double stroke.
 
 
 
2) axial feed movement. Axial feed motion is the axial motion of the workpiece relative to the grinding wheel. Axial feed refers to the axial movement distance of the workpiece relative to the grinding wheel in each turn or in each double stroke of the table, in mm/r or mm/ double stroke. In general, fa (or f) = (0.20.8) B, B is the width of the grinding wheel, the unit is mm.
 
 
 
3) circular (or linear) feed motion of the workpiece. Workpiece speed nu w is refers to the movement of the linear velocity, workpiece circular week or workbench (together with the workpiece) linear feed speed, the unit is m/s.
 
 
 
Grinding stage
 
 
 
During grinding, due to the large backplane force Fp, the process system elastic deformation, so that the actual grinding depth and the value displayed on the grinder dial have a difference. So the actual grinding process of ordinary grinding is divided into three stages.
 
 
 
(1) initial grinding stage. When the grinding wheel just begins to touch the workpiece, due to the elastic deformation of the process system, the actual grinding depth is smaller than the radial feed shown on the grinder dial. The less rigid the process system, the longer the initial grinding stage.
 
 
 
(2) stabilization stage: in the stabilization stage, when the elastic deformation of the process system reaches a certain level and the radial feed continues, the actual grinding depth is basically equal to the radial feed.
 
 
 
(3) cleaning stage. After the main machining allowance is removed, the radial feed can be reduced or no feed at all for a further period of time. At this point, the actual grinding depth is larger than the radial feed due to the gradual recovery of the elastic deformation of the process system. As the workpiece is ground layer by layer, the actual grinding depth approaches zero and the grinding spark gradually disappears. The main purpose of the cleaning stage is to improve the grinding accuracy and surface quality.
 
 
 
About grinding fluid:
 
 
 
Grinding can achieve high dimensional accuracy and low surface roughness. Grinding, grinding speed, high calorific value of grinding temperature can be as high as 800 ~ 1000 ℃, is even higher, easy to cause the workpiece surface burns and surface cracks due to the effect of thermal stress and deformation of workpiece, the grinding wheel wear passivation, grinding grain fall off, and wear debris and the grinding powder easy splash, fall on the parts surface and affect the machining accuracy and surface roughness, machining toughness and plastic material, chip embedded plug in space or on the surface of the grinding wheel work wear debris and machining metal welded on the grinding wheel surface, deprive grinding wheel grinding ability, therefore, in order to decrease the temperature of grinding, rinse grindings and at the end of the grinding wheel, To improve the grinding ratio and surface quality of the workpiece, it is necessary to use a cutting fluid with good cooling and cleaning properties, and certain lubrication and rust resistance.

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