Yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender: txoj kev thiab cov lus qhia

Cov txheej txheem:

Yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender: txoj kev thiab cov lus qhia
Yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender: txoj kev thiab cov lus qhia

Video: Yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender: txoj kev thiab cov lus qhia

Video: Yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender: txoj kev thiab cov lus qhia
Video: Lub nplaj teb txawv lawm zuj zus | Nkauj ntseeg tawm tshiab 2021 2024, Hlis ntuj nqeg
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Kev txiav txim los ntawm kev tshuaj xyuas, ntau tus tswv ntawm lub tsev ntiag tug thiab lub tsev nyob rau lub caij ntuj sov yuav tsum tau ua haujlwm nrog cov kav dej profile. Qhov tseeb yog tias nws yooj yim heev rau kev sib sau ua ke rau cov qauv tsim los ntawm lawv, xws li tsev cog khoom, ntau lub tsev cog khoom, arbors thiab lwm yam khoom. Txawm li cas los xij, raws li cov kws tshaj lij, cov yeeb nkab dabtsi yog khoov yog ua tau nrog cov cuab yeej tshwj xeeb kim. Qhov no piav qhia vim li cas ntau tus neeg ua haujlwm hauv tsev xav paub yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender? Qhov no feem ntau yog txaus siab rau cov uas yuav mus ua ib lub tsev xog paj. Koj yuav kawm yuav ua li cas khoov cov yeeb nkab profile rau lub tsev cog khoom los ntawm kab lus no.

khoov ib lub yeeb nkab profile tsis muaj cov yeeb nkab bender rau lub tsev cog khoom
khoov ib lub yeeb nkab profile tsis muaj cov yeeb nkab bender rau lub tsev cog khoom

khoom taw qhia

Ua ntej koj xav paub yuav khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender,koj yuav tsum paub seb nws yog dab tsi. Raws li cov kws tshaj lij, qhov profile tuaj yeem suav hais tias yog cov khoom lag luam uas muaj cov duab plaub, oval, hexagonal lossis square seem. Tsis zoo li cov yeeb nkab nrog lub voj voog hla, cov yeeb nkab profile tau muaj zog ntau dua vim muaj cov npoo uas siv los ua stiffeners.

khoov cov yeeb nkab profile nrog koj tus kheej txhais tes yam tsis muaj cov yeeb nkab bender
khoov cov yeeb nkab profile nrog koj tus kheej txhais tes yam tsis muaj cov yeeb nkab bender

Yog li, qhov profile tuaj yeem tiv taus qhov tseem ceeb bending loads. Cov kav dej zoo li no yog ua los ntawm cov hlau tsis tshua muaj siab thiab qis. Raws li kev tsim khoom siv, cov kav dej profile yog hluav taws xob-welded, txias-dov los yog kub-dov thiab seamless. Cov khoom tuaj yeem muaj qhov sib txawv qhov siab thiab phab ntsa thicknesses. Kev txiav txim los ntawm kev txheeb xyuas, tsis yog tsuas yog vaj tsev cog khoom vaj tsev yog tsim los ntawm cov kav dej profile, tab sis kuj yog cov qauv arched, ntaiv thiab railings. Yog tias koj tsis paub yuav khoov cov yeeb nkab profile li cas, koj tuaj yeem siv ib txoj hauv kev, ntxiv rau qhov twg - hauv qab no.

Dab tsi yog qhov nyuaj ntawm cov txheej txheem?

