Working principle of the plasma cutting machine:
A processing method which takes oxygen or nitrogen as working gas, make use of high-temperature plasma arc heat to melt and evaporate the incision of the metal part and by means of the momentum of high-speed plasma flow to remove the molten metal in order to form slotting seam.
The working principle of the laser cutting machine:
The laser beam which generated by laser device transmitted through a series of the reflector, then focus on the workpiece surface by focus lens and produce local heat at the focal point, to cause the hot spot of the workpiece to melt or vaporize to form a slot. At the same time, the auxiliary gas is used in the cutting process to blow out the slag from the slot and finally achieve the purpose of processing.
Plasma cutting is suitable for cutting all kinds of metal materials. It is mainly used to cut the medium thickness plate.
The advantage is fast cutting speed, narrow cutting slots, small heat affected area, small deformation, low operation cost. The disadvantage is that there is 0.5-1.5°angle at the vertical cross section and hardening incision.
Laser cutting is mainly used to cut medium thin plate, and the cutting materials are in a very wide range (metal, non-metal, ceramic, glass, etc.).
Because the laser has the characteristics of high direction, high brightness and high intensity, the laser cutting speed is fast, the machining precision is high, and the cutting seam is very narrow, and there is no need for subsequent processing.
To sum up,
In terms of cutting materials: laser-cut materials have a wider range of choice than plasma cutting;
In terms of thin sheet cutting, laser cutting has more obvious advantages;
In terms of cost, plasma cutting is much cheaper than laser cutting.
Compared with the general cutting method, a laser cutting machine has some obvious advantages:
① Small cut slots, the cutting surface can be used directly for welding without grinding.
② Fast cutting speed: it can reach 10m/min for the thin sheet which is much faster than plasma cutting.
③ Good cutting quality: Small deformation, low surface roughness, low oblique cutting edge.
④ High precision: positioning accuracy can reach 0.05mm and re-positioning accuracy can reach 0.02mm.
⑤ Wide cutting materials: in addition to cutting metal, it can also cut wood, plastic, rubber, PVC, leather, textiles and organic glass etc.
However, laser cutting also has its disadvantages:
High cost ranks first. Both initial investment and later maintenance require higher costs.
At present, the laser cutting for the thin plate is more cost-effective. However, when cut the thick plate, the efficiency is low, so the laser cutting is not suitable unless the quality requirement is high.
For plasma cutting, it also has its advantages and disadvantages:
In the process of cutting a medium thick plate, it can achieve very high cutting speed, much higher than laser cutting and flame cutting.
The initial equipment investment is lower than the laser, and the later maintenance cost is also much lower.
① Poor perpendicularity of cutting surface: on the side of the cutting surface there will be a large oblique cutting edge, and the perpendicularity will be poor.
② Produce more cutting slag: the cutting slag will be produced during the cutting process at the bottom of the cutting surface. In order not to affect the quality of the post-process, this slag must be removed by grinding, which also increases the labor cost.
③ Generate harmful gases and arc light: the principle of plasma cutting determines the harmful dust and arc light will be produced during the cutting process. However, underwater plasma cutting is also been used to avoid this defect.
④ In the later period, it will consume more cutting nozzle, and the cost is very high.
According to our previous experience, laser cutting machine and plasma cutting machine are compared as follows:
- The laser cutting machine does not damage the workpiece, while the plasma cutting machine has damage to the plate. Especially during the cutting process, when the torch and nozzle of the plasma cutting machine have problems, it will cause obvious defects to the plate.
- Because the laser beam is focused into tiny light points, so the cutting slot of the laser cutting machine is narrow. The cutting slot of the plasma cutting machine is slightly larger than that of the laser cutting machine.
- Laser cutting machine has faster-cutting speed: the speed can reach 10m/min of laser cutter which is much faster than the plasma cutter.
