文献翻译-冲压设备选用
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冲压设备选用
冲压设备的选择,是冲压工艺及模具设计中的一项重要内容。
它直接关系到冲压设备的安全和合理使用,也关系到冲压件的生产能否顺利进行和产品质量、模具寿命、生产率、产品成本等一系列问题。
冲压设备的选用包括选择设备类型和确定设备规格两项内容:
○1冲压设备类型的选择
冲压设备类型的选择,主要是根据冲压工艺性质、生产批量大小、冲压件的几何形状、尺寸及精度要求等因素来确定的。
冲压件生产中常用的是曲柄压力机和液压机。
在中小型冲裁件、弯曲件或浅拉深件的冲压生产中,主要选用开式压力机。
这种压力机具有三面敞开的操作主问、操作方便、容易安装机械化装置和成本低廉等优点。
但刚度较差,工作时床身的角变形会导致冲模间隙分布不均,降低冲模的寿命和冲裁件的质量.因而适于精度要求不太高的冲压件生产。
在大中型和精度要求较高的冲压件的生产中,主要选用闭式压力机。
这种压力机床身的弹性变形较小,刚度较好,精度较高。
对于大型、较复杂的拉深件则应采用闭式双动拉深压力机。
它具有两个滑块,拉深用的内滑块和压边用的外滑块。
模具结构简单,压边可靠易调,即根据工艺要求,调节压边力。
在小批生产尤其是大型厚板件的成形工艺中,多选用液压机。
液压机虽然速度侵、效率低、制件尺寸精度因受操作影响不太稳定,但压力大,没有固定行程,因而不会因为板材的厚度超差而过载,特别对于工作行程较大的冲压工艺具有明显的优点。
但液压机一般不适于冲裁工作。
在大量生产中应选用高速自动压力机或多工位自动压力机。
高速自动用力机具有效率高、精度高等特点、一台多工位自动压力机能够代替多台手工位压力机,并且消除了工序间半成品的堆放和运输问题。
对于平面精压和体积精压等工艺.其特点是工件变形量小、精度要求向。
而精压机的丁作机构是曲柄肘杆机构,滑块工作行程很小,肘杆机构及机架刚度较大。
因此,既能适应精压工艺工作行程很小的需要.又能达到提高精压工件精度的目的。
精冲上艺除要求精度高、刚性好和冲裁速度较低外,还特别要求压力机除主滑块外,要有压边和反压装置,一般应选用专用的三动精冲压力机或精冲液压机。
当采用专用精冲模具时,也可在普通压力机上实现精冲。
2.冲压设备规格的选择
在压力机的类型选定之后,应进—步根据变形工厅的特点、变形力的大小、冲压件与毛坯的形状和尺寸、模具参数和操作上的要求来确定设备的规格;对曲柄压力机所要考虑的主要技术参数如下所述。
(1)公称压力(吨位) 压力机的承载能力受压力机本身各主要构件强度的限制,其滑块上所容许承受的最大作用力(许用负荷)是随曲柄转角位置的不同而变化的。
公称压力g F 是指滑块离下死点前某一特定的距离(此距离称为公称压力行程p S )或转到离下死点前某一特定的角度(此特定角度称为公称压力角αp)时,滑块上所容许承受的最大作用力。
在选择压力机吨位时,应保证在全行程范围内,压力机的许用负荷在任何时刻均大于相应时刻所需变形力的总和。
也就是说,应该使公一次行程内所要完成的各种冲压工序所需力的合力曲线,在全行程范围内均低于压力机的许用负荷曲线。
在使用中,为了简便起见,对于工作行程小于压力机公称压力行程的冲压工序,如一般的落料、冲孔、弯曲、压印等上序.可直接按压力机的公称压力选择设备。
对于工作行程较大的工序,可按压力机许用负荷曲线选取。
对于拉深工序,由于其工作行程较大,不能按压力机的公称压力选用,而近似地取为:
在深拉深时.最大拉探力)6.0~5.0(≤F 压力机公称压力g F ;
在浅拉深时,最大拉探力)8.0~7.0(≤F 压力机公称压力g F 。
(2)电动机功率 一船在保证了工艺力的情况厂,电动机功率是足够的。
但是,在某些情况下.如大型件的斜刃冲裁、深度很大的拉深等,也会出现压力足够而功率不足的现象,此时必须对压力机的电动机功率进行校核,并选择电动机的功率大于冲压所需总功率的压力机。
η
210A A A +=
冲压时压力机所供应的
功E ∆应大于一个行程所需
功儿,即0A E >∆。
E ∆可近似用下列公式计算
(如图1—1阴影部分面积):
s F s F E g p g 15
1≈=∆ 式中s ——滑块行程(mM)。
1A —--工件变形功;
2A ——拉深垫工作功; 图1-1 E ∆计算图
η——压力机总效率,η=50%--60%
(3)滑块行程和行程次数 滑块从上死点到下死点所经过的距离称为滑块行程。
行程次数是指滑块每分钟住复行程的次数。
滑块行程大小的选择。
应保证方便毛坯的放人和零件的取出。
拉深和弯曲工序一般需要较大的行程.对于拉深工序其行程一般为拉深件高度的2.5倍。
冲裁、精压工序所需行程较小。
根据用途不同,压力机的行程有的做成可调式的。
行程次数主要根据生产率、操作的可能性和允许的变形速度来确定。
在确定滑块行程次数时,滑块的运动速度要符合冲压生产工艺的要求。
对拉深工艺来说,若速度过高,则会引起工件破裂。
拉深工艺的合理速度范围如表1—1所列.进行拉深工艺的压力机,滑块速度不应超过这个数值。
表1-1 拉伸工艺的合理速度范围
(4)装模高度 压力机的装模高度是指滑块在下死点位置时,滑块下表面到工
作势板上表面的距离。
装模高度加上垫板厚度即为压力机的封闭高度。
没有垫板的压力机,其装模高度与封闭高度相等。
模具的封闭高度是指工作行程终了时,模具上模座上表面与下模座下表面之间的距离。
选择压力机时,必须使模具的封闭高度介于压力饥的最大装模高度与最小装模高度之间(见图1—2),一般应满足
105+≥≥-Min Max H H H
式中 Max H ----连杆调节到最短(偏心冲床的行程应调到最小)时.压力饥的装
