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無論是手工編程還是自動編程,在編程前都要對所加工的零件進行工藝分析,擬訂工藝方案,選擇合適的刀具,確定切削用量。在編程中,對一些工藝問題(如對刀點,加工路線等)也需要做一些處理。因此,數(shù)控編程的工藝處理是一項十分重要的工作。 一.數(shù)控加工的基本特點:
1.數(shù)控加工的工序內容比普通機加工的工序內容復雜。
2.數(shù)控機床加工程序的編制比普通機床工藝規(guī)程的編制復雜。這是因為在普通機床的加工工藝中不必考慮的問題,如工序內工步的安排、對刀點、換刀點及走刀路線的確定等問題,在編制數(shù)控加工工藝時卻要認真考慮。二.數(shù)控加工工藝的主要內容
1.選擇適合在數(shù)控上加工的零件,確定工序內容。
2.分析加工零件的圖紙,明確加工內容及技術要求,確定加工方案,制定數(shù)控加工路線,如工序的劃分、加工順序的安排、非數(shù)控加工工序的銜接等。設計數(shù)控加工工序,如工序的劃分、刀具的選擇、夾具的定位與安裝、切削用量的確定、走刀路線的確定等等。
3.調整數(shù)控加工工序的程序。如對刀點、換刀點的選擇、刀具的補償。
4.分配數(shù)控加工中的容差。
5.處理數(shù)控機床上部分工藝指令。三.常用數(shù)控加工方法
1.平面孔系零件
常用點位、直線控制數(shù)控機床(如數(shù)控鉆床)來加工,選擇工藝路線時,主要考慮加工精度和加工效率兩個原則。
若考慮效率,則上述零件采用圖1的路線比圖2好,因為經(jīng)過計算前者刀具空行程路線短。若考慮精度,則采用圖3的路線比圖4差,因為后者消除了反向間隙。
2.旋轉體類零件
常用數(shù)控車床或磨床加工。
(1)考慮加工效率:在車床上加工時,通常加工余量大,必須合理安排粗加工路線,以提高加工效率。實際編程時,一般不宜采用循環(huán)指令(否則,以工進速度的空刀太大)。比較好的方法是用粗車盡快去除材料,再精車。
(2)考慮刀尖強度:數(shù)控車床上經(jīng)常用到低強度刀具加工細小凹槽。圖5的b采用斜向進刀,不宜崩刃,a則易崩刃。
3.平面輪廓零件
常用數(shù)控銑床加工。應注意:
(1)切入與切出方向控制:圖6左圖的徑向切入,工件表面留有凹坑;右圖切向切入、切出,工件表面光滑。
(2)一次逼近方法選擇:只具有直線和圓弧插補功能的數(shù)控機床在加工不規(guī)則曲線輪廓時,需要用微小直線段或圓弧段去逼近被加工輪廓(其誤差稱為一次逼近誤差),逼近時,應該使工件誤差在合格范圍同時程序段的數(shù)量少為佳。
4.立體輪廓零件
(1)考慮工件強度及表面質量:圖7b,該形狀的工件受力后,強度較a差,c的表面質量最好。
(2)考慮機床的插補功能:加工飛機大梁直紋扭曲面時,若加工機床三軸聯(lián)動,只好用效率較低的球頭銑刀;若機床為四軸聯(lián)動,則可以選用效率較高的圓柱銑刀銑削(圖8)。
less of is the manual programming or programs automatically, all must to the components which processes carry on the craft analysis before the programming, drafts the craft plan, chooses the appropriate cutting tool, the determination cutting specifications.In the programming, to some craft question (for example to knife spot, processes route and so on) also to need to make some processing.Therefore, numerical control programming craft processing is an extremely important work. One. Numerical control processing essential feature:
1. numerical control processing working procedure content is more complex than the ordinary machining working procedure content.
2. numerical control engine bed processing procedure establishment is more complex than the ordinary engine bed technological process establishment.This is because does not need to consider in the ordinary engine bed processing craft the question, like in the working procedure a labor step arrangement, to knife, trades knife and feeds the route indeed to grade the question, when establishment numerical control processing craft must consider earnestly actually.Two. Numerical control processing craft primary coverage
1. choices suits the components which processes in the numerical control, definite working procedure content.
