Cng ngh gia cng l su

1.Tng quan v l su

Nhng l c t l gia chiu di v ng knh l/d >= 5 c gi l l su.Thc t chng ta gp nhiu l su nh: xi lanh thy lc ,nng sng pho... cc chi tit ny,thng t l trn vt xa so vi quy c,vi cc loi xi lanh thy lc hay cc nng sng b binh t l trn l 15 n 20 ln, cn vi cc loi pho c ln t l trn ln n 60 thm tr 70 ln.Cng do tnh cht ging nhau khi gia cng nng sng v gia cng cc l su khc nn trong ngnh c kh nhiu khi thut ng khoan nng sng c dng ch chung cho phng php gia cng l su v cc dng c chuyn dng khoan l su cng c gi l dao khoan nng sng.

Hinh1. Xy lanh thy lcL su thng c hnh dng khng qu phc tp nhng yu cu k thut i hi kh cao,do vy cng ngh gia cng l su l mt cng ngh kh,c nhiu c im ring v khc bit so vi l thng thng,cng ngh gia cng l su cn trang thit b, dng c chuyn dng v ch gia cng c bit.Nhng kh khn trong gia cng l su l:- Kh to phoi khi ct v kh thot phoi ra khi vng ct- Kh bi trn v lm ngui dng c ct- Kh bo m cng vng,trnh rung ng ca h thng cng ngh nn kh bo m thng theo yu cu v v tr ng n ca tm l gia cng- Kh theo di kim tra cht lng b mt gia cng v s lm vic ca dng c,c bit l bo m bn mn ca dng c ct trong sut qu trnh lm vic.Cc phng php gia cng l su:1.Gia cng ct gt:y l phng php c s dng ph bin hn c.L su c to thnh t phi thanh bng cc phng php khoan su ct i phn kim loi d. gia cng l su chnh xc ,ty theo phi c dng trc c hay trc rng m nhng nguyn cng c bn phi tin hnh l: khoan, khot th,khot tinh,v cc nguyn cng gia cng ln cui nh:khot mng,doa,mi khn,nh bng,trt p,ln p...

2.Gia cng in haDa trn nguyn l n mn in cc dng trong dung dch in phn khi c dng in i qua.Phng php ny t dng do trang b cng ngh phc tp, kh s dng,ch yu gia cng vt liu kh gia cng v c chiu su khng ln.3.Gia cng bin dng do:Thc cht y l qu trnh rn khun,da trn c s bin dng do ca kim loi, kim loi c gia nhit n nhit rn,sau dn u kim loi trn li bng rn,t yu cu k thut cao.Phng php ny ch yu p dng cho cc l c ng knh khng ln cho chnh xc cao nhng yu cu trang b cng ngh phc tp.2. Gia cng l su bng phng php ct gt

2.1.My:Xut pht t c dim ca l su l c chiu di phi ln nn cc my s dng y hu ht l cc my chuyn dng c th gia cng t mt pha ,hai pha vi chiu di bng my bo m sao cho ln hn 1.5 n 2 ln chiu di phi.Vi nhng l qu di c th s dng phng php ni di thm bng my hoc dng hai my quay ui ni tip nhau gia cng.

Hnh 2.My c dng trong gia cng l su2.2.Dng c ct :Dng c ct chuyn dng cho gia cng l su kh a dng v chng loi v kt cu. S ra i cc vt liu siu cng cho php ch to ra nhng loi dao ct nhiu li c tc cao cho nng sut ln. Cc yu cu c bn ca dng c ct ny l :- D dng a dung dnh trn ngui v thot phoi ra khi vng gia cng- Dn hng tt v c cng vng cao- Trit tiu ti a lc lm cong cn dao- Mi v thay th d dngDng c dng trong gia cng l su thng c cu to gm 3 phn:phn ct,phn dn hng v phn thn- Phn ct: lm bng thp gi,hp kim cng hay cc vt liu sin cng (ceramic,kim cng) yu cu c bn nhit ,bn mn cao- Phn dn hng :yu cu ma st t v kh nng n hi cao,thng s dng g hoc cht do tng hp- Phn thn :lm bng thp thng thng, ngoi ni phn ct v dn hng cn s dng ni thm phn cn ni di u ct gia cng nhng l c chiu di ln.Dng c o kim:L gia cng c chiu su ln nn trong qu trnh gia cng bng phng php ct gt, thng gp cc dng sai hng sau: lch trc l, cong trc l, chiu dy thnh khng ng u, to bc, gy trc l khi khoan hai u, l elp, phnh tang trng, a cnh ho b mt l, l bcn.

