High-precision plasma cutting is a fast and productive tool for cutting metals. Cutting speeds can reach up to a hundred inches per minute with high cut accuracies and narrow kerf widths. In addition, advanced systems can reduce necessary preparation times. Baileigh’s industrial plasma table, for instance, comes with design software, a water bath, and the ability to control the torch with a handheld panel.
The plasma arc cutting process emerged in the 1950s, when energy densities were used for the creation of a cutting arc instead of a welding arc. Several years later, plasma torches and power sources were used in the process of cutting steel. A secondary gas was used to serve as a shield surrounding the main plasma arc. This would constrict the arc and force it to produce greater energy density. The gas combinations included nitrogen and oxygen. This dual-flow characteristic of cutting allowed cutters increased speed, reduced top rounding, deeper cuts, and minimized dross below the cuts.
Electrode life continued to be extended with additional technological advancements and discoveries. This included the process of fitting the emitter into the top of the copper cylinder and opening the back so water would be able to transfer heat away from the electrode. This could extend the electrode’s service life. The same method continues to be used today.
Plasma cutting systems with high-precision capabilities can direct arc energy to a limited, focused area. There are several ways to achieve this precision.
Initiation and Termination of Plasma Arc
Electrode life is affected by how the plasma arc is initiated and terminated. Torches normally emit a brief but high-voltage impulse for the air to turn electrically conductive. The pilot arc can then be established with a much lower voltage. The energy given off should always be well-controlled and timed to reduce the component’s wear.
At termination, the arc is collapsed at a steady and controlled rate. This involves slowly turning down the voltage, current, and gas flow. If the arc is not gradually shut off, the electrode is likely to experience wear at a faster rate.
Torch Height Control
Another factor that affects cut precision and electrode wear is the torch height control. Some systems employ voltage sampling as a way to keep up with consumable wear. They ensure the nozzle remains at the optimal distance from the plate. Through time and the more an electrode wears out, the arc becomes longer. The torch height has to come progressively closer to the plate in order to maintain a consistent width and cut quality.
It’s important that metal fabricators ensure that both the height controller and torch lifter are functioning well when they’re assembling an automated plasma system. Variations in torch height can lead to differences in the quality of cuts. While using a plasma cutting system, manufactures should minimize the amount of molten metal present at the beginning of cutting, as well as eliminate electrode wear.
Fabricators should evaluate the cut quality of test parts and ensure equipment features are operating at optimal levels to ensure cutting remains efficient and precise.