by Jim Colt
What is the most important consideration when buying a torch for your plasma system?
As a long time plasma cutting guy, I would consider this question easier to answer if it was restated as: “what are the most important considerations when buying a plasma cutting torch/system?” I would have a hard time pointing out (with the many choices of power levels and system capabilities, with mechanized and hand cutting plasma systems) any one consideration that would place the best choice of torches in a buyer’s possession.
First we must consider cutting capacity. For that, we have the pierce capacity, the production capacity, and the severance capacity. Pierce capacity is the maximum thickness that a particular plasma cutter can pierce (in a mechanized cutting application) without adversely affecting the torch consumable parts life. Production capacity is the maximum thickness the plasma system can cut at its duty cycle rating. On many systems, this would be the same or close to the pierce capacity, although different manufacturers may rate this differently. Severance capacity is the absolute maximum thickness that can be cut with a particular system using an edge start (no piercing as this thickness in many cases is double the pierce capacity.) It is always wise to specify a plasma system that has the pierce capacity of the thickest material you could envision cutting. This keeps the power supply and torch safely within its design constraints for long life and best performance.
Second, is the capital equipment cost more important (low purchase price) or is cut quality and operating cost the driving factor in purchasing this system? This may depend on the intended use of the plasma cutter in terms of the production expectation. There are a variety of relatively low cost air plasma cutters on the market with excellent cut quality and reliability that can be used for both mechanized and handheld cutting applications. There are also a number of high end industrial rated plasma systems (considerably more costly to purchase) that produce better cut quality on a variety of materials, offer faster cut speeds, and dramatically lower operating costs. An air plasma is a great choice when purchase price and capital equipment budgets are the limiting factors. These systems are often the best choice for smaller operations with less demanding cutting needs and lower throughput requirements. The industrial 100 per cent duty cycle systems will feature liquid cooled torches with long life consumables, oxygen cutting capability for steel as well as other gas mixes for non-ferrous materials, and the ability to cut under multi-shift high production requirements without missing a beat.
Of course the decision needs to be made regarding the intended use of the plasma cutter from a few different perspectives:
- Will it be used for handheld cutting only?
- Will it need the ability to be used for handheld cutting as well as automated cutting (pipe cutter, track burner, CNC machine, etc.) each on a part time basis, with an easy plug and play transition from one mode to the next?
- Will the system be specified for just mechanized cutting?
There are some plasma cutting systems that can quickly become portable for shop and field use, and in minutes be configured back on a mechanized device for either field or hand cutting. Other systems are less portable, but are designed to spend their life on the shop floor producing high production for decades. Plasma manufacturers have dramatically enhanced the versatility of this process with some machines that can operate on household power, are the size of a two slice toaster, and can sever over ½ in. (12.7 mm) thick steel, to the other end of the spectrum with 800 amp industrial plasma systems that can cut over 6 in. (152.4 mm) thick non-ferrous materials three shifts a day without breaking a sweat.
There are many more considerations on the purchase of a plasma torch, including ease of use, power requirements, portability, safety, torch ergonomics and design, edge metallurgy, hole quality, beveling capability, to name a few. The above are likely some of the first questions I would ask if speaking with a potential buyer. Be sure to cover all of your needs and talk to the experts on the subject before jumping into the wide world of modern plasma cutting technology. SMT
Jim Colt is application technology manager with Hypertherm Inc., Hanover, NH.
