Brief description of working process and operation method of plasma cutting machine
Three-phase power supply supplies power to three-phase transformer through AC contactor. After rectifying the secondary of transformer, a DC power supply suitable for plasma arc cutting is obtained. AC contactor is controlled by intermediate relay.
After opening the front panel to control the power switch, press the torch switch, the air valve is first turned on. After the compressed air passes through the air filter pressure reducing valve and the air valve, the direct current power supply suitable for plasma arc cutting is established between the torch electrode (negative electrode) and the workpiece (positive electrode). At the same time, the high frequency arc igniter starts to work, and produces the high frequency and high voltage required for arc ignition, and the arc ignition time is about 1-2S. When plasma arc ignition is successful, the voltage on the high frequency arc igniter automatically reduces the extinguishing arc, and the high temperature and high speed plasma arc beam is emitted from the torch nozzle, which melts the part of the workpiece rapidly. At the same time, the melted metal is blown away by the high speed air flow, and a narrow cut is formed to complete the cutting process. After cutting, the torch switch is released and the plasma arc is extinguished.
The capacity of_three-phase power supply, (LGK-30, 40H) type distribution box insurance or circuit breaker should not be less than 45A, the cable cross-sectional area of connecting cutting machine should not be less than 4mm2, (KLG-60H) type distribution box insurance or circuit breaker should not be less than 50A, and the cable cross-sectional area of connecting cutting machine should not be less than 6mm2, (KLG-80, 100H) type distribution box insurance or circuit breaker. Not less than 60A, the cross-sectional area of the cable connecting the cutting machine should be no less than 8mm2. (KLG-120H) type distribution box safety or circuit breaker shall not be less than 60A, and the cross-section area of the cable connecting the cutting machine shall not be less than 10mm2. (When using generators, use generators with compensating coils with input capacity more than 2 times of the cutting power supply)
_The flow rate of the air compressor should be no less than 0.3m3/min and the working range should be 0.4-0.8MPa (according to the different power supply, the requirements are also different).
_The protective grounding wire must be reliably grounded from the M8 bolt behind the cutter by using a cable with a cross-sectional area not less than 10 mm2.
_When installing input and output cables or gas pipes, installing torches or loading and unloading torch fittings, the input power must be cut off.
_The inner diameter of trachea should not be less than 8 mm.
_Check to confirm whether the electrodes, gas distributors and nozzles of the cutting torch are tightened.
Do not move the cutting machine when the power is on. Do not dismantle the case and contact live parts (including nozzles) after the power is on.
_Arc ignition cutting should start from the edge of the workpiece. When the workpiece must be cut from the middle, a small hole should be drilled first, and then the arc ignition should start from the edge of the small hole.
Turn on the power switch and let the gas flow for several minutes to remove the condensate vapor in the cutting torch. When cutting begins, the nozzle of the cutting torch should contact the workpiece (such as non-contact cutting torch, the nozzle should leave the workpiece 3-5mm), press the cutting torch switch, ignite the plasma arc automatically, and the cutting begins formally. In the process of cutting, the cutting speed ensures that the workpiece can be cut through. Too fast not only can not cut through the workpiece, but also can cause back slag to burn the nozzle. Too slow will cause the nozzle to rise too high temperature, reduce the service life of the nozzle, widen the slit, increase residual slag, and possibly cause arc breaking. When stopping cutting, the torch switch should be loosened first, and then the torch should be removed from the workpiece. During the cutting process, the arc is extinguished because the torch leaves the workpiece higher than the height, then the switch needs to be re-pressed to start the arc again.
Matters needing attention:
Check the air pressure before each operation, so as not to burn the nozzle when the air pressure is abnormal.
Often check the electrodes and nozzles, if the loss is serious, it should be replaced in time to avoid affecting the cutting thickness and width. When the alloy wire consumes more than 2.0 mm or can not start arc, the electrodes can be installed and used in reverse or updated.
The output voltage of the cutting machine is very high. When assembling and replacing the electrodes or nozzles, the power supply must be turned off and protective gloves must be put on. The electrodes and nozzles should be tightened vertically upward and tightened again after two or three minutes.
Cutting torch should not be placed on the workpiece that has just been cut to avoid burning the torch and sheath.
Do not cut the sealed container unless necessary safety measures are taken.
_Cutting machine should take rain and wind protection measures when it is used outdoors. The rainproof shed and windshield should be at least 200 mm away from the cutting machine. The rainproof shed should prevent rainwater from entering the machine and make the cutting machine ventilated well.
When cutting, the operator should be in the upper wind position as far as possible, and should not operate against smoke.
Cutting workpiece should be carried out in a well ventilated environment. When cutting in a poorly ventilated or container, effective measures should be taken to enhance ventilation.
For ordinary carbon steel or stainless steel, the cutting limit thickness of 40 type is 15 mm, 60 type is 25 mm and 100 type is 35 mm. The cutting speed should be slowed down with the increase of cutting thickness in this range.
In the cutting process, the plasma flame should be perpendicular to the workpiece as far as possible, so as not to increase the plasma arc trajectory, which is equivalent to increasing the actual thickness of the workpiece. The cutting torch can be cut by pressing a button when it contacts the workpiece. Cutting can start from the edge of the workpiece. When the thickness of the sheet is less than 5 mm, it can start in the middle of the workpiece. But the torch must be inclined slightly to one side about 20 degrees in order to blow away the molten metal and cut through the metal. Otherwise, the melted metal will be blown back and the nozzle will burn.
Slow cutting speed will widen the cutting seam, increase the burrs and edges at the lower part of the cutting edge; too fast cutting speed not only can not cut through, but also easy to make molten metal blow back, adhere to the nozzle to disturb the flame flow and burn the nozzle.
Air pressure is generally adjusted from 0.4 to 0.4 at work.