Plasma and Laser Technologies Applied To Industrial Metal Cutting

/ September 25th, 2011 / 2 Comments »

Plasma Cutting – a technologies that grew out of plasma welding inside the 1960s – emerged as a
extremely productive method to cut sheet metal and plate inside the 1980s. It had the benefits over
classic “metal against metal” cutting of producing no metal chips and giving accurate
cuts, and produced a cleaner edge than oxy-fuel cutting. Early plasma cutters
were significant,
somewhat slow and
high-priced and, therefore, tended to be dedicated to repeating cutting
patterns in a “mass production” mode. As with other machine tools, CNC plasma (
pc
numerical control)
technologies was applied to plasma cutting machines in the late 1980s into
the 1990’s, giving plasma cutting machines
higher flexibility to cut diverse shapes “on
demand”
based on a set of directions that had been programmed into the machine’s numerical
control. These CNC plasma cutting machines
were, even so, usually limited to cutting
patterns and parts in flat sheets of steel,
utilizing only two axes of motion (referred to as X
Y cutting). Industrial laser
technology followed a commercialization path for industrial
use
comparable to that of plasma, but roughly a decade later. Industrial laser cutting
technology for metals has the positive aspects more than plasma cutting of getting far more precise and utilizing
much less energy when cutting sheet metal, even so, most industrial lasers can’t cut by way of the
higher metal thickness that plasma can. Newer lasers machines operating at higher power
(6000 watts, as contrasted with early laser cutting machines’ 1500 watt ratings) are
approaching plasma machines in their
ability to cut by way of thick materials, but the capital
cost of such machines is considerably higher than that of plasma cutting machines capable of cutting
thick
supplies like steel plate. The majority of industrial laser cutting machines are
also
utilised to cut flat materials, using two axes of motion for the cutting head. Starting in
the late 1990s, programmable industrial robots
had been integrated with plasma and laser cutting
to
permit these metal cutting technologies to be applied to more generalized cutting of non-
flat shapes. These “3D Systems” use the industrial robot to move the laser or plasma cutting
head
about the element to be cut, so that the cutting path may encompass the entire outer
surface of the element.
Numerous systems also grip the element to be cut in a “chuck” to ensure that
the element itself
may be rotated or indexed forward or backward in concert with the
movement of the cutting head. This serves to
reduce overall cutting time and increase
accuracy by optimizing the motion of the element
with the motion of the cutting head.
Robotic 3D laser cutting systems
often make use of this technique of moving the element
to be cut,
because laser systems function nicely with smaller thin-wall elements such as tubes. As
OD and wall thickness of the pipe/tube increases, 3D laser cutting becomes
much less attractive
on account of the increased cutting time and higher capital price of laser cutting technology.
Robotic plasma cutting is
much more widely used for 3D cutting of pipe, including HSS, utilized as
structural steel elements. Vernon Tool
Organization was an early innovator in developing 3D
plasma cutting machinery for oil/gas field and structural tube/pipe.
Comparable systems
introduced by QuickPen, Watts Specialties and Bickle Manufacturing are capable of cutting
pipe diameters
as much as 32 inches and producing straight, angled and saddle cuts, such as
beveled-edge cuts
required for joining together various pipes. The task of robotic plasma
cutting of
a lot more diverse shapes, like beams and channels, has proven to be far more
difficult. The large sizes and variety of shapes involved make the technique of gripping
the structural steel element in a chuck impractical. This
places the whole burden of
cutting motion back on the robot.
To be able to have the cuts and attributes placed exactly where they
are intended on the element, the robot
must be given some instruction as to the location,
size and shape of the element. Burlington Automation developed
software capable of reading
CAD drawings of the structural element, and combining this
details with motion control
and sensor feedback to arrive at a 3D plasma cutting
program that in impact “sees” the
structural steel element
it really is to cut. There are no vision systems involved, rather the
robotic arm that carries the plasma torch head gently touches (probes) the element to be cut
in
multiple locations and combines this data along with the CAD drawing information to
establish the precise contours of the element in three dimensions. With this info, the
robotic plasma cutting
system, which goes by the trade name PythonX is able to cut a assortment
of
functions (bolt holes, copes, notches) or marks into precise locations along the structural
elements. This extends the automated 3D plasma cutting machine capability pioneered by
Vernon Tool and
others to the complete range of structural steel elements, therefore allowing the
PythonX
system to replace beam drill lines, coping machines, bandsaws and plate burning
centers. If the past is prologue, it
may possibly be expected that robotic 3D laser cutting
technologies will soon be frequently applied to the fabrication of structural steel elements, as
has already been
carried out with plasma cutting. The steel thickness limitation of laser cutting
has been overcome by the evolution of
more powerful laser systems. Nevertheless, as a common
rule, tolerances on structural steel elements are
less exacting than for other manufactured
steel goods (
including auto components), consequently the extra precision that laser cutting
provides is usually not required for structural steel. Locations of exception might be structural
elements for ships and
large, very customized fabrications for power plants. For the time
being, the lower capital expense and higher cutting speeds of robotic 3D plasma cutting make it
the
technologies of option for generalized fabrication of structural steel elements.

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