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What To Consider Before Buying A Plasma Cutter

Most reasonably well-equipped farm shops have more than one tool on hand to cut metal. Oxy acetylene systems, chop saws and grinders are just a few options. But what about a plasma cutter? We’ve all heard of them and many have likely seen one in action. With all that other gear already in the shop, though, does it make sense to shell out up to $2,000 or more for one of these high-tech tools?

“It’s nice to have,” says Steve Hidden, product manager for the Plasma Group at Miller Electric Mfg. Co. “Most farmers already have some way to cut metal, but plasma has some advantages over all those methods.” He knows the higher price tag can scare off some farmers.

Unlike oxy acetylene, a plasma cutter will work on any metal that conducts electricity. That includes aluminum and stainless steel. The reason is a plasma cutter uses a different process to cut than the chemical reaction involved with oxy acetylene. “In farming it’s always been mild steel you needed to cut, but now there’s a lot more aluminium being put onto equipment,” says Hidden. “It seems like every year there’s more.”

Plasma cutters are able to handle that wider variety of materials by using an ionized gas (compressed air). When electricity is added through the electrode, the air becomes electrically conductive, creating a plasma arc that is forced through the cutter’s nozzle. Increasing the voltage and the air pressure intensifies the arc, making it hotter and able to cut thicker metals.

SHOP REQUIREMENTS

To get enough air to make a cutter work, shops will need a compressor with adequate volume. Hidden says Miller’s small Spectrum 375 model, capable of cutting mild steel up to 3/8- inch thick will need about 4.5 cubic feet per minute (cfm) at 90 psi. For a larger model, like Miller’s Spectrum 875, good for mild steel up to 7/8-inch, that increases to 6.75 cfm. “A lot of people think about the power

they need for a plasma cutter but they don’t think about the air,” says Hidden. “It’s extremely important.”

Plasma cutters can create a very smooth cut, and because their nozzle tips are so small, the kerf width is also narrower

than with oxy acetylene. With a narrow nozzle, heat is focused so there is less distortion in the surrounding metal, which makes plasma cutters ideal for sheet metal work. The focused heat also makes it possible to use temporary cutting guides made out of non-metal material such as MDF.

Plasma cutters are also remarkably small, so moving them around is easy. There is no need to handle compressed gas cylinders or worry about the safety concerns associated with them.

The process is easy to learn with just a little practise. “All you’re doing is pulling a trigger and the movement is similar to oxy acetylene,” says Hidden. There is no setup time required. “You’re able to cut right away and there’s no cleanup.”

TIPS FOR BUYING A PLASMA CUTTER

When shopping for a plasma cutter, the first step is to determine what thickness of metal it will typically be used for. “Every manufacturer rates their machines a little bit differently,” says Hidden. “But the thing is, how fast can you cut at a certain thickness? We talk about inches per minute (of cut). So ensure you evaluate that ability when comparing different models.”

Machines are generally rated for a maximum thickness. But Hidden suggests picking a machine that is rated a little higher than the usual jobs will require. “What you’re buying, if you spend more money, is speed,” he says. The thicker the material, the slower the cutting speed. Higher-capacity machines speed up the cutting rate.

Plasma cutters have duty cycles just like welders, which typically vary from 35 to 50 per cent. A duty cycle refers to how many minutes out of 10 a machine can operate continuously. Five per cent may not sound like a lot, says Hidden, but he notes that is usually enough for hand-held work. “Our testing and research shows most people cut for 20 seconds or less at a time,” he says. But if the cutter will be used on something like a CNC machine to cut large patterns, 35 per cent may not be enough.

For portable applications, a plasma cutter can be powered by a generator and a storage tank can supply compressed air during field repairs.

For anyone considering buying a plasma cutter, Hidden has some advice. “My recommendation to a farmer or rancher is to look (carefully) at the size capacity. What can it cut? How thick and how fast can it cut it? And what is its piercing capability? You want to be able to do the job.”

ScottGarveyismachineryeditorforGrainews.

Contacthimat [email protected]

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For portable applications, a plasma cutter can be powered by a generator and a storage tank can supply compressed air during field repairs.

About the author

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Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.

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