Mitsubishi Electric LY2-3750-B1T User manual

A180E301P02
INSTRUCTION MANUAL
SINGLE-NEEDLE LOCKSTITCH UPPER AND LOWER FEED
AUTOMATIC UNDERTRIMMER
INDUSTRIAL SEWING MACHINE
LY2-3750-B1T
MODEL

PRECAUTION BEFORE STARTING OPERATION
1 Safety Precautions
1 . Whenturningthepoweron,keepyourhandsandngersawayfromtheareaaround/
undertheneedleandtheareaaroundthepulley.
2 . Thepowermustbeturnedo󱐯whenthemachineisnotused,orwhentheoperator
leaveshis/herseat.
3 . Thepowermustbeturnedo󱐯beforetiltingthemachinehead,installingorremoving
the“V”belt,adjustingthemachine,orreplacingparts.
4 . Avoidplacingngers,hairs,obstacles,etc.nearthepulley,“V”belt,bobbinwinder
wheel,ormotorwhenthemachineisinoperation.Injurycouldresult.
5 . Don’tputngersintothethreadtake-uplevercover,around/undertheneedle,or
pulleywhenthemachineisinoperation.
6 . Ifthebeltcover,thengerguard,and/ortheeyeguardareinstalled,don’toperate
themachinewithoutthesesafetydevices.
2 Precaution before Starting Operation
1 . Ifthemachine’soilpanhasanoilsump,neveroperatethemachinewithoutllingoil
init.
2 . Ifthemachineislubricatedbyadropoiler,neveroperatethemachinewithout
lubricating.
3 . Whenanewsewingmachineisoperated,verifytherotationaldirectionofthepulley
withthepoweron.
 (Thepulleyshouldrotatecounterclockwisewhenviewedfromthepulley.)
4 . Verifyvoltageand(singleorthree)phaseindicatedonthenameplateofthemotor.
3 Precaution for Operating Conditions
1 . Avoidusingthemachineatabnormallyhightemperature(35℃orhigher)orlow
temperature(5℃orlower).Otherwise,machinefailuremayresult.
2 . Avoidusingthemachineindustyconditions.
3 . Avoidusingthemachineinconditionslledwithalotofelectricnoisessuchashigh-
frequencywelders.
INTRODUCTION
ThankyouverymuchforpurchasingMitsubishiindustrialsewingmachine.
Pleasereadthisinstructionmanualbeforeoperatingthesewingmachine.Pleasereadalso
“SafetyManual”,“InstructionmanualforMitsubishiLimiservoX”andoperatethesewing
machinecorrectlyandsafely.

CONTENTS
PREPARATION FOR OPERATION ……………………………………………… 1
1Adjustmentoftheneedlestoppingposition……………………………………… 1
USAGE PRECAUTION ……………………………………………… 1
1Installationofthekneelifter ……………………………………………………… 1
2Lubrication …………………………………………………………………………… 2
3Lubricationcondition………………………………………………………………… 2
4Adjustmentoflubricationtotherotatinghook ………………………………… 2
5Adjustmentoflubricationtotheuppershaft …………………………………… 2
6Adjustmentoftheoilpump………………………………………………………… 2
7Periodicalcleaning…………………………………………………………………… 3
8Precautionforthebuilt-intypedetector ………………………………………… 3
9Installationofthebeltcover ……………………………………………………… 3
:Precautiononoperation …………………………………………………………… 3
HOW TO USE ……………………………………………… 4
1Installationoftheneedle …………………………………………………………… 4
2Windingofthebobbinthread……………………………………………………… 4
3Threadingoftheneedlethread…………………………………………………… 5
4Adjustmentoffeed(stitch)lengthandbackstitch……………………………… 5
5Balanceofthreadstension ………………………………………………………… 5
6Adjustmentoftheneedlethreadtension………………………………………… 6
7Adjustmentofthebobbinthreadtension………………………………………… 6
8Adjustmentofthepresserfootpressure………………………………………… 6
9Adjustmentofthefeeddogheight ……………………………………………… 7
:Adjustmentofthefeeddoginclination…………………………………………… 7
AAdjustmentofforward/backwardstitchlength………………………………… 7
BManualPresserbarlifter…………………………………………………………… 8
CAdjustmentofthefeedfootandthepresserfoot ……………………………… 8
DAdjustmentofthefeedtiming …………………………………………………… 10
EAdjustmentofthethreadtrimmerdevice ……………………………………… 10
FTherotatinghook,bobbincase,andbobbin……………………………………… 13
GAdjustmentofthegapbetweenthepulleyandthemachinehead…………… 13
SPECIFICATIONS ……………………………………………… 14

