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Common questions
Common Questions
10 totalWhat drive roll types are recommended for different wire types on the Miller Multimatic 255?
The Multimatic 255 uses V-Grooved rolls for hard wire, U-Grooved rolls for soft and soft shelled cored wires, U-Cogged rolls for extremely soft shelled wires (usually hard surfacing types), and V-Knurled rolls for hard shelled cored wires. Drive roll types may be mixed to suit particular requirements, such as combining a V-Knurled roll with a U-Grooved roll. (Page 12)
What wire diameters and sizes are supported by the Multimatic 255?
The Multimatic 255 supports wire diameters of .023/.025 in., .030 in., .035 in., and .045 in. in fractional measurements, or 0.6 mm, 0.8 mm, 0.9 mm, and 1.2 mm in metric measurements. Each wire size has corresponding drive roll and wire guide kits available. (Page 12)
What are the main components of the Multimatic 255?
The main components include a base, center baffle assembly, front panel assembly, rear panel assembly, wire feed drive assembly, windtunnel assembly, circuit card assembly with IGBT modules, power cord set, and electronics enclosure. These assemblies work together to provide the multiprocess welding functionality. (Page 2-3)
What is included in the front panel assembly of the Multimatic 255?
The front panel assembly includes a bezel, handle, USB dust cover, control switch membrane, LCD display interface circuit card, encoder knobs, toggle switch, twist lock receptacles, gas fitting, and various connectors and hardware. The replaceable lens cover protects the display. (Page 5-6)
What components are in the wire feed drive assembly?
The wire feed drive assembly contains a wire drive motor, machined drive housing, pressure roll lever, drive roll carriers, tension adjustment knob, clevis pins, spring pins, and various screws and washers. It also includes the wire inlet guide and drive rolls for feeding wire at the correct speed. (Page 8-9)
What are the key electrical components in the Windtunnel assembly?
The Windtunnel assembly includes input and output inductors, a multi-process main transformer, an integrated bridge rectifier, boost inverter heat sink, output rectifier heat sink with diodes, power module diodes, and a current sensing transducer. The assembly also contains fans for cooling and thermal protection with a thermistor. (Page 10-11)
Full Manual
13 pages
Multimatic 255
Mj509225N - Zz222222R
© Miller Electric Mfg. LLC 2026 Effective with Serial NumberPm- 278174 B
Parts Manual
Multimatic 255 1 Page 2 1 7 8 9 10 11 2 3 4 5 6 Main Assembly
Qty Description Multimatic 255 2 Page 1 277329 1 Base No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. Main Assembly / 229325 4 Foot, Mtg Unit (See following for subassembly information) 2 1 Center Baffle Assembly (See following for subassembly information) 3 1 Front Panel Assembly (See following for subassembly information) 4 1 Rear Panel Assembly (See following for subassembly information) 5 1 Wire Feed Drive Assembly (See following for subassembly information) 6 1 Windtunnel Assembly 7 286024 1 Circuit Card Assy, Control w/IGBT Modules Mp 8 273869 1 Cord Set, 600V T Tng 10ga 3/C 12ft St Jkt 9 278556 1 Lead Assy, Drive Polarity 10 277905 1 Enclosure, Electronics 11 285532 1 Kit, Wrapper w/Labels / 277356 1 Wrapper Assy / 230363 1 Latch, Slide Flush Mtg Hole 1.750 Wide x 1.500 Lg / 278114 1 Label, Parameter/Polarity / 231983 1 Label, Warning General Precautionary (En/Sp) / 283727 2 Label, Warning Falling Equipment (En/Fr/Sp) / 277984 1 Plug Assy, Elect (Gas Valves) / 281222 1 Harness, Wrg Unit Main / 117865 1 Conn, Rect Mini 045 14skt 2row Plug Cable Lkg
Plg15
/ 189238 1 Conn, Circ Ms/Cpc 10skt Size 18 Rcpt Panel PushinRc53
/ 081560 1 Conn, Circ Cpc 4skt Size 11 Rcpt Panel PushinRc54
