The Kemppi FastMig KM 400 (FastMig KM400) is a used MIG/MAG welder from the Finnish FastMig family, built for heavy and medium steel fabrication. The source holds 380 A at 100% duty cycle, and you set the voltage and wire with two knobs, without synergic curves or programs. The set includes the four-roll MF 33 wire feeder, a FastCool 10 cooling unit, a trolley, a 5 m Kemppi torch, a 4 m earth cable and a 1.5 m interconnection cable.
- 380 A at 100% duty cycle. At 40°C. That is more than the FastMig Pulse 350 (330 A) and the FastMig X 450 (350 A) from the same family. The source holds 400 A for 8 minutes out of every 10.
- Simple operation and full power. Kemppi aimed the FastMig Basic line, to which the KM belongs, at basic MIG/MAG in heavy and medium industry: steel structures, shipyards, offshore, repair and maintenance.
- MF 33 wire feeder for wires up to 2.4 mm. Four 32 mm rolls and a Euro connector. With the D28 gear it feeds wire at up to 18 m/min, with D40 up to 25 m/min. It handles steel wires up to 1.6 mm, cored wires up to 2.0 mm and aluminium wires up to 2.4 mm.
- LongSystem for long interconnection cables. The LSy mode in the menu prepares the machine for interconnection cables longer than 40 m, so the wire feeder can work far from the source, for example inside a hull or high up on a structure. It requires a longer interconnection cable, and the set includes a 1.5 m one.
- Wire stop when the arc fails to strike. If the arc does not ignite, the wire feeder stops and does not push metres of wire out through the torch.
Welding processes of the Kemppi FastMig KM 400
MIG/MAG with manual control
With the left knob you set the wire speed, with the right knob the voltage, independently of each other. It is like a car with a manual gearbox: you choose the gear for the road yourself, and the machine does exactly what you tell it. During welding the display shows the actual current and voltage, and after welding Weld Data recalls the values of the last weld.
On thick plate you weld with spray arc using 1.2 mm wire in an argon mixture, and in pure CO2 you work with short arc or globular arc. On thinner sheet you weld with short arc and the dynamics set to soft. Flux-cored wires run just as well as solid ones, because you set the voltage and wire speed for the specific wire and gas instead of choosing from a list of programs.
Weld start and end
Gas pre-flow from 0.0 to 9.9 s. Gas post-flow automatic (1 s for every 100 A) or from 0.1 to 32.0 s. Initial wire feed from 10 to 170% of the setting: a slow start for clean ignition or a faster one with thick wire. Correction of the ignition pulse and wire burnback from -9 to +9. The wire feeder electronics make sure the wire does not stick to the contact tip.
Functions and settings
- Arc dynamics from -9 to +9. Negative values give a soft arc and less spatter, positive values a harder, stable arc. Kemppi recommends this setting especially when welding steel in pure CO2.
- LOCAL and REMOTE. You set wire and voltage on the source or on the wire feeder panel, right at the workpiece.
- Gas test from 10 to 60 s and wire inching. You set the flow without feeding wire, and you run the wire through the torch without gas and without voltage.
- 2T and 4T modes. Long welds without holding the trigger.
- FastCool 10 cooling unit. Capacity 1 kW, tank of about 3 l, TEST button and coolant circuit alarm. The liquid-cooled torch copes with long work at high current.
- Trolley. The source with the cooling unit stands on the trolley, so you roll the workstation around the shop.
- Protection. Thermal protection, shutdown at too low mains voltage, overvoltage protection and overload monitoring of the wire feed motor.
How the Kemppi FastMig KM 400 compares within the FastMig family
In the FastMig family the same source power was available as the KMS with synergic control and Wise functions. The KM is the version for those who prefer simplicity: fewer settings that someone can change, and full control over the arc. Synergic MIG/MAG welders also weld with flux-cored wires, so you choose the KM for simplicity and predictability, not for lack of an alternative.
A used KM 400 with the MF 33 and FastCool 10 is a complete 400 A workstation, ready to work.
Technical data
| Manufacturer | Kemppi Oy, Lahti, Finland |
|---|---|
| Model | FastMig KM 400 (also written as: KM400, FastMig KM400) with MF 33 wire feeder |
| Type | inverter MIG/MAG welder, manual control |
| Mains supply | 3 x 400 V, from -15 to +20%, 50/60 Hz |
| Mains fuse | 35 A time-delay |
| MIG/MAG range | from 20 to 400 A, from 12 to 36 V |
| Duty cycle 40°C | 400 A at 80% (34 V), 380 A at 100% (33 V) |
| Mains power | 18.5 kVA at 80%, 16.9 kVA at 100% |
| Open circuit voltage | 65 V |
| Efficiency and power factor | 87% and 0.9 |
| IP rating | IP23S |
| Source dimensions (L x W x H) | 590 x 230 x 430 mm |
| Source weight | 35 kg |
| Arc dynamics | from -9 to +9 |
| MF 33 wire speed | up to 18 m/min (D28 gear) or up to 25 m/min (D40 gear) |
| Wire diameters | steel from 0.6 to 1.6 mm, cored from 0.8 to 2.0 mm, aluminium from 1.0 to 2.4 mm |
| Cooling unit | FastCool 10, 1 kW, about 3 l, 11 kg |
What you get
- Kemppi FastMig KM 400 power source
- MF 33 wire feeder
- FastCool 10 cooling unit
- trolley
- Kemppi torch, 5 m long
- earth cable, 4 m long
- interconnection cable, 1.5 m long
What to watch out for
The source needs a 3 x 400 V connection with a 35 A time-delay fuse. This is a pure MIG/MAG welder: there is no synergic control, pulse, MMA or TIG, and they cannot be added. For aluminium you need U-groove drive rolls and a PTFE liner, and aluminium wire is harder to feed through a 5 m torch than steel wire. The housing has signs of use visible in the photos.
Questions about the Kemppi FastMig KM 400
Can the KM 400 handle continuous work at high current?
Yes. The source gives 380 A at 100% duty cycle at 40°C. In long work at high current the limit is set by the torch rating, which is why the set includes a FastCool 10 cooling unit and a liquid-cooled torch.
How does the KM 400 differ from the KMS 400?
The source power is the same. The KMS has synergic control and Wise options, the KM has manual control: you set wire and voltage separately, without programs.
Can I weld with flux-cored wire?
Yes. You match the voltage and wire speed by hand to the specific cored wire: rutile flux-cored, basic flux-cored or metal-cored. Arc dynamics from -9 to +9 let you adjust the character of the arc.
What power connection do I need?
Kemppi specifies a 35 A time-delay fuse, and for 100% load the manual also lists 25 A time-delay. A CEE 32 A socket can be protected by at most 32 A, so choose the connection for work at 400 A together with an electrician.
How we sell used machines
Unit checked in our service centre in Krotoszyn, with measurements to PN-EN 60974-4 and a load test. The price includes the first year of the service package: cleaning, basic inspection and electrical measurements. The measurement report is part of the paid service package. You can buy further years. We ship across the European Union, personal collection by appointment.