1 Installation of the knee lifter
1 . Pulloutkneeliftershafts(ontherightand
left)asfaraspossible,andsetthem.
2 . Installthedrivingcrankoneachshaft.
3 . Setalinkbetweentherightandleftdriving
crankstoconnectthem.
4 . Installthekneelifterleverontheleftdriving
crank.
5 . Theoperatingforcecanbelightenedby
connectingalinkwiththeinsidescrew Ⓐin
theleftdrivingcrankasshowninthedotted
lineofthegure.However,inthiscasethe
operationamountofthekneelifterleveris
increased.
PREPARATION FOR OPERATION
1 Adjustment of the needle stopping position
1 . Adjustment of “UP” position
Whenthepedaliskickeddownbyheel,themachinestopsat“UP”position.
Ifmarksdeviatelargerthan3mm,adjustasfollows.
( 1 )Disconnecttheplug(12pins)ofcablefromthemachinehead.
( 2 )Runthemachineandstopat“UP”position.
( 3 )Whileholdingthepulley,insertthe“Adjustingtool”inthehole Ⓐ,thenturnthetool.
2 . Adjustment of “Down” position
Whenthepedalis“Neutral”themachinestopsat“Down”position.
Ifmarksdeviatelargethan3mm,adjustasfollows.
( 1 )Disconnecttheplug(12pins)ofcablefromthemachinehead.
( 2 )Runthemachineandstopat“Down”position.
( 3 )Whileholdingthepulley,insertthe“Adjustingtool”inthehole Ⓑ,thenturnthetool.
3 . Conrmthestopoperation,thensettheplug(12pins)comingfromthemachineheadintothe
receptacle.
USAGE PRECAUTION
Timingmark
Rotatingdirection
1stmark Upposition
Downposition
White
Black3rdmark
3rdmark
1stmark
Adjustingtool
later
earlier
Blackmark
Whitemark
Timingoftheneedle
Ⓐ
Ⓑ
Kneeliftershaft
Drivingcrank
Kneelifterlever
Collar
Hingedscrew
Link
screw Ⓐ
—1 —

2 Lubrication
Filltheoilreservoirwithoilupto“H”line.
Oillevelshouldbeperiodicallychecked.Ifoillevel
isfoundbelow“L”linereplenishoilto“H”line.
Foroil,use“MC70M”speciedbyMitsubishi.
※Refer
 MC70M：Specicgravity(15℃ )=0.86(g/cm3)
  ：Viscosity(40℃ )=10.9(mm2/s)
Kneelifterpin
Drainoilscrew
Ⓗ Ⓛ
3 Lubrication condition
Checkthattheoilsplashedtheoilsightwindow.
Oilsightwindow
4 Adjustment of lubrication to the
rotating hook
Adjustthelubricationamountoftherotatinghook
byturningthescrew Ⓐ.
IncreaseDecrease
ScrewⒶ
5 Adjustment of lubrication to the
upper shaft
Removethefaceplate,andadjustthelubrication
amountbyturningtheuppershaftlubrication
adjustingscrew.
Increase Decrease
Crank
Uppershaft
Maximum Standard Minimum
AdjustingscrewⒶ
6 Adjustment of the oil pump
Thestandardadjustmentisasfollows:
Theadjustingplatekeepsthebypassholefully
closed.Todecreasesplashing,openthebypass
holeappropriately.
Adjustingplate
Bypasshole
USAGE PRECAUTION
—2 —

