一、數控銑床刀具種類
數控(kong)加工(gong)(gong)中(zhong)刀具(ju)的(de)選擇和切削(xue)用(yong)量(liang)(liang)確(que)定(ding)是(shi)在人機(ji)交(jiao)互(hu)狀態下完成,要求編(bian)程人員必須(xu)掌握刀具(ju)選擇和切削(xue)用(yong)量(liang)(liang)確(que)定(ding)的(de)基本原則(ze),在編(bian)程時充分考(kao)慮(lv)數控(kong)加工(gong)(gong)特點(dian),正確(que)選擇刀刃(ren)具(ju)及切削(xue)用(yong)量(liang)(liang)。數控(kong)加工(gong)(gong)技(ji)術(shu)涉及的(de)范圍很廣(guang),就(jiu)應用(yong)方面而言,其加工(gong)(gong)技(ji)術(shu)的(de)特點(dian)和難點(dian)仍在于如何高(gao)速、高(gao)效(xiao)(xiao)率地正確(que)選用(yong)數控(kong)機(ji)床刀具(ju)編(bian)制出符(fu)合產(chan)品技(ji)術(shu)要求的(de)數控(kong)加工(gong)(gong)工(gong)(gong)藝(yi)及程序(xu)。數控(kong)加工(gong)(gong)可以大幅度縮短產(chan)品的(de)制造周期,有效(xiao)(xiao)的(de)解決機(ji)械產(chan)品中(zhong)復(fu)雜(za)、精密、單(dan)件(jian)小批量(liang)(liang)、形狀多變的(de)零件(jian)加工(gong)(gong)。
數控銑床加(jia)工刀(dao)具種類很多,為(wei)了(le)(le)適應數控(kong)機床(chuang)高(gao)速、高(gao)效和自動化(hua)程度高(gao)的(de)特點,所用(yong)刀(dao)具正朝著(zhu)標(biao)準化(hua)、通(tong)用(yong)化(hua)和模塊化(hua)的(de)方向(xiang)發展(zhan),主(zhu)要(yao)分(fen)為(wei)銑(xian)削刀(dao)具和孔加(jia)工刀(dao)具兩大類。為(wei)了(le)(le)滿(man)足高(gao)效和特殊的(de)銑(xian)削要(yao)求,又發展(zhan)了(le)(le)各種特殊用(yong)途的(de)專(zhuan)用(yong)刀(dao)具。
(1)刀柄結構形式
數控(kong)銑(xian)床刀(dao)(dao)具(ju)刀(dao)(dao)柄(bing)的(de)結構形式分為模(mo)塊式與整體(ti)式兩種(zhong)。模(mo)塊式刀(dao)(dao)具(ju)系統(tong)是一種(zhong)較先進的(de)刀(dao)(dao)具(ju)系統(tong),其每(mei)把(ba)刀(dao)(dao)柄(bing)都可(ke)通過各種(zhong)系列(lie)化(hua)的(de)模(mo)塊組裝而成。針對不同的(de)加工零件和(he)機床,采取不同的(de)組裝方(fang)案,可(ke)獲得(de)多種(zhong)刀(dao)(dao)柄(bing)系列(lie),從(cong)而提(ti)高(gao)刀(dao)(dao)柄(bing)的(de)適應能力(li)和(he)利(li)用率(lv)。
整體式(shi)刀柄(bing)(bing)(bing)裝(zhuang)夾刀具的(de)(de)工作部分與(yu)機床(chuang)上安裝(zhuang)定位用的(de)(de)柄(bing)(bing)(bing)部是一體的(de)(de)。這(zhe)種刀柄(bing)(bing)(bing)對(dui)機床(chuang)與(yu)零件的(de)(de)變換適應能力(li)較(jiao)差。為適應零件與(yu)機床(chuang)的(de)(de)變換,用戶必須儲(chu)備各種規格的(de)(de)刀柄(bing)(bing)(bing),因此刀柄(bing)(bing)(bing)的(de)(de)利用率(lv)較(jiao)低(di)。