模高度,即最大装模高度(mm);
Min H ----连杆调节到最长(偏心冲床的行程应调到最大)时,压力矾的装
模高度,即最小装模高度(mm);
H ----模具的封闭南度(mm):
上式中的5mm 是考虑到装模方便所留间隙,10mm 是保证修模所留尺寸。
图 1-2 模具的封闭高度
由于考虑到连杆受力情况,希望以最短的连杆上作,考虑到修模而使模具封闭高度减小等原因,一般模具设计最好接近压力机的最大装模高度。
如果模具封闭高度过小,可在压力机台面上加放垫板。
(5)下作台而和滑块底面尺寸 工作台面(或工作势板)和滑块下平面的大小
应足以安装模具,并留有余地,一般情况下,冲床工作台回加大于模具底座尺寸50—70mm以上,同时应保证能牢固地安装及固定模具,并能正常工作。
工作台和滑块的形式要考虑冲压工艺上的需要,即必须与模具的打料装置、出料装置、卸料装置等的结构相适应,例如工作台的孔,应能容纳模具的卸料装置或使出料顺利进行:
(6)压力机的精度和刚度压力机的精度,主要是指压力机在静态情况下,所测得的压力机应达到的各种精度指标,故又称静态精度。
它主要包括:工作台的平面度,滑块下平面的平面度,工作台面同滑块下平面的平行度,滑块行程同工作台面的垂直度,滑块中心孔和滑块行程的平行度等。
压力机静态精度的高低,对冷冲压上作有很大影响。
压力机的精度高,则冲出的工件质量也高,冲模不易损坏,使用寿命长。
精度低的压力机,不仅工件质量低,模具寿命也低。
若滑块行程勺与工作台面垂直度差,则导致上、下模的同轴度降低,冲模刃口易于损坏。
但是,压力机的静态精度却要靠压力机的刚度来保证。
压力机的刚度主要是指压力机在工作时抵抗弹件变形的能力,对开式压力机来说,有垂直刚度和角刚度两种指标。
所谓垂直刚度是指压力机的装模高度产生单位垂直变形时,压力机所承受的作用力.而角刚度是指压力机的滑块相对于工作台而产生单位角变形时,压力机所承受的作用力。
在冲压力的作用下,床身会弹性伸长,工作台平面会弹性挠曲。
这些弹性变形破坏了压力机的某些静态精度、对冷冲压件的质量有很大的影响。
对冲裁工序.尤其是精密冲裁(包括整修和精冲)和要求较高精度冲裁件的普通冲裁工序,模具间隙要求小而均勾,并且在上、下模闭合时要有准确的入模量。
压力机如果角刚度不足,不们会造成废品,而且会大大缩短模具的使用寿命。
Press the equipment and select the choice
Press the equipment and select the choice which presses the equipment for use, press an important content in the craft and mold design. It concerns directly that presses the security of the equipment and uses rationally, production could such a series of questions as going on and product quality , life-span of the mould , productivity , cost of goods ,etc. smoothly the one that concern and press one too . Two contents including choosing the type of the equipment and confirming the specification of equipment of exertion of pressing the equipment:
1.A choice of pressing the type of the equipment of choice of pressing the type of the equipment, according to press craft nature , production batch size , press geometry form , size and precision person who require factor of piece come confirmed mainly.
A commonly used one is crank press and liquid press in a production of pressing .
Or draws lightly in the deep production of pressing of one in the medium and small-scale blanking one, crooked one, select the turning on type press for use mainly.This kind of press has three unlimited operation advantage of mainly ask , easy to operate , apt to install mechanized device and cost cheaping etc.. But rigidity is relatively bad, the angle of the lathe bed out of shape will cause the interval maldistribution of the trimming die while working, reduce the life-span of the trimming die and quality of one of blanking. Therefore the one that is suitable for expecting very much in precision presses one to produce.
