一、數控銑床刀具種類
數(shu)控(kong)加(jia)工(gong)(gong)中刀具的(de)(de)選(xuan)擇和切(qie)削用(yong)量(liang)(liang)確(que)定(ding)是在(zai)人(ren)機(ji)交互狀態下完(wan)成,要(yao)求編程(cheng)人(ren)員必(bi)須(xu)掌握刀具選(xuan)擇和切(qie)削用(yong)量(liang)(liang)確(que)定(ding)的(de)(de)基本原則,在(zai)編程(cheng)時充分考慮數(shu)控(kong)加(jia)工(gong)(gong)特點,正確(que)選(xuan)擇刀刃具及(ji)(ji)切(qie)削用(yong)量(liang)(liang)。數(shu)控(kong)加(jia)工(gong)(gong)技(ji)(ji)術涉及(ji)(ji)的(de)(de)范圍很廣,就應用(yong)方面而言,其加(jia)工(gong)(gong)技(ji)(ji)術的(de)(de)特點和難點仍在(zai)于如(ru)何高速、高效率地(di)正確(que)選(xuan)用(yong)數(shu)控(kong)機(ji)床刀具編制(zhi)出符合產品技(ji)(ji)術要(yao)求的(de)(de)數(shu)控(kong)加(jia)工(gong)(gong)工(gong)(gong)藝(yi)及(ji)(ji)程(cheng)序。數(shu)控(kong)加(jia)工(gong)(gong)可(ke)以大幅度縮短(duan)產品的(de)(de)制(zhi)造(zao)周期,有效的(de)(de)解決機(ji)械(xie)產品中復雜、精密、單件小(xiao)批量(liang)(liang)、形(xing)狀多變的(de)(de)零(ling)件加(jia)工(gong)(gong)。
數控銑床加工刀(dao)(dao)具(ju)(ju)(ju)種(zhong)類(lei)很(hen)多,為(wei)了(le)適應數控機(ji)床高(gao)(gao)速、高(gao)(gao)效和(he)(he)自動化程度高(gao)(gao)的(de)(de)特點(dian),所用刀(dao)(dao)具(ju)(ju)(ju)正朝著標準(zhun)化、通用化和(he)(he)模(mo)塊化的(de)(de)方向(xiang)發展,主要(yao)分為(wei)銑削刀(dao)(dao)具(ju)(ju)(ju)和(he)(he)孔(kong)加工刀(dao)(dao)具(ju)(ju)(ju)兩大類(lei)。為(wei)了(le)滿足高(gao)(gao)效和(he)(he)特殊的(de)(de)銑削要(yao)求(qiu),又(you)發展了(le)各(ge)種(zhong)特殊用途的(de)(de)專用刀(dao)(dao)具(ju)(ju)(ju)。
(1)刀柄結構形式
數控(kong)銑床刀(dao)(dao)具(ju)(ju)刀(dao)(dao)柄的(de)(de)結構形式分為模塊(kuai)式與整(zheng)體式兩種。模塊(kuai)式刀(dao)(dao)具(ju)(ju)系統是(shi)一種較先進的(de)(de)刀(dao)(dao)具(ju)(ju)系統,其每把刀(dao)(dao)柄都(dou)可通過各(ge)種系列化的(de)(de)模塊(kuai)組裝(zhuang)而(er)成。針對不同(tong)的(de)(de)加工零件和(he)機床,采取不同(tong)的(de)(de)組裝(zhuang)方案,可獲得多種刀(dao)(dao)柄系列,從而(er)提(ti)高刀(dao)(dao)柄的(de)(de)適應能力和(he)利(li)用率。
整體式刀柄裝夾刀具的(de)工作部分(fen)與(yu)(yu)機床上安裝定位用的(de)柄部是一體的(de)。這種(zhong)刀柄對機床與(yu)(yu)零件的(de)變換適(shi)應能(neng)力較差。為適(shi)應零件與(yu)(yu)機床的(de)變換,用戶(hu)必須儲備各種(zhong)規(gui)格的(de)刀柄,因此刀柄的(de)利用率較低。