Hnh.4. u ct v cn ni di2.3 Cc dng c ph:Cc dng c ph bao gm : g, thit b cp thu dung dch trn ngui,dng c o kim- g :mm kp 3,4 chu;Khi V;luy nt;khi tm:ng n hi...- Thit b cp v thu dung dch trn ngui: c kt cu phc tp, i hi phi ng b,thit b cp a s s dng bm cao p,thit b thu c ni trc tip u l gia cng v c b phn lc nhanh chng cp tr li.- Dng c o kim:L gia cng c chiu su ln nn trong qu trnh gia cng bng phng php ct gt, thng gp cc dng sai hng sau: lch trc l, cong trc l, chiu dy thnh khng ng u, to bc, gy trc l khi khoan hai u, l elp, phnh tang trng, a cnh ho b mt l, l bcn.[Hnh 5. u o l su dng laser v cm bin in

2.4 Dung dch trn nguiDung dch trn ngui ng vai tr rt quan trng trong gia cng l su.Ngoi tc dng bi trn v lm mt n cn cun phoi ra khi vng gia cng v gim lc ct. V vy dung dch trn ngui cn c cp lin tc m bo vi p sut v lu lng ln.Thnh phn dung dch gm 90%sunfoferejon +10%du ha hoc 7-10% Emunxi +0,2% Na2CO3 + ncCc loi dng c ct phi c kt cu d dng a dung dc trn ngui vo vng gia cng v thot phoi d dng.Thng c 3 kiu sau:- a dung dch qua l cn dng c,phoi thot theo khe h gia cn v thnh l- a dung dch qua khe h gia cn v thnh l,phoi thot theo l cn- Dung dch v phoi i qua 2 l cn lng nhau .

Hinh6. Kt cu dn thu dung dich trn ngui khi khoan2.5.Cc nguyn cng chnh trong gia cng l su:

2.5.1 Khoan:Khoan l phng php to l t phi c hoc phi ng trn cc my khoan tin hoc my vn nngKhoan t cp chnh xc IT14 IT12, cp nhm 3-5 khoan cc l c ng knh nh hn 100mm thng dng phng php khoan c,nhng l c ng knh ln hn 100mm thng s dng phng php khoan vng.2.5.2.Khot:Khot l phng php gia cng m rng l trn my khoan, my tin ,my phay hay my doa.Nguyn cng ny nhn sa thng trc tm ca l v khot i phn ln kim loi cn li sau khi khoan.Kh nng cng ngh ca khot c th t ti cp chnh xc IT11- IT10,cp nhm 5-7Nguyn cng khot c th chia lm 2 bc : khot th v khot tinhKhot c 2 phng php l :khot y v khot ko

2.5.3 Doa:Doa l phng php gia cng tinh l qua nguyn cng khoan v khot.Kh nng cng ngh c th t cp chnh xc IT 9- IT7, nhm t n Ra =0.63 -1.25 thm ch ra =0.6Doa c 2 phng php c bn : Doa cng bc v doa ty ng

2.5.4.Mi khnMi khn l qu trnh ct t vi kim loi vi s tham gia tng hp ca rt nhiu ht mi trong iu kin c y dung dc bi trn v lm ngui.Mi khn cho php nng cao chnh xc kch thc,gim sai s hnh dng hnh hc v nhm b mt gia cng. chnh xc kch thc sau mi khn t cp 2 -3, nhm Ra= 0,08- 0,32Mi khn c th c cc bc sau: mi th,mi ph, mi bn tinh, mi tinh,mi gng,mi t hp.