2. analysis processing components blueprint, is clear about the processing content and the specification, the determination processing plan, the formulation numerical control processing route, like working procedure division, processing order arrangement, non-numerical control processing working procedure engagement and so on.The design numerical control processing working procedures, like the working procedure division, the cutting tool choice, the jig localization and the installment, the cutting specifications determination, feeds route determination and so on.
3. adjustment numerical control processing working procedure procedure.If to knife, trades a knife choice, the cutting tool compensation.
In 4. assignment numerical control processing tolerance.
On 5. processing numerical control engine bed partial craft instruction.Three. The commonly used numerical control processing method
1. even faces are the components
commonly used spot position, the linear control numerical control engine bed (for example numerical control drilling machine) process, when choice craft route, mainly considers the processing precision and the processing efficiency two principles.
If consideration efficiency, then above components use Figure 1 route compared to Figure 2 well, because the process calculates the former cutting tool spatial traveling schedule route to be short.If consideration precision, then uses Figure 3 routes compared to Figure 4 the difference, because the latter eliminated the reverse gap.
2. solid of revolution class components
commonly used numerical control lathe or grinder processing.
(1) consideration processing efficiency: Processes when the lathe, usually processes the remainder to be big, must arrange the rough machining route reasonably, enhances the processing efficiency.When actual programming, (otherwise not suitably uses the circulation instruction generally, enters speed by labor run-out too to be big).Is removes the material as soon as possible compared with the good method with the roughing, again lathe finishing.
(2) consideration knife point intensity: On the numerical control lathe uses the low intensity cutting tool to process the tiny scoop channel frequently.Figure 5 b uses the diagonal feed, not suitable breaking, a then easy breaking.
3. plane outline components
commonly used numerical control milling machine processing.Should pay attention:
(1) cuts into with cuts the directional control: Figure 6 left chart radial directions cut into, the work piece surface leaves leeway the pit; The figure to the right tangential cuts into, cuts, the work piece surface is smooth.
(2) (2) one time approaches the method choice: Only has the straight line and the circular arc interpolation function numerical control engine bed when the processing irregular curve outline, needs to use the small tangential path or the round segmental arc approaches is processed the outline (its error to be called a time approximate error), when approaches, should cause the work piece error segment quantity to be short good for while the qualified scope.
(3) 4. three-dimensional outline components
(4) (1) consideration work piece intensity and surface quality: Chart 7b, after this shape work piece stress, the intensity compares a difference, the c surface quality is best.
(5) (2) considers the engine bed the interpolation function: When processing airplane summer beam straight burr distortion surface, if the processing engine bed three axle linkage, has to use an efficiency low ball milling cutter; If the engine bed is four axis linkages, then may select the efficiency high column milling cutter milling (Figure 8).
一.數(shù)控機床編程的方法
數(shù)控機床程序編制的方法有三種:即手工編程、自動編程和CAD/CAM 。
1.手工編程
由人工完成零件圖樣分析、工藝處理、數(shù)值計算、書寫程序清單直到程序的輸入和檢驗。適用于點位加工或幾何形狀不太復雜的零件,但是,非常費時,且編制復雜零件時,容易出錯。
2.自動編程
使用計算機或程編機,完成零件程序的編制的過程,對于復雜的零件很方便。
3.CAD/CAM
利用CAD/CAM軟件,實現(xiàn)造型及圖象自動編程。最為典型的軟件是Master CAM,其可以完成銑削二坐標、三坐標、四坐標和五坐標、車削、線切割的編程,此類軟件雖然功能單一,但簡單易學,價格較低,仍是目前中小企業(yè)的選擇。
二.數(shù)控機床程序編制的內容和步驟
1.數(shù)控機床編程的主要內容
分析零件圖樣、確定加工工藝過程、進行數(shù)學處理、編寫程序清單、制作控制介質、進行程序檢查、輸入程序以及工件試切。
2.數(shù)控機床的步驟
?。治隽慵D樣和工藝處理
根據(jù)圖樣對零件的幾何形狀尺寸,技術要求進行分析,明確加工的內容及要求,決定加工方案、確定加工順序、設計夾具、選擇刀具、確定合理的走刀路線及選擇合理的切削用量等。
同時還應發(fā)揮數(shù)控系統(tǒng)的功能和數(shù)控機床本身的能力,正確選擇對刀點,切入方式,盡量減少諸如換刀、轉位等輔助時間。
?。當?shù)學處理
編程前,根據(jù)零件的幾何特征,先建立一個工件坐標系,根據(jù)零件圖紙的要求,制定加工路,在建立的工件坐標系上,首先計算出刀具的運動軌跡。對于形狀比較簡單的零件(如直線和圓弧組成的零件),只需計算出幾何元素的起點、終點、圓弧的圓心、兩幾何元素的交點或切點的坐標值。
?。帉懥慵绦蚯鍐?
