外文翻譯---模具高速銑削加工技術(shù)

1、<p><b>　　外文資料翻譯</b></p><p>　　Mold high speed milling processing technology</p><p>　　The abstract Introduced the high speed milling in the mold processing application as well as

2、 the influence, and brief introduction high speed milling engine bed structure, control system and cutting tool. Has carried on the simple analysis to the high speed processing craft.</p><p>　　Key word high

3、 speed milling; mold processing</p><p>　　First, foreword</p><p>　　In the modern mold production, along with to models artistic and the function must obtain more and more high, models the interna

4、l structure to design more and more complex, the mold contour design day by day is also complex, the free curved surface accounts for the proportion to increase unceasingly, the corresponding mold structure also designs

5、more and more complex. These all set a higher request to the mold processing technology, not only should guarantee the high manufacture precision and th</p><p>　　The numerical control high-speed cutting proc

6、essing took in the mold manufacture a most important advanced manufacture technology, is the collection is highly effective, high quality, the low consumption in a body advanced manufacture technology. Is opposite in the

7、 traditional machining, its cutting speed, entered to the speed had the very big enhancement, moreover cut the mechanism not to be same. The high-speed cutting caused the machining to have the leap, its specific power m

8、etal excision r</p><p>　　The high speed processing technology has had the huge influence to the mold processing craft, changed the traditional mold processing to use "the annealing → milling processing

9、→ heat treatment → to rub truncates" or "the electric spark machining →manually polishes, polishes" and so on the complex long technical process, even might use the high-speed cutting processing substituti

10、on original complete working procedure. The high speed processing technology besides may apply in the hard mold cavity</p><p>　　Second, high speed milling processing engine bed</p><p>　　The high

11、-speed cutting technology is one of machining technology main development directions, it along with foundation technology the and so on CNC technology, microelectronic technology, new material and new structure developme

12、nt but steps a higher stair. Because the mold processes particular as well as high speed processing technology own characteristic, (processed engine bed, numerical control system, cutting tool to the mold high speed proc

13、essing related technology and the craft system and s</p><p>　　1.High stable engine bed strut part</p><p>　　The high-speed cutting engine bed lathe bed and so on supports the part to be supposed

14、 to have very well moves, the static rigidity, hot rigidity and best damping characteristic. The majority of engine beds all use high grade, the high rigidity and Gao Kangzhang the gray iron took the strut part material,

15、 some engine bed companies also increase the high damping characteristic in the foundation polymer concrete, by increases its vibration-proof and the thermostability, this not only may guarantee</p><p>　　2.

16、Engine bed main axle</p><p>　　The high speed engine bed main axle performance is the realization high-speed cutting processing important condition. The high-speed cutting engine bed main axle rotational spee

17、d scope is 10000~100000m/Min, the main axle power is bigger than 15kW. Is not bigger than 0.005mm through the main axle compressed air of or axial play between the cooling system control hilt and the main axle. Also requ

18、ests the main axle to have the fast vertical speed, to assign the performance which the position is fas</p><p>　　3.The engine bed actuates the system</p><p>　　In order to satisfy the mold high

19、speed processing the need, high speed processes the engine bed the actuation system to be supposed to have the following characteristic:</p><p>　　(1) high entering for speed.</p><p>　　The resear

20、ch indicated that, regarding the minor diameter cutting tool, enhances the rotational speed and each tooth enters for the quantity is advantageous in reduces the cutting tool attrition. At present commonly used entering

21、for the speed range is 20~30m/Min, like uses leads greatly the ball bearing guide screw transmission, enters may reach 60m/ for the speedMin; Uses the straight line electrical machinery then may enable to achieve 120m/ t

22、o the speedMin.</p><p>　　(2) high acceleration.</p><p>　　Has the good acceleration characteristic to the three dimensional complex curved surface silhouette high speed processing request actuati

23、on system, the request provides the driver which the high rapid advance or progress gives (to enter speed approximately 40m/ quicklyMin, the 3D outline processing speed is 10m/Min), can provide 0.4m/S2 to 10m/The s2 acce

24、leration and reduces the speed.</p><p>　　The engine bed manufacturer mostly uses the entire closed loop position servo-control slightly to lead, the great size, the high grade ball bearing guide screw or lea

25、ds greatly many guide screws. Along with the electrical machinery technology development, the advanced straight line electric motor already was published, and the success applied in the CNC engine bed. The advanced strai

