What conditions do we offer for laser cutting? The two most modern ways to cut sheet metal for production are laser and plasma. Both make you think of science fiction movies. Laser swords, plasma cannons… Fortunately, both of these destructive forces are now being used for exclusively peaceful industrial purposes.
The laser is a super-powerful beam of light.
Plasma is an ionized gas. The fourth aggregate state of matter is on a par with solid, liquid and gaseous. In fact, it is a gas that is so hot that it acquires completely different properties.
Both are used for cutting metal because they are able to heat it up to extremely high temperatures point-by-point. The molten metal is blown out of the resulting hole — in laser machines by a special jet of compressed gas, and in plasma machines-by the plasma jet itself. The beam or plasma arc moves, cutting the metal into reamers and cutting holes in them, laid in the program.
Here we will understand how laser cutting differs from plasma cutting for a production worker. What is the difference between laser and plasma holes, for which metal it is better to use these types of cutting.
Laser cutting-precision and cleanliness on sheet metal parts
The laser is guided more precisely than the plasma. The plasma arc is unstable. Of course, with the right setting, it will not start jumping all over the sheet of metal. But the plasma constantly fluctuates, making the corners and cutouts less clear. For small parts, especially complex shapes, this is critical. The laser cuts the metal clearly where it was directed, and does not move. This is essential for parts that require high quality and exact compliance with the project.
A laser can make narrower slits than a plasma. Clear holes in plasma cutting should have a diameter of one and a half times the thickness of the metal — and not less than 4 mm. The laser makes holes with a diameter equal to the thickness of the metal-from 1 mm. This expands your capabilities when designing parts and housings that have laser-cut reamers.
With laser cutting, thermal deformations are minimal. Theoretically, you can even overheat a part with a laser — if you write a special mocking cutting program. For example, the laser does not cut out very small and frequent holes for ventilation — this can cause overheating of the metal. For laser cutting, the vents are made larger and less frequent. In other cases, the deformations from the laser will not be noticeable. Plasma can not boast of this — the heated zone there is wider and the deformations are more pronounced. According to this indicator, the laser again gives a better result than the plasma.
The laser does not leave any scale on the sheet metal. This means that after laser cutting, the reamers are not sent for stripping, but immediately for bending. This saves working hours on the production of parts — and therefore saves the customer money in the end.
The holes, laser-cut, more perpendicular to the edge. Taper holes are a serious problem in plasma machines. From laser cutting machines metal thickness up to 4 mm wall will remain perpendicular, and at a thickness above 4 mm will get an easy bevel in the area of 0.5 degrees, the bottom hole will be slightly larger in diameter than the top. At the same time, however, there will be no distortion of their shape, and the upper and lower holes will remain strictly round — and the holes from the plasma with an increase in the thickness of the metal begin to tend to an elliptical shape.
Laser cutting machines have a high speed of operation — but it is also high for plasma machines. Here, both methods are good. And both lose speed if you increase the thickness of the metal.
The laser is ineffective for medium-to high-thickness metal. This is its main drawback compared to plasma technology. At thicknesses from 20 to 40 millimeters, it is used much less often, and over 40 millimeters-practically not used at all.
Plasma cutting — lower quality, more freedom in thickness
Greater freedom in the thickness of the metal for cutting is the main advantage of the plasma compared to the laser. Plasma cutting is appropriate for:
- steel up to 150 mm thick;
- cast iron up to 90 mm thick;
- aluminum up to 120 mm thick;
copper with a thickness of up to 80 millimeters.
High speed-as already mentioned, this is a common plus for both types.
Taper holes. This must be taken into account when choosing a plasma cutting machine. And if such carelessness of the holes is unacceptable for a particular order — it is better to cut it with a laser. The walls of the hole during plasma cutting deviate from the vertical by 3-10 degrees. The laser, let me remind you-0.5 degrees. Unlike a laser, plasma makes the lower hole narrower than the upper one. If the metal thickness is about 20 millimeters, the difference between the upper and lower cut diameters can exceed 1 millimeter.
Less precision, wider minimum slots relative to the thickness of the metal, increased thermal deformations — the opposite of all that the laser is good at.
The scale is often formed. It is worth saying that the scale from plasma cutting is removed from the metal quite easily — but it still has to be removed, and this is a man‐hour consumption and a corresponding increase in the cost of production.
The cost of plasma cutting increases rapidly as the number of holes per part increases. This is due to the fact that the consumable elements of plasma installations serve a certain number of “on‐off”cycles. The presence of windows in the scan increases the wear of consumables — and this has to be taken into account in the cost of cutting. The consumables of laser machines are less dependent on the “on‐off” cycles — accordingly, cutting through the windows in the scan has less impact on the cost of an hour of work.Summary: for which tasks is a laser better, and for which — plasma
Both competing types of cutting are worthy and necessary. It cannot be said that one of them is universally better than the other. Each of them is advantageous for its tasks — you need to understand the differences and use each for its intended purpose, so as not to lose the quality of the parts and not to overpay for them.
Laser cutting is definitely the leader in working with sheet metal. Especially with parts that require a precise match to the project, and with parts that are complex in shape. The use of laser cutting for metal with a thickness of more than 20 millimeters may be economically unjustified. For metal with a thickness of more than 40 millimeters-it is almost always unjustified.
Plasma cutting has lower accuracy and lower cut quality — and either should not be used for parts that require precise design compliance, or should be used with additional processing. However, it is cost-effective when working with sheet metal up to 150 millimeters.