CNC加工中刀具的選擇與切削用量的確定

1、CNC加工中刀具的選擇與切削用量的確定刀具的選擇和切削用量的確定是數(shù)控加工工藝中的重要內(nèi)容，它不僅影響數(shù)控機(jī)床的加工效率，而且直接影響加工質(zhì)量。CAD/CAM技術(shù)的發(fā)展，使得在數(shù)控加工中直接利用CAD的設(shè)計(jì)數(shù)據(jù)成為可能，特別是微機(jī)與數(shù)控機(jī)床的聯(lián)接，使得設(shè)計(jì)、工藝規(guī)劃及編程的整個(gè)過(guò)程全部在計(jì)算機(jī)上完成，一般不需要輸出專(zhuān)門(mén)的工藝文件?，F(xiàn)在，許多CAD/CAM軟件包都提供自動(dòng)編程功能，這些軟件一般是在編程界面中提示工藝規(guī)劃的有關(guān)問(wèn)題，比如，刀具選擇、加工路徑規(guī)劃、切削用量設(shè)定等，編程人員只要設(shè)置了有關(guān)的參數(shù)，就可以自動(dòng)生成NC程序并傳輸至數(shù)控機(jī)床完成加工。因此，數(shù)控加工中的刀具選擇和切削用量確定是在

2、人機(jī)交互狀態(tài)下完成的，這與普通機(jī)床加工形成鮮明的對(duì)比，同時(shí)也要求編程人員必須掌握刀具選擇和切削用量確定的基本原則，在編程時(shí)充分考慮數(shù)控加工的特點(diǎn)。本文對(duì)數(shù)控編程中必須面對(duì)的刀具選擇和切削用量確定問(wèn)題進(jìn)行了探討，給出了若干原則和建議，并對(duì)應(yīng)該注意的問(wèn)題進(jìn)行了討論。一、數(shù)控加工常用刀具的種類(lèi)及特點(diǎn)數(shù)控加工刀具必須適應(yīng)數(shù)控機(jī)床高速、高效和自動(dòng)化程度高的特點(diǎn)，一般應(yīng)包括通用刀具、通用連接刀柄及少量專(zhuān)用刀柄。刀柄要聯(lián)接刀具并裝在機(jī)床動(dòng)力頭上，因此已逐漸標(biāo)準(zhǔn)化和系列化。數(shù)控刀具的分類(lèi)有多種方法。根據(jù)刀具結(jié)構(gòu)可分為：整體式；鑲嵌式，采用焊接或機(jī)夾式連接，機(jī)夾式又可分為不轉(zhuǎn)位和可轉(zhuǎn)位兩種；特殊型式，如復(fù)合式刀

3、具，減震式刀具等。根據(jù)制造刀具所用的材料可分為：高速鋼刀具；硬質(zhì)合金刀具；金剛石刀具；其他材料刀具，如立方氮化硼刀具，陶瓷刀具等。從切削工藝上可分為：車(chē)削刀具，分外圓、內(nèi)孔、螺紋、切割刀具等多種；鉆削刀具，包括鉆頭、鉸刀、絲錐等；鏜削刀具；銑削刀具等。為了適應(yīng)數(shù)控機(jī)床對(duì)刀具耐用、穩(wěn)定、易調(diào)、可換等的要求，近幾年機(jī)夾式可轉(zhuǎn)位刀具得到廣泛的應(yīng)用，在數(shù)量上達(dá)到整個(gè)數(shù)控刀具的30%40%，金屬切除量占總數(shù)的80%90%。數(shù)控刀具與普通機(jī)床上所用的刀具相比，有許多不同的要求，主要有以下特點(diǎn)：剛性好（尤其是粗加工刀具），精度高，抗振及熱變形??；互換性好，便于快速換刀；壽命高，切削性能穩(wěn)定、可靠；刀具的尺寸