Yuav ua li cas khoov cov yeeb nkab profile rau lub tsev cog khoom koj tus kheej? Yuav ua li cas yuav tsum tau ua kom tsis txhob lwj lub workpiece? Vim qhov tseeb tias cov khoom muaj lub zog loj, nws muaj peev xwm muab nws txoj kev nkhaus-nqus configuration tsuas yog nyob rau hauv siab. Nws qhov taw qhia tuaj yeem txo qis yog tias qhov chaw xaiv tau raug cua sov. Txawm li cas los xij, ntau tus pib muaj ntau yam teeb meem hauv kev ua haujlwm. Piv txwv li, wrinkles tuaj yeem tsim nyob rau sab hauv ntawm qhov profile. Yog li ntawd, cov khoom yuav zoo li corrugation. Yog tias qhov khoov tau ua tiav lawm, cescov folds no yuav sib npaug. Technically, cov txheej txheem dabtsi yog khoov yog nqa tawm nyob rau hauv ob txoj kev: tsuas yog siab los yog siab nrog cov cua kub ntxiv tuaj yeem siv rau cov khoom. Yog li, nyob rau hauv qhov chaw xaiv, sab hauv ntawm qhov profile yog raug compression, thiab sab nrauv yog stretched. Yuav ua li cas khoov ib tug profile yeeb nkab rau lub tsev xog paj kom lub workpiece nyob twj ywm lawm? Qhov kev txaus siab no tau piav qhia los ntawm qhov tseeb tias feem ntau cov hlau thaum lub sij hawm nruj tsis tuaj yeem tiv taus lub zog. Lwm qhov teeb meem yog vim qhov kev hloov pauv ntawm cov duab, qhov profile, uas yog nws cov tawg, poob kev sib raug zoo. Yog li ntawd, tom qab khoov, qhov chaw ntawm cov yeeb nkab yuav nyob rau hauv cov dav hlau sib txawv. Raws li cov kws tshaj lij, qhov no tuaj yeem ua tau yog tias txoj kev khoov raug xaiv tsis raug.

yuav ua li cas khoov ib tug profile yeeb nkab rau ib lub tsev xog paj koj tus kheej
yuav ua li cas khoov ib tug profile yeeb nkab rau ib lub tsev xog paj koj tus kheej

xav txog dab tsi?

Yog tias koj tsis paub yuav khoov cov yeeb nkab profile koj tus kheej li cas, koj yuav tsum coj mus rau hauv tus account qee qhov nuances. Piv txwv li, koj yuav tsum paub txog cov yas muaj peev xwm ntawm qhov profile. Txhawm rau txiav txim siab rau lawv, cov kev txwv xws li phab ntsa tuab, qhov loj thiab cov duab ntawm ntu yog siv. Paub txog cov txiaj ntsig no, suav lub vojvoog ntawm qhov ua tau sib npaug. Nws yog qhov tsis tsim nyog los khoov cov yeeb nkab nrog lub vojvoog me me. Txhawm rau txiav txim siab qhov tsawg kawg nkaus, siv qhov siab ntawm ntu. Qhov siab ntawm cov yeeb nkab yog ntsuas, thiab tom qab ntawd ob zaug ntawm phab ntsa thickness ntawm qhov profile yog xam los ntawm nws.

yuav ua li cas khoov ib tug profile yeeb nkab ntawm 90 degrees
yuav ua li cas khoov ib tug profile yeeb nkab ntawm 90 degrees

Raws li cov kws tshaj lij, qhov khoov zoo li cas yuav yog (tag nrho lossis ib nrab) nyob ntawm phab ntsa tuab. Lub thicker nws yog, qhov qisQhov tshwm sim uas, thaum lub sijhawm ua haujlwm, qhov yuav raug tsoo lossis qhov sib txawv yuav tsim rau ntawm nws qhov chaw. Qhov no yuav tsum tau coj mus rau hauv tus account los ntawm cov neeg uas yuav khoov lub 20x40 mm profile yeeb nkab nrog lawv tus kheej txhais tes. Cov kws tshaj lij craftsmen tsis pom zoo kom sim qhov no nrog cov khoom siv hlau dav. Hauv qhov no, nws yog qhov zoo dua los siv vuam. Tsis tas li ntawd, koj yuav tsum paub tus nqi ntawm qhov tsis kam. Qhov kev pom zoo no yog vim qhov tseeb tias cov hlau tsis tshua muaj hlau thiab cov pa roj carbon monoxide muaj qhov elasticity siab, thiab yog li ntawd, tom qab khoov, lawv tuaj yeem rov qab mus rau lawv cov qauv qub. Raws li qhov tshwm sim, koj yuav tau rov ua kom haum siv lub pre-made template. Raws li cov kws ua haujlwm paub txog, nws yog qhov yooj yim tshaj plaws los ua haujlwm nrog cov kav dej profile nrog tus nqi qis tshaj plaws ntawm cov yas tsis kam.