Hinh7. Kt cu m phng mi khoan xon v mt u doa tinh lm bng ch s dng mt ln

2.6.Chn chun cng ngh trong gia cng:Gia cng l su rt kh kim sot sai s trong qu trnh ct gt nn vic chn chun gia cng c ngha quyt nh i vi cht lng sn phm sau gia cng. Chn chun hp l c th gim ng k sai s ny.Theo quan im cng ngh th b mt no c yu cu k thut , chnh xc cao c chn lm chun gia cng. Do vy cc nguyn cng m rng l,b mt tr trong c yu cu cao v hnh dng hnh hc, nhm c chn lm chun gia cng.Khi c l,dng mt trong lm chun gia cng mt ngoi,sau dng mt ngoi va gia cng xong lm chun mc l dn hng,lc ny b mt l hng ny c ly lm chun gia cng b mt trong cn li.Qu trnh lp li lin tc n khi hon thnh cc nguyn cng.- Cc nguyn cng tin mt tr ngoi th chun l hai l tm ca chi tit- Chun ca cc bc gia cng mt u, vt mp, mc l hng l b mt tr ngoi lng chun v khi vic r trn iu chnh chi tit c thc hin trn b mt nh v ny.- Cc nguyn cng khoan, khot m rng sau bc mc l hng th chun c xc nh ban u l b mt tr trong mc l hng. Chiu su l hng phi m bo nh v bn bc t do cho u dao trnh u dao b dao ng ban u. Khi u dao i qua ht chiu di l hng th chun lc ny l b mt l trong va gia cng.- Cc nguyn cng khot tinh, doa, mi khn khng c bc mc l hng trc th chun l b mt trong va gia cng nguyn cng ngay trc . Khi , cc b mt tr ngoi lng chun trc tr thnh cc mt t ni cp mm cp, ni t cc luynt.

2.7.m bo cng vng ca h thng cng nghQu trnh gia cng l su,cc trang thit b u c chiu di ln,vic bo m cng vng s hn ch ng k sai s gia cng- Chiu di phi ln d b vng,km n nh- Bng my nhiu khi phi ghp ,khe h xut hin lm rung ng trong qu trnh ct gt- Cn dng c c ni di,trong khi i su vo l d cong vnh do rung ngV vy y l vn ln trong qu trnh m bo cc yu cu k thut v phi c chun b t trc khi gia cng- s dng cc c cu lm tng cng ca h thng ( luynt tnh, luynt ng)- Chn vt liu v quy trnh nhit luyn hp l- m bo ng tm gia l chi tit v ng tm my chc chn phi c bng vic r trn v iu chnh. ng tm gia tm l chi tit v tm u dao cng phi c m bo nh cc dn hng lp trn u dao,bn thn cc dn hng phi m bo cong, trn u trn ton chiu di ca n (t c nh mi)- Nguyn cng mi khn, u khn phi t la thng qua khp ni ( khp cu, khp cc ng) gia u khn v cn ni di.

Ti c thc mc nh mong anh [b]huyhoang84[b] gii p gip, anh c vit "Khi c l,dng mt trong lm chun gia cng mt ngoi,sau dng mt ngoi va gia cng xong lm chun mc l dn hng,lc ny b mt l hng ny c ly lm chun gia cng b mt trong cn li.Qu trnh lp li lin tc n khi hon thnh cc nguyn cng.". anh l mnh s to ra 1 l dn hng mi khng ng tm vi l cn gia cng ? Nu vy th mnh s g t nh th no nu dng trn my tin ? Cm n anh.

Cu y mi ch l nghe ni v Post li thng tin thi, theo ti l th.Bn hi cu ny chng t bn c 1 nng lc nht nh v ngh, ti ko dm ni nhiu trc khi tho lun thm vi bn v vn ny, vy xin hi bn l bn c nhng hiu bit v vn Khoan, Doa xu cha?Bn cng bit l ly i, ly li chun th chng bit u ny ng cha nhng u kia sai bt nh ri nu tin hnh gia cng.Vy nn khoan xu ch mang tnh to hnh, sau khi gn sn phm c nh ln u , ngi ta mi dng doa di ng doa xu l khoan. Chc chn rng mt chun s rt a dng v ph thuc vo tnh cht cng vic ly chun m Doa xu.Mong bn v mi ngi tip tc ch th v ny.Em cng c mt vi th hi linh tinh xin c ni ra !tha cc aj cath nht: cng ngh phc hi l xu c bit l l cn ngi ta s dng chnh l cn y nh v chun th gia cng ( c th tin sau khi hn p) b mt tr tr ngoi hoc cng c th l b mt bt k theo em quan st c ngi ta c th si c trn my tin c anh Hong Khanh .tin n mt cp no sau ngi ta kp ba chu gia cng li b mt cn sau ngi ta li dng chnh b mt cn va gia cng c gia cng tinh li b mt ngoi , ri dng b mt ngoi tinh li b mt cn (c th tr nhng tr d dng hn).ngi ta s mi tinh b mt ngoi t li dng b mt ngoi dng lm chun tinh li mi tinh li l Cn( tr) c iu chn chun qua li s xut hin sai s chun , ngi ta s chp nhn trong mt gii hn no , hoc kh sai s chun PP th em cha d lm ,anh liu ngn nh c th b xung c k .Th Hai : vn gia cng l su ch to nng sng c rnh xon theo em c bit ngi ta s c . sau ngi ta tin xon , quan trng l nguyn cng tinh h s trut v trt nh th no?ngi ta dng mt g dao c bit c th cho dao ( trut ) c th xoay t la theo rnh xon Dao s chuyn ng tnh tin v t xoay nh g dao . Em xin li l my em hng AutoCad nn cha post ln c.ci ny th em c thc tp ri v em cng cng cc bc ng my lm . xin ht kin