加工路線和工藝參數(shù)確定以后,根據(jù)數(shù)控系統(tǒng)規(guī)定的指定代碼及程序段格式,編寫零件程序清單。
.程序輸入
?。绦蛐r炁c首件試切
三.數(shù)控加工程序的結構
1.程序的構成:由多個程序段組成。
O0001;O(FANUC-O,AB8400-P,SINUMERIK8M-%)機能指定程序號,每個程序號對應一個加工零件。
N010 G92 X0 Y0;分號表示程序段結束
N020 G90 G00 X50 Y60;
...;可以調用子程序。
N150 M05;
N160 M02;
2.程序段格式:
(1)字地址格式:如N020 G90 G00 X50 Y60;
最常用的格式,現(xiàn)代數(shù)控機床都采用它。地址N為程序段號,地址G和數(shù)字90構成字地址為準備功能,...。
(2)可變程序段格式:如B2000 B3000 B B6000;
使用分割符B各開各個字,若沒有數(shù)據(jù),分割符不能省去。常見于數(shù)控線切割機床,另外,還有3B編程等格式。
(3)固定順序程序段格式:如00701+02500-13400153002;
比較少見。
其中的數(shù)據(jù)嚴格按照順序和長度排列,不得有誤,上面程序段的意思是:N007 G01 X+02500 Y-13400 F15 S30 M02;
One. The numerical control engine bed programs the method
numerical control engine bed programming method has three kinds: Namely manual programming, automatic programming and CAD/CAM.
1. manual programming
by completes the components pattern analysis, craft processing, the value computation, the written procedure detailed list artificially until the procedure input and the examination.Is suitable in the position processing or the geometry shape not too complex components, but, extremely time-consuming, when also establishment complex components, easy to make a mistake.
2. automatic programming
use computer or Cheng Bianji, completes the components procedure the establishment process, is very convenient regarding the complex components.
3.CAD/CAM
uses the CAD/CAM software, the realization modelling and the image automatic programming.The most typical software is Master CAM, its may complete the milling two coordinates, three coordinates, four coordinates and five coordinates, the turning, the line cutting programming, although this kind of software the function is unitary, but simple easy to study, the price is low, was still the present small and medium-sized enterprise choice
Two. The numerical control engine bed programming content and
the step 1. numerical control engine bed programs the primary coverage
analysis components pattern, the determination processing technological process, carries on mathematics processing, the compilation procedure detailed list, the manufacture control medium, carries on the program check, the input routine as well as the work piece tries to cut.
2. numerical control engine bed step
. The analysis components pattern and the craft processing
basis pattern to the components geometry shape size, the specification carries on the analysis, is clear about the processing the content and the request, decided the processing plan, the determination processing order, designs the jig, chooses the cutting tool, the determination reasonable feeds the route and the choice reasonable cutting specifications and so on.
Simultaneously also should display the numerical control system the function and the numerical control engine bed itself ability, the correct choice to the knife spot, cuts into the way, reduces as far as possible such as trades the knife, indexing and so on the non-cutting time.
