What Are the Pros and Cons of Plasma Cutters?

Plasma arc cutting machine is a machine for processing metal materials by means of plasma cutting technology.

Plasma cutting machine

Plasma is a gas that is heated to a very high temperature and is highly ionized. It transfers the power of the arc to the workpiece. The high heat causes the workpiece to melt and be blown off, forming a working state of plasma arc cutting.

Compressed air enters the cutting torch and is distributed by the air chamber in two ways, that is, plasma gas and auxiliary gas are formed. The plasma gas arc serves to melt the metal, while the auxiliary gas cools the components of the torch and blows away the molten metal.

The cutting power supply consists of two parts, the main circuit and the control circuit. The electrical principle: the main circuit consists of a contactor, a three-phase power transformer with a high leakage reactance, a three-phase bridge rectifier, a high-frequency arcing coil and a protection element. Power supply external characteristics caused by high leakage impedance. The control circuit completes the entire cutting process through the push button switch on the torch:

Pre-ventilation-main circuit power supply-high frequency arc starting-cutting process-interest arc-stop.

The power supply of the main circuit is controlled by the contactor; the gas flow is controlled by the solenoid valve; the control circuit controls the high-frequency oscillator to ignite the arc and stop the high-frequency operation after the arc is established.

In addition, the control circuit also has the following internal lock function: the thermal control switch operates and stops working.

1.Before use and when cutting

1. Check and confirm that the power supply, air source, and water source are free from leakage, air leakage, and water leakage. It is safe and reliable to ground or connect to zero.

2. The trolley and the workpiece should be placed in an appropriate position, and the workpiece and the positive electrode of the cutting circuit should be connected, and a slag dissolving pit should be provided under the cutting working surface.

3. The nozzle diameter should be selected according to the material, type and thickness of the workpiece, and the cutting power, gas flow rate and electrode shrinkage should be adjusted.

4. The automatic cutting trolley shall be operated by an empty trolley, and the cutting speed shall be selected.

5. Operators must wear protective masks, welding gloves, hats, filter dust masks, and soundproof earmuffs. Persons without protective glasses are strictly prohibited from directly observing the plasma arc, and bare skin is strictly prohibited from approaching the plasma arc.

6. When cutting, the operator should stand upwind. Air can be drawn from the lower part of the workbench, and the open area on the workbench should be reduced.

7. When cutting, when the no-load voltage is too high, check the electrical grounding, zero connection, and insulation of the torch handle. Insulate the workbench from the ground, or

1.Manual non-contact cutting

(1) Touch the torch roller to the workpiece, and adjust the distance between the nozzle and the plane of the workpiece to 3 ~ 5mm. (When the host machine cuts, the "Cut Thickness Selection" switch is upscale).

(2) Turn on the torch switch to ignite the plasma arc. After cutting through the workpiece, move to the cutting direction at an even speed. The cutting speed is based on the premise of cutting through, which should be fast or slow. Too slow will affect the quality of the incision, and even break the arc.

(3) After cutting, turn off the torch switch and the plasma arc goes out. At this time, compressed air is sprayed out at a delay to cool the torch. After a few seconds, the ejection stops automatically. Remove the cutting torch to complete the entire cutting process.

2.Manual contact cutting

(1) The "Cut Thickness Selection" switch is at the low level, which is used when the single machine cuts thinner plates.

(2) Place the cutting torch nozzle at the starting point of the workpiece to be cut, turn on the cutting torch switch, ignite the plasma arc, cut through the workpiece, and then move uniformly along the cutting direction.

(3) After the cutting is completed, open and close the torch switch. At this time, the compressed air is still spraying, and after a few seconds, the spraying is automatically stopped. Remove the cutting torch to complete the entire cutting process.

3.Automatic cutting

(1) Automatic cutting is mainly suitable for cutting thick workpieces. Select the "Cut Thickness Selection" switch position.

(2) After removing the cutting torch roller, the cutting torch and the semi-automatic cutting machine are firmly connected, and the attachment is provided in the random accessories.

(3) Connect the power of the semi-automatic cutting machine, and install the guide rail or radius rod according to the shape of the workpiece (if it is a linear cutting rail, if you are cutting a circle or arc, you should choose a radius rod).