Cng ngh gia cng cc l bn huyhoang84 ni cng chi tit lm v c l ,nhng cng khng ch n gin nh th u.Hnh s 4 c ci u ct ngn qu(drill head adapter).Trc y khi lm cho hng ISCAR ,ti tng lm qua ci u mi khoan ,n khng th dng khoan su c ,v ch nn dng cho st mm,d c khoan su th cng khng thng u.Mun khoan su th phn thn u li ct c chiu di ti thiu th phi gp 5 ln ng knh (phn ni vo thn khoan).Ngoi ra dung dch lm ngui l mt loi du trn kh chy,bm du th phi c mt loi my c bit c lc p ln n 2000 PSI nu khoan nhng l nh nh 2mm (ngha l lc p khong 900 kg trn 1 inch vung) vi lc p ny ,tia du nu vng trc tip trn ngi th rt l au y.Ci my khoan c tn gi lGUN DRILL(sng khoan).Hng ti lm ang nn t mt GUN DRILL loi ln c th khoan l di n khong 7 mt vi ng knh l ln n 6 inch.Ni ch xi mng lm ci nn mng t khoan thi m ti n loay hoay 2 tun ri by gi vn cha xong.(va lm va chi)

Bn yopopovp ni nng sng l st c gia cng ng son,khng bit c phi l c khun (mold casting)c l sn ch cn khoan s s ri lm ng kinh tuyn khng....?Nu lm th th bn ch khng cht m ng i b thng.L do l c th nng sng chng bao lu s b.Nu lm nng sng th phi l cy st c,v em hp vi nhit nht nh ,sau khoan l v lm ng kinh tuyn,mang i mi,cui cng nhng cht chng mn v thui (ngha l chui pht qua lp v ngoi ) cho n dai cng lp v ngoi thi,lm cng qu bn trong th khng cn thit ,nng qu th nng sng s bin th v khng thng na i khi l nh vy.

@HoangKanh: ca HK l nu nh dng b mt ngoi lm chun mc l dn hng th c th xy ra trng hp tm l dn hng khng trng tm my phi khng? ng l s xy ra iu nhng n c lin quan g n ga t chi tit trn my tin u nh, y ch l cng on to chun cng ngh cho bc gia cng tip theo thi m.Gi s phi qua cng on khoan su to l. Cc nguyn cng tip theo l khot m rng l. Qu trnh g t hnh dung nh sau:- u tin ,chi tit c chng tm hai u, thc hin tin bc v ngoi cn gi l lng chun.- -Sau chi tit c kp trn mm cp, u cn li trn luy-nt, r trn bo m o v tr v khng song song gia tm chi tit vi tm my theo YCKT . Mc l dn hng, l ny s dng lm chun thc hin cng on khot m rng l, b mt l lc ny c vai tr nh v , cc thanh dn hng ca u khot t vo nh v cho dao n su tip.