4、便于調(diào)整，以減少換刀調(diào)整時(shí)間；刀具應(yīng)能可靠地?cái)嘈蓟蚓硇?，以利于切屑的排除；系列化，?biāo)準(zhǔn)化，以利于編程和刀具管理。二、數(shù)控加工刀具的選擇刀具的選擇是在數(shù)控編程的人機(jī)交互狀態(tài)下進(jìn)行的。應(yīng)根據(jù)機(jī)床的加工能力、工件材料的性能、加工工序、切削用量以及其它相關(guān)因素正確選用刀具及刀柄。刀具選擇總的原則是：安裝調(diào)整方便，剛性好，耐用度和精度高。在滿(mǎn)足加工要求的前提下，盡量選擇較短的刀柄，以提高刀具加工的剛性。選取刀具時(shí)，要使刀具的尺寸與被加工工件的表面尺寸相適應(yīng)。生產(chǎn)中，平面零件周邊輪廓的加工，常采用立銑刀；銑削平面時(shí)，應(yīng)選硬質(zhì)合金刀片銑刀；加工凸臺(tái)、凹槽時(shí)，選高速鋼立銑刀；加工毛坯表面或粗加工孔時(shí)，可選取鑲

5、硬質(zhì)合金刀片的玉米銑刀；對(duì)一些立體型面和變斜角輪廓外形的加工，常采用球頭銑刀、環(huán)形銑刀、錐形銑刀和盤(pán)形銑刀。在進(jìn)行自由曲面加工時(shí)，由于球頭刀具的端部切削速度為零，因此，為保證加工精度，切削行距一般取得很能密，故球頭常用于曲面的精加工。而平頭刀具在表面加工質(zhì)量和切削效率方面都優(yōu)于球頭刀，因此，只要在保證不過(guò)切的前提下，無(wú)論是曲面的粗加工還是精加工，都應(yīng)優(yōu)先選擇平頭刀。另外，刀具的耐用度和精度與刀具價(jià)格關(guān)系極大，必須引起注意的是，在大多數(shù)情況下，選擇好的刀具雖然增加了刀具成本，但由此帶來(lái)的加工質(zhì)量和加工效率的提高，則可以使整個(gè)加工成本大大降低。在加工中心上，各種刀具分別裝在刀庫(kù)上，按程序規(guī)定隨時(shí)進(jìn)

6、行選刀和換刀動(dòng)作。因此必須采用標(biāo)準(zhǔn)刀柄，以便使鉆、鏜、擴(kuò)、銑削等工序用的標(biāo)準(zhǔn)刀具，迅速、準(zhǔn)確地裝到機(jī)床主軸或刀庫(kù)上去。編程人員應(yīng)了解機(jī)床上所用刀柄的結(jié)構(gòu)尺寸、調(diào)整方法以及調(diào)整范圍，以便在編程時(shí)確定刀具的徑向和軸向尺寸。目前我國(guó)的加工中心采用TSG工具系統(tǒng)，其刀柄有直柄（三種規(guī)格）和錐柄（四種規(guī)格）兩種，共包括16種不同用途的刀柄。在經(jīng)濟(jì)型數(shù)控加工中，由于刀具的刃磨、測(cè)量和更換多為人工手動(dòng)進(jìn)行，占用輔助時(shí)間較長(zhǎng)，因此，必須合理安排刀具的排列順序。一般應(yīng)遵循以下原則：盡量減少刀具數(shù)量；一把刀具裝夾后，應(yīng)完成其所能進(jìn)行的所有加工部位；粗精加工的刀具應(yīng)分開(kāi)使用，即使是相同尺寸規(guī)格的刀具；先銑后鉆；先進(jìn)

