How To Choose and Work With A Hand-Held Plasma Cutter
A plasma cutter is a simple tool to cut steel and other electrically-conductive metals, using a high-voltage electrical arc and a compressed gas - mostly air. The distinct advantages of using a plasma cutter is the surface of the metal outside of the cutting area remains cool and thus prevents the warping and paint damage that can occur with other flame cutters. Besides, plasma cuts up to five times faster than traditional torches and requires no highly-flammable gases. Many plasma cutters also perform well as gougers and can pierce metal rapidly and at the same time precisely.
Plasma cutters come in all sizes and shapes. There are small, handheld units that you might buy for a do-it-yourself workshop. But regardless of size or shape, all plasma cutters function with the same efficiency. The question is: How to use a hand-held plasma cutter for cutting, gouging and maintenance?
For Cutting with hand-held plasma cutter, the method is as follows:
• Place the drag shield on the edge of the base metal, or hold the correct standoff distance and direct the arc straight down.
• Press the trigger. After allowing for a few seconds of pre-flow air, the pilot arc acts.
• Once the cutting arc activates, move the torch across the metal. Set the right speed so that the cutting sparks go through the metal and out the bottom of the cut.
• At the end of a cut, angle the torch slightly toward the final edge to sever the metal completely.
• To cool the torch, allow the flow air to continue for 20 to 30 seconds after you release the trigger.
For gouging and piercing the method is as follows:
• Remove earlier welds using a gouging tip. It is to be noted that the hole on a gouging tip is roughly four times wider than a regular tip. Its cone shape pushes out the plasma arc, which can remove more material than a regular tip.
• Some new plasma machines feature a stronger design that creates an arc 1 to 1-1/2 inches long. Of course, carbon arc gouging removes metal faster. But plasma arc gouging has its own merits as it produces less smoke and noise and offers more control over the arc.
• To gouge, hold the torch at a 45-degree angle to the base metal. Press the trigger, and the pilot arc will start after a couple of seconds of pre-flow air. Set an arc length of 1 to 1-1/2 inches and move the torch across the metal, adjusting torch speed, arc length, and angle as needed. Do not gouge too deeply in one pass but take multiple passes if needed.
• To pierce metal, create a hole, such as for inserting a valve, place the torch at a 40-degree angle to the work piece and press the trigger. After the machine initiates the cutting arc, bring the torch tip to a 90-degree angle and the arc will pierce the base metal.
Some troubleshooting areas that call for attention are:
•If an arc is prematurely lost, or if the arc fails to penetrate metal adequately, then you must check the quality of the consumables. The electrode and tip will wear a little bit with every start/stop cycle and may have to be replaced if overly worn out. Bear in mind that low air pressure leads to bad performance, particularly at high amperages.
• If the pressure gauge does not move much beyond the optimum setting, adjust pressure at the gas source, because minimum flow rate may not maintain enough pressure through several hundred feet of pipe or hose. To ensure sufficient pressure at the machine, set the source gauge 30 to 40 PSI higher than the pressure gauge on the machine.
• To ensure sufficient air pressure at a plasma machine, the gas hose has to be 3/8-inch internal diameter and hose fittings should match or even be more than the rating recommended in the owner's manual.
• Remember that if water enters the torch, it can cause internal arcing that can destroy the torch. Make it a point to routinely change the air filters on a plasma setup as saturated filters do not remove moisture.
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