A Quick Guide to Buying a Plasma Cutter
Do you plan to buy a plasma cutter? It can be difficult to purchase a type of equipment you’re not familiar with, especially that there are several models and manufacturers to consider.
To start with, answer the following questions before you go out shopping:
> How often in a day do you plan to use the equipment? In other words, what duty cycle do you need it to have?
> What type of electrical service is available where the machine will be used? Is it 50 amp 220 volt single phase, or maybe 30 amp 110 volt single phase? What other equipment will be sharing the circuit with the plasma cutter?
> What level of portability should your plasma cutter have? Are you going to use it in your shop exclusively, or do you have to take it to the job? Do you have way of supplying compressed air to the machine when you take it to a remote location? Will you use a portable compressor or an air bottle? What about the electric current onsite?
> What type of material do you intend to cut, and how thick will it probably be?
> Do you only plan to do manual cutting or with a CNC cutting machine? Generally, the greater the plasma cutter’s amperage output , the greater the duty cycle will be at lower amperages. Plenty of people think that a machine with greater capacity is always better, but not necessarily. Fabricators usually consider oxy-fuel as superior to plasma for cutting steel that have a thickness of .5 inch or more; this is because of the 4 to 6-degree bevel in the cut face made by the plasma. You won’t notice it in thinner materials, but as the thickness increases, it becomes more obvious. Also, plasma has no advantage over oxy-fuel in terms of speed at thicknesses beyond .5 inch.
It would be almost useless to get a plasma cutter if acetylene will be used for the work anyway. If your intention is to cut aluminum, stainless or any other non-ferrous metal, which oxy-fuel cannot cut, get a 50 to 80 amp 220 volt plasma cutter. If you’re going to use your plasma cutter outside the shop from time to time, consider getting one of those new breed semi-portable types. These are little powerhouses weighing below 100 lbs., but they have the ability to cut .75″ to 1″ in a snap. You’re going to need a bottle of air or a compressor, as well as a portable generator.
If you think you may automate your plasma cutting at some stage, you should choose a unit that uses a low frequency starting circuit. A high-frequency start is like your vehicle’s spark plug. Instead of using a comparably lower voltage pilot arc for initiating the plasma process, it depends on a high voltage spark, which brings about electrical interference such as destroying files, locking up the computer, destroying files, and the like.