Lincoln Electric LF-72/74 service manual Required Equipment, BB-3

Page 67

BB-3

OPERATION

BB-3

 

 

 

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PRODUCT DESCRIPTION

General Physical Description

The LF-74 is optimized for GMAW and FCAW welding. The powerful 4 roll MaxTrac™ drive, heavy duty enclo- sure and wire reel stand combine to make an easy to install, easy to use wire feeder for everyday welding. Powering the wire drive is a high performance motor gearbox. A heavy duty hinged door opens easily, which provides an ample amount of room for assembling pre- cision drive components and the welding gun.

MaxTrac™ technology delivers great feeding because:

•Patent pending drive rolls improve traction.

•The precision machined, rigid aluminum alloy frame results in maximum drive roll clamping pressure.

•Drive hubs with steel inner cores have 3 ball bear- ings inside each hub.

•The drive hubs are supported by large, heat treated and ground shafts for maximum rigidity and accurate drive roll alignment.

•Patent pending dual spring pressure arms have sen- sitivity for feeding soft wires without crushing them, and have plenty of compression force for feeding solid or stiff wires.

Easy to configure, easy to service parts give MaxTrac™ drives the edge in productivity.

•Patented split wire guides fully support the wire and virtually eliminate birdnesting.

•No tools required to change the drive rolls and wire guides.

•Changeable gun bushings easily accept guns from many manufacturers.

•Brass-to-brass connections between the electrode connection and the gun minimize voltage drop varia- tions, resulting in consistent arc performance all day, every day.

Three models of the LF-74 are available to satisfy many customer set-ups:

•The base model is enhanced for GMAW welding with consumables from bulk packages or when a boom mounting is required.

•The bench model with heavy duty wire reel stand tar- gets operators performing GMAW or FCAW welding using consumables on spools.

•The high torque model features high ratio gearing for feeding larger diameter FCAW or GMAW wires.

All models use a high performance motor-gear box with an integrated tachometer.

General Functional Description

The LF-74 fulfills the need for an economical wire feed- er with a high performance wire drive. Functional fea- tures included are those that offer the most value – a WFS knob with a calibrated printed scale, cold-feed/ gas purge switch, trigger interlock switch and tachome- ter motor control.

RECOMMENDED PROCESSES

•GMAW

•FCAW

PROCESS LIMITATIONS

•The LF-74 is not recommended for GMAW-Pulse Synergic, GTAW, GTAW-Pulse, CAG, SMAW

•The LF-74 is not compatible with push-pull equip- ment.

•For the heavy duty bench models K2426-2 and K2426-3, the maximum spool size = 60 lb. (27.2 kg).

REQUIRED EQUIPMENT

Lincoln’s LF-74 is designed for use with the CV and DC family of power sources. These include:

• CV-250

• DC-400

• CV-300

• DC-600

• CV-305

• DC-655

•CV-400 • Invertec V350

•CV-655

OTHER COMPATIBLE POWER SOURCES

•Ranger 250

•Ranger 305

•Commander 300

•Vantage 300

•Vantage 500

•Air Vantage 500

EQUIPMENT LIMITATIONS

•Maximum GMAW gun length = 25’ (7.6m)

•Maximum FCAW gun length = 15’ (4.6m)

•Maximum conduit length = 30' (9.1m)

•Maximum total control cable length = 100ft (31m)

•The LF-74 operates on 24-42VAC and not 115 VAC

•The K1733-1 and K1733-3 wire straighteners are not compatible with the LF-74

•Gun bushings are required for welding guns that do not have a Magnum (Tweco #2-#4 compatible) back end.

•The LF-74 does not attach to K303 or K377 wire reel stands.