26、ght line direct motor drive enable the CNC engine bed no longer to have the mass inertia, in advance, question and</p><p>　　4.Numerical control system</p><p>　　The advanced numerical control sy

27、stem is guaranteed the mold complex curved surface high speed processing quality and the efficiency key aspect, the mold high-speed cutting processing to the numerical control system basic request is: </p><p&g

28、t;　　A. High speed numerical control return route (Digital control loop), including: 32 or above 64 bit parallel processors and 1.5Gb hard disk; Extremely short straight line electrical machinery sampling time. </p>

29、<p>　　B. Speed and acceleration feed-forward control (Feed forward control); Digital actuation system crawling control (Jerk control).</p><p>　　C. Advanced inserts makes up the method (to insert based

30、 on the NURBS transect makes up), by obtains the good surface quality, the precise size and the high geometry precision. </p><p>　　D. Pretreatment (Look-ahead) function. The request has the large capacity cu

31、shion register, may read in advance and inspects many segments (for example the DMG engine bed to be possible to reach 500 segments, the Simens system may reach a 1000~2000 segment), in order to when is processed the sup

32、erficial shape (curvature) changes may promptly adopt changes for measure and so on speed by avoids cutting and so on. </p><p>　　E. The error compensatory function, including because the straight line electr

33、ical machinery, the main axle and so on gives off heat the hot error which causes to compensate, the quadrantal error compensates, the measurement system error compensates and so on the function. In addition, the mold hi

34、gh-speed cutting processing very is also high to the data transmission speed request. </p><p>　　F. The traditional data connection, like the RS232 serial mouth transmission speed is 19.2kb, but many advanced

35、 processings centers have used the ether local area network (Ethernet) to carry on the data transmission, the speed may reach 200kb.</p><p>　　5.Cooling lubrication</p><p>　　The high speed proc

36、essing uses the belt coating the hard alloy tools, in high speed, the high temperature situation does not need the cutting compound, the cutting efficiency to be higher. This is because: The milling main axle high speed

37、 revolves, the cutting compound if achieved the cutting area, first must overcome the enormous centrifugal force; Even if it overcame the centrifugal force to enter the cutting area, also was possible as a result of the

38、cutting area high temperature but to evap</p><p>　　Third, high-speed cutting processing cutting tool</p><p>　　The cutting tool is in the high-speed cutting processing one of most active importan

39、t factors, it is affecting the processing efficiency, the production cost and the product processing precision directly. The cutting tool must withstand load and so on high temperature, high pressure, friction, impact an

40、d vibration in the high speed processing process, the high-speed cutting cutting tool should have the good machine capability and the thermostability, namely has the good anti- impact, the wearabi</p><p>　　I

41、n the processing cast iron and in the alloy steel cutting tool, the hard alloy is the most commonly used cutting tool material. Hard alloy tools resistance to wear good, but the solidity ratio cube boron nitride and the

42、ceramics are low. In order to enhance degree of hardness and the superficially attractive fineness, uses the cutting tool coating technology, the coating material for the titanium nitrides (TiN), the aluminium nitride ti

43、tanium (TiALN) and so on. The coating technology causes the</p><p>　　Fourth, mold high speed processing craft</p><p>　　The high speed processing including take removes the remainder as the goal

44、rough machining, the residual rough machining, as well as take gains the high grade processing surface and the slight structure as the goal half precision work, the precision work and the mirror surface processing and so

45、 on.</p><p>　　1.Rough machining</p><p>　　The mold rough machining essential target is pursues in the unit time material removing rate, and is half precision work preparation work piece geometry

46、 outline. In the high speed processing rough machining should adopt the craft plan is the high cutting speed, Gao Jin giving rate and the small cutting specifications combination. The contour processing way is one proces

47、sing way which the multitudinous CAM software uses generally. Using is spiral contour and so on the Z axis contour two ways whic</p><p>　　2.Half precision work</p><p>　　The mold half precision

48、work essential target is causes the work piece outline shape smoothly, surface finish remainder even, this especially is important regarding the tool steel mold, because it will affect time the precision work cutting too

49、l layer of cutting area change and cutting tool load change, thus influence cutting process stability and precision work surface quality.</p><p>　　The rough machining is based on the volume model, the precis

50、ion work then is based on the face mold. Before develops CAD/The CAM system to the components geometry description is not continual, after because has not described in front of the rough machining, the precision work pro