數控銑床刀(dao)(dao)柄(bing)與主軸(zhou)(zhou)孔的配合錐(zhui)面(mian)采用(yong)(yong)(yong)7:24圓(yuan)錐(zhui)柄(bing),并采用(yong)(yong)(yong)相(xiang)(xiang)應型式的拉釘(ding),與機床主軸(zhou)(zhou)相(xiang)(xiang)結(jie)合。錐(zhui)柄(bing)具有不自鎖,換刀(dao)(dao)方便等特點。刀(dao)(dao)柄(bing)常用(yong)(yong)(yong)的規格有40號(hao)、45號(hao)和50號(hao)。目前(qian)在我國應用(yong)(yong)(yong)較為廣(guang)泛的有IS07388—1983.MAS403—1982.ANSI/ASME 135.50—1985等,選(xuan)擇時應考慮刀(dao)(dao)柄(bing)規格與機床主軸(zhou)(zhou)、機械(xie)手相(xiang)(xiang)適應。JT:表(biao)示采用(yong)(yong)(yong)國際標準(zhun)(zhun)IS07388號(hao)加工中心機床用(yong)(yong)(yong)錐(zhui)柄(bing)柄(bing)部(bu)(帶機械(xie)手夾持槽);其后(hou)(hou)數(shu)(shu)字(zi)為相(xiang)(xiang)應的ISO錐(zhui)度號(hao)。BT:表(biao)示采用(yong)(yong)(yong)日本標準(zhun)(zhun)MAS403號(hao)加工中心機床用(yong)(yong)(yong)錐(zhui)柄(bing)柄(bing)部(bu)(帶機械(xie)手夾持槽);其后(hou)(hou)數(shu)(shu)字(zi)為相(xiang)(xiang)應的ISO錐(zhui)度號(hao)。對于高速切削(xue)一般采用(yong)(yong)(yong)HSK系列刀(dao)(dao)柄(bing)。
為提高(gao)加工(gong)(gong)效率(lv)(lv),應盡可(ke)能選用高(gao)效率(lv)(lv)的刀具和刀柄。選用強(qiang)力銑(xian)夾(jia)(jia)(jia)頭刀柄,夾(jia)(jia)(jia)持精度高(gao),可(ke)以用來夾(jia)(jia)(jia)持直柄刀具,因卡簧自(zi)身(shen)夾(jia)(jia)(jia)緊變形小自(zi)鎖性(xing)好,夾(jia)(jia)(jia)緊力大(da),可(ke)以用于強(qiang)力銑(xian)削加工(gong)(gong);還可(ke)以用于高(gao)精度銑(xian)鉸孔(kong)加工(gong)(gong),也(ye)可(ke)通(tong)過接桿夾(jia)(jia)(jia)持帶孔(kong)類刀具。
選(xuan)用彈(dan)簧卡(ka)頭(tou)刀(dao)(dao)柄(bing),卡(ka)簧彈(dan)性變形量為(wei)1mm,主要(yao)夾(jia)持小規格銑刀(dao)(dao),如鉆頭(tou)、銑刀(dao)(dao)、鉸刀(dao)(dao)、絲錐(zhui)等。選(xuan)用模塊式工(gong)(gong)具(ju)(ju)系(xi)統由于其(qi)定位精度高,裝卸方(fang)便,連(lian)接(jie)剛(gang)性好,具(ju)(ju)有良好的抗振性,是目前(qian)用得較(jiao)多(duo)的一(yi)種型(xing)式,它(ta)由刀(dao)(dao)柄(bing)、中間接(jie)桿(gan)以(yi)及(ji)工(gong)(gong)作頭(tou)組成(cheng)。選(xuan)用粗鏜(tang)孔可(ke)選(xuan)用雙刃鏜(tang)刀(dao)(dao)刀(dao)(dao)柄(bing),既可(ke)提高加工(gong)(gong)效率,又有利(li)于減少(shao)(shao)切削振動;對于批(pi)量大、加工(gong)(gong)復(fu)雜的典型(xing)工(gong)(gong)件,應盡(jin)可(ke)能(neng)選(xuan)用復(fu)合刀(dao)(dao)具(ju)(ju)。盡(jin)管復(fu)合刀(dao)(dao)具(ju)(ju)與刀(dao)(dao)柄(bing)價格較(jiao)為(wei)昂貴,但(dan)在數控(kong)機床上采用復(fu)合刀(dao)(dao)具(ju)(ju)加工(gong)(gong),可(ke)以(yi)使工(gong)(gong)序集中,把多(duo)道(dao)工(gong)(gong)序合并成(cheng)一(yi)道(dao)工(gong)(gong)序、由一(yi)把刀(dao)(dao)具(ju)(ju)完(wan)成(cheng),有利(li)于減少(shao)(shao)加工(gong)(gong)時(shi)間和換刀(dao)(dao)次數,顯著提高生產(chan)效率。
