The ESS Squarearc 356C is a used TIG AC/DC welder from the German ESS factory in Bad Waldsee, a more powerful model than the 276C in the Squarearc series (276, 356, 506), with built-in liquid cooling. It delivers 350 A and holds 270 A at 100% duty cycle, so it is a source for thicker aluminium and long welds in production: tanks, structures, hulls, machine parts. We have 2 units, each with an 8 m TIG torch and a 4 m earth cable.
- 270 A without a break. At 100% duty cycle at 40°C. This is the current at which you run long welds on aluminium several millimetres thick without waiting for the source to cool down. You have 350 A for 6 minutes out of every 10.
- Square-wave AC without continuous HF. The current switches from one polarity to the other with a steep edge, and the arc reignites at every polarity reversal without help from HF. The arc is quiet and stable, and because HF works only at ignition, the electronics on the shop floor get much less interference.
- AC frequency from 30 Hz. The rating plate of the 356C gives AC from 30 to 200 Hz (Fronius MagicWave from 40 Hz, EWM Tetrix and Kemppi MasterTig AC/DC from 50 Hz). The bottom of the range gives a soft, wide arc for thick aluminium.
- Open circuit voltage of 100 V. The same as EWM and higher than in Fronius and Kemppi machines, so the arc reignites more reliably at the polarity reversal.
- Adjustable positive-pole ignition. On AC the arc starts with the electrode on the positive pole, and the tungsten tip melts into a small cap. Starts are repeatable on oxidised aluminium as well.
- Two units to choose from. You can take one, or equip two workstations with the same model straight away.
Welding processes of the ESS Squarearc 356C
TIG AC: thicker aluminium
On aluminium both halves of the alternating current do work. With the electrode positive the arc breaks up the oxide layer, which melts only at about 2050°C, while aluminium itself melts at 660°C. With the electrode negative the arc puts heat into the workpiece and cools the tungsten. With a square waveform the zero crossing is very short, so the arc reignites immediately.
Frequency works like switching a pressure washer nozzle from a fan to a narrow jet. At 150 to 200 Hz a narrow beam goes into the root of a fillet weld and into corners. At 30 to 60 Hz a wide spot spreads heat on thicker material, in surfacing and in wide grooves. You can also choose between two software-controlled AC waveforms.
TIG DC: structural and stainless steel
With direct current you weld carbon and stainless steel. HF strikes the arc without contact, and soft contact ignition remains for places where the HF pulse interferes with electronics.
Pulsed TIG
The pulse current I1 melts the material, the base current I2 lets the weld pool partly solidify, and you set the times of both phases in t1 and t2. On thicker aluminium pulse helps you with root control and positional welding, and on thin stainless steel it limits heat input, discolouration and distortion.
MMA with covered electrodes
Electrodes from 1.5 to 6.0 mm. The rating plate of the 356C gives 320 A at 60% and 250 A at 100% duty cycle in MMA, which is enough for basic electrodes up to 6 mm on structures and repairs. You buy the electrode holder separately.
Functions and settings
- Panel with JOB memory. LCD display with current or voltage readout, SP, AC, AC/DC and MMA buttons, and a weld cycle bar with LEDs: gas pre-flow, electrode diameter Ø, upslope, I1, I2, t1, t2, downslope and gas post-flow.
- Second current from the torch. With a two-button torch you switch between I1 and I2 during welding, so you take heat out at the edge without a foot pedal.
- Current upslope and downslope. A reliable start and a filled crater at the end, which on aluminium reduces the risk of crater cracks.
- Gas post-flow. Shields the tungsten and the end of the weld while they cool.
- 2T and 4T modes. Short tack welds and long welds without holding the button.
- Cooling with a pump and temperature-controlled fans. The pump switches off a set time after welding ends, and the fans run only when needed. Less dust in the machine and a quieter workstation.
- Automation interface with 12 functions. FP 100 foot pedal, FS 200 remote control or mechanised equipment.
- IP23 and S mark. Work also inside tanks and confined steel structures.