yuav ua li cas khoov ib tug profile yeeb nkab rau ib lub tsev xog paj
yuav ua li cas khoov ib tug profile yeeb nkab rau ib lub tsev xog paj

About txias khoov

Txoj kev no yog tsim nyog yog tias koj ua haujlwm nrog cov kav dej nrog ntu me me, uas yog 10 x 10 mm, 10 x 20 mm. Tsis tas li ntawd, phab ntsa thickness ntawm qhov profile yuav tsum tsis txhob ntau tshaj 1.5 hli. Yuav kom deform cov khoom, lub cev nqaij daim tawv ntawm lub tsev craftsman yog xav tau, uas tswj lub xeev ntawm cov hlau siv ib tug tshwj xeeb template. Cov cuab yeej no ntsuas txoj haujlwm ntawm cov yeeb nkab hauv kab rov tav thiab ntsug.

About preheating

Yog tias nws muaj teeb meem rau koj khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender, koj tuaj yeem ua kom sov cov khoom nrog lub qhov cub, roj burner lossis blowtorch. Lub workpiece yuav tsum ua tiav yuav tsum tig liab. Thaum ua kom sov, cov hlau yuav ua kom nruj dua thiab pliable, uas yog qhov tseem ceebyuav ua kom cov txheej txheem yooj yim dua. Tam sim no cov yeeb nkab tuaj yeem khoov tau, nyob ntawm qhov kev teeb tsa koj tau xaiv. Koj yuav tsum ua kom sov li cov yeeb nkab profile raws nraim hauv qhov chaw koj yuav khoov nws. Cov neeg uas txiav txim siab siv lub tshuab hluav taws xob lossis lub teeb yuav tsum paub tias yog tias cov hlau rov qab ua kom sov dua nrog cov cua txias ntxiv, nws yuav nkig. Tsis tas li ntawd, rhuab hlau muaj ib qho kev xav rov qab mus rau nws qhov qub. Yog li ntawd, koj yuav tau ua kom cov yeeb nkab kub, nkhaus profile energized kom txog thaum nws tau txias tag.

Nrog cov ntsiab lus sab hauv

Cov neeg uas xav paub yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab khoov lawv tus kheej tuaj yeem raug pom zoo kom sau nws cov kab noj hniav nrog xuab zeb, tshuab roj lossis dej. Nyob rau hauv cov ntaub ntawv no, cov khoom hlau tsis deformed, lub quav yuav muaj zog thiab txawm. Kev txiav txim los ntawm ntau qhov kev tshuaj xyuas, vim muaj cov khoom tsim nyog, txoj kev no yog qhov yooj yim heev thiab siv tau zoo heev. Txhawm rau khoov cov yeeb nkab profile tsis muaj cov yeeb nkab bender nrog koj tus kheej txhais tes, koj yuav tsum xub ua ob lub wedges los ntawm ntoo, uas yuav tom qab ntsaws cov kab noj hniav ntawm cov khoom hlau. Ua ntej, ib tug wedge yog tsav mus rau hauv ib kawg ntawm qhov profile. Tom qab ntawd sab hauv ntawm cov yeeb nkab yog ntim nrog xuab zeb. Nws yog ib advisable mus pre-sift thiab qhuav nws. Yog li hais tias nws tsis nchuav tawm ntawm cov yeeb nkab, koj yuav tsum tau ntsaws nws qhov thib ob kawg nrog ib tug ntoo wedge. Tom qab qhov xav tau qhov chaw yog rhuab thiab khoov yog ua. Thaum kawg ntawm kev ua hauj lwm, cov wedges raug tshem tawm, thiab cov xuab zeb yog nchuav tawm. Rau cov neeg uas txiav txim siab khoov cov yeeb nkab profile rau lub tsev cog khoom tsis muaj cov yeeb nkab bender siv dej,cov kws txawj pom zoo kom khov nws. Txoj kev no yog tsim rau lub caij txias. Koj tsuas yog yuav tsum tau sau lub workpiece nrog dej, thiab tom qab ntawd tuav nws sab nraud ib ntus kom txog thaum nws khov. Cov dej khov yuav tsis cia cov khoom tawg los ntawm kev kub siab. Hauv qhov no, ntoo wedges yuav tsis ua haujlwm. Tus kws tsim khoom hauv tsev yuav tau txuas ob qhov kawg ntawm qhov profile.