/ 130693 1 Conn,Rect Mini 045 5skt 1row Plug Cable LkgPlg9
/ 231985 1 Label, Warning Electric Shock
Millermatic 255 3 Page 1 2 3 4 5 6 7 8 9 10 11 12 13 Center Baffle Assembly 1 277359 1 Baffle, Center Qty Description No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. 2 279504 1 Knob, Tensioner 1/2-13 Thread 3 602247 2 Washer, Flat .531 Id x 1.062 Od x 0.95T Stl Pld Ansi .500 4 186437 1 Spring, Cprsn .845 Od x .110 Wire x 1.500 5 231211 1 Washer, Anti-Turn 6 280091 1 Nut, Hub 7 279587 1 Hub, Spool 12 Inch 8 287119 1 Washer, Brake Plastic 9 271415 1 Shaft, Support Spool 10 274304 1 Channel, Support Spool Hub 11 274305 1 Brace, Support Spool Shaft 12 602216 1 Washer, Lock .502 Id x 0.879 Od x .151T Stl Pld Split .500 13 601879 1 Nut, .500-12 .75 Hex .44H Stl Pld
Multimatic 255 4 Page 1 2 3 4 5 6 7 14 8 9 10 11 13 12 20 19 18 17 15 16 Front Panel Assembly
Qty Description Multimatic 255 5 Page 1 282075 1 Panel Assy, Front w/Pems No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. Front Panel Assembly 2 277362 1 Bezel, Front 3 277653 1 Handle, Half 4 278541 1 Cover, Dust Usb w/Tether / 236343 1 Screw, 008-15 x .37 Hexwhd w/Gndrng Stl Pld Slf Tpg 5 277656 1 Membrane, Switch Control 6 276813 1 Circuit Card Assy, Interface Lcd Display
Pc2
/ 276416 1 Cable, Ethernet Cat5E Utp Rj45 24.000 In Lg (Blue) / 249747 1 Core, Ferrite Round Cable .201 Id Clamp-On Emi Supp 7 277663 1 Lens Cover, Replaceable 8 266591 2 Knob, Encoder 1.250 Dia x 6mm Id Push On w/Spring 9 278971 1 Switch, Tgl Dpst 40A 600 Vac Scr Term Narrow Tgl 10 1 Label, Nameplate (Order by Model and Serial No.) 11 279111 2 Receptacle, Twist Lock Brass Fem Panel Mtg (Dinse) 12 277691 1 Fitting, Gas 13 277690 1 Insulator, Bulkhead 50mm 14 291522 1 Choke, Common Mode 8 Turns 10Ga 15 600760 1 Term, Frict .250 x .032 Uninsul Male .130 Stud Mtg 1pr 16 277973 1 Lead List, Small (Gnd) 17 284861 2 Capacitor, Cer Disc .01 uF 1000 Vdc 18 185717 2 Nut, M20-1.5 1.00Hex .19H Brs Locking 19 278163 2 Terminal, Connector Friction Three Position 20 229338 2 Washer, Domed Load .812 Id x 1.450 Od x .070 Thk
Multimatic 255 6 Page 3 1 2 3 4 5 6 7 8 9 10 Rear Panel Assembly 1 277949 1 Panel, Rear Qty Description No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. 2 262572 2 Valve, 24 Vdc 1Way 750-14 Thd 2mm Orf 100Psi 3 282261 1 Bushing, Strain Relief .709/.984 Id x 1.375 Mtg Hole 4 277950 1 Bezel, Rear 5 277653 1 Handle, Half 6 182445 1 Nut, Conduit 1.000 Npt Pld 1.688 Od x .200 Thk 7 272186 2 Nut, .750-14 Nps 1.312Hex .413H Nyl 8 250864 2 Hose, Gas 27 In (MIG) 9 285815 1 Kit, Gas Valve Assy 10 278406 1 Label, Gas Valve MIG/TIG
Multimatic 255 7 Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 25 29 Wire Feed Drive Assembly
Qty Description Multimatic 255 8 Page 1 277437 1 Insulator No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. Wire Feed Drive Assembly 2 281378 1 Motor, Wire Drive w/Lead Assemblies 3 277657 1 Housing, Drive (Machined) 4 277795 1 Lever, Pressure Roll (Machined) 5 172075 1 Carrier, Drive Roll w/Components 24 Pitch 6 173619 1 Carrier, Drive Roll w/Components 24 Pitch 10mm Shaft 7 221976 1 Knob, Tension Adjust Assy 8 273112 1 Pin, Clevis .250 Od x 1.751 Lg w/Groove and Cham 9 010224 1 Pin, Spring CS .187 x 1.000 10 282942 1 Screw, 500-13 x .75 Hex Hd-Phl Stl Pld Slf Tpg Ab 11 174610 3 Screw, M 6 - 1.0 x 20 Soc Hd Button Cap Blk 12 602200 1 Washer, Lock .168 Id x 0.293 Od x .040T Stl Pld Split #8 13 173620 3 Bushing, Motor Mtg 14 604538 1 Washer, Flat .344 Id x 0.688 Od x .065T Stl Pld Ansi .312 15 151828 1 Pin, Cotter Hair .042 x .750 16 602009 1 Screw, .250-20 x 1.25 Soc Hd-Hex Gr8 Pln 17 209079 1 Screw M4 x 0.7 x 16 18 604534 1 Screw, .312-18 x 1.25 Hex Hd-Pln Gr5 Pld 19 166072 1 Spacer, Gear 20 192029 3 Washer, Flat .250 Id x 0.437 Od x .015T Stl Pln 21 233030 1 Screw, .250-20 x .25 Hexwhd Machine Stl Pld 22 602216 1 Washer, Lock .502 Id x 0.879 Od x .151T Stl Pld Split .500 23 263411 1 Fitting, Barbed Gas 24 222035 1 Knob, T 1562 Bar w/312-18 Stud 1000 Lg Plstc 25 189285 2 Roll, Drive V Groove .035-.045 Wire 26 221912 1 Guide, Wire Inlet Nylon .023 - .052 27 602247 1 Washer, Flat .531 Id x 1.062 Od x 0.95T Stl Pld Ansi .500 28 230801 1 Spring, Torsion 29 280210 1 Bolt, Hex Head Flange Stl .375-16 x .500 Gr8 Pld Zc