@ Liu Ngn nh : y l chuyn ngnh ca bn em m, ch u phi ch nghe ngi ta ni khng, em cng c xem cng nhn lm ri..Chnh v gia cng l su rt kh kim sot sai s v tr tng quan ca cc ng tm nn tng nguyn cng phi to chun h l v l chun thng nht cho cc bc tip theo, nh vy lm sao xy ra chuyn gia cng u ny m u kia sai c???ng l vi phi c th bc khoan l u tin ch mang tnh to hnh, lm sao c ci l l c. Cc nguyn cng m rng l v gia cng tinh mi quan trng, vi nhng l ln cn c thm nhiu nguyn cng khoan cng nh khot m rng, cn doa hay mi khn l cng on gia cng tinh v sau. Khi cc u doa hay mi khn l ty ng (ch khng phi di ng ) ngha l n s t iu chnh theo khng song song ca tm l so vi my thng qua khp ni dng cu hay Cc ng ni u dao v cn.Anh c gng vit v phn ny thm i, em ngh anh c nhiu kinh nghim y.

@ dondoan: theo mnh c bit th u ct ca hng Sandvick ,c nhiu li dng khoan, vi l su th c l ch gia cng c cc l c chiu di khng ln lm, tt nhin l phi c cn ni di th mi khoan cCn cng ngh gia cng l su bng ct gt th bi ca mnh vit y ph hp vi iu kin cng ngh trong nc thi, nhng nc tin tin c th h s c cng ngh khc ,nh bn ni y, l 2mm th c th bng khoan thng thng hay gia cng tia laser, xung in.Bn ni n my GUN DRILL ,nu c th bn post vi ci nh ln v gii thiu qua v n cho mi ngi cng bit c khng.

@ yopopovp: Gia cng l su c 2 kiu : l trn v l c rnh xon ,vi l c rnh xon th ban u vn phi tri qua cc bc to l trn nh ni trn. Vi c gia cng rnh xon cng c nhiu kiu bn , mi dng rnh xon khc nhau cng s c cc phng php khc nhau, ch u ch c chut nh bn ngh . Cn tin xon th th thc mnh cha nghe ni bao giCn phi gia cng nng sng th nh dodoan ni y, nu ch n gin l c ri ct rnh xon th cha bit c bn c ch hay khng th ngi bn toi ri . c ch dng to phi cho cc l c tit din v chiu di khng ln (nh nng sng ngn chng hn), v c d sinh ra cc khuyt tt tinh th vt liu lm c tnh gim, khi chu p sut ln hay iu kin lm vic khc nghit chi tit rt d bi hng, nh nng sng chu p sut tc thi th s b nt v, cc h thng xi lanh thy lc di p sut cao lin tc s b r r cht lng . Cho nn vi cc chi tit nh vy th phi thng lm bng cc loi mc thp c bit , ch yu l phi cn v rn, sau qu trnh gia cng c s c nhit luyn v tri qua mt vi giai on ram nng cao c tnh, kh b khuyt tt ; tip phi kim tra t m lm ri mi mi t kch thc v bng yu cu ,cui cng em i x l b mt bo v chng n mn .Ngay vic tng chng nh n gin l gia cng l trn cc xilanh c ln dng trong hm m than,m l c mt ti cp nh nc lm mi ,th i th li mi xong, v ng xi lanh chu p sut cao qu nn nu khng x l vt liu sau nhit luyn ng quy cch th c tnh khng bo m em i dng mt thi gian l du d qua cc khe h t vi gia cc tinh th lm gim tui th nhanh chng.M yopopovp hc CTM3 HVKTQS th kiu g trong lp ch c mt vi bn lm n tt nghip v phn ny , kha CTM2 va ra trng cng c cu hi mnh v gia cng l trn y.

Tm li, gia cng l su l cng ngh tng i c th. Bi trn ch l mt phn trong lot bi v cng ngh gia cng l su m mnh nh vit. Mc ch cng l tham kho kin ca mi ngi, v vy rt mong c c phn bin ca cc thnh vin ,v c s tham gia vit cng ca cc bc c kinh nghim trong lnh vc ny .Khi no di, mnh vit tip cc phng php gia cng cn li.

Gip thm huyhoang84 mt t hnh nh v ti liu.Tht ra Gundrill l ci tn cng cm ca my khoan l su c ngi Chu u ch ra hn 200 nm trc chuyn tr khoan nng sng.By gi Gundrill oc dng trong rt nhiu ngnh ch khng dng ring khoan nng sng na.Nhng ngi ta vn dng ch Gundrill ch loi my chuyn tr khoan su ny.Thnh thong ti vn thng gi hng i my ch gundrill khoan l su,khng ring g sn phm hnh tr ,m h c th khoan l su cc dng khi khc.My gundrill

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KhoanClick this bar to view the full image.

u mi khoan

C nhiu loi khoan,hnh trn ch l s .