7 Periodical cleaning
1 . Machine
2 . Motor
Removedustfromthemotorltereveryoneortwomonths.(Continuedoperationwiththelter
cloggedwithlintordustmayoverheatthemotor.)
3 . Control Box
Removedustfromtheconnector.(Iftheconnectoriscoveredwithdust,themachinemight
malfunction.)
8 Precaution for the built-in type
detector
1 . Sincetheopticaltypedetectingelement
isusedinthedetector,preventdustoroil
fromstickingtothedetectingplatewhen
thesewingmachinepulleyisremovedfor
adjustment.
 Iftheyhavestuck,wipethemo󱐯with
softclothcarefullysothatthesurfaceis
notscratched,donotletoilpermeatethe
clearanceonthedetectingplate.
2 . Incaseofdisconnectionoftheposition
detectorconnector,runningo󱐯thebelt
orcompleteconstraintandoverload,the
motorisautomaticallyturnedo󱐯after
predeterminedtimetopreventburningof
themotor.(However,incaseofhalf-constraint
andoverload,thepowermaynotbeturned
o󱐯.)Afterthefailureiseliminated,thenormal
operationisresumedbyturningo󱐯thepower
oncethenturningonagain.
 Thesameoperationoccursforthedetector
malfunctionorthelinebreakage.
9 Installation of the belt cover
1 . Installthebeltcoveronthemachineside
forsafety.Refertotheprovidedinstruction
documentcontainedinthesamepackage.
2 . Installthebeltcoveronthemotorsidefor
safety.
: Precaution on operation
( 1 ) Whenthepoweristurnedonoro󱐯,keepfoot
awayfromthepedal.
( 2 ) Itshouldbenotedthatthebrakemaynot
workwhenthepowerisinterruptedor
powerfailureoccursduringsewingmachine
operation.
( 3 ) Sincedustinthecontrolboxmightcause
malfunctionorcontroltroubles,besureto
keepthecontrolboxcovercloseduring
operation.
( 4 ) Donotapplyamultimetertothecontrol
circuitforchecking,otherwisevoltageof
multimetermightdamagesemiconductor
componentsinthecircuit.
USAGE PRECAUTION
Hook
Feeddog
Hook
Feedbar
Oilpumpscreen
●Removethethroatplateand
cleanthefeeddog.Reassembly
shouldbedonebyscrewingin
thescrew2-3rotationsbyhand
atrst,thentighteningthem
evenlyusingalong-shafted
screwdriver.
●Leanthemachineheadand
cleanthehookandremove
anydustand/orlintinsidethe
bobbincase.
●Leanthemachineheadand
removeanydustand/orlinton
theoilpumpscreen.
—3 —

1 Installation of the needle
Note: Before installing the needles, be sure to turn o󱐯 the power.
HOW TO USE
Inserttheneedleuptothebottomof
needleclampandtightenthescrew
keepingthelonggrooveside
facingtotheleft.
Insufficientinsertion Needledistorted
Gap
Longgroove
leftside Timingmark
forDB×1
Timingmark
forDP×17
Needlebar
Note：Ifthreadsnappingoccursduringreversesewingwith
polyesterthreads,itmaybeavoidedbyttingtheneedle
withthelonggrooveshiftedtothefrontside.Normally,
avoidttingtheneedlewiththegroovefacingbackward.
BothneedlesDP × 17and
DB × 1canbeused.
Usethetimingmarksas
showninthegure.
2 Winding of the bobbin thread
Note: When bobbin thread is wound, keep the presser foot lifted.
Adjustment ●Tension of wound thread Slackwindingisrecommendedforpolyesterthreadand
nylonthread.
●Conically wound thread Movethethreadguidetowardsmallerdiameterofwound
threadlayer.
●Amount of wound thread Loosenthewindingamountadjustmentscrewtodecrease
threadwindingamountandtightenthescrewtoincrease
threadwindingamount.
Windingtension
adjustmentnut
Evenwinding
amountof80%
offullcapacity
Windingamount
adjustmentscrew
Threadguide
—4 —