In the production of pressing one of expecting much in the large-and-middle-scale and precision , select the closing type
press for use mainly. The elasticity of this kind of pressure lathe body is out of shape and relatively small, rigidity is better, the precision is relatively high. As to drawing deep one and should adopt closing type pair and move and draw the deep press large-scaly, more complicated. It have two slip piece, draw use deeply slip piece and outside used to press slip yuan inside. The mould is of simple structure, press reliable and easy to adjust, namely according to the technological requirement, regulate and press strength.
Produce, especially large-scale it in the craft of taking shape of one of the thick board in
small batches, select for use more liquid presses. Liquid press though speed invade , low making pieces of size precision because of is it influence very much steady to operate efficiency, unless but it is the heavy in pressure, it have regular journey,therefore can overload because of ultra difference of thickness of the panel, especially have obvious advantages to the craft of pressing that the working journey is greater. But the liquid press is seldom suitable for the blanking work.
Should select the automatic press of high speed or many automatic presses of worker's location for use in producing in a large amount. Exert oneself plane have with high efficiency , precision high characteristic , one Taiwan more than worker location automatic press can replace many sets of craft location press automatically at a high speed, and has dispelled piling up and transportation problem of the semi-manufactured goods among the process.
Press to the level precisely and such crafts as the volume is pigeonholed precisely. Its there is characteristic it is the little in deformation amount in work piece , require precision to. And precise man of press make organization crank elbow pole organization , slip pieces of working very much little journey, elbow pole organization and framework rigidity are relatively great. So can meet precise to keep craft work journey little need
very. Can achieve the goal of improving and pressing the precision of the work piece precisely .
