The Merkle M 451 DW is a transformer MIG/MAG power source for thick steel, with a separate wire feeder and a built in liquid cooler. The documentation gives 450 A at a duty cycle of 40% at a temperature of 40 °C and 320 A at continuous load 100%, with a supply of 3 x 400 V. The protection class is IP 21 or IP 23, depending on the version.
What this machine is for
This is a power source for heavy industry, steel structures and shipyards. A reserve of 450 A at a 40% duty cycle lets you lay thick fillet welds and multi run welds on sections and on plate with large cross sections, and under continuous work the machine gives 320 A, so you run long beads with no stops for cooling. A classic transformer with a copper winding takes overloads, dust and voltage swings better than inverter electronics, and its repair comes down to simple components.
The letters DW in the name mean a separate wire feeder. The drive stands on its own and joins the power source with an interconnection cable, so the welder moves away from the machine by the length of that cable and works on a large structure without rolling the whole set. The feeder housing shields the spool from dust and from mechanical damage. The reach is set by the length of the interconnection cable, and that is the only limit of this layout.
The data sheet lists the uses: welding of heavy steel structures, of machine frames and undercarriages, prefabrication of hull sections and deck equipment in shipyards, production of pressure vessels and thick walled pipelines, repairs of rail rolling stock and construction machines, series production that needs a high duty cycle, bridge building and civil engineering works, and the working of black steel and stainless steel in metal workshops.
MIG/MAG is welding with a wire fed in a continuous way, under a shielding gas. The wire melts in the arc and fills the groove at once, so you deposit a lot of weld metal per minute and you do not chip slag after every bead. On thick parts the current reserve and the duty cycle count, because a multi run weld is made in several passes, one after another, with no cooling of the station. Here the machine gives 450 A and 320 A under continuous work, and the liquid circuit takes the heat from the torch, so the torch stops being the bottleneck.
The machine will also pull aluminium after a change of parts: rollers with a U groove, a teflon liner in the torch and argon as the shielding gas. Liquid cooling is an extra plus here, because soft alloys are welded at high energy and a gas cooled torch would soon give up.
Features and equipment
- Separate wire feeder of the DW series: the drive is parted from the power source and tied to it with an interconnection cable, so you manoeuvre around large structures without moving the machine.
- Built in liquid cooler with a circulation pump: it takes the heat from the torch and from the power modules, so at 450 A the wear parts, the gas nozzle and the contact tip, live longer than in a gas cooled system.
- 4 roll drive with pressure adjustment: four driven rollers guide the wire in line and without slip, hard steel wires as well as soft aluminium ones, also with torches from 4 to 5 m long.
- Stepped voltage adjustment, multi stage: the switch sets the characteristic to the material thickness, and a chosen position gives the same parameter at every arc start.
- 2T, 4T and spot modes: two stroke for short assembly welds, four stroke for long beads without holding the trigger, spot for repeatable tacks of the same time.
- Burn back time adjustment: it sets the length of the free wire stick out after the bead, protects the contact tip against sticking and shortens the preparation for the next arc start. The potentiometer sits inside the feeder, so the setting does not change by accident.
- Support for the TEDAC system: you change parameters from the torch handle and read them on the diode indicator on the torch, without going back to the power source. It needs a Merkle TEDAC torch.
- Gas test and wire feed buttons on the feeder: you set the flow on the regulator and pull the wire through the interconnection cable without striking an arc, which saves gas and filler.
- Steel housing on large transport wheels: you roll the set across the shop floor in spite of its high weight.
- Copper main transformer: it takes overloads and voltage swings, and the arc burns in a stable way with little spatter, so the welds need less finishing work.
Technical data
| Brand | Merkle |
|---|---|
| Type | transformer MIG/MAG semi automatic welder with a separate feeder |
| Supply | 3 x 400 V |
| Maximum welding current | 450 A |
| Duty cycle 40% at 40 °C | 450 A |
| Duty cycle 100% at 40 °C | 320 A |
| Welding current in the shop catalogue data | up to 500 A |
| Voltage adjustment | multi stage, step switches |
| Cooling | liquid, integrated cooler |
| Wire feeder | separate, 4 roll |
| Protection class | IP 21 or IP 23 |
| Control from the torch | support for the TEDAC system |
What to watch out for
The machine needs a 3 x 400 V connection. Protection class IP 21 or IP 23 means work under a roof, with no water on the housing. A 40% duty cycle at 450 A gives four minutes of welding in a ten minute window, and only 320 A lets you work with no limit, while the values are given for an ambient temperature of 40 °C. Stepped adjustment does not change the voltage while the arc burns, you pick the step before the bead.
The liquid circuit needs a check of the level and a fluid made for welding, because ordinary fluid speeds up corrosion inside the circuit. Control from the handle works only with a Merkle TEDAC torch, the power source alone does not replace it, so before you buy confirm which torch is in the set. You match the rollers, the liner and the contact tip to the diameter and the type of wire, and for aluminium you need U rollers and a teflon liner.
Check the length of the interconnection cable between the power source and the feeder, because it sets the working radius of the welder and you cannot extend this part as you wish. Verify also the state of the interconnection cable and of the sockets, because with a separate feeder the current, the gas, the control and the coolant all run through it. A liquid cooled torch has to be matched to a current of 450 A, a gas cooled torch would burn out fast in such conditions.
The weight of the set is high. The machine stands on transport wheels, so you roll it across the shop floor on your own, but between buildings you move it on a trolley or a fork lift. The data sheet gives neither the weight nor the dimensions, so ask before transport.
This unit is sold
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