(4) If the torch switch plug is turned off, replace the remote switch plug (prepared in the accessories).

(5) Adjust the appropriate walking speed according to the thickness of the workpiece. And set the "up" and "down" switches on the semi-automatic cutting machine to the cutting direction.

(6) Adjust the distance between the nozzle and the workpiece to 3 ~ 8mm, and adjust the center position of the nozzle to the starting strip of the workpiece slit.

(7) Turn on the remote control switch. After cutting through the workpiece, turn on the power switch of the semi-automatic cutting machine to cut. In the initial stage of cutting, pay attention to the cutting seam at any time and adjust to a suitable cutting speed. And pay attention to whether the two machines work normally at any time.

(8) After cutting, turn off the remote control switch and the power switch of the semi-automatic cutting machine. At this point, the entire cutting process is completed.

4.Manual cutting circle

According to the material and thickness of the workpiece, choose the single or parallel cutting method, and select the corresponding cutting method. Tighten the cross bar in the random attachment into the screw hole on the torch holder. If one is not long enough, you can connect them one by one. To the required radius and tighten, then adjust the distance from the tip to the torch nozzle according to the radius of the workpiece (the width of the slit must be considered). After adjustment, tighten the center fastening screws to prevent loosening, and loosen the cage to tighten the knurled screws. At this point, you can cut the workpiece.

The advantages of plasma cutting machines are

1. No-load voltage and arc column voltage

The plasma cutting power supply must have a high enough no-load voltage to easily start the arc and make the plasma arc steadily burn. The no-load voltage is generally 120-600V, and the arc column voltage is generally half of the no-load voltage. Increasing the arc column voltage can significantly increase the power of the plasma arc, thereby increasing the cutting speed and cutting larger thickness metal plates. The arc column voltage is often not reached by adjusting the gas flow and increasing the electrode internal shrinkage, but the arc column voltage cannot exceed 65% of the no-load voltage, otherwise the plasma arc will be unstable.

2. Cutting current

Increasing the cutting current can also increase the power of the plasma arc, but it is limited by the maximum allowable current, otherwise the plasma arc column will become thicker, the slit width will increase, and the electrode life will decrease.

3 Gas flow

Increasing the gas flow can not only increase the arc column voltage, but also enhance the compression effect on the arc column, so that the plasma arc energy is more concentrated and the spray force is stronger, so the cutting speed and quality can be improved. However, if the gas flow is too large, the arc column will be shortened, the heat loss will increase, and the cutting ability will be weakened until the cutting process cannot be performed normally.

4 Electrode shrinkage

The so-called internal shrinkage refers to the distance from the electrode to the end face of the cutting tip. A suitable distance can make the arc well compressed in the cutting tip, obtain a plasma arc with high energy concentration and high temperature for effective cutting. If the distance is too large or too small, the electrode will be severely burned, the cutting tip will be burned, and the cutting ability will be reduced. The shrinkage is generally 8-11mm.

5. Nozzle height

The cutting nozzle height refers to the distance from the end of the cutting nozzle to the surface of the workpiece to be cut. The distance is generally 4 ~ 10mm. It is the same as the internal shrinkage of the electrode, and the distance must be appropriate to give full play to the cutting efficiency of the plasma arc, otherwise the cutting efficiency and cutting quality will be reduced or the cutting nozzle will be burned out.

6. Cutting speed

The above various factors directly affect the compression effect of the plasma arc, that is, the temperature and energy density of the plasma arc, and the high temperature and high energy of the plasma arc determine the cutting speed, so the above various factors are related to the cutting speed. On the premise of ensuring the cutting quality, the cutting speed should be increased as much as possible. This not only improves productivity, but also reduces the amount of deformation of the part being cut and the heat-affected zone of the slit area. If the cutting speed is not suitable, the effect will be reversed, and the sticky residue will increase and the cutting quality will decrease.

1. Correctly assemble the torch

Install the cutting torch correctly and carefully to ensure that all parts fit well and that the air and cooling air flow through. Installation Place all parts on a clean flannel to prevent dirt from sticking to the parts. Add appropriate lubricant to the O-ring. The O-ring becomes brighter. Do not add more.