Precise to dash to skill except require precise skin high , rigidity fine and speed getting low blanking, require press except slip piece mainly , pigeonhole and pigeonhole the device instead especially also, should generally select three special-purpose for use and move the precise strength pressing machine or wash the liquid press precisely . When adopting and washing the mould special-purpose and precisely , can realize on the ordinary press that washes precisely .
2.The choice of pressing the specification of the equipment is after the type selection of the press, should enter - according to the characteristic in the drawing room of worker out of shape , size of the strength out of shape , pressing the form and size of one and blank of step,Mould parameter and demand had to operate is it confirm specification of equipment to come; Stated main technical parameter considered to the crank press as follows.
(1)The bearing capacity of the press is restricted by the press intensity of every main member for the nominal pressure (tonnage ), it slip piece is it permit bear large effort (let with load ) change with the crank corner position most to have. Nominal
F is it slip piece from lay a certain specific distance pressure
g
in front of ordering extremely to mean (whether distance this call
nominal pressure journey
S), turn into from lay in front of
p
ordering extremely when the a certain specific angle (specific angle this call nominal α of pressure corner αp ), slip piece have heavy effort most that bear permitted.
While choosing the tonnage of the press, should guarantee it within the range of the whole journey , the letting to be greater than the total of the strength out of shape of the need of corresponding moment at any moment with load of the press. That is to say , should make common one journey various kinds of finished to want press process necessary with joint efforts curve
of strength, lower than letting to use the load curve of the press within the range of the whole journey .
In using, for being simple and convenient, smaller than the process of pressing of the nominal pressure journey of the press to the working journey , if general blanking , washes holes , crooked and impressing the preface of waiting foring. Can choose the equipment according to the nominal pressure of the press directly . The process to that the working journey is greater, can let to choose with the load curve according to the press . For drawing the deep process, because its working journey is relatively big, can't select for use according to the nominal pressure of the press , and fetch
approximatly :
When draw deeply deeply.
Most heavy to is )6.0~5.0(≤F it
visit strength press nominal
pressure to draw g F ;
When draw lightly deeply,
most heavy to is )8.0~7.0(≤F it
visit strength press nominal pressure to
draw g F .
(2)Power of the motor A ship is guaranteeing the situation factory of craft strength , the power of the motor is enough. However, in some cases. Large-scale oblique edge of piece blanking, depth very heavy to draw getting dark for instance, can appear pressure enough too but power enough phenomenon, must check the power of the motor of the press at this moment , choose to be greater than the press which presses the necessary total power in power of the motor.
The work that the press E ∆ supplies should be greater than the necessary work of a journey while pressing, namely 0A E >∆
.
E ∆ It is calculated with the following formulae that very approximate(such as the area of 1-1 shaded area of the Fig.):
s F s F E g p g 15
1≈=∆ in the type , S --Slippery journeys (mm ).
1A ---Work out of shape of the work piece ;
2A --Draw and pad the working work deeply ;
η--The total efficiency of the press, η =50% --60%
(3)Slippery pieces of journey and journey number of times slip piece from having and extremely clicking to lay distance undergone to order call slippery journeys extremely. Journey number of times mean slip piece is it reply number of times of journey to live in minute while being every.
Slippery journeys size choice. Should guarantee to facilitate putting the taking out of people and part of the blank . It generally needs greater journey to draw the deep and crooked process. For drawing its journey of deep process generally in order to draw 2.5 times pieces of height deep. Blanking , pressing the necessary journey of process precisely smaller.
Different according to uses, some journeys of the press are done into but the mode.