51、cesses the model the average information, therefore the rough machining surface surplus processing remainder distribution and the great surplus processing remainder is unknown. Therefore should fifty-fifty the precision

52、</p><p>　　The existing mold high speed processes CAD/The CAM software has the surplus processing remainder analysis function mostly, and can act according to the surplus processing remainder the size and the

53、 distribution situation uses the reasonable half precision work strategy. After like the MasterCAM software provided has tied the shape milling (Pencil milling) and the surplus milling (Rest milling) and so on the method

54、 eliminates the rough machining the surplus processing remainder big quoin by to gu</p><p>　　3.Precision work</p><p>　　The mold high speed precision work strategy is decided by the cutting tool

55、 and the work piece contact point, but the cutting tool and the work piece contact point but changes along with the processing surface curved surface slope and the cutting tool effective radius change. Regarding by the c

56、omplex curved surface processing which many curved surface combination but becomes, should carry on the continuous treating as far as possible in a working procedure, but is not carries on the processing se</p>&l

57、t;p>　　In the ordinary circumstances, the precision work curved surface radius of curvature should be bigger than the cutting tool radius 1.5 times, by evades the no admittance to the direction suddenly transformation.

58、 In the mold high speed precision work, when each time cuts into, cuts the work piece, enters for the direction change should as far as possible use the circular arc or the curve switches over, avoids using the straight

59、line to switch over, by maintains the cutting process the stability.</p><p>　　Fifth, concluding remark</p><p>　　The high-speed cutting technology is one of machining technology main development

60、directions, at present mainly applies in the automobile industry and the mold profession, in the processing complex curved surface domain, work piece itself or the cutting tool system rigidity request high processing dom

61、ain and so on, is the many kinds of advanced processings technology integration in particular, its is highly effective high grade, esteems for the people. It not only involves to the high speed proc</p><p>　

62、　模具高速銑削加工技術(shù)</p><p>　　摘 要 介紹了高速銑削在模具加工中的應(yīng)用以及影響，并簡要的介紹了高速銑削機(jī)床的結(jié)構(gòu)、控制系統(tǒng)和刀具。對(duì)高速加工的工藝進(jìn)行了簡單的分析。</p><p>　　關(guān)鍵詞 高速銑削；模具加工</p><p><b>　　前言</b></p><p>　　在現(xiàn)代模具生產(chǎn)中，隨著對(duì)塑件的

63、美觀度及功能要求得越來越高，塑件內(nèi)部結(jié)構(gòu)設(shè)計(jì)得越來越復(fù)雜，模具的外形設(shè)計(jì)也日趨復(fù)雜，自由曲面所占比例不斷增加，相應(yīng)的模具結(jié)構(gòu)也設(shè)計(jì)得越來越復(fù)雜。這些都對(duì)模具加工技術(shù)提出了更高要求，不僅應(yīng)保證高的制造精度和表面質(zhì)量，而且要追求加工表面的美觀。隨著對(duì)高速加工技術(shù)研究的不斷深入，尤其在加工機(jī)床、數(shù)控系統(tǒng)、刀具系統(tǒng)、CAD/CAM軟件等相關(guān)技術(shù)不斷發(fā)展的推動(dòng)下，高速加工技術(shù)已越來越多地應(yīng)用于模具型腔的加工與制造中。</p><

64、;p>　　數(shù)控高速切削加工作為模具制造中最為重要的一項(xiàng)先進(jìn)制造技術(shù)，是集高效、優(yōu)質(zhì)、低耗于一身的先進(jìn)制造技術(shù)。相對(duì)于傳統(tǒng)的切削加工，其切削速度、進(jìn)給速度有了很大的提高，而且切削機(jī)理也不相同。高速切削使切削加工發(fā)生了本質(zhì)性的飛躍，其單位功率的金屬切除率提高了30%~40%，切削力降低了30%，刀具的切削壽命提高了70%，留于工件的切削熱大幅度降低，低階切削振動(dòng)幾乎消失。隨著切削速度的提高，單位時(shí)間毛坯材料的去除率增加了，切削時(shí)間減少