數控銑床刀柄與(yu)主(zhu)軸孔的(de)(de)配(pei)合(he)錐面(mian)采用(yong)(yong)(yong)(yong)(yong)7:24圓(yuan)錐柄,并采用(yong)(yong)(yong)(yong)(yong)相應(ying)型式的(de)(de)拉釘(ding),與(yu)機床主(zhu)軸相結合(he)。錐柄具有不自鎖,換刀方便等特點。刀柄常用(yong)(yong)(yong)(yong)(yong)的(de)(de)規(gui)(gui)格(ge)有40號(hao)、45號(hao)和50號(hao)。目(mu)前在我國應(ying)用(yong)(yong)(yong)(yong)(yong)較為廣泛的(de)(de)有IS07388—1983.MAS403—1982.ANSI/ASME 135.50—1985等,選擇時應(ying)考慮刀柄規(gui)(gui)格(ge)與(yu)機床主(zhu)軸、機械(xie)(xie)手(shou)相適(shi)應(ying)。JT:表(biao)示采用(yong)(yong)(yong)(yong)(yong)國際標準IS07388號(hao)加工(gong)中心(xin)機床用(yong)(yong)(yong)(yong)(yong)錐柄柄部(bu)(帶機械(xie)(xie)手(shou)夾持(chi)槽(cao));其后數字為相應(ying)的(de)(de)ISO錐度號(hao)。BT:表(biao)示采用(yong)(yong)(yong)(yong)(yong)日本標準MAS403號(hao)加工(gong)中心(xin)機床用(yong)(yong)(yong)(yong)(yong)錐柄柄部(bu)(帶機械(xie)(xie)手(shou)夾持(chi)槽(cao));其后數字為相應(ying)的(de)(de)ISO錐度號(hao)。對于高速切削一般(ban)采用(yong)(yong)(yong)(yong)(yong)HSK系(xi)列刀柄。
為提高(gao)(gao)加工效率,應盡可(ke)能選用高(gao)(gao)效率的刀(dao)具和刀(dao)柄(bing)。選用強(qiang)力銑夾(jia)(jia)頭刀(dao)柄(bing),夾(jia)(jia)持(chi)(chi)(chi)精(jing)度(du)高(gao)(gao),可(ke)以(yi)用來(lai)夾(jia)(jia)持(chi)(chi)(chi)直(zhi)柄(bing)刀(dao)具,因卡簧自身夾(jia)(jia)緊變形小自鎖性好,夾(jia)(jia)緊力大,可(ke)以(yi)用于強(qiang)力銑削加工;還可(ke)以(yi)用于高(gao)(gao)精(jing)度(du)銑鉸孔加工,也可(ke)通過接(jie)桿(gan)夾(jia)(jia)持(chi)(chi)(chi)帶孔類刀(dao)具。
選(xuan)用(yong)彈簧卡頭(tou)刀(dao)(dao)(dao)柄,卡簧彈性變(bian)形量為1mm,主要夾持小規格銑刀(dao)(dao)(dao),如鉆頭(tou)、銑刀(dao)(dao)(dao)、鉸刀(dao)(dao)(dao)、絲錐等(deng)。選(xuan)用(yong)模塊式工(gong)(gong)(gong)具(ju)系(xi)統由于(yu)其定位精度高,裝卸方便(bian),連接剛性好,具(ju)有良好的(de)抗振性,是目前(qian)用(yong)得較(jiao)多的(de)一種(zhong)型式,它由刀(dao)(dao)(dao)柄、中間(jian)接桿以(yi)及工(gong)(gong)(gong)作頭(tou)組成(cheng)。選(xuan)用(yong)粗(cu)鏜(tang)孔(kong)可(ke)選(xuan)用(yong)雙刃鏜(tang)刀(dao)(dao)(dao)刀(dao)(dao)(dao)柄,既可(ke)提(ti)高加工(gong)(gong)(gong)效率,又(you)有利于(yu)減少(shao)切(qie)削振動;對(dui)于(yu)批量大、加工(gong)(gong)(gong)復(fu)雜的(de)典型工(gong)(gong)(gong)件,應盡可(ke)能選(xuan)用(yong)復(fu)合(he)(he)刀(dao)(dao)(dao)具(ju)。盡管復(fu)合(he)(he)刀(dao)(dao)(dao)具(ju)與刀(dao)(dao)(dao)柄價格較(jiao)為昂貴,但在數控(kong)機(ji)床(chuang)上(shang)采用(yong)復(fu)合(he)(he)刀(dao)(dao)(dao)具(ju)加工(gong)(gong)(gong),可(ke)以(yi)使(shi)工(gong)(gong)(gong)序(xu)集中,把多道工(gong)(gong)(gong)序(xu)合(he)(he)并成(cheng)一道工(gong)(gong)(gong)序(xu)、由一把刀(dao)(dao)(dao)具(ju)完成(cheng),有利于(yu)減少(shao)加工(gong)(gong)(gong)時間(jian)和換刀(dao)(dao)(dao)次數,顯著(zhu)提(ti)高生產效率。
