Plasma cutters are used by all industries that would have previously solely used oxyfuel – from the most significant industrial companies down to the smallest hobby and craft shops. Due to the varying needs of each individual or business, the type of cutter required will differ considerably (source). How do you choose a plasma cutter, to begin with?
Choosing a type of plasma cutter depends on the intended use. Some of the variations to consider are portability, productivity, and usability. Due to its high speed, precision, and low cost, a plasma cutter offers great utility for many projects.
Plasma cutters work with an air compressor, which can be built-in or bought separately. Pricing differs significantly between them, but no doubt, convenience will dictate which is better suited for your use and job requirements.
Check out another article we wrote on inexpensive plasma cutters here after you read through this and understand the different types.
What is Plasma Cutting?
Plasma cutting is a process whereby an accelerated jet of hot plasma cuts through electrically conductive materials such as steel, stainless steel, aluminum, brass, and copper—utilized mostly within the automotive repair, industrial construction, salvage, and scrap metal operations.
Before purchasing any piece of equipment, one should have a brief understanding of what the tool does and how it does it so ensure that the user has space and capability to use the equipment safely.
How does Plasma Cutting Work?
Plasma is the fourth state of matter. While we usually only give reference to three states of matter generally, that is solid, liquid, and gas, plasma is the state that exists when the heat and steam are combined, and the gas becomes ionized and electrically conductive (source).
A plasma cutter uses this electrically conductive gas, now plasma, to transfer the energy from a power supply to a conductive material. A plasma arc begins when a gas, such as oxygen, nitrogen, or argon, is forced through a small nozzle orifice inside the torch.
The electrical arc generated from the external power supply is introduced to this high-pressure gas flow, thereby resulting in a plasma jet. The plasma jet can reach temperatures of up to 40.000° F, and easily slices through metals like a hot knife through butter.
Choosing a Plasma Cutter
When choosing a plasma cutter, it is essential to understand that there are differences in units manufactured for industrial and domestic use. Without proper training, purchasing, and using the wrong one may cost you both time and money in the long run.
Portability, Productivity, Usability
Small plasma cutters are portable, allowing many contractors and tradespeople the opportunity to use it while on the job instead of bringing the job to their workshops or paying premium costs to have specific sizes cut for them by someone else. If you want to learn more about small plasma cutters, check out this article.
The varied uses of plasma cutters may surprise you. Even though they are quite obviously a handy tool to have in most industries, they are also somewhat useful in several other areas of productivity.
Artistic Use Of Plasma
Many artists create art through cut metal, and of course, these cuts need to have almost surgical precision. A high level of detail is possible with a plasma cutter that can be programmed to cut along the finest line drawings without warping or bending the metal in any way.
Another use for plasma cutters is to create the intricate templates and stencils that allow other creatives to make their art pieces, thus making the tool an essential device in the arts and crafts world.
Commercial Plasma Uses
The plasma cutter is a good piece of equipment for a plumber to have in his arsenal. Cutting pipes while out in the field is a timesaver, and the precision of cut plasma pipes beats any handheld saw cut, making the pipes fit together cleanly and without frayed edges.
General and subcontractors use plasma cutters for all construction elements requiring sheet metal. The work can be undertaken directly on-site without hassle as long as there is an available power source (source).
Ships are usually built in a shipyard by shipwrights specializing in naval engineering. These shipwrights use plasma cutters to size the plate steel required to construct the bulkhead, deckhead, and the hull.
Refrigeration and air conditioning companies use plasma cutters to cut through metal for installations and to fabricate and make repairs on metal ducts without necessitating back, and forth trips to the workshop.
In industry fabrication, detailed precision cuts can be done in bulk when a CNC machine and plasma cutter and used in conjunction. Multi-axis cuts also make seam welding better. A plasma cutter in the shop industry allows for repeated patterns to be cut with precision and speed.
Car detailers use plasma cutters to fabricate exhaust manifolds for turbo conversions and also to remove damaged sections of a car before inserting other pieces. The plasma cutter also comes in handy to remove rust from the body of the vehicle.
