How to Select and Operate a Hand-Held Plasma Cutter
It is relatively easierto use a hand-held plasma cutter. Many professionals and even hobbyist who try these cutters seldom want to return to using an oxy-acetylene method or the mechanical process of using cut-off wheels, saws, snips or shears.
The hand-held plasma cutter works equally good for all; contractors, fabricators, maintenance workers, do-it-yourselfers or artists.
Anyone who uses itjust once will get hooked on this form of cutting. The hard part about using a plasma cutter comes with trying to choose a machine that will match the application you are going to do and knowing what accessories will be needed.
How to use a hand plasma cutter (Soure : youtube.com)
What is Plasma?
Plasma conducts electricity, even though it behaves like a high-temperature gas, and can handle any electrically conductive material. A gas is electrically heated, which is often air, to a very high temperature and it results in a plasma arc. The atoms become ionized and are able to conduct electricity. The gas will spin around an electrode in what is called a swirl ring and this is what the plasma torch uses. The gas will heat up in the chamber between the tip and the electrode causing the gas to ionize and create the plasma. As the gas expands in volume and pressure and is constricted by the small, narrow tip it accelerates the plasma toward the piece of work at an incredibly high speed.
The plasma jet which is of very high intensity will melt a localized area. The arc has enough push to force its way through the piece of work and remove molten material. This will easily allow a cut through metals with poor heat conductivity or excellent conductivity. Professionals will not even use the oxy-fuel method as it causes excess warping cuts in stainless steel and aluminum; the plasma arc is their standard method when working with these metals.
Benefits of Plasma cutting
Cutting expenses are lowered and productivity is improved if the plasma method is used. It will perform faster and does not need a pre-heated cycle; will handle any material that conducts electricity; can be carried easily around job sites; creates cuts with a small width and minimizes the heat-affected zone. The plasma machines are also able to bevel, create holes, gouge, pierce and trace shapes.
How to choose a Plasma cutter
There are three important things you need to know before you choose your plasma cutter.
- What will be the thickest piece of material that you will work with most often?
- What is the thickest type of material that you could possibly need to cut?
- How fast doyou intend to cut?
A plasma cutter's size is determined by it amperage and voltage capacities. Welding machines are also determined in size the same way, however; the welding process requires low voltage and high amperage levels while the plasma cutter is just the opposite, requiring high voltage and low amperage. Do not judge a plasma cutter by the amperage alone; the total output power in watts will equal amperage times voltage. To get an accurate product comparison you will have to do the math with the numbers you find.
To calculate the production rates, you will need to know what speed you will need for different thicknesses of the material you will be cutting. These rates are normally calculated in parts per hour. This is important so that when you are performing the cut portion of your job there is no bottleneck created. The speeds most often determine the quality of the cut and the user's satisfaction while performing hand-held operations. You can find charts from most manufacturers of plasma cutters listing the different speeds to make it easier to compare performances.
There are three standard cuts:
- Rated cut is how thick your material can be that allows you to cut thinner steel by using a minimum speed and obtain a smooth and steady cut. This will provide the best possible results.
- Quality cut rating is how you can handle thicker material, but with a slower rate.
- Sever cut rating allows you to push the machine to its maximum capability. Your speed will be very slow and you will have to clean up the material significantly. Speeds are faster with material not as thick.
Cutting speeds will vary greatly among differentmodels of plasma cutters as will be the cutting differences of your material.
There are two basic elements that a plasma cutter requires; air and electricity. Choosing a plasma cutter will need that you know what type of power will be available to you. When you will have 115V as your primary service, then there are several plasma cutters that will operate using this service. When you have access to a 30-amp breaker you can also get good capacity with both 12 and 25 amp cutter.
If you work where there is no power and you have to rely on a generator you may want to go with a lightweight plasma cutter as it will be much more mobile.
If you use auxiliary power, you should consider selecting a machine with Auto-Line technology. Without this technology you mighthave unstable cutting arcs, circuit boards blowing out, breakers frequently tripping, and it will be prone to premature transformer failure. These incidents happen as you initiate the plasma cutter and it places an increased load on the line which will cause voltage levels to drop below the levelthe plasma cutter requires to operate.