. Before mathematics
processing programming, according to the components geometry characteristic, establishes a work piece coordinate system first, according to the components blueprint request, the formulation processing road, in the establishment work piece coordinate system, first calculates the cutting tool the path.Regarding the shape quite simple components (for example straight line and circular arc composition components), only must calculate the geometry element the beginning, the end point, the circular arc center of circle, two geometry element point of intersection or the tangential point coordinate figure.
. Compilation components procedure detailed list
processing route and after craft parameter determination, stipulates according to the numerical control system assigns the code and the segment form, the compilation components procedure detailed list.
. Procedure input
. The program check tries with first to cut
Three. Numerical control processing procedure structure
1. procedure constitutions: Is composed by many segments.
O0001; O(FANUC-O, AB8400-P, SINUMERIK8M-%) function assigns the procedure number, each procedure number corresponds processing components.
N010 G92 X0 Y0; The semicolon expressed the segment finished
N020 G90 G00 X50 Y60;
…; May transfer the subroutine.
N150 M05;
N160 M02;
2. segment forms:
(1) word address format: If N020 G90 G00 X50 Y60;
The most commonly used form, the modern numerical control engine bed all uses it.Address N is the segment number, address G and the digital 90 constitution character address is the preparation function,….
(2) invariable segment form: If B2000 B3000 B B6000;
Use minute tally B opens each character respectively, if does not have the data, divides the tally not to be able to omit.Common in numerical control line cutting engine bed, moreover, but also has forms and so on 3B programming.
(3) fixed smooth segment form: If 00701+02500-13400153002;
Quite rare.
Data strictly according to the order and the length arrangement, acts without fail, above segment meaning is: N007 G01 X+02500 Y-13400 F15 S30 M02;
盡管對高速加工的研究已有多年,但現(xiàn)在對高速加工還缺少一個明確簡潔的定義和解釋。高速加工的基本出發(fā)點是高速低負荷狀態(tài)下的切削可較低速高負荷狀態(tài)下切削更快地切除材料。低負荷切削意味著可減輕切削力,從而減少切削過程中的振動和變形。使用合適的刀具,在高速狀態(tài)下可切削高硬質的材料。同時,高速切削可使大部分的切削熱通過切屑帶走,從而減少零件的熱變形。
上述這些優(yōu)點僅在合適的加工策略的情況下才能實現(xiàn)。如果使用了不適當?shù)募庸げ呗?,輕則會導致刀具壽命的降低,重則可能導致更加可怕的結果。有一點必須記住,這就是高速加工并不是簡單地使用現(xiàn)有刀具路徑,通過提高主軸轉速和進給率實現(xiàn)。
高速加工刀具路徑
高速銑削刀具路徑有多種限制,當將這些限制逐一列出后,則之所以需要這些限制的原因就一目了然。
1. 刀具不能和零件產(chǎn)生碰撞
2. 切削負荷必須在刀具的極限負荷之內
3. 殘留材料不能大于指定極限
4. 應避免材料切除率的突然變化