How the ESS Squarearc 356C compares with other TIG AC/DC welders
The Squarearc 356C belongs to the class of 350 A industrial TIG AC/DC cabinets and was made in Bad Waldsee from about 2006 to 2013. In the 2013 catalogue a new 356C cost 7,170 EUR without the digital WS100 panel and accessories. Its contemporaries are the EWM Tetrix 351 AC/DC, the Kemppi MasterTig AC/DC 3500W and the Fronius MagicWave 4000.
EWM, Kemppi and Fronius state more at 100% duty cycle (from 280 to 310 A). ESS, on the other hand, has the lowest minimum AC frequency in this group (30 Hz against 40 and 50 Hz), an open circuit voltage of 100 V, the same as EWM and higher than Fronius and Kemppi, and an automation interface with 12 functions as standard. A used 356C is a 350 A source with cooling and an 8 m torch, ready for everyday work on aluminium.
Technical data
| Manufacturer | ESS Schweißtechnik, Bad Waldsee, Germany |
|---|---|
| Model | Squarearc 356C (also written as: SquareArc 356 C, ESS 356C), C stands for built-in liquid cooling |
| Type | inverter TIG AC/DC welder with pulse and MMA |
| Mains supply | 3 x 400 V |
| Mains fuse | 25 A time-delay |
| Current range | from 5 to 350 A |
| TIG duty cycle 40°C | 350 A at 60%, 270 A at 100% |
| MMA duty cycle (model rating plate) | 320 A at 60%, 250 A at 100% |
| AC frequency (model rating plate) | from 30 to 200 Hz |
| Open circuit voltage | 100 V |
| Ignition | HF or soft contact, positive-pole ignition on AC |
| Panel | LCD, JOB, I1 and I2, t1 and t2, SP, AC, AC/DC, MMA |
| MMA electrodes | from 1.5 to 6.0 mm |
| IP rating | IP23, S mark |
| Torch cooling | liquid, built-in unit with pump |
| Dimensions (L x W x H) | 950 x 435 x 980 mm |
| Weight (catalogue data) | 110 or 120 kg, depending on the catalogue |
What you get
- ESS Squarearc 356C power source, one of two units to choose from
- liquid cooling unit
- TIG torch, 8 m long
- earth cable, 4 m long
Two units: how they differ
The price is for one unit. The first unit has a grey front panel with the lettering SquareArc ESS 356, the second a blue housing with the lettering Squarearc 356 C. The panel layout and equipment are the same on both. Tell us which one you prefer, or take both.
What to watch out for
This machine needs a 25 A time-delay fuse on a 3 x 400 V supply, which is a stronger connection than for the 276C, where 16 A is enough. Both panels have an SP button. ESS sold the Speed Puls option up to 3000 Hz separately for this series. We will check on the running machine whether it is active on the unit you choose and show you the result before shipping.
ESS ended production in 2013, and we service these units here in Krotoszyn under the service package. We do not include argon, tungsten or TIG filler rods. The housings have signs of use visible in the photos.
Questions about the ESS Squarearc 356C
What thickness of aluminium can I weld with the ESS Squarearc 356C?
As a rough guide, about 40 A per millimetre is assumed, so the 356C has enough current in reserve for aluminium up to about 8 mm. Above about 4 mm you bevel butt joints and weld them in multiple passes. 350 A is available at 60% duty cycle, and for continuous work you count on 270 A.
Is the 356C suitable for shift work in production?
Yes. 270 A at 100% duty cycle at 40°C and built-in liquid cooling let you weld continuously at up to 270 A, without breaks for the source to cool down.
What power connection do I need?
3 x 400 V with a 25 A time-delay fuse, for example a CEE 32 A socket.
Are parts and service still available for the ESS Squarearc?
ESS, based in Bad Waldsee, declared bankruptcy in 2013, and from 2014 its machines were serviced by Dinse. We service both units here in Krotoszyn.
How does the 356C differ from the 276C?
The same controls as the ESS Squarearc 276C, but 350 A instead of 270 A, 270 A instead of 220 A at 100% duty cycle, and MMA electrodes up to 6.0 mm instead of 5.0 mm.
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.