If you are working in an environment where there is a lot of dust and shavings from machines or grinding, you should consider a plasma cutter with the Wind Tunnel feature. These models also usually include the Fan-On-Demand feature and provide much better reliability. This technology cools the air that flows through the machine and does not allow it to blow on other electronic parts of the unit. This means grinding dust cannot settle on the PC boards and other critical parts. The Fan-On-Demand feature means the fan will only operate if there is a need so there is less debris entering the machine. In the traditional units, the fan operates continuously and sucks in all air-borne particles.
Air Supply For hand-held plasma cutters, manufacturers normally recommend usingordinary air as gas. If you are working in the field and do not have ordinary air available then you may use bottled nitrogen as it is cheaper than the bottled air and contractors have had success with it. When you work with stainless steel you may find that it creates less oxidation as it is not as wet as compressed air. There are some models that have built-in air compressor features.
The plasma cutters use a 'high-frequency start' or a 'contact start' technology to initiate the arc. Depending on where you intend to use your plasma cutter you will want the proper start function. The high-frequency start could interfere with telephones, CNC machines, computers and other electronic equipment. The 'contact start' would work better near these machines.
Tips on how to operate the hand-held Plasma cutter
When cutting, use a regular or extended tip. With a plasma machine greater than 40 amps, there is a built-in drag shield to protect the regular tip. Machines less than those amps can have the tip placed directly on your work piece. Following straight edges or tracing, you can use this method as it will allow you to bear against the edge of the drag shield on a ruler or piece of wood to start cutting.
When you have to work in a corner and want a better view, you may prefer an extended tip. The extended tip will stick out up to 1 inch from the retaining cup and allow you to direct the flow of plasma better so it reaches into the corner. It will be important that you keep your hand steady because hitting the work piece too many times you will create an enlarged hole and the arc will no longer constrict sufficiently.
If you cannot keep your hand steady, you should consider using roller guides and circle guides. Any hand movement will be reflected in the cut. Using guides will allow you to stay in position and maintain a consistent standoff height and stop the tip from touching your work piece. Guides will also enable you to travel in a line or to make a perfect circle. Roller and circle guides make beveling easier as the guides permit independent adjustments of the wheel height to set the bevel angle.
- Removing imperfect or old welds
If you have to remove an old weld or one that was done incorrectly, you should use a gouging tip. The gouging tip hole is three to four times wider than theregular tip. It has a cone shape that will push out the plasma to remove a lot more material than a regular tip. There are some users of the plasma cutter who do not believe the gouging tip works in these conditions, but that was only true years ago when the older models had weaker arcs. The carbon gouging will remove material faster, the plasma gouging will produce less smoke and noise and will offer you more control over the arc.
Final tips before you start to cut
- Always follow safety instructions and wear the correct personal safety equipment. These are all explained in the Owner's Manual.
- Look the tip over as well as the electrode and shield cup and make sure they are not worn out. Replace any item that shows signs of wear and tear. These can affect your results and the expense to replace them is well worth not having imperfect results or your frustration in using your unit.
- Make sure the gas or air pressure is correct.
- Turn your plasma machine on.
- Set the amperage control to maximum and make sure the air pressure is correct.
- Remove by grinding off rust or paint where you are going to secure the ground clamp. When using a smaller amp machine this is especially critical as it just won't have the power to go through paint and rust like a larger machine can.
- The ground clamp needs to be placed as close as you can to the cut and put the clamp on the work piece. Make sure there are no loose connections between the clamp and the work clamp.
- Do not hold on too tightly, as it will cause your hand to shake more.
- You are ready to start cutting.
Follow these tips to perform perfectcutting:
- Place the drag shield on the edge of the material base. The arc should be directed down. (Remember the arc will start as soon as you press the trigger)
- Take the lock off and press the trigger.
- With the arc begin to move very slowly across your work piece.
- You will want the sparks to go through the material and out to the bottom so you may need to keep a good eye on your speed to ensure this happens. If there are no sparks coming out of the bottom of your plate, then you are not going through your piece. You may be moving too quickly or have inadequate amperage. You may also not have significant grounding causing this. Check what the problem is and correct before continuing.
- Reaching the end of the cut, turn the torch just a little towards the final edge before letting go of the trigger so that the piece is no longer attached.
- You will want the torch to cool down now. The machine is designed to let post-air flow continue about 30 seconds after you release the trigger. When you are ready to begin again, press the trigger.
The plasma system and the oxy-fuel both have pros and cons with their functions and uses. It will depend on what material youare working on and what kind of power you will have on hand when you need the machine. The plasma system is easier to use which may make your decision easier.