Whether you are a first time buyer or have existing installations of plasma and/or oxy-fuel shape cutting systems, continuous advancements in technology and a growing landscape of low-cost manufacturers and integrators has clouded the automated plasma shape cutting machinery landscape.
Plasma cutting is caused by introducing an electrical arc via a gas that’s blown via a nozzle at high pressure, inducing the gas to turn into plasma and making a focused flame that reaches temperatures of 50,000 degrees Fahrenheit. Automated plasma cutting systems are classified as either conventional or precision (high-definition), on the basis of the characteristics of the cutting flame. Precision plasma systems are designed for producing parts to tighter tolerances, achieving faster cut rates, and producing less kerf and bevel than conventional plasma systems. The expense of these units may also be significantly more than conventional plasma systems. It is therefore extremely very important to properly match the shape cutting machine with the right plasma cutting system.
One of the very most common and costly pitfalls buyers encounter is when manufacturers or integrators mismatch machines and power sources. This is often caused by manufacturers not finding the time to comprehend the buyer’s requirements, having a limited or single-product line of machines, limited OEM use of power sources, and/or too little industry/application knowledge. These manufacturers will then often sell with an emphasis on lowest price instead of lowest cost of ownership, highlighting the strong point of the plasma system or the machine without regard to the limitations of the other. The most effective precision plasma power source available won’t provide users with the desired cut quality and accuracy if it’s not mated to a proper base machine.
There are various kinds of plasma shape cutting machines available available in the market today. The most frequent machines are bridge or gantry style machines created from either fabricated steel or extruded aluminum. Construction of the machine is extremely important relative to your application. Machines made out of extruded aluminum are normally considered to be hobbyist or artisan machines and most appropriate when doing a limited quantity of cutting or when cutting light gauge materials. The plasma and oxy-fuel cutting processes create large amounts of heat that will be retained in the materials being cut and can cause deflection or warping of aluminum machine components traveling within the hot cutting surfaces, greatly effecting accuracy and cut quality. Fabricated steel machines are highly recommended for almost any continuous cutting process, cutting of plate steel, and where auxiliary oxy-fuel torches might be used. Auxiliary heat shields may also be available to further protect the machine and components from extreme heat conditions.
Cutting machines are available with many different drive systems including single-side drive, single-motor dual-side drive, and true two-motor dual-side drive systems. A well constructed single-side drive system or single-motor dual-side drive system will perform very well in conventional plasma applications. The benefit of the extra precision provided by two-motor dual-side drive systems won’t be realized in conventional plasma applications because of the limitations in the precision of the standard plasma cutting process itself. Two-motor dual-side drive systems provides the accuracy and performance required to accomplish optimal results from a precision plasma process.
Sizing of the motors and gear boxes relative to the mass of the machine can be extremely important. Undersized motors and gearboxes won’t have the ability to effectively change the direction of the mass of the machine at high traverse and cut speeds, causing un-uniform cut quality and washed-out corners. This not just affects the cut quality, but will also lead to premature mechanical failures.
The CNC control is the system that ties together all the functionality and options that come with the machine and plasma source. There are basically two classes of controls applied to most of these machines today. Most industrial applications use industrial PC-based control systems such as those made by Burny or Hypertherm. These units have user-friendly touchscreen control panels and are housed in enclosures that can resist the harsh environments they operate in. Smaller machines of the hobbyist or artisan types often utilize standard PCs with I/O cards to manage the drives and plasma systems. Industrial based controls are highly recommended for almost any application, are made for industry specific requirements, are less vulnerable to the normal PC problems, but can be cost prohibitive in smaller applications.
Another important, and often overlooked, feature to think about when selecting a device is the construction of the rail system. Plasma cutting machines produ Dual beam digital laser material cutter ce and reside in a harsh environment. It is therefore critical that the components found in the construction of the rail system be robust enough to exist in this environment. All rail surfaces must be made out of hardened materials and cleaned frequently in order that they do not become pitted and gouged by the splatter of molten steel that will inevitably fall on them. Self-cleaning wheels are also a proposed feature to help keep the wheels clean between regular preventive maintenance (PM) cycles. Sizing of the rails should also be robust enough to avoid deflection as the machine travels across them.
The mix of all the above factors results in the precision and accuracy of a system. Unlike other mechanical machining processes, it is difficult to assign a standard tolerance to plasma cutting processes. Many manufacturers will strongly promote the fact that their machines have positional accuracy of +/-0.007 in. and repeatability of +/-0.002 in.. The fact is that nearly any machine available on the market can hold tolerances that far exceed the tolerance and capability of the plasma cutting process itself. There are many factors that will influence the cut quality you’ll achieve on your parts including: the characteristics of the part itself, power settings, consumables, gases used, material type, gauge/thickness of material, part layout on plate, etc.. Ask the maker to give you cut examples of your parts or parts that closely approximate the parts you will soon be cutting, made on a machine/plasma combination that’s comparable to what you are looking at. This provides you with the most realistic representation of what you may anticipate from a certain machine/plasma combination and the plasma cutting process itself.