yuav ua li cas khoov ib lub yeeb nkab profile
yuav ua li cas khoov ib lub yeeb nkab profile

About sector cutting

Rau cov neeg uas tsis paub yuav khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender, peb tuaj yeem pom zoo kom siv lub kaum sab xis grinder (grinder) nruab nrog lub tshuab txiav. Lub ntsiab ntawm cov txheej txheem yog ua ob peb transverse triangular txiav (txiav) nyob rau hauv ib tug hlau khoom. Tom qab txiav tawm cov seem ntawm qhov profile, lawv raug tshem tawm. Tom qab ua tiav cov kauj ruam no, koj tuaj yeem khoov cov yeeb nkab profile ob leeg ntawm 90 degrees thiab ntawm lwm lub kaum sab xis yam tsis muaj kev siv zog. Tom qab ntawd, koj yuav welding cov npoo ntawm cov txiav siv nyias electrodes. Tus naj npawb ntawm cov slots nyob ntawm qhov khoov vojvoog. Qhov loj dua, qhov tsawg dua qhov yuav xav tau. Feem ntau koj tuaj yeem txwv koj tus kheej kom tsuas yog peb. Kev txiav txim los ntawm ntau qhov kev tshuaj xyuas, cov txheej txheem no yog qhov nyuaj, tab sis qhov tshwm sim yog qhov zoo: curvature thiab deformation tsis tau pom nrog txoj kev khoov no. Thaum kawg, thaj chaw uas lawv tau ua haujlwm los ntawm vuam yog ua tib zoo polished, kom cov khoom zoo nkauj heev. Txawm hais tias tsis muaj qhov npoo npoo thiab tsis muaj qhov txo qis hauv lub zog ntawm qhov taw tes, kev txiav cov ntu tsis muab qhov zoo meej roundness. Qhov tseeb yog qhov chaw ntawm qhov quavsawv cev los ntawm ob peb ntu ncaj nraim uas nyob ntawm lub kaum sab xis rau ib leeg.

Siv lub caij nplooj ntoo hlav

Ntau zaus, cov neeg pib xav paub yuav ua li cas khoov cov yeeb nkab profile kom tsis txhob deform lossis tawg. Rau lub hom phiaj no, cov kws tshaj lij qhia kom siv lub caij nplooj ntoos hlav hlau nyias nyias thiab ntev. Nws tuaj yeem ua los ntawm cov hlau hlau nrog 2 hli hla ntu. Txhawm rau kom cov khoom txav tau yooj yim hauv cov yeeb nkab, nws yog ib qho tsim nyog yuav tsum tau khoov cov hlau raws li cov duab profile kom txhua ntu ntawm lub caij nplooj ntoos hlav me dua li qhov sib thooj. Tom qab lub caij nplooj ntoos hlav npaj txhij, nws tau muab tso rau hauv qhov profile, thiab ib txoj hlua khi rau ib qho kawg ntawm nws. Qhov kev ntsuas no yog qhov tsim nyog kom thaum kawg ntawm kev ua haujlwm koj tsis muaj teeb meem tshem lub caij nplooj ntoos hlav los ntawm qhov profile. Tom ntej no, xaiv ntu ntawm cov yeeb nkab yog rhuab thiab pib khoov. Thaum kawg ntawm kev ua haujlwm, cov kws tshaj lij tsis pom zoo kom siv dej kom txias rau qhov profile. Txwv tsis pub, cov kab nrib pleb tuaj yeem tshwm rau ntawm qhov chaw ntawm cov khoom los ntawm qhov kub thiab txias hloov tam sim ntawd. Nws yog qhov ua tau tias yav tom ntej xws li profile yuav tawg. Kev txiav txim siab los ntawm kev tshuaj xyuas ntau, nws yog qhov zoo tshaj plaws kom txias cov yeeb nkab profile nrog cov roj cav siv. Rau cov neeg uas xav paub yuav ua li cas khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender, cov kev qhia hauv qab no tuaj yeem pom zoo.