3 Threading of the needle thread
Withthethreadtake-upleverlocatedattheuppermostposition,passtheneedlethreadintheorder
showninthefollowinggure.
4 Adjustment of feed (stitch)
length and backstitch
●Adjustmentoffeed(stitch)length…Adjustfeed
lengthbyturningthefeedlengthsettingdial
whilepushingPUSHlever.
●Backstitch…Directionofstitchingcanbe
reversedbydepressingthereversesewing
leverorpushingthetouchbackswitch.
●Touchbackswitch…Inthecasethattheswitch
isturnedtothearrowdirectionby180°,no
backwardstitchingoccursevenwhenthe
switchispushed.
 Usethisfunctiontoavoidthemalfunctionsuch
asunnecessaryreversestitchinginthecase
thatthefabriccomesincontactwiththeswitch
duringsewing.
5 Balance of threads tension
HOW TO USE
①
②
③
④
⑤
⑥
⑦
⑧
⑨
⑩
⑪
Leadthethreadrightward
PUSHlever
Feedlength
settingdial
Reversesewing
lever
Thread
③
④
⑤
⑥
⑧
Touchbackswitch
A○
B×
C×
Balancedtension
Tighttheneedlethreadtensionor
loosethebobbinthreadtension
Loosetheneedlethreadtensionor
tightthebobbinthreadtension
—5 —

6 Adjustment of the needle
thread tension
●Theneedlethreadtensionshouldbeadjusted
onthebasisofthebobbinthreadtension.
●Adjusttheneedlethreadtensionbyturningthe
threadtensionnut.
 Theneedlethreadtensioncanbealsoadjusted
bychangingintensityandmovablerangeof
thethreadtake-upspringincaseofsewingthe
specialfabricandthread.
7 Adjustment of the bobbin
thread tension
1 . Thebobbinthreadtensioncanbeadjusted
byturningthescrewⒶ.
8 Adjustment of the presser foot
pressure
1 . Adjustthepresserfootpressureaccordingto
thefabricbyturningthepressureadjusting
screw.
2 . Pressureontheboththepresserfootand
thefeedfootcanbeadjusted.(Theadjusting
screwpositionisfactory-adjustedasshownin
thegure.)
3 . Sewingpressureshouldbeadjustedtothe
minimumrequiredstrength.
HOW TO USE
Tighten
Loosen
Threadtensionnut
ScrewⒶ
Threadtensionspring
Loosen
Tighten
Strengthen
Weaken
Standard
30mm
〈Presserfootpressure〉
Standard
20mm
Weaken Strengthen
〈Feedfootpressure〉
—6 —