(2)數控銑床刀具的分類
數控銑床刀(dao)具(ju)的(de)分類(lei)有多種方法,根據刀(dao)具(ju)結構可(ke)分為:①整體式(shi)②鑲嵌式(shi),采用焊接(jie)(jie)或機夾式(shi)連接(jie)(jie),機夾式(shi)又可(ke)分為可(ke)轉位(wei)和不可(ke)轉位(wei)兩種③特殊型式(shi),如復合式(shi)刀(dao)具(ju),減震式(shi)刀(dao)具(ju)等。
根據制造刀具所用的材料可分為:①高速鋼刀具②硬質合金刀具:硬質合金根據國際標準ISO分類,把所有牌號分成用顏色標識的六大類,分別以字母P、M、K、N、S、H表示。P類用于加工長切屑的鋼件;M類用于加工不銹鋼件;K類用于加工短切屑的鑄鐵件;N類用于加工短切屑的非鐵材料;s類用于加工難加工材料H類用于加工硬材料。鍍層硬質合金刀具又分為:化學氣相沉積CVD和物理氣相沉積PVD兩種。③金(jin)剛石刀具④陶(tao)瓷刀片材料如(ru)氮(dan)(dan)化(hua)硅陶(tao)瓷Si3N4,立方(fang)氮(dan)(dan)化(hua)硼CBN。
從切削工藝上可(ke)分為:銑削類刀(dao)(dao)具(面銑刀(dao)(dao)、立銑刀(dao)(dao)、圓鼻刀(dao)(dao)、球(qiu)頭銑刀(dao)(dao)、錐(zhui)(zhui)度(du)銑刀(dao)(dao))、孔加工類刀(dao)(dao)具(麻花鉆(zhan)、鉸刀(dao)(dao)、鏜刀(dao)(dao)、絲錐(zhui)(zhui)等(deng))。
為了滿足數控機床對刀具耐用、易調、穩定、可換等要求,機夾式可轉位刀具得到廣泛的應用,占整個數控刀具的40%-50%,金屬切除量占總數的80%~90%。
二、數控加工刀具的選擇
刀具(ju)(ju)選擇(ze)的(de)(de)總原則:安裝調整方便、可靠性好、剛(gang)性好、耐用度和精度高。在滿足加工要求(qiu)的(de)(de)前(qian)提(ti)下,盡量選擇(ze)刀柄較短的(de)(de)刀具(ju)(ju),以增強加工的(de)(de)剛(gang)性。
(1)根據工件的表面尺寸選擇刀具
選(xuan)取刀(dao)(dao)(dao)(dao)具(ju)時(shi),要使(shi)刀(dao)(dao)(dao)(dao)具(ju)的(de)尺寸與(yu)被加(jia)工(gong)(gong)件的(de)表面(mian)(mian)(mian)尺寸相適應用(yong)(yong)。生產中,加(jia)工(gong)(gong)平(ping)(ping)面(mian)(mian)(mian)零(ling)件周邊的(de)輪廓,常采用(yong)(yong)立銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao);銑(xian)(xian)(xian)(xian)削(xue)平(ping)(ping)面(mian)(mian)(mian),應選(xuan)硬質合金刀(dao)(dao)(dao)(dao)片銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao)。