(2)數控銑床刀具的分類
數控銑床刀(dao)具的分(fen)類有多(duo)種(zhong)方法,根(gen)據刀(dao)具結構可分(fen)為:①整體式(shi)(shi)②鑲(xiang)嵌式(shi)(shi),采用焊接或機夾式(shi)(shi)連接,機夾式(shi)(shi)又可分(fen)為可轉位和(he)不可轉位兩種(zhong)③特殊(shu)型式(shi)(shi),如復合式(shi)(shi)刀(dao)具,減震(zhen)式(shi)(shi)刀(dao)具等。
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(gang)石刀具④陶(tao)瓷刀片材料(liao)如(ru)氮化硅陶(tao)瓷Si3N4,立(li)方氮化硼CBN。
從切削工藝上可分為(wei):銑(xian)(xian)削類刀(dao)具(ju)(面銑(xian)(xian)刀(dao)、立銑(xian)(xian)刀(dao)、圓鼻刀(dao)、球頭銑(xian)(xian)刀(dao)、錐(zhui)度銑(xian)(xian)刀(dao))、孔加工類刀(dao)具(ju)(麻花(hua)鉆(zhan)、鉸刀(dao)、鏜刀(dao)、絲錐(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(de)40%-50%,金屬切除(chu)量占總數的(de)80%~90%。
二、數控加工刀具的選擇
刀具選擇的總原則:安裝調整方便、可靠性好、剛性好、耐(nai)用(yong)度(du)和(he)精度(du)高。在滿足加工(gong)要求的前提下,盡量選擇刀柄較短的刀具,以增強加工(gong)的剛性。
(1)根據工件的表面尺寸選擇刀具
選取(qu)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)具時(shi),要使刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)具的(de)尺寸(cun)(cun)與被加(jia)(jia)工件(jian)(jian)的(de)表面(mian)(mian)尺寸(cun)(cun)相適應用。生產中,加(jia)(jia)工平面(mian)(mian)零(ling)件(jian)(jian)周邊的(de)輪廓,常采用立銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao);銑(xian)削平面(mian)(mian),應選硬(ying)質合(he)(he)金刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)片(pian)銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)。加(jia)(jia)工凸臺、凹槽時(shi),選高速(su)鋼立銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao);加(jia)(jia)工毛坯(pi)表面(mian)(mian)或孔粗加(jia)(jia)工時(shi),可(ke)選用鑲硬(ying)質合(he)(he)金刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)片(pian)的(de)玉米銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao);對一些立體型面(mian)(mian)和變斜面(mian)(mian)輪廓外形的(de)加(jia)(jia)工,選用盤形銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)、圓鼻(bi)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)、平刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)做粗加(jia)(jia)工,選用球頭銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)、環形銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)、錐形銑(xian)刀(dao)(dao)(dao)(dao)(dao)(dao)(dao)做精加(jia)(jia)工。