9 Adjustment of the feed dog
height
1 . Turnthepulleyandstopitattheposition
wherethefeedliftingrockshaftcrankswings
totheinnermostposition.
2 . LoosenthescrewⒶ.
 Note:Becarefulnottomovethefeedlifting
rockshaftcrankinthelateraldirection.
3 . Adjustthefeeddogheightbyswingingthe
feedliftingrockshaftforkandmovingthe
feedbar.
4 . Afteradjusting,fullytightenthescrewⒶ.
The feed dog height is factory-adjusted to 1.0 mm.
Throatplate
Feedliftingrockshaftfork
1.0mm
Feedbar
Feeddog
Feedliftingrockshaftcrank ScrewⒶ
: Adjustment of the feed dog
inclination
Thefeeddoghasbeensettostandard
(horizontally).Ifnecessary,adjusttheinclination
accordingtothematerialtobesewnasfollows.
1 . SlightlyloosenscrewⒶ.
2 . Whilepressingthegroovelocatedinthe
eccentricpinbyusingascrewdriver,turn
theeccentricpinclockwise(tolowerthefront
end)orcounterclockwise(toliftthefrontend).
3 . Afteradjusting,tightenthescrewⒶ.
Mark
Eccentricpin
Screwdriver
ScrewⒶ
A Adjustment of forward/
backward stitch length
1 . LoosenfoursetscrewsⒶ.
2 . Turnthestitchlengthadjustingpinuntilthe
desiredlengthisreachedasfollows:
( 1 ) Clockwise:Increasesthestitchlengthin
forwardsewing,anddecreasesthestitch
lengthinbacksewing.
( 2 ) Counterclockwise:Decreasesthestitch
lengthinforwardsewing,andincreasesthe
stitchlengthinbacksewing.
HOW TO USE
SetscrewⒶ Bracket Stitchlengthadjustingpin
Positionofmarkon
theeccentricpin Feeddog
Horizontal Standard
Rightabove Frontup
(MAX.)
Rightbelow Frontdown
(MAX.)
—7 —

B Manual Presser bar lifter
1 . Turnthepresserbarlifterinthedirectionof
thearrow.Thisraisesthepresserfoot.
C Adjustment of the feed foot
and the presser foot
1 . Adjustment of alternating movement
(1) Thealternatingmovementonthefeedfoot
andthepresserfootcanbeadjustedbyusing
theadjustingdiallocatedonthetopcover.
(2)Facethedesirednumberprintedonthe
dialtothematchingmarklocatedonthe
topcover.
(3) Thenumberprintedonthedialrepresentsthe
possibleprotrusionofthefeedfootandpresser
footfromthethroatplatewhenthealternating
movementsontheseareevenlyset.
(4)Ifthealternatingmovementsareevenly
set,theycanbereadjustedupto2.0to
5.0mm.
2 . To change the balance of the alternating movements
between the feed foot and presser foot
(1) Forexample,toincreasetheriseofthefeed
foot,anddecreasetheriseofthepresserfoot.
①Removetherubberpluglocatedonthetop
cover.
②Turnthepulleyuntilthepresserfootis
slightlyraisedfromthethroatplate.
③LoosenthesetscrewⒶ(ontherightside)
locatedonthefeedliftingrockshaftcrank
(right).
④Thebuilt-inspringpullsdownthepresser
footuntilitmakescontactwiththethroat
plate.Then,tightenthesetscrewⒶ.
⑤Thiscompletestheadjustment,i.e.,the
protrusionofthepresserfoothasbeen
decreasedbyasetdistance.And,the
verticalmotionofthefeedfoothasbeen
increasedbythatsamedistance.
(2)Asacontrarycase(1),todecreasetherise
ofthefeedfoot,andincreasetheriseofthe
presserfoot.
 First,turnthepulleyuntilthefeedfootis
slightlyraisedfromthethroatplate.Next,
loosenthescrewⒶ.Finally,tightenthe
screwⒶagain.
 Thisdecreasestheriseofthefeedfoot.
HOW TO USE
Presserbarlifter
Alternatingmovement
adjustingdial
Matchingmark
Presserfoot
Feedfoot
2.0to5.0mm
Rubberplug
SetScrewⒶ
Feedliftingrock
shaftcrank(right)
—8 —

