As mentioned before, the plasma cutting process is based on melting down the steel and throwing out it debris with high density electric arch of plasma, which burns between infusibility electrodes and cutted object. Infusible electrode is made of copper with zirconium plate (or hafnium) and needs very intense colling down by air or water. The temperature of plasma stream depends of electric currency, arch narrowness degree and also a kind and ingredients of plasmatic gas.
For steel cutting are used only gas burners with iron arch. The spark on arch is obtained by high voltage electric impulse or by high frequency current. This makes possible to cut every conducting material (cast iron, steel, cuprum, aluminium etc.). Nonmetalic materials can be cutted only with plasma torches based on independent arch.

will be continued…

We can distinct the two groups of plasma when comparing a temperature.

• cold plasma, which is created in plasmatrons – temperature range: 4000 to 30,000 K
• hot plasma, found in the stars and nuclear fusions – above 30,000 K

When the electricity is conducted within the plasma cell, which has very high conductivity property, it has to pass the double layer. This is where almost all voltage potential is dropped. When we look closer to the plasma and electrical currency, we differ a three states:

1. very low electrical currency – no visible effects
2. moderate electrical currency – the visible light appears
3. electrical currency exeeds a given treshold – electric arc forms

The third one is the one we are interested especially when it comes to steel cutting. Steel cutting by plasma precisely. The electric arc allows to cut all electrically conductive materials and it is widely used in the industry in the mid of the previous century. Development of technology and electronics esteblished it in the steel machining world and deployed a strong competitor for the other cutting methods, like laser cutting steel for example. We will continue the topic in the next article.

Plasma cutting machines are dedicated for manual and automated handling. Plasma and air jumble is useful with cutting electrical conducting parts made of steel, alloys, aluminium and it’s alloys, coppers, brasses and even a cast iron. Plasma cutting machines shows it’s versatile also when it comes to different enviromental conditions allowing to cut deep underwater for example. Coeval plasma machines are usually instant ready to use and with special accesories can cut in places with limited access for the other tools.

The main advantages for plasma machines:

• high speed of cutting
• cutting without overheating – quick nailing
• small influence in the area of cutting on the steel
• narrow slit
• allows to cut without overburning thin fabrics.

And here comes some disadventages:

• loud work noise
• strong radiation
• much of exhausts – gases and fumes
• Some structure degeneration in cutting area
• perpendicular keeping is sometimes difficult.

Let’s see and listen some example:

Customizable power usage: 1500W/2500W/4000W
Max. cutting thickness: 7/8″ mild steel
Bed sizes: 4′ x 4′
Z-axis stroke: 16.5″
Features: Multi-process! 2D sheet & Plate, 3D formed parts, plus tube, pipe and structural.

• fastest method for metal elements development – In most cases, elements deployed from laser cutting machine are ready to use or montage right after cutting without further machining or processing, even polishing.
• narrow area affected by laser temperature – high focus of laser beam on operating area significantly limits side effects of high temperature. Thanks to that the structural features of steel are not changed by temperature (no crispness increase)
• minimize wastes – computer programmed track of laser movement (CNC) allow to maximize usage of material which can compensate higher cutting costs (in comparison to classic ways of cutting steel). Useless trash and wasted material can be reduced to minimum.
• repetitiveness of cutting process – laser header (lens) operates without physical contact with cutted material. Thanks to that there are no deterioration effect of cutting header during the process. In conjunction with computer steering, we can receive same looking elements with exact same features during the process and between succeeding production stages.
• laser cutting machines are great for singular, unique products and high number series production. It’s easy to make project on computer screen, test ready product, and make quick corrections if there are any required.

• in most cases, minimal radius of the the hole made by laser beam is equal to half of steel sheet thickness.
• the quality (smoothness) of cutted edge for the final products (elements) in most cases when meagre sheets are machined. With the increasing thickness of steel sheets the edge can not be so smooths, and further processing can be required sometimes. It is caused by the laser beam power so if you are going to cut thicker material you need more power than declared “highest values” in machine specification manual.
• the most of cutting machines doesn’t allow to set up laser beam axis so you can cut in the right angle only.

Maximum sheets dimensions (working range): 3000×1500 mm
Max sheet thickness: 20 mm
Speeds(X,Y): 60 m/mn

Wood cuted by Redsail M900 machine with some nice music as the background.

Laser cutting of steel

Automated process of optimise cutting way can save the material in the way no other method can stand with. Average quality of edge cutted by the laser is very smooth and the accuracy is keep at 0,01 parts of the milimeter). Thanks to the computer driven laser beam patch the waste can be pressed to the minimum. Movements of the laser beam during the process are quick, which means very quick delivery time but also minimizes the termical influence on the material so it preserves natural steels features as much possible.