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Thm nhiu ti liu y :

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Sn dp, n c tri tn, post 1 ci hnh c .Hnh en trng khng cn r lm v cc nguyn cng ch to sng.Hai hnh di cng l my khoan v doa su cho nng sng.Cc my mc ny cha c m t.Trc quay c nh mt h thng rng rc.

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B sung thm thng tin v gia cng l su cho huyhoang84.............................................

Gia cng l su theo phng php ct gt th c 3 phng php .1) Phng php khoan BTA2) Phng php khoan GUNDRILL3) Phng php khoan SBR cn gi l Skyving M/C1)Phng php khoan BTA...........y l phng php khoan theo phn u ca bi vit ca huyhoang84. Mi khoan l mi c th gm c 3 phn l phn dn hng, phn thn v u khoan. Phn thn khoan thng rng rut dng pipe, khi khoan phi s c cun theo du tn nhit vo ng trong phn thn v thi ra ngoi. Khi khoan th c 2 phn phi v mi khoan c g trn 2 mm cp v cng quay.Mt s my BTA vi h thng cp phi ng yn khng quay gi l BTA Floor hot ng ging nh my khoan GUNDRILL nhng dng mi khoan BTA. BTA c dng khoan cc l su v c ng knh ln t 15mm n 2000mm, chiu su khong khong 200 ln so vi ng knh mi khoan (khong t 1 n 15m). u khoan cng c chia lm 3 loi l SOLID BORING, TOREBAN BORING v COUNTER BORING. Xem hnh di

u im ca dng khoan ny lKhoan l ln, diKhi khoan do phn phi thi ra s chy vo trong rut mi khoan i ra nn b mt sn phm khoan bng lng, khng b st nh khoan thng.i vi cc l khoan c ng knh t 10 n 30mm th ngi ta cng c th khoan bng k thut GUN DRILL , nhng nu dng u khoan BTA th c th khoan nhanh hn GUNDRILL v tnh cng vng ca mi khoan.Thng thng vi my khoan dng BTA th h thng dn hng rt cng vng nn chnh xc rt cao. Vi cc my mi ngi ta c th khoan l chnh xc vi lch tm v chnh xc vng trn ( chn vin ) trong dung sai 0.05mm c ly khoan 11m v sai lch 0.01 trong phm vi khoan 1m.

Nhc im:Khng khoan l nh c.Thit b my ln, tin u t rt cao. Nu khng c vic lm hng lot lin tc th u t my ny rt kh thu h vn

Ton thn my khoan BTA KD25

Trc chnh v mm cp

H thng dn hng chng rung phi

bng iu khin

mm cp sau kim h thng y p lc cao

h thng dn hng chng rung mi khoan

2. Phng php khoan GUNDRILLy l phng php khoan da trn k thut khoan nng sng m ch em svb cp trn. Mi khoan gundrill cng l dng c th khc vi mi khoan BTA. Xem hnh di . Khi khoan cn phi c h thng phu nda62u ct tc cc chanh, cc mnh. Du ct s i theo ng dn trong thn mi khoan v phi ct s theo ng thot trn thnh thn li khoan thot ra ngoi.

my khoan Gundrill NC, c kh nng khoan mt ln nhiu mi khoan

my khoan Gundrill dng KneetypeClick this bar to view the full image.

Mi khoan Gundrillu im:Phng php ny c th khoan chnh xc c l c ng knh nh t 3mm n 30mmGi thnh my r so vi my khoan BTANhc imKhoan l ng knh ln khng c. H thng chng rung yu so vi my BTA nu cng khoan l 30mm th b mt sn phm ca phng php khoan BTA tt hn

3. Phng php khoan SBRH thng khoan gn gng vi h thng khoan BTA nhng khc chkhi khoan vo th n khoan th, khi rt mi ra th n gia cng tinh. Cho b mt sn phm c bng rt cao t 0.5 n 3S. C th khoan l ln t 100mm n 1000mm , chiu su c th khoan t 1m n 15m

Ton b thn my khoan SBR

Mi khoan SBR

Mi khoan SBR

Chc cc em vui v. Ai bit thm na th b sung thm.