3 . Installing the feed regulator bracket
Shoulditbenecessarytodismountandthefeed
regulatorbracketanditsrelatedparts,usethe
procedureexplainedbelow.
Note:Ifthefeedregulatorbracketispoorly
positioned,theresultantalternatingmovements
maybetooshortorlong,causingdefective
machineoperation.
( 1 ) Settheclearancebetweenspecialscrew
Ⓐlocatedontheregulatorstudandthe
sidewallofthemachinearmto26.5mmas
illustratedtotheleft.(Usea26.5mmspacer
betweentheseparts.Thisfacilitatesthe
operation.)
( 2 ) Withthefeedregulatorstudheldas
explainedinstep( 1 )above,adjustthefeed
regulatorbracket.Thisadjustmentshould
insureaclearanceof12mmbetween
theperipheryofpinⒷlocatedonthe
feedregulatorbracketandthetopcover
mountingfacelocatedonthearm.Tighten
screwsⒸ.
4 . Feed pitch adjustment of feed foot
Theratiooftheupperfeedamount(ofthefeed
foot)tothelowerfeedamount(ofthefeeddog)
hasbeenadjustedto1:1.However,thefeedfoot
feedingamountcanbeincreasedordecreased
dependingontheoperatingconditions.
( 1 ) Loosenthenutlocatedontheupperfeed
rockshaftcrank(left),andshifttoadjust
thepositionofthesquareblockupwardor
downward.
 Upperposition:Feedpitch→Small
 Lowerposition:Feedpitch→Large
HOW TO USE
Ⓑ
Ⓒ Ⓐ
Feedregulatorbracket
Feedregulatorstud
26.5mm
12mm
Nut
Upperfeedrock
shaftcrank(left)
—9 —

D Adjustment of the feed timing
1 . Thestandardpositionoftheeccentricfeed
camandeccentricfeedliftingcamare
illustratedtotheright.
2 . Toadjusttheposition,rstopenthetop
cover.Properlyslidetheeccentriccam.
3 . Theeccentricfeedcamcanalsobeadjusted
byremovingtherubberpluglocatedonthe
topcover,andtheuppereccentricfeedlifting
camcanalsobeadjustedbyremovingthe
rubberpluglocatedonthearm.
 Inthelattercase,however,thebuilt-inbevel
gearisconcealed;careshouldbetakenwhen
adjusting.
E Adjustment of the thread trimmer device
1 . Conguration of the thread trimmer devise
2 . Precautions for adjustment
TheLY2-3750usesathreadtrimmerdrivesystemwithalowershaftcam.Soifyouturnthe
machinebyonerevolutionwiththethreadtrimmersolenoidactivated(i.e.,withtherollerlocated
onthecamfollowercrank( 2 )keptengagedwiththethreadtrimmercam),themovableknife(left)
willmakecontactwiththeneedle,breakingthecontactingparts.
Activatethebuilt-insolenoidonlywhenthenormalthreadtrimmingcycleisactive(lowerposition
→upperposition).
HOW TO USE
Bevelgear
foruppershaft
1stscrew 1stscrew
Rubberplug
Rubberplug
Topcover
Uppershaft 2ndscrew
Uppereccentricfeed
liftingcam
Eccentric
feedcam
Fixedknifebracketunit
Threadguide
Fixedknife
Movableknife(left)
Knifedrivingcrank
Knifedrivingshaft
Camfollower
crank(1)
Camfollower
crank(2) Drivelever Stopperplate
Stopper
Spring
Spring
Coilspring
Collar
Threadtrimmercam
Flexiblewire
Knifebaseunit
Threadtrimmersolenoidunit
Threadtrimmersolenoid
—10 —