Multimatic 255 9 Page 1 2 3 4 5 6 7 8 15 16 22 10 11 12 17 18 19 20 21 23 13 14 9 Windtunnel Assembly
Qty Description Multimatic 255 10 Page / 278704 1 Assembly, Magnetics Windtunnel No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. Windtunnel Assembly 1 277435 1 Windtunnel, Lh 2 277108 1 Inductor, Input
L1
3 277336 1 Inductor, OutputL2
4 277859 1 Xfmr, Multi-Process MainT1
5 278705 1 Channel, Wire Plastic / 278707 1 Assembly, Heat Sink Windtunnel 6 277436 1 Windtunnel, Rh 7 277439 1 Heat Sink, Boost Inverter/Input Rectifier 8 275288 1 Rectifier, Integ Bridge 90. Amp 1600V 1ph 9 206258 1 Relay, Encl 24 Vdc Spst 30S/24 Vdc 4-Pin Flange Mtg / 281796 1 Assembly, Output Rectifer Heat SinkD1,D2
10 281797 1 Heat Sink, Output Rectifier 11 290137 2 Diode, Ultra-Fast 164Ns 400A 600V Dual To-244 12 280976 1 Resistor/Capacitor Assy 13 278442 1 Thermistor, NTC 30K Ohm @ 35 Deg C 30in LeadRt1
14 199952 1 Diode Power Module 55 Amp 600V 1PH Fast Recovery 15 278711 1 Assembly, Fan / 277505 1 Holder, Plastic Front Fan / 278710 2 Fan, Muffin 24 Vdc 8000 Rpm 175 Cfm 3.248 Mtg HolesFm1,Fm2
16 277506 1 Transducer, Current 300A Module Supply V +/- 15vCt1
/ 277676 1 Cable, Lem 23 In 17 278726 1 Bus Bar, Positive Output 18 279057 4 Bracket, Mtg Circuit Card Assy 19 277697 1 Xfmr, Current Sensing 200/1 Encapsulated w/6in Lds / 278885 2 Grommet, Rubber 20 281133 1 Tubing, Htshnk Clear Mfp .500/.250 Dia x 4.000 21 277948 1 Thermistor, NTC 30k Ohm @ 25 Deg C 22.00in LeadRt2
22 282223 1 Washer, Lock Stl Intl/Ext Tooth No 10 Zc Pld Sftmtl 23 265408 6 Screw, K50 x 12 Hexwhd Stl Pld Blk Pt Thread Forming
11 Page Drive Roll And Wire Guide Kits Base selection of drive rolls upon the following recommended usages: 1 V-Grooved rolls for hard wire. 2 U-Grooved rolls for soft and soft shelled cored wires. 3 U-Cogged rolls for extremely soft shelled wires (usually hard surfacing types). 4 V-Knurled rolls for hard shelled cored wires. 5 Drive roll types may be mixed to suit particular requirements (example: V-Knurled roll in combination with U-Grooved). Ref. S-0026-B/7-91 Wire Diameter Fraction Decimal Metric .023/.025 in. .030 in. .035 in. .045 in. .023/.025 in. .030 in. .035 in. .045 in. 0.6 mm 0.8 mm 0.9 mm 1.2 mm Kit No. 087131 079594 079595 079596 Drive Roll Part No. Type 087130 053695 053700 053697 V-Grooved V-Grooved V-Grooved V-Grooved Inlet 056192 056192 056192 056193 Wire Guide .030/.035 in. .030/.035 in. 0.8/0.9 mm 204579 203526 V-Grooved 056192 Drive Roll And Wire Guide Kits
Qty Description 12 Page / 087131 Drive Roll And Wire Guide Kits No. Item Mkgs. Dia. No. Part *Recommended Spare Parts ~ Optional Hardware is common and not available unless listed. + When ordering a component originally displaying a precautionary label, the label should also be ordered. when ordering parts from your local distributor. To maintain the factory original performance of your equipment, use only Manufacturer's Suggested Replacement Parts. Model and serial number required Item includes other parts. Item is part of a subassembly. Drive Roll And Wire Guide Kits V-Grooved / 087130 Drive Roll / 056192 Inlet Wire Guide / 204579 Drive Roll And Wire Guide Kits V-Grooved / 203526 Drive Roll / 079594 Drive Roll And Wire Guide Kits V-Grooved / 053695 Drive Roll / 079595 Drive Roll And Wire Guide Kits V-Grooved / 053700 Drive Roll / 079596 Drive Roll And Wire Guide Kits V-Grooved / 053697 Drive Roll / 056193 Guide, Wire Inlet