- The cutting surface of the laser cutting machine is smooth, without burr, with good cutting quality, is a non-contact cutting. The heat affected area of cutting edge is very small, and there is almost no thermal deformation of the workpiece, which completely avoids turned-down edge when punching and shearing the material. Generally, the cutting edge does not need secondary processing, but the plate thickness is limited and the processing cost is high. However, the plasma cutting machine can cut 6-40mm steel plate with various model and power. The processing cost is relatively small.
- The laser cutter has high precision: the positioning accuracy of the laser cutting machine is 0.05mm, and the re-positioning accuracy is 0.02mm, but require higher the working environment condition. Although the machining accuracy of plasma cutting machine is not equal to that of the laser cutting machine, it has a low requirement for the working environment and strong mobility, and it has a wide range of cutting and requires lower skills for operators than that of the laser cutting machine.
The advantage of the laser cutting machine:
The cutting precision is higher, the speed is fast, the sheet deformation is small, suitable for the parts with a complicated shape, but the cutting thickness is limited. In general, for the plate under 8mm, the laser cutting machine is been used for blanking of the workpiece which requires high precision, because the blanking cost is higher, and the cleanliness of the plate is also required.
The advantage of plasma cutting machine:
Wide cutting range, all metal plates can be cut; fast cutting speed and high efficiency; cutting precision and fineness are higher than NC oxyfuel cutting. The disadvantage is cutting thick plate, especially for the 20mm+ plate, will be difficult. At this time, higher plasma power will be needed, which definitely will increase the equipment costs.
1. Comparison table for laser cutting and plasma cutting
|Laser cutting (CO2 laser 4kW)||Plasma cutting (O2 plasma 230A)|
|Cuttable materials||Metal: carbon steel, low alloy steel, stainless steel, high alloy steel, aluminum, copper alloy etc;
Nonmetal: ceramics, plastics, rubber, wood, leather, cloth, paper, film etc.
|High alloy steel such as carbon steel, low alloy steel and stainless steel.
Other non-metallic high viscosity materials (rubber, film, etc.), brittle materials (ceramics, glass, etc.) cannot be processed.
|Max. cutting thickness||25mm(mild steel)||150mm(ss, ms)|
|Thickness < 1||>10,000||Can’t cut|
|> 100||Can’t cut||――――|
|Slot width||Narrow||Very wide|
|Around 0.6mm for 16mm mild steel cutting||Around 0.5mm for 16mm mild steel cutting|
|Cutting size precision(cut off deformation)||Very good||Normal|
|Error ±0.15mm||Error 0.5～1mm|
|Advantage||・Capable of high precision machining.||・Portable|
|・There is very little thermal deformation.||・High speed cut off with low cost|
|Disadvantage||・With the increase of plate thickness, the hole drilling time increases sharply.
・The state of the material surface determines the processing quality.
・The difference in the composition of the material affects the quality of the cut surface.
|・Short service life of the electrode and nozzle (2 changes per day)
・Wide incision and big deformation.
・The width and shape of the incision are changed due to the consumption of the nozzle and electrode.
・The noise is loud when cutting.・Large amount of dust production
・Big hole dia.(φ12mm-16mm)
・Can not cut easily magnetized material.
2． The cutting slot comparison for laser cutting and plasma cutting
3．Oxygen plasma consumable life.
|Cutting method||Type of electrode||The processing of electrodes.||Electrode life||Nozzle life|
|Oxygen plasma cutting.||S-type||Early developed||60 min||45 min|
|F-type||Insert the modified version||120 min||60 min|
|LL-type||Insertion of special metals.||180 min||60 min|
|Water-adding type oxygen plasma cutting||Similar to F-type||Insert the modified version||120 min||150 min|
1 cycle of arc opening/closing, 1 min longevity comparison of endurance tests (Cut off current value: 250A)
4．The relationship between plate thickness and cost.
5．The incision width and cutting precision of various cutting methods.
6．Cutting conditions of various cutting methods.