3 . Relationship between the xed knife and the
movable knife (left) edge
(1)Thestandardpositionisillustratedtothe
right.
(2) Ifthedistance(0.3mm)istoowide,sucha
situationmayallowfor“triple”threadbreakage
tooccur,resultingindetachedneedlethread
afterthreadsarecut.Also,ifitistoonarrow,
suchasituationmayleadtounexpectedly
uncutthreads.Pleasekeepthisinmind.
(3)Theadjustmentnecessaryinstep(2)can
bedonebycorrectlyinstallingthexed
knifebracketunitorcorrectlymounting
thexedknife.
(4)Thexedknifebracketunithasbeen
installedusingscrewⒶwiththebobbin
caseholderpositionbracketremoved(See
Fig.totheright).
4 . Knife driving shaft
(1) Thestandardpositionisillustratedtotheright.
(2) Whenassembling,theknifedrivingshaftmust
rstbeputthroughtheknifedrivingcrank.
(3)Thecamfollowercrank(1)mustbe
positionedasillustratedtotheright,and
settotheatontheknifedrivingshaft.
( 4 ) Thestoppermustbesettotheatonthe
knifedrivingshaftinsuchawaythatthe
knifedrivingshaftissnugandsmoothly
turnsintheshaftdirection.
5 . Installing the thread trimmer solenoid unit
(1)Operationstrokeofthethreadtrimmer
solenoid
①Standardoperationstrokeis6mm.
②ThisstrokecanbeadjustedbyusingnutⒶ.
(2)Installingtheunit
①Theunitcanbemountedbyusingscrews
Ⓑ and Ⓒ.
②Clearanceof1mmmustbeinsured
betweenthedrivingleverandcamfollower
crank(2)withstoppernutⒶmadecontact
withthesolenoid.
③Insuchasituation,activatingthesolenoid
shouldcreateaclearanceof0.5mm
betweencamfollowercrank(1)and(2).
Thissituationisstandard.Tomeetthis
standard,slidethesolenoidmounting
bracketinthedirectionofthearrowas
illustrated,ifadjustmentisneeded.
HOW TO USE
ScrewⒶ
Fixedknife
bracketunit
Drivinglever
Camfollower
crank(2)
Camfollowercrank(2)
Camfollower
crank(1)
Solenoidmounting
bracket
6mm
1mm
Ⓒ
ⒶⒷ
0.5mm
Coilspring
Camfollowercrank(1)
Camfollowercrank(2)
Stopper
Bushing
87.5mm
Knifedrivingshaft
Movableknife(left)
0.3mm
Fixedknife
(Knifeedge)
—11 —

6 . Installing the thread trimmer cam
(1)Facethe2ndtimingmarkⒶ(Green)
locatedonthepulleytothematchingmark
onthearm.
(2)Withthethreadtrimmersolenoidactivated,
turnthethreadtrimmercamforwarduntil
thecammakescontactwiththeroller.
Then,setthecam.
(3)Withthethreadtrimmersolenoid
deactivated,allowthecamfollowercrank
(2)toreturntoitsoriginalposition.This
shouldcreateaclearanceof0.5to1.0mm
betweenthecamandrollerend.This
distanceisstandard.
7 . Adjustment of knives engagement
(1) Positionofmovableknife(left)andxedknife
①Seetheillustration.Thestandarddistances
fromtheneedlecenterare7.5mmand
5mmfromthemovableknife(left)and
xedkniferespectively.
(2)Adjustmentofknivesengagingamount
①Withthesolenoidactivated,turnonthe
machine.Thisturnsthethreadtrimmer
camwhichturnsthemovableknife(left).
Whenthemovableknife(left)hasmovedto
itsfarthestdistance,thestandardengaging
amountofknivesis1.5to2.0mm.
②Theengagingamountcanbeadjustedby
properlymountingthedrivingcrank.
(3)Adjustmentofknivesengagingpressure
①Seetheillustration.Insuchasituation,
themovableknife(left)andthexedknife
shouldrstmakecontactwitheachother.
Thissituationisstandard.
②Ifathreadispoorlycut,particularlywhen
itisthick,slightlyincreasetheengaging
pressure.Thisshouldsolvetheproblem.
③Theengagingpressurecanbeadjustedin
thisway:LoosenlocknutⒷ(SeeFig.),and
adjustitbyusingadjustingscrewⒶ.
HOW TO USE
Camfollowercrank(2)
Knifedrivingshaft
Matchingmark
0.5to1.0mm
0.6mm
1mm
Ⓐ
Threadtrimmercam Threadtrimmercam
Roller
Roller
Lower
shaft
Knifedrivingcrank
1.5to2.0mm
3mm
7.5mm 5mm
Fixedknife
Movableknife(left)
Movableknife(left)
Ⓑ Ⓐ
Fixedknife
Movableknife(left)
Fixedknife
Note: Thestandardpositionofcamfollower
crank(2)beforeactivationisillustrated
totheright.Ifthispositionhasbeen
changedduetoremovalofstopper
plate,etc.,rstperformthespecied
adjustmentbyusingtheadjustingbolt
locatedonthestopperplatebefore
adjustingasabovesteps(1)to(3).
—12 —