加(jia)工(gong)(gong)凸臺、凹槽時(shi),選(xuan)高速鋼立銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao);加(jia)工(gong)(gong)毛坯表面(mian)(mian)(mian)或孔粗加(jia)工(gong)(gong)時(shi),可選(xuan)用(yong)(yong)鑲硬質合金刀(dao)(dao)(dao)(dao)片的(de)玉米銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao);對一些(xie)立體型面(mian)(mian)(mian)和變斜面(mian)(mian)(mian)輪廓外形的(de)加(jia)工(gong)(gong),選(xuan)用(yong)(yong)盤形銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao)、圓(yuan)鼻(bi)刀(dao)(dao)(dao)(dao)、平(ping)(ping)刀(dao)(dao)(dao)(dao)做(zuo)粗加(jia)工(gong)(gong),選(xuan)用(yong)(yong)球頭(tou)銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao)、環形銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao)、錐形銑(xian)(xian)(xian)(xian)刀(dao)(dao)(dao)(dao)做(zuo)精加(jia)工(gong)(gong)。
(2)根據工件的表面形狀選擇刀具
在(zai)(zai)進行模(mo)具(ju)(ju)加(jia)工(gong)時,由(you)(you)于(yu)球(qiu)頭刀(dao)具(ju)(ju)的(de)(de)端部切(qie)削速度(du)為零(ling),因(yin)此(ci),為保證加(jia)工(gong)精(jing)度(du),切(qie)削行距(ju)一般采用頂端密距(ju),故球(qiu)頭銑刀(dao)常用于(yu)曲面(mian)的(de)(de)精(jing)加(jia)工(gong)。而(er)平頭刀(dao)具(ju)(ju)在(zai)(zai)表面(mian)加(jia)工(gong)質量和切(qie)削效率方面(mian)都優(you)于(yu)球(qiu)頭刀(dao),因(yin)此(ci),只要在(zai)(zai)保證不過切(qie)的(de)(de)前提下,無論是曲面(mian)的(de)(de)粗加(jia)工(gong)還是精(jing)加(jia)工(gong),都應優(you)先選擇平頭刀(dao)。另外,刀(dao)具(ju)(ju)的(de)(de)耐用度(du)和精(jing)度(du)與刀(dao)具(ju)(ju)價格關系(xi)極大,必須引起注意的(de)(de)是,在(zai)(zai)大多數情況(kuang)下,選擇好(hao)的(de)(de)刀(dao)具(ju)(ju)雖然增(zeng)加(jia)了刀(dao)具(ju)(ju)成本,但由(you)(you)此(ci)帶來的(de)(de)加(jia)工(gong)質量和加(jia)工(gong)效率的(de)(de)提高,則可以使整個加(jia)工(gong)成本大大降低。
(3)合理安排刀具的排列順序
在經濟型數控(kong)機床的(de)加(jia)(jia)工(gong)(gong)(gong)過程中(zhong),由于刀具的(de)磨損、測(ce)量和更換多為(wei)人工(gong)(gong)(gong)手動(dong)進(jin)(jin)行(xing),占(zhan)用輔助時(shi)間(jian)較(jiao)長,因此,必(bi)須(xu)合理安排(pai)刀具的(de)排(pai)列順序(xu)。一般應遵循以下原則:①工(gong)(gong)(gong)序(xu)集中(zhong)一次(ci)裝夾,同一把刀具能(neng)完成其進(jin)(jin)行(xing)的(de)所有加(jia)(jia)工(gong)(gong)(gong)步(bu)驟;②粗精(jing)(jing)加(jia)(jia)工(gong)(gong)(gong)的(de)刀具應分(fen)開使用;③先面后孔;④先進(jin)(jin)行(xing)曲面精(jing)(jing)加(jia)(jia)工(gong)(gong)(gong),后進(jin)(jin)行(xing)二維(wei)輪(lun)廓(kuo)精(jing)(jing)加(jia)(jia)工(gong)(gong)(gong);⑤合理利用數控(kong)機床的(de)自動(dong)換刀功能(neng),以提高生(sheng)產效率(lv);⑥盡量減少(shao)刀具數量。