The ionized gas has more protons or positive ions than it usually would in nature, making it super-heated. It changes into another state of matter called plasma. It is the interaction between the plasma protons and the metal that allows plasma to cut through conductive metals. The protons are attracted to the conductive metal, which has a slightly positive charge, much like the opposing poles of a magnet. When the plasma gas comes into contact with the metal, the electrons from the plasma are transferred to the metal.
Being in an ionized state means that the electrons can freely move between the atoms of the gas and to the metal. The transfer of these electrons creates heat energy and essentially melts the metal that it comes in contact with. The melting of the metal creates a clean, uniform cut through the metal. The basics of plasma cutting are essential to know if you want to experience the money and time-saving process that is plasma cutting.
Other than the exact plasma cutting science previously mentioned, you must also understand a few more things about the plasma cutting process. The two gases which are used in Plasma Cutting are oxygen and Nitrogen. The consequences of using any less purity gas than recommended are:.
A process called gas swirling is utilized in many plasma cutting machines because of the benefits that it provides in the process. The non-ionized gas is significantly cooler in temperature compared to the ionized particles.
The machine swirls the gas to allow the mixture of the ionized and non-ionized particles. The non-ionized particles act as a temperature barrier to protect the copper alloy nozzle from melting. The single most important factor is whether your plasma cutter is capable of using the ideal gasses at the ideal pressure level and cutting speed or not! With the proper selection of gases, you can get a dross-free surface and an excellent edge on aluminium with plasma. A low-cost air plasma system can only work with compressed air and as a result, the edge quality will never be as good as industrial plasma cutting systems, which can use specialised gases like argon-hydrogen.
Plasma cutting aluminium can offer significant advantages over laser cutting, particularly when it comes to thickness, as laser will only cut metals up to around 25 mm thick, while plasma can cut through aluminium up to mm. Plasma also wins financially as plasma cutting has both lower equipment and operating costs. The quality of cut delivered by plasma is sufficient for most applications and industries.
Earlier plasma cutting systems struggled to achieve results over this kind of range, modern systems face no such struggle and can cut aluminium with plasma from gauge thicknesses up to 38mm pierce and 50mm with an edge start.
With thicker plates, mixed gas options typically argon-hydrogen-nitrogen mixes at higher amperages and with high cutting speeds result in a quick and simple process and a very smooth surface.
For extreme thickness applications, the Hypertherm HPRXD can production-pierce up to 75mm aluminium plate and severance cut up to mm! This is a really incredible leap forward in plasma cutting technology that finally consigns the poor results of the past — to history. Cut quality plasma cutting aluminium with different plasma gasses.
You only need to think about the plasma gasses when you have a dual gas or multiple-gas system. If you want to reduce costs, use air as secondary gas. It is less expensive and the cut quality is good. If your system allows, water shield will provide the best edge quality and will extend your consumable life. If As mentioned earlier, with plasma you can cut aluminium up to mm. Most regular aluminium sheet and plate can be cut successfully with plasma, however, there are a couple of notable exceptions.
The first relates to anodised aluminium. When aluminium is anodised to increase the thickness of the natural oxide on the surface, that finish becomes vulnerable under the temperatures involved in plasma cutting and the heat of the plasma will damage the surface anodising close to the cut area.
The second exception is aluminium floor plate also known as diamond plate, durbar plate and tread plate. The raised sections on the plate makes it difficult to cut as they can interfere with the arc-voltage height control on the plasma cutting machine, resulting in poor cut quality or occasional tip touches. The third exception is aluminium-lithium alloys. Never cut aluminum-lithium alloys in the presence of water. You might have heard about the dangers of a chemical reaction when cutting aluminium on a plasma water table.
Hot aluminium has a big affinity for oxygen, and it can grab some away from the H2O molecules, creating free hydrogen. But it must be said this production of hydrogen is most likely harmless, especially if you are not cutting multiple sheets in a short period of time. You can already make an aeration manifold with 50mm PVC tubing combined with 25mm connection lines.