2. Consumables should be replaced in time before they are completely damaged

Do not replace consumables after they are completely damaged, because severely worn electrodes, nozzles, and vortex rings will generate uncontrollable plasma arcs, which can easily cause severe damage to the torch. Therefore, when the first time the cutting quality is found to be reduced, the consumable parts should be checked in time.

3 Cleaning the torch connection threads

When replacing consumable parts or during routine maintenance inspections, be sure to keep the internal and external threads of the torch clean. If necessary, clean or repair the connection threads.

4 Clean electrode and nozzle contact surface

In many cutting torches, the contact surface between the nozzle and the electrode is a charged contact surface. If there are dirt on these contact surfaces, the torch will not work properly and should be cleaned with a hydrogen peroxide-based cleaning agent.

5. Check gas and cooling gas daily

Check the flow and pressure of the gas and cooling air flow every day. If you find that the flow is insufficient or there is a leak, stop it immediately to troubleshoot.

6. Avoid torch collision damage

In order to avoid torch collision damage, it should be properly programmed to prevent the system from walking beyond the limit. Installing an anti-collision device can effectively avoid torch damage during collision.

7. The most common cause of torch damage

(1) The cutting torch collides.

(2) Destructive plasma arc due to consumable damage.

(3) Destructive plasma arc caused by dirt.

(4) Destructive plasma arc caused by loose parts.

8. Precautions

(1) Do not apply grease to the cutting torch.

(2) Do not overuse the O-ring lubricant.

(3) Do not spray splash-proof chemicals while the protective sleeve is still on the torch.

(4) Do not use a manual cutting torch as a hammer.

Serial number	Failure phenomenon	cause of issue	elimination method
1	Close the power switch Power light is off	1.The fuse is broken in the power supply switch	replace
		2.The fuse is broken after the power box	Check and replace
		3. Control transformer is broken	replace
		4. Power switch is broken	replace
		5. The indicator light is broken	replace
2	Cannot preset cutting gas pressure	1. The air source is not connected or the air source is empty	Connect the air source
		2. The power switch is not in the "ON" position	Move it
		3. Decompression valve is broken	Repair or replace
		4. Bad solenoid valve wiring	Check the wiring
		5.Broken solenoid valve	replace
3	No air flow when torch button is pressed during work	Pipeline leak	Fix leaks
		2. Solenoid valve is broken	replace
4	After the contact tip touches the workpiece, the torch button is pressed, but the work indicator is on but the arc is not cutting	1.KT1 is bad	replace
		2. High frequency transformer is broken	Check or replace
		3.Spark rod surface oxidation or improper clearance distance	Polished or adjusted
		4. Short-circuit of high-frequency capacitor C7	replace
		5. The air pressure is too high	Turn down
		6.Conductive tip loss is too short	replace
		7. Rectifier bridge rectifier element is open or short	Check and replace
		8. Poor contact or open circuit of torch cable	Repair or replacement
		9. The workpiece ground wire is not connected to the workpiece	Connect to workpiece
		10.Thick paint or thick dirt on the surface of the workpiece	Clear and make conductive
5	The contact tip touches the workpiece	1. Thermal control switch action	Allow to cool or work again
		2.The torch button switch is broken	replace

6	Control the blown fuse after high frequency startup	1. High frequency transformer is damaged	Check and replace
		2. Control transformer is damaged	Check and replace
		3. Contactor coil short circuit	replace
7	Main power switch fuse is broken	Short circuit of rectifier element	Check and replace
		2.Main transformer failure	Check and replace
		3. Contactor coil short circuit	Check and replace
8	High frequency occurs but no arc	1. Rectifier component is broken (abnormal sound in the machine)	Check and replace
		2. The main transformer is broken	Check and replace
		3.C1C7 bad	Check and replace
9	Can't afford long interrupted work	1. The temperature of the main transformer is too high, and the thermal control switch operates	Work after cooling down. Pay attention to whether the cooling fan is working and the wind direction.
		2. Line failure	Check repair