LF-72/74

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Contents LF-72/74 Safety Electric Shock can kill Iii Welding Sparks can cause fire or explosionSûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Installation Section Table of ContentsSection A-1 Amp Rating Duty Cycle InstallationLocation Safety PrecautionMounting Suspended Bench MountSwivel Mount Boom MountWeld Cable Sizes Weld Cable Connection Coaxial Weld CablesAnalog Control Cable INSTALLATIONA-7Control Cable Connections Analog Miller Control Cable Adapter K2335-1 Miller Power Source Lincoln Wire FeederPin Function High Frequency Protection Wire Drive SystemsWelding GUN/WIRE Feeder Trigger Connector Remote Sense Lead SpecificationsMagnum GUN and Cable Assemblies Welding GUNS, Torches and ACCES- SoriesWire Drive Configuration Procedure for Changing Drive and Idle Roll SetsRolls.FIGURE A.4 Gun Receiver For use With Bushing Pressure ARM AdjustmentSet the pressure arm as follows See Figure A.6 Wire Reel Loading Figure A.9 Weld Wire RoutingShielding GAS Connection For Codes 11209, 11210, 11211 and above Installing ElectrodeTo install Lincoln conduit See Figure A.10b Conduit KitsFigure A.12b Aluminum Wire PreparationsBase Model Bench Model Standard Duty Bench Model Heavy Duty INSTALLATIONA-18Cable Typical System ConfigurationsLF-72/74 Section B-1 Operation SectionGAS Input Work Connection OperationProduct Description Common Welding AbbreviationsRecommended Processes Figure B.1 Case Front Controls Description Front Panel Controls and ConnectionsRemote Voltage Control KIT Burnback and Postflow Timer KITCold FEED/GAS Purge Switch Step Trigger Interlock SwitchTrigger Interlock Wire Feed Speed KnobTrigger Connector 5-PIN Amphenol GUN Receiver Bushing K1500-2Section C-1 Accessories SectionOptional Kits AccessoriesLF-72s Accessories Key LF-72/74 Section D-1 Maintenance SectionRoutine Maintenance MaintenanceMaintenance Calibration SpecificationFigure D.1 Figure D.3 Major Component Location Section AA Section AA-1AA-2 WFS Range Wire SizesModel Figure AA.1 AA-3AA-4 AA-5 Coaxial Weld Cable AA-6AA-7 INSTALLATIONAA-7K1797-xx AA-8 AA-9 Drive Roll Kits Steel or Cored WiresFigure AA.3 AA-10Guides AA-11Changing the Gun Receiver Bushing Lation or changing drive rolls and/orAA-12 Assembly of Drive Rolls and Wire GuidesSet the pressure arm as follows See Figure AA.8 AA-13AA-14 Loading 16 to 44 lb .3 20kg Spools See figure AA.8 AA-15Figure AA.11 AA-16Figure AA.12a AA-17Figure AA.12b AA-18AA-19 Common Equipment SET-UPS AA-20INSTALLATIONAA-20AA-21 Figure AA.15 High Volume Production AA-22 Figure AA.16 Portable WeldingSection BB Section BB-1Fcaw Innershield or Outershield BB-2BB-3 Required EquipmentFigure BB.1 Case Front Controls Description BB-4K2426-1 and K2426-2 models BB-5K2426-3 model BB-6 SwitchSection CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD Section DD-1WFS knob setting Could remain energized Several seconds To verify the wire feed speedNal wiring When inching with gun trigger, electrodeDD-3 MAINTENANCEDD-3DD-4 Figure DD.3 Major Component LocationSection E-1 Theory of Operation SectionReturn to Section Theory of OperationControl Board LF-72/74 Section F-1 Troubleshooting & Repair SectionHOW to USE Troubleshooting Guide Troubleshooting & RepairPC Board Troubleshooting Procedures Function Problems Function Problems Troubleshooting & Repair Test Description Drive Motor and Tach Feedback TestTest Procedure GAS Solenoid Test Troubleshooting and RepairFigure F.3 Leads 552, 552B Test ProcedureDiode Bridge Test 552B + 552A Wire Speed Potentiometer Test 14F-14 Wire Speed Potentiometer TestPC Board Removal and Replacement Removal Procedure Replacement Procedure Control PC Board Removal and Replacement ProcedureTroubleshooting and Repair Procedure Wire Drive Motor and Gear BOX Removal and ReplacementProcedure Replacement Procedures Operation Verification SET UPLF-72/74 Section G-1 Electrical Diagrams SectionLF-72/74 Electrical DiagramsTimer KIT Board Normal Speed Micro Internal panel Motor Connecter Summary High Torque Setting engages Schematic Common Analog Control PC Board G4559 Sheet Electrical Diagrams Electrical Diagrams PC Board Assembly Common Analog Control G4560-2E0
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