The deformation tempo of the main foundation productivity of number of times of the journey , possibility and permission operated is confirmed . While confirming the number of times of slippery journeys, slip the speed of movement of one should accord with the demand of pressing the production technology. For drawing the deep craft, if the speed is too high, will cause the work piece to break . Draw dark reasonable speed of craft range if 1-1 form listed. Drawing the press of the deep craft , slippery speeds should not exceed this number value . 1-1 rational speed ranges which draws the craft forms 。
η 210A A A +=
list 1-1 Draw dark reasonable speed of craft range
(4)Install mould high press load with mould is it slip yuan is on the bottom while dying some positioning to mean highly, slip piece put surface get worker assume a posture distance , board of above surface. It is namely the close height of the press to put the mould and highly add the thickness of the backing board. Without press of the backing board, it puts the mould and is highly highly equal to with sealing . Mould close at refering to working the end such as journey highly, mould mould flat above surface lay mould flat distance to lay surface. It choose at the time of press,the close to lie between the a hungry ones the getting more heavy to load with most for pressure highly in mould to must make(last 1-2 of Fig.s), should generally be satisfied
105+≥≥-Min Max H H H
In the type Max H ----When the connecting rod is regulated to get shortest (the journey of the partial puncher should be transfered to minimumly ). Pressure hungry holding the height of the mould , namely put the height of the mould (mm ) the most largly;
Min H ----Connecting rod regulate when getting most
getting long, pressure vitriol load the height of the mould with, namely highly (mm ) put the mould smallest;
H ----Whether close the south degree of mould(mm).
5mm to have type to is it put mould convenient interval
left to consider, 10mm is it build size that mould leave to guarantee.
Because consider the connecting rod receives the strength situation , hope to do with the shortest connecting rod, is it
build mould and make mould it seals to be highly person who reduce reason to consider, general mold design had better close to press
most heavy to load mould
Fig. 1-2 moulds of close height Height with. If mould seal height to be too light, can add and put the backing board at the mesa in press.
(5)Is it make platform to make but and slippery pieces of bottom surface size job mesa (or worker assume a posture board ) and slip yuans of size to down level should be enough to install the mould, allowing some leeway, generally speaking, the puncher workingbench is gone back to strengthen in above mould base measurement 50-70mm, must install and fix the mould firmly while answering at the same time , and can work normally . Workingbench and slip form of piece is it is it press need of craft to consider to want , namely must with to play material device , produce structure , material of device , tripper ,etc. suit mould, such as the hole of the workingbench , should be able to hold the tripper of the mould or use the material and go on smoothly 。
(6)The precision of the press and precision of the rigidity press, mean mainly the press is in static cases, various kinds of precision index that the presses must examined should be up to, so also called the static precision. It includes mainly: Level
degree of the workingbench,Slip piece put level degree of level , job with slip piece lay parallel degree of level mesa, slippery journeys and vertical degree of the job mesa, slippery centre bores and parallel degree of slippery journeys ,etc..
Press static level of precision, to make have heavy influence very on being cold to press. The precision of the press is high, the work piece quality of going out is high too, the trimming die is difficult to damage , have long performance life. The press low in precision, not only the quality of the work piece is low, the life-span of the mould is also low. If slippery pieces of journey spoon and job mesa vertical degree bad, is it have , put coaxial degree of mould not to reduce to result in, the blade of the trimming die is easy to damage .
However, the static precision of the press will be guaranteed by the rigidity of the press . The rigidity of the press refers to the press and resists and plays a ability out of shape while working mainly, to opening type press , there are vertical rigidity and angle rigidity two kinds of indexes . So-called vertical rigidity mean to load mould with highly when being vertical and out of shape to produce the unit press, effort that the press bears . Whether and horn rigidity mean to slip piece to workingbench and produce press. Grow the unit when the angle is out of shape, the effort that the press bears . Under pressing the function of strength , the lathe bed will be extended flexibly, the workingbench level will bend flexibly . The elasticity out of shape has destroyed some static precision of the press , has very great influence on the cold quality of pressing one.
To the blanking process. The especially accurate blanking (and washes precisely including rebuilting ) and ordinary blanking process of requiring the more high-accuracy blanking one, the mould interval requires that colludes lightly and, and there should be accurate amount of mould entered while have , put the mould to closing. Press if the insufficient in horn rigidity ,no will cause by wasted product, and will shorten the service life of the mould greatly。