As we have seen before, the plasma cutting is a process in which a jet of ionized gas (plasma) is narrowed and directed through a nozzle and produces an arc that heats a metal electrically conductive above its melting point, it cuts the metal and throws molten metal (slag) through the cut slot.
This operation is carried out using equipment whose characteristics and basic components we saw in a previous article. Although there is a wide variety of plasma cutting machines Provided with features that vary according to the manufacturer and the needs of the client, we can distinguish two main types:
- Manual plasma cutting machines
- Mechanized plasma cutting machines
Next we are going to see these two large groups in detail and we are going to dwell a little more on the mechanized plasma cutting.
Manual plasma cutting machines
These are basically power supplies moderately small that use a hand-held plasma torch for cutting various types of metals. These rigs are manoeuvrable, versatile and can be used for a variety of cutting applications. Power supplies have a range of breaking capabilities that is based on the system output amperage and are commonly rated from 7-25 amps until 30-100 amps and, exceptionally, up to 200 amps.
The manual equipment plasma normally use air What plasma gas me shielding gas, and are designed to be used with a variety of input voltages. The input voltage is between 120 and 600V and use single-phase or three-phase power transmission.
The manual plasma cutting machines are generally used in workshops manufacturing facilities handling thin sheet metal, factory maintenance, agricultural maintenance, weld repair centers, metal service centers (scrap and scrap applications), buildings (such as buildings and bridges), commercial ship manufacturing, trailer manufacturing, auto repair, and works of art. Typically used in light metal applications to trim off excess material. A typical 12 amp hand torch cuts a maximum of 5mm of material at approximately 15 inches per minute. A typical 100 amp hand torch cuts a maximum of 32mm of material at approximately 20 inches per minute.
Generally a machine for manual plasma cutting is chosen according to thickness of the material to be cut and the cutting speed desired. Teams that offer high cutting amperage are the ones who have higher cutting speeds. However, when cutting at high amps, it becomes increasingly difficult to control the quality of the cut.
Mechanized plasma cutting machines
These teams are generally considerably larger than the manual machines and are used in conjunction with cutting tables (sometimes called pantographs), which include a water table or suction table and are provided with a gantry system or of portico -that is, a double motorization system on each side of the table, on the “X” axis- that works through various mechanisms, usually alternating current servomotes coupled to a rack-and-pinion system. In addition, the mechanized equipment They generally have cnc control and a torch height control (THC), which can include height sensing and voltage control at the start of the process.
The plasma cutting machines machining they can be incorporated in a punch press, as well as in laser cutting, oxyfuel, robotic cutting and other systems, forming true work centers automated. The size of a configuration mechanized plasma cutting it is based on the table and gantry being used. Tables can measure less than 1,500mm x 3,000mm or more than 14,000mm x 36,000mm. As you might expect, these systems are not easy to maneuver, so before installation all of their components must be considered in conjunction with the design of the enclosure that will house the machine.
In fact, the use of mechanized equipment introduces notable improvements in the quality and precision of the cut, as well as in productivity performance and lower costs compared to the flame cutting or the laser cutting. Many systems, furthermore, are designed with great operational simplicity, which enables its use by non-expert personnel.
Some of the characteristics of plasma cutting machines mmachined are the following:
Typical sources have a maximum amperage rating of 100-400A for him oxygen cutting Y 100-600A for him nitrogen cutting, while the input voltage is 200-600V with a three phase power transmission.
Gases: which ones and when are they used?
Gases commonly used for cutting mild steel (carbon steel), stainless steel, aluminum, and various exotic materials are compressed air, oxygen, nitrogen and a mix of argon/hydrogen. Combinations of these gases are used as plasma gas Y makeup gas. For example, for mild steel cutting, nitrogen is typically used as the plasma gas at the start of the cut, oxygen as the cutting plasma gas, and compressed air as the assist gas.
The oxygen it is used for mild steel because it produces high quality cuts in materials up to 32mm thick. Oxygen can also be used as plasma gas for gas cutting. stainless steel and aluminum, but an irregular looking cut is produced.
The nitrogen It is suitable as plasma gas and assist gas as it produces excellent cut quality on almost every type of metal. It is used for high current applications to cut metals up to 3 inches thick, and as the assist gas for nitrogen and argon/hydrogen plasma cutting.
The compressed air It is the most commonly used gas, either as a plasma gas or as an auxiliary gas. It works quite well for low current cutting applications on metal up to 1 inch thick, leaving a rusty cut surface. It is used as an auxiliary gas during air, nitrogen or oxygen plasma cutting.
For cutting stainless steel and aluminum, a mixture of argon/hydrogen as plasma gas. Provides a high quality cut and is required for mechanized cutting of material thicker than 3 inches.
The carbon dioxide It can also be used as an assist gas in nitrogen plasma cutting as it cuts most metals and provides good cut quality. Two other types of gases occasionally used in the plasma cutting process are nitrogen/hydrogen Y methane.
Plasmaforming and auxiliary gases are just two of the critical options that must be considered when installing or operating a mechanized plasma system. The Gas cylinders they are available for purchase or rent and are offered in different sizes, which means that space must be created to store them. The installation of a mechanized plasma system involves a considerable amount of cabling, as well as gas pipes Y refrigerant. In addition to the mechanized plasma system itself, the desk, the portico, the CNC and the THC. Manufacturers generally offer a variety of equipment options that are suitable for any cutting application.
How to make the correct selection of a team for mechanized plasma cutting?
Due to the complexity involved in selecting a mechanized plasma cutting equipment, a good amount of time should be spent investigating various system settings and criteria. To do this, we must consider the following:
- Types of pieces to cut.
- Number of production units cut per lot.
- Desired quality and speed of cut.
- Cost of consumables.
- Total operating cost of the configuration (including consumables, electricity, gas and labor).
The size, shape and quantity of production parts can set the type of CNC, table and gantry system. For example, small and intricate production parts may require a gantry with a specialized drive package. The rack and pinion drives, servo motors, drive amplifiers, and encoders used in the gantry determine the cut quality and speed capability of the plasma equipment..
The speed and quality of the cut also depend on the plasma equipment, the CNC and the gases selected. A mechanized equipment that offers gradual increases in current and gas flow at the beginning and end of the cut will increase the life of the consumable. In addition, a CNC with high storage capacity, a variety of programming capabilities (such as setting the torch height at the end of the cut), and fast processing speed (in/out communication) will lead to decreased downtime. and increased cutting speed and accuracy.
Ultimately, the decision to buy or upgrade a mechanized plasma cutting machine or use a manual equipment It must be based on the facts. Faced with such a decision, a client should consider the size, shape and thickness of the material to be cut.