(2)根據工件的表面形狀選擇刀具
在(zai)進行模具(ju)加(jia)(jia)工(gong)(gong)(gong)時,由于(yu)球(qiu)頭(tou)刀(dao)(dao)(dao)(dao)具(ju)的(de)(de)端(duan)部切(qie)削速度為(wei)零,因(yin)此,為(wei)保證(zheng)(zheng)加(jia)(jia)工(gong)(gong)(gong)精(jing)度,切(qie)削行距(ju)一般采用頂端(duan)密距(ju),故球(qiu)頭(tou)銑刀(dao)(dao)(dao)(dao)常用于(yu)曲(qu)面(mian)(mian)的(de)(de)精(jing)加(jia)(jia)工(gong)(gong)(gong)。而平頭(tou)刀(dao)(dao)(dao)(dao)具(ju)在(zai)表面(mian)(mian)加(jia)(jia)工(gong)(gong)(gong)質(zhi)量和(he)切(qie)削效率(lv)方面(mian)(mian)都優于(yu)球(qiu)頭(tou)刀(dao)(dao)(dao)(dao),因(yin)此,只要在(zai)保證(zheng)(zheng)不過切(qie)的(de)(de)前(qian)提下(xia),無論是曲(qu)面(mian)(mian)的(de)(de)粗加(jia)(jia)工(gong)(gong)(gong)還(huan)是精(jing)加(jia)(jia)工(gong)(gong)(gong),都應優先選擇(ze)平頭(tou)刀(dao)(dao)(dao)(dao)。另(ling)外,刀(dao)(dao)(dao)(dao)具(ju)的(de)(de)耐用度和(he)精(jing)度與刀(dao)(dao)(dao)(dao)具(ju)價格關系極(ji)大(da),必須引起(qi)注意的(de)(de)是,在(zai)大(da)多數情況(kuang)下(xia),選擇(ze)好的(de)(de)刀(dao)(dao)(dao)(dao)具(ju)雖然(ran)增加(jia)(jia)了(le)刀(dao)(dao)(dao)(dao)具(ju)成(cheng)(cheng)本,但由此帶來的(de)(de)加(jia)(jia)工(gong)(gong)(gong)質(zhi)量和(he)加(jia)(jia)工(gong)(gong)(gong)效率(lv)的(de)(de)提高(gao),則可以使(shi)整個(ge)加(jia)(jia)工(gong)(gong)(gong)成(cheng)(cheng)本大(da)大(da)降低。
(3)合理安排刀具的排列順序
在經濟型數(shu)控(kong)機(ji)(ji)床(chuang)的加(jia)工(gong)過程(cheng)中,由于刀(dao)具(ju)(ju)的磨損、測量和更(geng)換多為(wei)人工(gong)手動(dong)進(jin)(jin)行(xing)(xing),占(zhan)用輔(fu)助時間較(jiao)長,因此,必須(xu)合理安排刀(dao)具(ju)(ju)的排列順序(xu)(xu)。一(yi)般(ban)應遵循以下原(yuan)則:①工(gong)序(xu)(xu)集中一(yi)次裝夾,同一(yi)把刀(dao)具(ju)(ju)能(neng)完成(cheng)其進(jin)(jin)行(xing)(xing)的所有加(jia)工(gong)步驟(zou);②粗精加(jia)工(gong)的刀(dao)具(ju)(ju)應分開使(shi)用;③先(xian)(xian)面(mian)后孔;④先(xian)(xian)進(jin)(jin)行(xing)(xing)曲面(mian)精加(jia)工(gong),后進(jin)(jin)行(xing)(xing)二維輪廓精加(jia)工(gong);⑤合理利用數(shu)控(kong)機(ji)(ji)床(chuang)的自動(dong)換刀(dao)功(gong)能(neng),以提高(gao)生產(chan)效(xiao)率;⑥盡量減少(shao)刀(dao)具(ju)(ju)數(shu)量。