65、了，加工效率提高了，從而縮短了產(chǎn)品的制造周期，提高了產(chǎn)品的市場(chǎng)競爭力。同時(shí)，高速加工的小量快進(jìn)使切削力減少了，切屑的高速排出減少了工件的切削力和熱應(yīng)力變形，提高了剛性差和薄壁零件切削加工的可能性。由于切削力的降低，轉(zhuǎn)速的提高使切削系統(tǒng)的工作頻率遠(yuǎn)離機(jī)床的低階固有頻率，而工件的表面粗糙度對(duì)低階頻率最為敏感，由此降低了表面粗糙度。在模具的高淬硬鋼件(HRC45~HRC65)的加工過程中，采用高速切削可以取代電加工和磨削拋光的工序，從而避免了

66、電極的制造和費(fèi)時(shí)的電加工，大幅度減少了鉗工的打磨與拋光量。對(duì)于一些市場(chǎng)上越來越需要的薄壁模具工件，高速銑削也可順利完成，而且在高速銑削C</p><p>　　高速加工技術(shù)對(duì)模具加工工藝產(chǎn)生了巨大影響，改變了傳統(tǒng)模具加工采用的“退火→銑削加工→熱處理→磨削”或“電火花加工→手工打磨、拋光”等復(fù)雜冗長的工藝流程，甚至可用高速切削加工替代原來的全部工序。高速加工技術(shù)除可應(yīng)用于淬硬模具型腔的直接加工(尤其是半精加工和精加

67、工)外，在EDM電極加工、快速樣件制造等方面也得到了廣泛應(yīng)用。大量生產(chǎn)實(shí)踐表明，應(yīng)用高速切削技術(shù)可節(jié)省模具后續(xù)加工中約80%的手工研磨時(shí)間，節(jié)約加工成本費(fèi)用近30%，模具表面加工精度可達(dá)1 m，刀具切削效率可提高1倍。</p><p><b>　　高速銑削加工機(jī)床</b></p><p>　　高速切削技術(shù)是切削加工技術(shù)的主要發(fā)展方向之一，它隨著CNC技術(shù)、微電子技術(shù)、

68、新材料和新結(jié)構(gòu)等基礎(chǔ)技術(shù)的發(fā)展而邁上更高的臺(tái)階。由于模具加工的特殊性以及高速加工技術(shù)的自身特點(diǎn)，對(duì)模具高速加工的相關(guān)技術(shù)及工藝系統(tǒng)(加工機(jī)床、數(shù)控系統(tǒng)、刀具等)提出了比傳統(tǒng)模具加工更高的要求。</p><p>　　高穩(wěn)定性的機(jī)床支撐部件</p><p>　　高速切削機(jī)床的床身等支撐部件應(yīng)具有很好的動(dòng)、靜剛度，熱剛度和最佳的阻尼特性。大部分機(jī)床都采用高質(zhì)量、高剛性和高抗張性的灰鑄鐵作為支撐部

69、件材料，有的機(jī)床公司還在底座中添加高阻尼特性的聚合物混凝土，以增加其抗振性和熱穩(wěn)定性，這不但可保證機(jī)床精度穩(wěn)定，也可防止切削時(shí)刀具振顫。采用封閉式床身設(shè)計(jì)，整體鑄造床身，對(duì)稱床身結(jié)構(gòu)并配有密布的加強(qiáng)筋等也是提高機(jī)床穩(wěn)定性的重要措施。一些機(jī)床公司的研發(fā)部門在設(shè)計(jì)過程中，還采用模態(tài)分析和有限元結(jié)構(gòu)計(jì)算等，優(yōu)化了結(jié)構(gòu)，使機(jī)床支撐部件更加穩(wěn)定可靠。</p><p><b>　　機(jī)床主軸</b><

70、;/p><p>　　高速機(jī)床的主軸性能是實(shí)現(xiàn)高速切削加工的重要條件。高速切削機(jī)床主軸的轉(zhuǎn)速范圍為10000~100000m/min，主軸功率大于15kW。通過主軸壓縮空氣或冷卻系統(tǒng)控制刀柄和主軸間的軸向間隙不大于0.005mm。還要求主軸具有快速升速、在指定位置快速準(zhǔn)停的性能(即具有極高的角加減速度)，因此高速主軸常采用液體靜壓軸承式、空氣靜壓軸承式、熱壓氮化硅（Si3N4）陶瓷軸承磁懸浮軸承式等結(jié)構(gòu)形式。潤滑多采用