Different Types of Plasma Cutters
Automatic Plasma Cutters
Automatic plasma cutters are usually big units that handle large-scale work. Industrial production lines, where large steel-cutting projects occur, is where theses cutters can be found. Automatic cutters are computer operated with the control head generally mounted to a table.
When it comes to these plasma cutters, it is essential to know the maximum plate size you need, what the maximum plate thickness will be, how many sheets you need cut, how much space you have to work in, and what tooling you will require.
Computer Numerically Controlled or CNC plasma cutters also run on software, so it is essential to hire someone with the capability to create and edit the CAD files that the CNC imports. With the correct unit in place, the cost to accuracy ratio is maximized, and wastage is minimal.
The number of automated options on a CNC machine alone is impressive. There are as many variables and parameters as there are types of machines, so choose wisely before starting that new job.
Computer Numerically Controlled (CNC) Plasma Cutter
There are many different kinds of CNC plasma cutters. The three main configurations of these units are the 2D/2 axis, 3D/3+ axis, and tube and section CNC plasma cutters. The differences between them are quite significant.
This machine is the most common of the lot and produces flat profiles with cut edges that are at 90-degrees to the material’s surface. The machine’s configurations can cut metal plates up to 150mm thick.
This machine can also cut flat profiles, but instead of 90-degree angles, it can rotate on a third axis that allows it to also cut edges at angles that are not 90-degrees. The ability to cut other angles makes it useful in creating countersunk holes and chamfer edges of profiled holes.
Its versatility also makes it ideal for cutting profiles that are part of a welded fabrication. Getting a 30 or 45-degree cut allows pieces to be immediately welded together without secondary processes like grinding or machining, thereby bringing down costs.
Tube and Section
This machine is used to process tubing, piping, and other long sections of material. The cutting head is usually stationary but may tilt or rotate depending on its configuration. This movement can allow for the cutting of more angles.
Manual Plasma Cutters
Manual systems are ubiquitous handheld devices delivering high-cutting amperage. They are suitable for lighter work that involves trimming or cutting smaller pieces of metal. These devices can be in garages, auto repair shops, hobby shops, and even homes.
All handheld units use conventional plasma. Conventional plasma cutters use shop air instead of plasma gas, and the tip of the nozzle determines the shape of the arc. Amperage is in the range of 12-20 kilo amps per square inch.
High Definition Precision Plasma
Precision plasma units are engineered to create the highest definition cut possible for industrial use. The system may utilize multiple gases like a hydrogen/argon/nitrogen mixture, oxygen, nitrogen, or compressed air. A precision plasma arc is about 40-50 kilo amps per square inch.
Depending on the type of work and unit, methods of starting an arc vary. In some, the arc occurs once the unit is in contact with the workpiece. Other cutters use a high-voltage/high-frequency circuit to start an arc.
The disadvantages and risks incurred with the latter method include electrocution, inability to maintain the spark gap, difficulty of repair, and an increase in the number of radio-frequency emissions.
Units used near sensitive equipment like computers and other electronics start the arc by blowing the nozzle forward when the plasma gas begins to flow or through a capacitive discharge into the primary circuit via a silicon controlled rectifier.
As with any piece of equipment you purchase, the amount of dollars spent at the beginning is not the end of your investment for life. There are many components of a plasma cutter that get worn out with usage and will need replacing over time.
Be prepared to purchase various consumables like shields, deflectors, nozzles, retaining caps, swirl rings, and electrodes. These components will each have a different lifespan depending on their manufacturing quality and how you use your machine.
Most good manufacturers sell boxed kits for their machines with instructions on how to remove and replace a worn-out part. Disassembly is a child’s play-act, and the numbered pieces are easy to reference.
People who work with this tool say that using a plasma cutter is akin to holding a lightning bolt in your hand, so treat accordingly. As handy as this machine is, there is no doubt it can cause serious injury if misused.