7、行曲面精加工，后進(jìn)行二維輪廓精加工；在可能的情況下，應(yīng)盡可能利用數(shù)控機(jī)床的自動(dòng)換刀功能，以提高生產(chǎn)效率等。三、數(shù)控加工切削用量的確定合理選擇切削用量的原則是，粗加工時(shí)，一般以提高生產(chǎn)率為主，但也應(yīng)考慮經(jīng)濟(jì)性和加工成本；半精加工和精加工時(shí)，應(yīng)在保證加工質(zhì)量的前提下，兼顧切削效率、經(jīng)濟(jì)性和加工成本。具體數(shù)值應(yīng)根據(jù)機(jī)床說(shuō)明書(shū)、切削用量手冊(cè)，并結(jié)合經(jīng)驗(yàn)而定。切削深度t。在機(jī)床、工件和刀具剛度允許的情況下，t就等于加工余量，這是提高生產(chǎn)率的一個(gè)有效措施。為了保證零件的加工精度和表面粗糙度，一般應(yīng)留一定的余量進(jìn)行精加工。數(shù)控機(jī)床的精加工余量可略小于普通機(jī)床。切削寬度L。一般L與刀具直徑d成正比，與切削深度

8、成反比。經(jīng)濟(jì)型數(shù)控加工中，一般L的取值范圍為：L=（0.60.9）d。(3)提高v也是提高生產(chǎn)率的一個(gè)措施，但v與刀具耐用度的關(guān)系比較密切。隨著v的增大，刀具耐用度急劇下降，故v的選擇主要取決于刀具耐用度。另外，切削速度與加工材料也有很大關(guān)系，例如用立銑刀銑削合金剛30CrNi2MoVA時(shí)，v可采用8m/min左右；而用同樣的立銑刀銑削鋁合金時(shí)，v可選200m/min以上。主軸轉(zhuǎn)速n(r/min)。主軸轉(zhuǎn)速一般根據(jù)切削速度v來(lái)選定。計(jì)算公式為：式中，d為刀具或工件直徑（mm）。數(shù)控機(jī)床的控制面板上一般備有主軸轉(zhuǎn)速修調(diào)（倍率）開(kāi)關(guān)，可在加工過(guò)程中對(duì)主軸轉(zhuǎn)速進(jìn)行整倍數(shù)調(diào)整。進(jìn)給速度vF 。vF應(yīng)根

9、據(jù)零件的加工精度和表面粗糙度要求以及刀具和工件材料來(lái)選擇。vF的增加也可以提高生產(chǎn)效率。加工表面粗糙度要求低時(shí)，vF可選擇得大些。在加工過(guò)程中，vF也可通過(guò)機(jī)床控制面板上的修調(diào)開(kāi)關(guān)進(jìn)行人工調(diào)整，但是最大進(jìn)給速度要受到設(shè)備剛度和進(jìn)給系統(tǒng)性能等的限制。隨著數(shù)控機(jī)床在生產(chǎn)實(shí)際中的廣泛應(yīng)用，數(shù)控編程已經(jīng)成為數(shù)控加工中的關(guān)鍵問(wèn)題之一。在數(shù)控程序的編制過(guò)程中，要在人機(jī)交互狀態(tài)下即時(shí)選擇刀具和確定切削用量。因此，編程人員必須熟悉刀具的選擇方法和切削用量的確定原則，從而保證零件的加工質(zhì)量和加工效率，充分發(fā)揮數(shù)控機(jī)床的優(yōu)點(diǎn)，提高企業(yè)的經(jīng)濟(jì)效益和生產(chǎn)水平。In CNC processing cutting too

10、l choice and cutting specifications determinationThe cutting tool choice and the cutting specifications determination is in the numerical control processing craft important content, it not only influence numerical control engine bed processing efficiency, moreover affects the processing quality dire

11、ctly. CAD/The CAM technology development, enables in the numerical control processing to become directly using the CAD design data possibly, specially the microcomputer and the numerical control engine bed joint, causes the design, the craft plan and the programming entire process completes complete

12、ly on the computer, does not need to output the special technological document generally.Now, many CAD/The CAM software package all provides the automatic programming function, these software are generally prompt the craft plan in the programming contact surface the related question, for instance, c

13、utting tool choice, processing way plan, cutting specifications hypothesis and so on, programmers so long as have established the related parameter, may automatically produce completes the processing the NC procedure and the transmission to the numerical control engine bed. Therefore, in the numeric