71、油氣潤滑、噴射潤滑等技術(shù)。主軸冷卻一般采用主軸內(nèi)部水冷或氣冷。</p><p><b>　　機(jī)床驅(qū)動(dòng)系統(tǒng)</b></p><p>　　為滿足模具高速加工的需要，高速加工機(jī)床的驅(qū)動(dòng)系統(tǒng)應(yīng)具有下列特性：</p><p><b>　　高的進(jìn)給速度。</b></p><p>　　研究表明，對(duì)于小直徑刀具，提

72、高轉(zhuǎn)速和每齒進(jìn)給量有利于降低刀具磨損。目前常用的進(jìn)給速度范圍為20~30m/min，如采用大導(dǎo)程滾珠絲杠傳動(dòng)，進(jìn)給速度可達(dá)60m/min；采用直線電機(jī)則可使進(jìn)給速度達(dá)到120m/min。</p><p><b>　　高的加速度。</b></p><p>　　對(duì)三維復(fù)雜曲面廓形的高速加工要求驅(qū)動(dòng)系統(tǒng)具有良好的加速度特性，要求提供高速進(jìn)給的驅(qū)動(dòng)器(快進(jìn)速度約40m/min

73、，3D輪廓加工速度為10m/min)，能夠提供0.4m/s2到10m/s2的加速度和減速度。</p><p>　　機(jī)床制造商大多采用全閉環(huán)位置伺服控制的小導(dǎo)程、大尺寸、高質(zhì)量的滾珠絲杠或大導(dǎo)程多頭絲杠。隨著電機(jī)技術(shù)的發(fā)展，先進(jìn)的直線電動(dòng)機(jī)已經(jīng)問世，并成功應(yīng)用于CNC機(jī)床。先進(jìn)的直線電動(dòng)機(jī)驅(qū)動(dòng)使CNC機(jī)床不再有質(zhì)量慣性、超前、滯后和振動(dòng)等問題，加快了伺服響應(yīng)速度，提高了伺服控制精度和機(jī)床加工精度。</p>

74、;<p><b>　　數(shù)控系統(tǒng)</b></p><p>　　先進(jìn)的數(shù)控系統(tǒng)是保證模具復(fù)雜曲面高速加工質(zhì)量和效率的關(guān)鍵因素，模具高速切削加工對(duì)數(shù)控系統(tǒng)的基本要求為： a. 高速的數(shù)字控制回路(Digital control loop)，包括：32位或64位并行處理器及1.5Gb以上的硬盤；極短的直線電機(jī)采樣時(shí)間。 b. 速度和加速度的前饋控制(Feed forward con

75、trol)；數(shù)字驅(qū)動(dòng)系統(tǒng)的爬行控制(Jerk control)。 c. 先進(jìn)的插補(bǔ)方法( 基于NURBS的樣條插補(bǔ))，以獲得良好的表面質(zhì)量、精確的尺寸和高的幾何精度。 d. 預(yù)處理(Look-ahead)功能。要求具有大容量緩沖寄存器，可預(yù)先閱讀和檢查多個(gè)程序段(如DMG機(jī)床可多達(dá)500個(gè)程序段，Simens系統(tǒng)可達(dá)1000~2000個(gè)程序段)，以便在被加工表面形狀(曲率)發(fā)生變化時(shí)可及時(shí)采取改變進(jìn)給速度等措施以避免過切等。 e.

76、 誤差補(bǔ)償功能，包括因直線電機(jī)、主軸等發(fā)熱導(dǎo)致的熱誤差補(bǔ)償、象限誤差補(bǔ)償、測(cè)量系統(tǒng)誤差補(bǔ)償?shù)裙δ堋?此外，模具高速切削加工對(duì)數(shù)據(jù)傳輸速度的要求也很高。 f. 傳統(tǒng)的數(shù)據(jù)接口， 如RS232串行口的傳輸速度為19.2kb，而許多先進(jìn)的加工中</p><p><b>　　冷卻潤滑</b></p><p>　　高速加工采用帶涂層的硬質(zhì)合金刀具，在高速、高溫的情況下不用切削

77、液，切削效率更高。這是因?yàn)椋恒娤髦鬏S高速旋轉(zhuǎn)，切削液若要達(dá)到切削區(qū)，首先要克服極大的離心力；即使它克服了離心力進(jìn)入切削區(qū)，也可能由于切削區(qū)的高溫而立即蒸發(fā)，冷卻效果很小甚至沒有；同時(shí)切削液會(huì)使刀具刃部的溫度激烈變化，容易導(dǎo)致裂紋的產(chǎn)生，所以要采用油/氣冷卻潤滑的干式切削方式。這種方式可以用高壓氣體迅速吹走切削區(qū)產(chǎn)生的切削，從而將大量的切削熱帶走，同時(shí)經(jīng)霧化的潤滑油可以在刀具刃部和工件表面形成一層極薄的微觀保護(hù)膜，可有效地延長刀具壽命并提