8 . Adjustment of the needle thread tension release
(1)Withthethreadtrimmersolenoidactivated,
adjustmentshouldbesuchthatthethread
tensiondiscslocatedontheneedlethread
tensionregulatorareseparatedfromeach
otherbyabout1mm.
(2)Adjustmentcanbedoneinthisway:
LoosennutⒶandproperlymovethe
exiblewire.
(3)Movetheexiblewiretotherightto
increasetheopeningamount.

9 . Adjustment of the needle thread remaining
length
( 1 ) Thelengthofremainingthreadcanbe
adjustedbyturningtensionregulatingnut
Ⓐasfollows:
Clockwise → Shortinlength
Counterclockwise → Longinlength
F The rotating hook, bobbin case,
and bobbin
1 . Useaspecialbobbinformachineswiththread
trimmerswhoserotatinghookhasbobbin
threadguideslitⒶ.
2 . Also,useabobbincasewhosebottomhas
springⒷacapableofpreventingracing.
3 . Thebobbinprovidedinthepackagecanbeused.
G
Adjustment of the gap between
the pulley and the machine head
Thedetector’sreectionplateisinstalledonthe
innersideofthepulley.
Soacorrectdistancemustbekeptwiththe
detectorbody.
Thegapbetweenthepulleyandthemachine
headmustbe6.5mm.
HOW TO USE
1mm
Ⓐ
Threadtrimmersolenoid
Increasethe
openingamount
Flexiblewire
Ⓐ
Ⓐ
Ⓑ
Rotatinghook
Bobbincase
Detectorbody
6.5mm
Adjustingtool
(Enclosedinthe
accessarybox)
Pulley
Note:Ifthethreadtensiondiscsaretoo
narrowly,theneedlethreadmay
beliabletobebroken,resultingin
detachedneedlethread.Also,ifthe
spacebetweenthediscsistoowide,the
excessiveblankspacebetweenthediscs
mayresultinloosestitches.
—13 —

LY2-3750-B1T Specications
Model
Specications LY2-3750-B1T
Application Heavymaterial
Max.sewingspeed(rpm) 2,000
Stitchlength(mm) 0to8
Needlebarstroke(mm) 38.0
Threadtake-upleverstroke(mm) 73.0
Alternatingmovement(mm) 2.0to5.0(feedfoot)
Alternatingmovementchangingsystem Dial(One-touch)
Feeddogheight(mm) 1.0
Presserfootstroke(mm)
Hand 6.0
Knee 16.0
Needle DP × 17#22(DB× 1#22)
Hook(verticalrotatinghook) Large
Bobbincase Withracingpreventionspring
Bobbin Madeofsteelforthreadtrimmer
Lubricationsystem Automaticlubrication
Threadtrimmer Rotarytrimmingbyleftmovableknife
andrightxedknife
Touchback ○
Beddimensions(mm) 517 × 178
Note:●Thebobbinshouldbeofhighqualityfreefromdeformation.
 ●Somematerialsand/orsewingconditionsmayrequirespecicationsotherthanthoselisted
above.
 ●Thesespecicationsaresubjecttochangeformachineimprovement.

SPECIFICATIONS
—14 —

Printed in Japan