Just make sure you drill small holes in the distribution lines. Cap the ends of the distribution lines so that oxygen is delivered to all parts of the cutting area. Plasma cutting is typically easier for the novice to master, and on thinner materials, plasma cutting is much faster than oxyfuel cutting. However, for heavy sections of steel 1 inch and greater , oxyfuel is still preferred since oxyfuel is typically faster and, for heavier plate applications, very high capacity power supplies are required for plasma cutting applications.
Plasma cutting is ideal for cutting steel, and non-ferrous material less than 1 inch thick. Oxyfuel cutting requires that the operator carefully control the cutting speed so as to maintain the oxidizing process. Plasma is more forgiving in this regard. Plasma cutting really shines in some niche applications, such as cutting expanded metal, something that is nearly impossible with oxyfuel.
And, compared to mechanical mean of cutting, plasma cutting is typically much faster, and can easily make non-linear cuts. The plasma cutting machines are typically more expensive than oxyacetylene, and also, oxyacetylene does not require access to electrical power or compressed air which may make it a more convenient method for some users.
What to look for when purchasing a plasma cutting machine Once you have determined plasma cutting is the right process for you, look at the following factors when making a buying decision. Determine the thickness of the metal that you will most frequently cut One of the first factors you need to determine is the thickness of metal most frequently cut. Most plasma cutting power sources are rated on their cutting ability and amperage. Even though a smaller machine may be able to cut through a given thickness of metal, it may not produce a quality cut.
Instead, you may get a sever cut which barely makes it through the plate and leaves behind dross or slag. Every unit has an optimal range of thickness - make sure it matches up with what you need. Select your optimal cutting speed Do you perform most of your cutting in a production environment or in an atmosphere where cutting speed isn't as critical?
When buying a plasma cutter, the manufacturer should provide cutting speeds for all thickness of metal measured in IPM inches per minute. For production cutting, a good rule of thumb is to choose a machine, which can handle approximately twice your normal cutting thickness.
If you are performing long, time-consuming cuts or are cutting in an automated set-up, be sure to check into the machine's duty cycle. Duty cycle is simply the time you can continuously cut before the machine or torch will overheat and require cooling. Duty cycle is rated as a percentage of a ten-minute period. For example, a 60 percent duty cycle at 50 amps means you can cut with 50 amps output power continuously for six minutes out of a minute period.
The higher the duty cycle, the longer you can cut without taking a break. Can the machine offer an alternative to high frequency starting? Most plasma cutters have a pilot arc that utilizes high frequency to conduct electricity through the air. However, high frequency can interfere with computers or office equipment that may be in use in the area. Thus, starting methods that eliminate the potential problems associated with high frequency starting circuits may be advantageous.
Initially, the nozzle and the electrode physically touch. When the trigger is pulled, current flows between the electrode and the nozzle. Next, the electrode pulls away from the nozzle and a pilot arc is established. The transfer from pilot to cutting arc occurs when the pilot arc is brought close to the work piece. This transfer is caused by the electric potential from nozzle to work. Compare consumable cost versus consumable life Plasma cutting torches have a variety of wear items that require replacement, commonly called consumables.
Look for a manufacturer that offers a machine with the fewest number of consumable parts. A smaller number of consumables mean less to replace and more cost savings. Look in the manufacturer's specifications for how long a consumable will last - but be sure when comparing one machine against another that you are comparing the same data. Many plasma systems are capable of cutting via multiple processes, so they can be fine-tuned to meet application requirements, Brandt explained. Different amperages and gases provide different results, such as increased productivity, a good edge finish, or tight tolerances.
If they just want to cut fast and plan to do postcut treatments to the edge, they might cut at amps as fast as they can. They can choose from many gas levels and many current levels, and the decision usually is dictated by prioritizing the desired outcomes. Many plasma systems are capable of cutting via multiple processes, allowing fabricators to fine-tune them to meet application requirements.
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