5. 切削速度和加速度必須在機床能力范圍內
6. 切削方向(順銑/逆銑)應保持恒定
7. 應避免切削方向的突然變化
8. 盡量減少空程移動
9. 切削時間應減少到最短
然而,在實際零件的刀具路徑編制過程中,很難全部滿足上述要求。事實上,在加工復雜形狀的零件時,也根本無法全部滿足上述要求。在這種情況下,應盡可能地滿足這些要求,同時,在必要的情況下可忽視一個或多個限制。在上述限制中,有些限制相對其它限制來說顯然更加重要,應首先滿足這些限制。上述的這些限制是大致按其重要性而順序列出。
精加工為高速加工提出了一個特殊的問題,即刀痕問題。由于零件形狀的限制,對切削條件的妥協(xié)常常會在加工后的零件表面上留下可見刀痕。當然,可通過拋光的方法來消除這些刀痕,但這樣就違背了我們使用高速加工的初衷??珊苋菀椎貙Υ旨庸ず桶刖庸みM行優(yōu)化處理,因為在進行過這些操作后,CAM操作者有多種選擇來修改零件的形狀,刀痕可通過隨后的精加工來消除。
編程能力
好的高速加工程序在機床上執(zhí)行得非常快,但它的產(chǎn)生卻需花費很長的時間和大量的精力。在如模具制造這樣的單件加工領域,因等待加工程序而導致機床停機的現(xiàn)象非常普遍。如果簡單地將這種壓力強加給CAM操作者,讓他們更快地產(chǎn)生刀具路徑,常常會迫使他們走捷徑。其結果是所編制的程序并不經(jīng)濟、有效。盡管機床在繼續(xù)運轉,但加工速度卻大打折扣。
顯然,使用這種策略進行高速加工是不明智的。要得到最好的高速加工結果,必須提供足夠強大的CAM能力,以能得到高質量的加工程序,保證機床能全負荷地進行工作。為此需:
? 使用具備自動高速加工功能的CAM軟件。這樣可減少操作者優(yōu)化程序的工作量。
? 使用能快速計算出無過切刀具路徑的CAM軟件。批處理功能可將復雜程序的計算留在夜間進行。
? 使用高性能的計算機并經(jīng)常更新配置。確保計算機具有足夠內存,以提高其運行效能。
? 確保每臺機床都配備有足夠多的CAM編程人員。培訓機床操作者,使他們能直接在車間進行加工編程,這樣可最大限度地發(fā)揮他們的加工技能。
? 確保對操作者進行了適當?shù)母咚偌庸ぞ幊膛嘤枴?
安排加工順序
除最簡單的零件外,高速加工總是牽扯到多個加工步驟。在高速加工編程中,最重要的是選取正確的加工順序。Delcam所遇到的用戶問題,有很大一部分都是策略的使用順序問題,而不是策略本身的使用問題。盡管CAM軟件如PowerMILL的自動化水平日益提高和增強,但它最終代替不了用戶自己對加工零件和加工策略的理解和經(jīng)驗。
在這里我們無法詳細討論如何安排加工順序,在此,僅給出幾條安排加工順序的基本原則:
? 永遠同時考慮欲切除的材料,而不是僅僅考慮要加工成形的幾何形狀。
? 盡可能地將加工步驟減少到最少。
? 盡可能地使用連續(xù)策略,例如,偏置路徑通常比平行路徑好。
? 在可能情況下應盡量避免垂直下刀,盡量從材料外部切入材料。
? 在零件的一些臨界區(qū)域應盡量保證不同步驟的精加工路徑不重疊。這些區(qū)域如果出現(xiàn)路徑重疊,勢必會出現(xiàn)刀痕。
? 盡量不換刀,使用單個刀具精加工臨界區(qū)域。刀具設置錯誤常常導致精加工后加工表面出現(xiàn)刀痕。
? 盡可能使用短刀具。長刀具更容易磨損。如有可能,應考慮重新定位零件方向,使用短刀具來加工不容易加工的區(qū)域。
結論:
高速加工對加工工程中的每個環(huán)節(jié)的要求都很苛刻。使用正確的物理設備是進行高速加工的基本要求,可精確指定這些物理設備的參數(shù)。很難具體指定高速加工中需要什么樣的CAD和CAM功能,而CAD和CAM對高速加工的質量和穩(wěn)定性具有顯著影響。
供高速加工使用的CAD模型必須能精確地表達要加工出的模型形狀,這意味著兩點,其一,模型精度必須大于加工公差;其二,在可能的情況下,應將不需要進行銑削加工的模型特征從模型中刪除或遮蓋。
昂貴的高速加工設備必須配備以足夠的CAM編程人員,以保證機床使用的是最好的程序。讓機床加工人員在車間編制加工程序是提高編程質量的一個途徑。
確保CAM操作者和機床操作人員進行過良好的高速加工技術培訓。
仔細安排加工順序至關重要。適當使用CAM系統(tǒng)所提供的加工策略是獲得良好高速加工結果的最有效途徑。
Although had many years to the high speed processing research, but also lacks an explicit succinct definition and the explanation now to the high speed processing.The high speed processing basic starting point is under the high speed low load condition cutting may compare under the low speed high load condition to cut excises the material quickly.The low load cutting meant may reduce the cutting force, thus in reduced cutting process vibration and distortion.Uses the appropriate cutting tool, may cut the high flinty material under the high-speed run.At the same time, the high-speed cutting may cause the majority of cuttings to carry off hotly through the scrap, thus reduced components thermal deformation.