78、高零件的表面質(zhì)量。</p><p><b>　　高速切削加工的刀具</b></p><p>　　刀具是高速切削加工中最活躍重要的因素之一，它直接影響著加工效率、制造成本和產(chǎn)品的加工精度。刀具在高速加工過程中要承受高溫、高壓、摩擦、沖擊和振動(dòng)等載荷，高速切削刀具應(yīng)具有良好的機(jī)械性能和熱穩(wěn)定性，即具有良好的抗沖擊、耐磨損和抗熱疲勞的特性。高速切削加工的刀具技術(shù)發(fā)展速度很快

79、，應(yīng)用較多的如金剛石(PCD)、立方氮化硼(CBN)、陶瓷刀具、涂層硬質(zhì)合金、(碳)氮化鈦硬質(zhì)合金TIC(N)等。</p><p>　　在加工鑄鐵和合金鋼的切削刀具中，硬質(zhì)合金是最常用的刀具材料。硬質(zhì)合金刀具耐磨性好，但硬度比立方氮化硼和陶瓷低。為提高硬度和表面光潔度，采用刀具涂層技術(shù)，涂層材料為氮化鈦(TiN)、氮化鋁鈦(TiALN)等。涂層技術(shù)使涂層由單一涂層發(fā)展為多層、多種涂層材料的涂層，已成為提高高速切削

80、能力的關(guān)鍵技術(shù)之一。直徑在10~40mm范圍內(nèi)，且有碳氮化鈦涂層的硬質(zhì)合金刀片能夠加工洛氏硬度小于42的材料，而氮化鈦鋁涂層的刀具能夠加工洛氏硬度為42甚至更高的材料。高速切削鋼材時(shí)，刀具材料應(yīng)選用熱硬性和疲勞強(qiáng)度高的P類硬質(zhì)合金、涂層硬質(zhì)合金、立方氮化硼（CBN）與CBN復(fù)合刀具材料（WBN）等。切削鑄鐵，應(yīng)選用細(xì)晶粒的K類硬質(zhì)合金進(jìn)行粗加工，選用復(fù)合氮化硅陶瓷或聚晶立方氮化硼（PCNB）復(fù)合刀具進(jìn)行精加工。精密加工有色金屬或非金屬材

81、料時(shí)，應(yīng)選用聚晶金剛石PCD或CVD金剛石涂層刀具。選擇切削參數(shù)時(shí)，針對(duì)圓刀片和球頭銑刀，應(yīng)注意有效直徑的概念。高速銑削刀具應(yīng)按動(dòng)平衡設(shè)計(jì)制造。刀具的前角比常規(guī)刀具的前角要小，后角略大。主副切削刃連接處應(yīng)修圓或?qū)Ы?，來增大刀尖角，防止刀尖處熱磨損。應(yīng)加大刀尖附近的切削刃長度和刀具</p><p><b>　　模具高速加工工藝</b></p><p>　　高速加工包括以

82、去除余量為目的的粗加工、殘留粗加工，以及以獲取高質(zhì)量的加工表面及細(xì)微結(jié)構(gòu)為目的的半精加工、精加工和鏡面加工等。</p><p><b>　　粗加工</b></p><p>　　模具粗加工的主要目標(biāo)是追求單位時(shí)間內(nèi)的材料去除率，并為半精加工準(zhǔn)備工件的幾何輪廓。高速加工中的粗加工所應(yīng)采取的工藝方案是高切削速度、高進(jìn)給率和小切削用量的組合。等高加工方式是眾多CAM軟件普遍采

83、用的一種加工方式。應(yīng)用較多的是螺旋等高和等Z軸等高兩種方式，也就是在加工區(qū)域僅一次進(jìn)刀，在不抬刀的情況下生成連續(xù)光滑的刀具路徑，進(jìn)、退刀方式采用圓弧切入、切出。螺旋等高方式的特點(diǎn)是，沒有等高層之間的刀路移動(dòng)，可避免頻繁抬刀、進(jìn)刀對(duì)零件表面質(zhì)量的影響及機(jī)械設(shè)備不必要的耗損。對(duì)陡峭和平坦區(qū)域分別處理，計(jì)算適合等高及適合使用類似3D偏置的區(qū)域，并且可以使用螺旋方式，在很少抬刀的情況下生成優(yōu)化的刀具路徑，獲得更好的表面質(zhì)量。在高速加工中，一定要