Kev

Txhawm rau ua tiav qhov khoov, tus thawj tswj hwm txheej txheem ntaus ntu xaiv ntawm qhov profile nrog lub tshuab muaj zog nrog rauj. Koj yuav tau ua hauj lwm rau ntawm ib lub anvil nrog ib puag ncig saum. Txhawm rau tiv thaiv lub workpiece los ntawm slipping, nws yog ruaj ruaj nrog clamps. Tom qabkev npaj ua hauj lwm mus rau khoov. Thaum ua hauj lwm nrog rauj hnyav, koj yuav tsum tau ceev faj li sai tau. Qhov tseeb yog tias los ntawm kev quab yuam ntau dhau, cov khoom tuaj yeem flatten. Kev txiav txim los ntawm ntau qhov kev tshuaj xyuas, nws yog qhov zoo tshaj los tswj nrog ib ntu uas nws qhov ntev tsis tshaj 1 meter.

Raws li tus qauv

Hauv qhov no, lawv ua haujlwm ntawm pob zeb, asph alt lossis pobzeb qhov chaw. Ua ntej khoov cov yeeb nkab profile yam tsis muaj cov yeeb nkab bender, lub hauv paus yuav tsum xub tau nruab nrog arc contour. Qhov no yog ua los ntawm kev siv cov pins los yog cov kav hlau nyias, uas tau tsav mus rau hauv lub platform nrog lub sledgehammer. Tom ntej no, lub workpiece yog tsau los ntawm welding rau thawj tus pin. Tom qab ntawd lawv pib maj mam khoov nws, vuam nws mus rau cov pins lossis cov kav dej tom ntej. Tom qab qhov elasticity ntawm cov yeeb nkab profile tau dhau los ua tsawg, nws tuaj yeem raug tshem tawm ntawm lub hauv paus. Lub welded workpiece yog dismantled siv lub grinder. Nws yog txaus kom tsuas yog txiav cov khoom. Qhov tsis zoo ntawm txoj kev no yog qhov tsis tshua muaj dabtsi yog khoov. Tsis tas li ntawd xwb, tus tswv yuav tau siv zog ua lub cev ntau heev.

Txoj kev xauj tsev nyob hauv kev tsim txom

Txhawm rau tsim lub siab tsim nyog rau khoov cov yeeb nkab profile, qhov no koj yuav tau siv lub tsheb. Nws yog ib qho tseem ceeb uas nws cov log yog sab-steered thiab tsis muaj fenders. Ua ntej ntawm tag nrho cov, ib tug zawj yog ua nyob rau hauv lub pob zeb ua los ntawm steel, nyob rau hauv uas lub workpiece yuav nyob. Lub ntsiab lus ntawm txoj kev no yog nyob rau hauv txoj kev dov ntawm lub log raws cov yeeb nkab profile.

Siv lub mandrel

Txoj kev no yog tsim rau cov khoom profile nrogphab ntsa qhov siab tsis tshaj 25 mm. Koj yuav tau ua hauj lwm nrog kev pab los ntawm ib tug tshwj xeeb mandrel. Lawv muab tso rau ntawm lub rooj zaum ua haujlwm. Qhov loj tshaj plaws yog tias nws nto yog txaus rau xws li ib tug ntaus ntawv. Cov khoom siv rau mandrel yuav yog ib daim ntawv tuab ntawm MDF lossis plywood. Tom qab cov duab xav tau raug txiav, koj yuav tsum xav txog yuav ua li cas koj yuav nruab nws ntawm lub rooj zaum ua haujlwm. Cov kws tshaj lij craftsmen ua ob peb qhov ntawm ntug ntawm lub rooj, los ntawm qhov profile yeeb nkab yuav txuas rau saum npoo nrog ib kawg. Yog li ntawd, tib lub qhov yuav tsum tau ua thaum kawg ntawm lub workpiece. Lub mandrel yog tsau rau lub workbench nrog ob lub clamps. Tom qab ua tiav qhov kev npaj ua haujlwm, lawv pib khoov cov yeeb nkab. Cov kws tshaj lij pom zoo kom ua qhov no smoothly thiab tsis muaj jerks, maj mam nce siab. Nws yog qhov zoo dua los ua haujlwm nrog ob peb qhov khoob ntawm cov hlau mandrel ua los ntawm kaum.