The above these merits only can realize in the appropriate processing strategy situation.If has used not the suitable processing strategy, light can cause the cutting tool life depression, the heavy piece possibly causes a more fearful result.Some point must remember that, this is the high speed processing uses the existing cutting tool way simply, through enhances the main axle rotational speed and to feed rate realization.
High speed processing cutting tool way
The high speed milling cutting tool way has many kinds of limits, after lists one by one these limits, then the reason that needs these limits the reason to be clear.
1. The cutting tool cannot produce with the components collides
2. The cutting load must within the cutting tool limit load
3. The residual material cannot be bigger than assigns limit
4. Should avoid the material excision rate changing 5
suddenly. The cutting speed and the acceleration must in the engine bed area of competence
6. The direction of cut (down milling/up milling) should maintain constant
7. Should avoid the direction of cut changing
8 suddenly. Reduces the spatial regulation to move
9as far as possible. The cutting time should reduce short to
However, in the actual components cutting tool way establishment process, very difficult to satisfy the above request completely.In fact, when processing complex shape components, also is unable to satisfy the above request completely radically.In this case, should satisfy these requests as far as possible, simultaneously, may neglect or many limits in the essential situation.In the above limit, some limit relative other limits are obviously more important, should first satisfy these limits.But the above these limits are press its importance the order to list approximately.
The precision work asked a special question for the high speed processing, namely slash question.As a result of the components shape limit, to cuts the condition the compromise to be able to leave behind the obvious slash frequently on the processing components surface.Certainly, may eliminate these slashes through the polishing method, but has like this violated the original intention which we use process high speed.May very easily carries on optimized processing to the rough machining and the semi-finishing, because after has carried on these operations, the CAM operator has the multiple options to revise the components the shape, the slash may eliminate through afterwards precision work.
The programming ability
good high speed processing procedure carries out extremely quickly on the engine bed, but its production must spend the very long time and the massive energy actually.Makes such single unit processing domain in like the mold, causes the engine bed engine off because of the waiting processing procedure the phenomenon to be extremely common.If imposes simply this pressure on the CAM operator, lets them have the cutting tool way quickly, can force them frequently to walk the shortcut.Its result is the procedure which establishes is uneconomical, is effective.Although the engine bed is continuing to revolve, but the processing speed greatly sells at a discount actually.
Obviously, uses this kind of strategy to carry on the high speed processing is wise.Must obtain the best high speed processing result, must provide the enough formidable CAM ability, by can obtain the high grade processing procedure, guaranteed the engine bed can the capacity load carry on the work.Needs for this:
Forever simultaneously considered wants to excise the material, but is not considered merely must process formed the geometry shape.
? Processes the step to reduce few as far as possible to.
? Uses the continual strategy as far as possible, for example, the bias way is usually better than the parallel way.
? To be supposed to avoid the vertical under knife as far as possible in the possible situation, as far as possible cuts into the material from the material.
? In components some critical regions should guarantee as far as possible the different step the precision work way does not overlap.If these regions appear the way to overlap, will be able to appear the slash inevitably.
? Does not trade the knife as far as possible, the use single cutting tool precision work critical region.The cutting tool establishment wrong causes the precision work postprocessing surface to appear the slash frequently.
? Uses the short cutting tool as far as possible.The long cutting tool is easier to wear.If has the possibility, should consider locates the components direction, uses region which the short cutting tool processes not not easily to process.
Conclusion:
The high speed processing to processes in the project each link request very to be all harsh.Uses the correct physical equipment is carries on the high speed processing the basic request, but assigns these physical equipment precisely the parameter.Very difficult to assign in the high speed processing to need any type specifically CAD and the CAM function, but CAD and CAM have the remarkable influence to the high speed processing quality and the stabi