14、al control processing cutting tool choice and the cutting specifications determination is completes under the man-machine interactive condition, this forms the sharp contrast with the ordinary engine bed processing, at the same time also requests the programmers to have to grasp the cutting tool cho

15、ice and the cutting specifications determination basic principle, when programming full consideration numerical control processing characteristic. This article the cutting tool choice and the cutting specifications which must face to the numerical control programming in determined the question has c

16、arried on the discussion, has produced certain principles and the suggestion, and to the question which should pay attention has carried on the discussion.First, numerical control processing commonly used cutting tool type and characteristicThe numerical control processing cutting tool must adapt th

17、e numerical control engine bed high speed, is highly effective and the automatic high characteristic, should include the general cuttingtool, the general connection hilt and the few special-purpose hilts generally. The hilt must join the cutting tool and install on the engine bed power head, therefo

18、re already gradual standardization and seriation. The numerical control cutting tool classification has the many kinds of methods. May divide into according to the cutting tool structure: (1) Integral type; (2) The mosaic, uses the welding or machine clamps the type connection, machine clamps the ty

19、pe to be possible to divide into does not index and may index two kinds; (3) Special pattern, like compound expression cutting tool, absorption of shock type cutting tool and so on. According to makes the materialwhich the cutting tool uses to be possible to divide into: (1) High-speed steel cutting

20、 tool; (2) Hard alloy tools; (3) Diamond cutting tool; (4) Other material cutting tools, like cubic boron nitride cutting tool, ceramic cutting tool and so on. May divide into from the cutting craft: (1) The turning cutting tool, divides the outer annulus, in the hole, the thread, cuts the cutting t

21、ool many kinds of and so on; (2) Drills truncates the cutting tool, including drill bit, reamer, screw tap and so on; (3) Boring cutting tool; (4) Milling cutting tool and so on. In order to adapt the numerical control engine bed durably to the cutting tool, is stable, easy change, may trade and so

22、on the request, in recent years machine clamps the type to be possible to index the cutting tool to obtain the widespread application, reaches higher authorities in the quantity to the entire numerical control cutting tool 30% 40%, the metal excision quantity accounts for the total 80% 90%.On the nu

23、merical control cutting tool and the ordinary engine bed uses the cutting tool compares below, some many different requests, mainly have the characteristic:(1) Rigidity good (in particular rough machining cutting tool), precision high, the vibration-proof and the thermal deformation are small; (2) I

24、nter changeability is good, is advantageous for fast trades the knife; (3) Life high, the cutting value stable, is reliable; (4) Cutting tool size is advantageous for the adjustment, by reduces trades the knife time(5)Cutting tool ought to be able reliably to break the filings or the volume filings,

25、 by favors the scrap removing; (6) Seriation, the standardization, by favors the programming and the cutting tool management.Second, the numerical control processes the cutting tool the choiceThe cutting tool choice is carries on in under the numerical control programming man-machine interactive con

26、dition. Should according to the engine bed processing ability, the work piece material performance, the processing working procedure, the cutting specifications as well as other correlation factors correctly selects the cutting tool and the hilt. The cutting tool choice always principle is: Installm

27、ent adjustment convenient, rigidity good, the abrasive resistance and the precision are high. In satisfies the processing request under the premise, chooses the short hilt as far as possible, by enhances the rigidity which the cutting tool processes.When selects the cutting tool, must cause the cutt

28、ing tool the size with to process the work piece the superficial dimension to adapt. In the production, the plane components peripheral outline processing, often uses the end mill; When milling plane, elected hard alloy bit milling cutter; When processes raised Taiwan, the scoop channel, chooses the

29、 high-speed steel end mill; When processing semifinished materials surface or rough machining hole, may select inlays the hard alloy bit the corn milling cutter; And changes the drift angle outline contour to some three-dimensional profiles the processing, often uses a ball milling cutter, the ring-