Cov kws tshaj lij qhia dab tsi?

Yog hais tias cov yeeb nkab muaj qhov siab ntawm qhov tsawg dua 10 hli, nws tsis tas yuav sau cov xuab zeb, dej lossis lub caij nplooj ntoo hlav. Fillers yog tsim nyog nyob rau hauv cov ntaub ntawv uas cov khoom uas muaj ib tug profile saum toj no 1 cm yog khoov, Yog hais tias koj tsis paub seb yuav siv txias dabtsi yog khoov los yog kub dabtsi yog khoov, ces koj yuav tsum tau sim cov khoom hlau. Raws li cov kws txawj, nyob rau hauv lub xub ntiag ntawm ib tug yeeb nkab bender, ib tug txias ib tug kuj haum. Yog tias cov cuab yeej no tsis nyob ntawm tes, cov kws ua haujlwm paub txog ua cov hauv qab no. Ua ntej ntawm tag nrho cov, ib kawg ntawm lub workpiece yog nruj nreem clamped nyob rau hauv ib tug lwm, thiab ib tug yeeb nkab nrog ib tug loj nyob rau hauv seem yog muab tso rau hauv lub thib ob. Tom ntej no, khoov yog sim ua manually. Yog tias cov yeeb nkab pib khoov los ntawm kev cuam tshuam lub cev, ces koj tuaj yeem ua taudispense nrog preheating. Yog tias koj muaj teeb meem nyob rau theem no, feem ntau koj yuav tau ua kom sov qhov chaw xaiv ntawm lub workpiece. Yog tias qhov kev pom zoo no tsis quav ntsej, ces cov yeeb nkab profile yuav flatten.

Cov neeg uas txiav txim siab siv xuab zeb los ua ib qho muab tub lim yuav tsum ua tib zoo sift nws. Ua ntej, lub sieve yog siv rau lub hom phiaj no, lub hlwb uas muaj ib txoj kab uas hla tsis tshaj 2.5 hli. Cov txheej txheem no yog qhov tsim nyog kom pob zeb thiab pebbles me me tsis nyob hauv cov xuab zeb. Tom qab cov xuab zeb hla dhau 0.7 hli hlwb. Yog hais tias koj tawm txhua yam raws li nws yog, ces vim muaj cov plua plav inclusions thaum cua sov, cov xuab zeb yuav sinter. Judging los ntawm kev txheeb xyuas, nws yuav luag tsis yooj yim sua kom manually khoov profile kav nrog ib txoj kab uas hla loj. Yuav kom tsis txhob nkim lub zog thiab tsis lwj lub workpiece, nws yog qhov zoo tshaj rau koj mus yuav ib tug tshwj xeeb ntaus ntawv, uas yog hu ua ib tug yeeb nkab bender. Cov cuab yeej no muaj lub log tsav uas txav raws lub ntsej muag, khoov qhov profile hauv qhov xav tau. Cov yeeb nkab bender tuaj yeem ua tau phau ntawv (lub log yog tsav los ntawm tus kov tshwj xeeb) thiab hluav taws xob.

yuav ua li cas khoov ib tug profile yeeb nkab koj tus kheej tsis muaj cov yeeb nkab bender
yuav ua li cas khoov ib tug profile yeeb nkab koj tus kheej tsis muaj cov yeeb nkab bender

Nyob rau hauv rooj plaub tom kawg, cov khoom, txiav txim los ntawm kev tshuaj xyuas, yog ntau smoother. Tsis tas li ntawd, nws txuag lub sijhawm. Nws tsis yog qhov tsim nyog los yuav ib lub fixture yog tias koj tsis npaj yuav khoov cov kav dej. Nws yog qhov zoo tshaj los xauj ib lub cuab yeej. Yog tias koj muaj kev paub me ntsis, ces nws yog qhov zoo dua tsis txhob muaj kev pheej hmoo, tab sis siv cov kev pabcuam ntawm cov kws tshaj lij.

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