September 13, 2005
To get a better idea of just how far plasma cutting has coe, let's take a look at where it started and where it's headed.
|Plasma cutting has come a long way since paper
September 13, 2005
To get a better idea of just how far plasma cutting has coe, let's take a look at where it started and where it's headed.
|Plasma cutting has come a long way since paper punch machines were used to write G-codes for the cutting controller. For example, 10-gauge cold-rolled steel sheet that's cut with a high-precision plasma torch yields a part with an accuracy of ±0.012 in.|
It wasn't that long ago that plasma cutting was the domain of seasoned metal fabrication veterans who knew just how to tweak gas settings and adjust torch height to get the best cut on a plasma cutting table. Today many of the highly trained technicians have left the shop floor.
What is left is the plasma cutting system, which in many cases still provides a quality cut but without the expertise needed to guide the machine. For many fabricators, this type of plasma cutting is the only type of plasma cutting they use.
That doesn't have to be the case, however. Technological advances have helped to automate programming for plasma cutting systems, and highly precise plasma cutting is now a reality.
To get a better idea of just how far plasma cutting has come, let's take a look at where it started and where it's headed.
Plasma cutting was invented in the mid-1950s. The patent holder learned that by sending a high-velocity jet of superheated gas through a constricted opening, ionized gas, or plasma, is created that can melt metal.
The predominant method of thermal cutting at that time was oxyacetylene cutting. An operator was required to control the torch head by hand, following a template, or the torch head could be mounted to a gantry-style trace-eye machine or a linear tracking rail.
By the mid-1960s NC gantry machines started becoming popular. The marriage of oxyacetylene to the NC gantry machines revolutionized the flame cutting process.
Plasma torches also were available on the NC gantry machines. Paper punch machines were used to write G-codes to the controller; however, only a limited number of people were capable of programming the machines.
Manufacturers and fabricators did not generally accept plasma cutting until the mid-1970s in the U.S. The reason for the delay in the popularity of plasma cutting can be attributed to the:
|User-friendly controls, at the cutting machine or on a nearby desktop, make setup on today's plasma cutting machines much simpler and quicker.|
In the 1980s plasma cutting grew in popularity as more low-amperage systems began to be manufactured. Thinner metals now could be cut with plasma. Electronic torch height control also was introduced. Electronically controlling the torch-to-workpiece distance allowed the torch head to pierce the material at a greater distance from the workpiece, which minimized consumable wear and contributed to a more precise cut.
The PC also gained in popularity during this period. Equipment programmers used the PC to generate machine G-code or ASCII text files that were used to direct the machine controller. Many machines continue to use this technology today.
CAD programs that could generate machine code became available in the late 1980s. The CAD programs combined with the PC provided a simple solution to programming the machine. The knowledge of G-code programming was no longer the only source to program the machine control. CNCs that allowed programming at the machine also became popular.
Also in the 1980s, Apple introduced the icon-style user interface to the computer, and Microsoft soon after released the first Windows® operating system to compete. The navigation of the PC via text alone became outdated.
The 1980s were a time that encouraged some pioneering fabricators to run machine tools directly from the PC. Many who operated their machines in this way found the user interface to be much more user-friendly when compared to rudimentary commercial control software offerings.
High-precision plasma cutting became available in the 1990s. Many cutting applications required the edge quality a laser machine could produce—no dross and smooth edges—but not the precise accuracy. These high-precision-plasma cutting machines became an affordable option for these types of applications.
Today fabricators benefit from the combination of the innovations that emerged in the previous decades. The refinement of high-precision plasma technology, such as the HyDefinition® torches from Hypertherm and the FineLine® torches from InnerLogic Inc.; the advancement of electronic torch height control systems; and the evolution of computer control technology have resulted in a popular contour cutting solution.Machine motion has improved because of advancements made in linear guiding, servomotors, and gearing:
|Automatic nesting software, common with many new plasma cutting machines, has made it easier to maximize material usage.|
Plasma cutting systems that feature these technologies have machine motion positioning accuracy of 0.004 inch. Systems of the past without sinusoidal AC servomotors, antibacklash gear heads, and precision linear guides normally would achieve only 0.015-in. positioning accuracy.
The tighter tolerance as related to positioning accuracy minimizes corner overshoot and maintains strai