30、like milling cutter, the coned milling cutter and the disc cutter.When carries on the free curved surface processing, because the ball cutting tool nose cutting speed is a zero, therefore, for the guarantee processing precision, the cutting row spacing obtains generally very can be dense, therefore

31、ball commonly used in curved surface precision work. But the flat head cutting tool all surpasses a ball knife in the face work quality and the cutting efficiency aspect, therefore, so long as under the premise which the guarantee only cuts, regardless of is the curved surface rough machining precis

32、ion work, all should first choose the flat head knife. Moreover, the cutting tool abrasive resistance and the precision and the cutting tool price relations are enormous, must bring to the attention is, in the majority situation, the cutting tool which chooses although increased the cutting tool cos

33、t, but from this the processing quality and the processing efficiency enhancement which brings, then may cause the entire processing cost to reduce greatly. In the processing center, each kind of cutting tool installs separately in the knife storehouse, according to the procedure stipulated carries

34、on as necessary chooses the knife and trades the knife movement. Therefore must use the standard hilt, in order to makes to drill, the boring, to expand the standard cutting tool which, working procedure and so on milling uses, is rapid, accurately installs to the engine bed main axle or the knife s

35、torehouse comes up. The programmers should understand on the engine bed uses the hilt the structure size, the adjustment method as well as the adjustment scope, in order to in programming time determines the cutting tool the radial direction and the axial size. At present our countrys processing cen

36、ter uses the TSG tool system, its hilt has the straight handle (three kind of specifications) and the bit holder (four kind of specifications) two kinds, altogether includes 16 kinds of different uses the hilts. In economy numerical control processing, because the cutting tool sharpens, surveys and

37、replaces many manual carries on for the man-power, takes the non-cutting time to be long, therefore, must reasonably arrange the cutting tool the order of rank. Should follow the principle below generally: (1) Reduces the cutting tool quantity as far as possible; (2) After a cutting tool attire clam

38、ps, should complete all processing spot which its can carry on; (3) The thick precision work cutting tool should separate the use, even if is the same size specification cutting tool; (4) The mill drills after first; (5) The advanced good curved surface precision work, latter carries on the two-dime

39、nsional outline precision work; (6) In the possible situation, to be supposed automatically to trade the knife function as far as possible using the numerical control engine bed, by enhances the production efficiency and so on.Third, numerical control processing cutting specifications determinationT

40、he reasonable choice cutting specifications principle is, when rough machining, by enhances the productivity generally primarily, but also should consider the efficiency and the processing cost; When half precision work and precision work, should in under the guarantee processing quality premise, th

41、e proper attention to both cutting efficiency, the efficiency and the processing cost. The concrete value should act according to the engine bed instruction booklet, thecutting specifications handbook, and the union experience but decides.(1) Depth of cut t. In the engine bed, the work piece and in

42、the cutting tool rigidity permission situation, t was equal to processing remainder, this is enhances the productivity a effective action. In order to guarantee the components the processing precision and the surface roughness, should keep the certain remainder generally to carry on the precision wo

43、rk. The numerical control engine bed precision work remainder may be smaller than slightly the ordinary engine bed.(2)Cutting width L. General L and cutting tool diameter d has the direct ratio, has the inverse ratio with the depth of cut. In the economy numerical control processing, the general L v

44、alue scope is: L= (0.6 0.9) d. (3) Enhances v also is enhances the productivity a measure, but v and the cutting tool abrasive resistance relations quite are close. Along with v increasing, the cutting tool abrasive resistance drops suddenly, therefore v choice mainly is decided by the cutting tool

45、abrasive resistance. Moreover, the cutting speed and the processing material also have the very big relations, for example when anther jingang 30CrNi2MoVA with the end mill milling, v may use 8m/About min; When with same end mill milling aluminum alloy, v may choose 200m/Above min.(4) Main axle rotational speed n (r/Min). The main axle rotational speed general basis cuts the speed v to designate. The formula is: The in the formula, d is the cutting tool or the work piece diameter(mm). On the numerical control engine bed control panel has the main