HOW TO EVALUATE ENTRY LEVEL PLASMA CNC MACHINES

A large market has developed for low cost CNC plasma cutting machines used by hobbyists and homeowners, small welding shops, and even maintenance departments of larger companies to cut precise parts in house without breaking the bank. These machines can provide great performance at even better prices, but make sure they fit your needs.

CNC plasma cutting machines have been around for over four decades. These machines, often combined with CNC oxyfuel torches, have seriously influenced the metal fabricating industry, with dramatic improvements in productivity as well as reduced fabricating costs of fabricated metal components.

INDUSTRIAL SYSTEMS
The earliest CNC plasma systems evolved from photocell tracing machines and were often of a cantilevered design to accommodate a table for tracing drawings of the parts to be cut. Later on, bridge or gantry style machines were developed with sizes from about 4 ft wide to as much as 50 ft wide, and with cut table lengths exceeding 300 ft in some large shipyard applications.

In the last 20 or so years, complex bevel heads have been adapted to larger gantry style machines that allow for full rotation and contour beveling of plate. These bevel capable plasma CNCs have become lower priced and much more common for doing complex, multi-pass plate edge bevels for a variety of secondary uses. Also during this timeframe, the precision in terms of extremely tight tolerances has been consistently improved – all while having high acceleration and de-acceleration rates and the ability to maintain the necessary speeds required for high definition plasma cutting.

In the background, developments made in the field of computer technology, mechanical motion control designs, servo motor technology and high performance electronic motor controls used in many different industrial applications helped to dramatically improve technologies in the CNC plasma cutting machine fields. Of course the manufacturers of the plasma cutting process itself have been hard at work developing better performance, longer consumable life and ease of use with their industrial grade high definition plasma systems.

The latest industrial CNC plasma systems are highly accurate, extremely productive, and automated to the point where high precision metal parts can be produced three shifts a day by almost anyone that can navigate a Windows-based computer. The key to making these systems as simple to operate as possible, yet having the ability to cut holes with minimal taper in extremely high cut-to-cut cycle times, lies with having the brains of the machine, the CNC, work intimately with the plasma system, the gas flow control, the height control system, the CAM-based software, and, of course, the motion control of all the components of the cutting machine.

Sound expensive? Given that these large scale industrial machines do have a wide capability and option range, they can start in the $30,000 price range and scale up to the million dollar range for large shipyard machines. But remember that these systems are expected to produce high volume parts, three shifts a day for 20 years or more.

FOR THE SMALL SHOP
But what are the options for the small shop, the hobbyist, or even the homeowner that likes to do some weekend metal fabrication but simply cannot justify the cost of these industrial-grade CNC machines? The major industrial plasma cutter manufacturers also have great products in the hand-held plasma markets and use inverter-based power supply technology, along with torches that fire using a “blowback start” method (no high voltage, high frequency start necessary).

These low-powered air plasma systems have been around for years in the bottom end of the CNC plasma market, mostly in high speed, low tolerance cutting machines used in the HVAC sector to cut 24 ga and 26 ga galvanized steel for ductwork. PC-based desktop and laptop computers today have the power to run all of the motion and input/output signals necessary for a small CNC machine. And low-powered stepper and servo motor drive components have come way down in price.

Over the last six to ten years, a rather large market has developed in the form of low cost CNC plasma cutting machines. These machines, using an off-the-shelf PC or laptop Windows-based computer combined with relatively small, low cost stepper motor  or servo drive packages, are available from over a dozen manufacturers. (No, the vast majority of them are not from China! They are designed and manufactured in the U.S. and Canada.)