Education on a ‘hot' topic
April 1, 2010
Developed more than 50 years ago, plasma cutting has come a long way. The process, which uses ionized, electrically conductive gas to cut mild steel, aluminum, stainless steel, brass and other non-ferrous materials, was at one point too bulky and expensive to be practical for the HVAC and sheet metal industry.
Times have changed. With system size and price having been on a downslide for years, units that were once 50 pounds and $2,500 are now under 20 pounds and $1,000, providing both affordability and practicality. Additionally, some smaller, more portable plasma cutting systems are now self contained and can run off any 110-volt circuit, meeting the flexibility and portability needs of today’s HVAC or sheet metal professional.
One of the most common types of processes in the cutting and welding industry, plasma provides both speed and precision. However, before using this process, operators must possess the knowledge and familiarity needed to achieve the desired results and get the most from the plasma cutting process.
How does it work?Many different gases can be used as plasma, including air, oxygen, argon-hydrogen and nitrogen. Once the pressurized gas is heated to an extremely high temperature, it becomes ionized and electrically conductive. At this point, the gas reaches the fourth state of matter and is considered to be plasma. The induced plasma stream carries the electrical current to the work piece and the intense heat melts the material. The molten metal is then blown away by the plasma stream. The result is a cut or severed material.
The intense heat of the plasma arc, around 40,000°F, results in a cut that is clean with little or no dross. Done properly, the process usually requires very little rework or cleanup. The heat also allows the arc to burn through most surface coatings such as paint and rust, so less preparation work is needed. Plasma can cut ferrous and nonferrous metals with little or no heat-affected zone. This is especially useful when cutting thin material such as ductwork, as it will not warp or bend.
Making the most of itAnswering a few basic questions will allow you to choose a plasma system that best fits your needs. Ask yourself:
• How thick is the material to be cut?
• What level of cut quality do I require?
• What type of material am I cutting?
• What is my primary input power?
Knowing the answers to these questions will help your local distributor guide you in the right direction.
As you consider the advantages of plasma cutting and the applications for which you expect to use it, you should also take some time to understand some basic terminology, and basic uses of the technology. Manufacturers use terms such as severance, pierce, recommended cut and rated to refer to a machine’s cutting capabilities. Amperage draw, input voltage and maximum amperage output refer to the amount and type of power used and the amount of power transferred to the material being cut.
Safety and troubleshootingAs with most welding and cutting processes, there are always potential safety hazards to be aware of. Remembering the saying “Safety first” is extremely important to all welding professionals, helping to ensure that appropriate measures and precautions are taken.
The appropriate personal protective equipment is required to protect hands from heat and eyes from the intense light of the plasma stream.
Even though plasma machines require little routine maintenance, supplying clean, dry air and keeping the consumables in good condition will help to ensure optimal performance day in and day out. Moisture will reduce the effective life of the consumables, while air contaminants will clog filters and reduce flow - and both will affect the unit’s efficiency.
Because of the demanding environments the equipment is placed into, most plasma machines are fairly rugged and are able to withstand minor abuse. However, units that have protection against the inevitable fall or impact can lead to a longer productive life than those that do not. The addition of a roll bar is a simple way to protect all the gauges and connections from being damaged in a fall. Quick disconnects will allow damaged torches to be replaced quickly or allow lead extensions to be added so that work can be done up to 100 feet away from the power supply.
Some of the more advanced models aid in troubleshooting with onboard diagnostics that indicate what type of setup or error condition is occurring. For example, if incoming air pressure drops below an acceptable level for optimal performance, the unit will shut down and a small light will flash a low-pressure-condition message on the front panel. Or, if the consumable components are not installed correctly, another light will show a parts-in-place error. Units have become user-friendlier in recent years with the focus being on up-time and ease of use.
Although plasma cutting is one of the most highly recognized and applicable cutting processes, it is imperative to use safety and precaution before starting your cut. Utilizing all the knowledge, tips and techniques required will allow for a productive plasma experience.
Kent Swart is marketing manager of Thermadyne’s Thermal Dynamics brand of plasma systems. Contact him at firstname.lastname@example.org.