Here are some safety gear recommended by the professionals:
- a plasma shield/helmet to protect your face and eyes
- a welding beanie to protect your hair from catching alight from sparks
- a welding jacket to protect your arms and torso from sparks
- a pair of welding gloves to protect your hands from the plasma arc
- a pair of utility jeans to protect your legs from sparks + welding leathers if you have some
- a couple of tightly laced boots to protect your feet from falling pieces of sheet metal or molten steel
- a fire extinguisher
Proper eye protection is required to prevent eye-damage from flying debris or arc-eye caused by exposure to radiant energy. Different filter lenses manufactured to counter the latter are essential.
The Occupational Health and Safety Act regulates all protective gear supplied to employees working in the industry with a grading scale ranging from light to heavy on filter lenses that protect from radiant energy (source).
OSHA recommends shades between #7 and #9 for arc currents less than 300 A but notes that lesser shades like the #5 may be appropriate if the workpiece or protective shield hides the visible arc.
Photokeratitis, commonly called arc-eye, is like getting a sunburn on the cornea and conjunctiva of the eye. It can be several hours after exposure that the symptoms become evident. The recorded symptoms include tearing up with a feeling of intense pain likened to having grains of sand in the eyes.
Concerning safety equipment, the eyes are not the only concern. I recommend leather gloves, aprons, and jackets to prevent burns from sparks and hot metal.
It goes without saying that all work with a plasma cutter should be undertaken in a clean environment, free of all flammable liquids, materials, and gases within at least a 6-foot radius. Sparks can fly quite far, so ensure the work area is free from all such fire hazards.
Potential Safety Hazards
Any metalworker knows that cutting metal has the potential to be dangerous. However, when cutting metal using a plasma cutter, the danger is at its highest at the beginning of the job and then decreases in some ways after the first cut.
When beginning a new cut, there is always the possibility that metal will spray upwards until the plasma arc has wholly pierced through the steel you are cutting. This is commonly referred to as “blowback” (source).
While this mostly occurs with thicker metal, and only for a fraction of a second if that, the sparks are substantial enough to cause severe damage. Burns to your face, head, hair, and clothes are all a possibility, so make sure you wear protective gear from the very beginning.
Steel-capped protective boots are a must-have for anyone cutting substantial sections of metal because the offcuts may crush your feet when they fall. They can also protect you from sparks and burns if you lace them up properly and tie them tightly around your ankles.
Tips to Plasma Cutting
To get the best cut quality requires using the right tool with the correct amperage for the right piece of metal. While skill is essential, the most skilled artisan will get a poor quality cut if his tools are shoddy.
Before pulling a manual plasma trigger, let’s look at some tips and tricks to make the job easier and also to make sure you still have all your fingers and toes left at the end of your exciting project. Here are some suggestions to note for manual cutters:
- brace your cutting hand with your non-cutting hand for added stability
- practice your cuts before you start, tracing the pattern a couple of times to get into the flow
- make a test cut on a similar piece of metal to ensure you use the right amperage and speed
- on thicker material, pause to sever the last part or roll the torch tip
- to bevel, the edges of your cut, tilt the cutter at a 30 or 40-degree angle
- roller guides make cutting straight edges a breeze
- circle guides give you perfectly cut circles of various sizes every time
Automatic cutters are entirely different, if not easier, than manual units, and the technique used is a precise science. Therefore, with a CNC cutter, keeping your eye on the details early on will reward you tenfold later. Here are some tips for using automatic cutters:
- replace the consumables regularly to ensure you always get the cleanest cut
- match the power level to the thickness of the material to get the best cut quality
- maintain the correct suspension, so no damage occurs to the torch
- reduce dross by using the right power setting, torch height, and cutting speed
- get someone knowledgeable and trained to draw up the CAD plan
As with any power tool, you are purchasing the best quality machine that you can afford early on will give you years of reliable work and generally excellent after-sales service as well, if you buy locally manufactured machines.
Make sure you buy a unit that has consumables readily available. Ordering a machine from overseas sounds good dollar-wise while the consumables last, but after that, you are bound to shipping in what you need and having to wait a long time to get parts.
Manufacturers are continually coming up with new ways to make plasma cutters more useful than ever. So, do your research before buying and expect to find a full range of great plasma cutters from which to choose.