Thick SS plates plasma-arc cut without dross

Gas plasma-arc machine cuts 150mm plate thickness with a capacity of clean cut at 130mm, that means a smooth dross-free cut with bevel of less than 2 deg taper.

Arcraft Plasma Equipments (I) Pvt has designed manufactured and commissioned Gas plasma cutting machine for cutting 150 mm plate thickness with a capacity of clean cut at 130mm.

By clean cut we mean a smooth dross free cut with bevel of less than 2 deg taper.

The machine has been sold to Godrej, one of India,s largest manufacturers and fabricators, at their Vikhroli plant.

In fact, even the people at Godrej were not expecting a clean cut at 130mm as the the competitive quote received from foreign manufacturer specified a clean cut of 120mm that too using costly gas mixture of argon and hydrogen for cutting and nitrogen at high pressure and flow as swirl gas.

Arcraft has used cheap nitrogen gas at a pressure of only 2.5 bar and flow of only 23 litre/min to achieve the same.

The machine was designed , manufactured and supplied in a short period of only 45 days .

Last year Arcraft had achieved another first in India by selling three high tech keyhole plasma-arc welding systems to the same company which swung this order in its favour.

The 'beauty' of the machine is the concept of master slave where two 80mm capacity cutting machine work in parallel.

Independently these machines can be used as stand alone machine as both the machines have built in pilot arcing system.

The machines are built with conventional transformer/rectifier topology.

Each machine has four 100A transformers, each capable of cutting 20mm thick material.

The output power can be selected as 100, 200, 300, 400A by selecting combination of the transformers to cut MS/SS from 1 to 80mm.

Incase of 150mm cutting two such power sources are used in parallel where a concept of 'Master/Slave' is used.

In such condition the machines communicate with each other through PLC.

Any machine can be used as Master or Slave which can be selected by the operator.

The master controls full sequence of operation including cutting power and pilot arcing.

Slave only delivers the cutting power and the pilot arcing is inhibited.

Any combination of power, e g, 100A from Master and 200A from slave or 300A from master and 100A from slave etc can be adjusted.

The output current can be adjusted between 100 to 800A to cut 1 to 150mm of SS/MS.

The technical data establishing the actual cutting cost is as follows, for 304 stainless steel.

Machine used - Model 150-4S - 125-4S.

Cut thickness - 130 - 100mm.

Electricity used is as follows.

Power used - 105 - 72kVA.

Power factor - 0.78 - 0.78.

Power used - kW/min - 81.9 - 56.16 - (kVA x power factor).

Duration - 1h - 1h Units in 1h - 81.9 - 56.16 (power used x 1h) Cost per unit - (Rupees) - 6.00 - 6.00.

Cost of electricity (Rupees) - 492.00 - 337.00 (Units x Unit cost).

* Gas used - nitrogen.

Gas flow - (litre/min) - 23 - 20.

Gas used in 1h (litres) 1380 - 1200 (litres/min x 60 min).

Cylinder (litres) - 7000 - 7000.

Cost of cylinder (Rupees) - 250 - 250.

Cost of gas (Rupees) - 49.50 - 43.00 (250/7000 x Gas used).

* Consumables.

Cost of Nozzle (Rupees) - 550.00 - 550.00.

Life of nozzle (m) - 30.00 - 70.00.

Cost of nozzle/m - 19.00 - 8.00 (Cost/life).

Cost of Electrode (Rupees) - 550.00 - 550.00.

Life of electrode (m) - 30.00 - 70.00.

Cost of electrode/m - 19.00 - 8.00 (Cost/life).

* Cutting speed.

Cutting speed (mm/min) - 83 - 83.

Cutting in 1h (m) - 5 - 5 (speed x 60 min).

Cost in 1h (Rupees) - 579.50 - 396.00.

Cost/m (Rupees) - 116.00 - 79.00 (Cost in 1h/Cutting in 1h).

* Notes.

1 - Labour cost not included.

2 - One US dollar is approximately 46 Indian Rupees.

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