84、采取圓弧切入、切出連接方式，以及拐角處圓弧過渡，避免突然改變刀具進(jìn)給方向，禁止使用直接下刀的連接方式，避免將刀具埋入工件。加工模具型腔時(shí)，應(yīng)避免刀具垂直插入工件，而應(yīng)采用傾斜下刀方式(常用傾斜角為20°~30°)，最好采用螺旋式下刀以降低刀具載荷。加工模具型芯時(shí)，應(yīng)盡量先從工件外部下刀然后水平切入工件。刀具切入、切出工件時(shí)應(yīng)盡可能采用傾斜式(或圓弧式)切入、切出，</p><p><b&

85、gt;　　半精加工</b></p><p>　　模具半精加工的主要目標(biāo)是使工件輪廓形狀平整，表面精加工余量均勻，這對(duì)于工具鋼模具尤為重要，因?yàn)樗鼘⒂绊懢庸r(shí)刀具切削層面積的變化及刀具載荷的變化，從而影響切削過程的穩(wěn)定性及精加工表面質(zhì)量。 粗加工是基于體積模型，精加工則是基于面模型。以前開發(fā)的CAD/CAM系統(tǒng)對(duì)零件的幾何描述是不連續(xù)的，由于沒有描述粗加工后、精加工前加工模型的中間信息，故粗

86、加工表面的剩余加工余量分布及最大剩余加工余量均是未知的。因此應(yīng)對(duì)半精加工策略進(jìn)行優(yōu)化以保證半精加工后工件表面具有均勻的剩余加工余量。優(yōu)化過程包括：粗加工后輪廓的計(jì)算、最大剩余加工余量的計(jì)算、最大允許加工余量的確定、對(duì)剩余加工余量大于最大允許加工余量的型面分區(qū)(如凹槽、拐角等過渡半徑小于粗加工刀具半徑的區(qū)域)以及半精加工時(shí)刀心軌跡的計(jì)算等。 現(xiàn)有的模具高速加工C A D /CAM軟件大都具備剩余加工余量分析功能，并能根據(jù)剩余加工

87、余量的大小及分布情況采用合理的半精加工策略。如MasterCAM軟件提供了束狀銑削(Pencil milling)和剩余銑削(Rest milling)等方法來清除粗加工后剩余加工余量較大的角落以保證后續(xù)</p><p><b>　　精加工</b></p><p>　　模具的高速精加工策略取決于刀具與工件的接觸點(diǎn)，而刀具與工件的接觸點(diǎn)隨著加工表面的曲面斜率和刀具有效半

88、徑的變化而變化。對(duì)于由多個(gè)曲面組合而成的復(fù)雜曲面加工，應(yīng)盡可能在一個(gè)工序中進(jìn)行連續(xù)加工，而不是對(duì)各個(gè)曲面分別進(jìn)行加工，以減少抬刀、下刀的次數(shù)。然而，由于加工中表面斜率的變化，如果只定義加工的側(cè)吃刀量(Step over)，就可能造成在斜率不同的表面上實(shí)際步距不均勻，從而影響加工質(zhì)量。 一般情況下，精加工曲面的曲率半徑應(yīng)大于刀具半徑的1.5倍，以避免進(jìn)給方向的突然轉(zhuǎn)變。在模具的高速精加工中，在每次切入、切出工件時(shí)，進(jìn)給方向的改變

89、應(yīng)盡量采用圓弧或曲線轉(zhuǎn)接，避免采用直線轉(zhuǎn)接，以保持切削過程的平穩(wěn)性。</p><p><b>　　結(jié)束語</b></p><p>　　高速切削技術(shù)是切削加工技術(shù)的主要發(fā)展方向之一，目前主要應(yīng)用于汽車工業(yè)和模具行業(yè)，尤其是在加工復(fù)雜曲面的領(lǐng)域、工件本身或刀具系統(tǒng)剛性要求較高的加工領(lǐng)域等，是多種先進(jìn)加工技術(shù)的集成，其高效、高質(zhì)量為人們所推崇。它不僅涉及到高速加工工藝，而且