Controlling Arc Voltage for Bevel-Cutting and I-Cutting

Through the last 5 years input costs for CNC Plasma have greatly increased, causing users to look for ways to reduce operating costs. By controlling the arc voltage, which is the amount of voltage between the electrode and work piece, operators will be able to extend consumable life; one of the main input costs in plasma cutting. Depending on if the machine is performing bevel cutting or I-cutting, there are different ways to control the arc voltage. Here are some tips for controlling the voltage of your plasma and ultimately improving cut quality for each of these applications.

Arc voltage control for bevel-cutting

Bevel_Cutting_Plasma_03When bevel-cutting with a plasma machine, the voltage is created between the tip of the electrode and the bottom of the electrically-conductive work piece. This voltage is proportional to the distance between the tip of the hafnium and the bottom of the plate. Generally speaking, the larger the distance between the tip and the bottom of the plate the greater the voltage will be. This voltage is fed back to the torch height control (THC) and subsequently moves the THC up or down to maintain the same voltage as required. For example, if the voltage is too low for the cutting process, the THC will move up to expand the distance and consequently increase the voltage.

Arc voltage control for I-cutting

When I-cutting the voltage control changes as the torch head is used and consumables are becoming worn. The torch will need to be moved closer to the plate to maintain constant arc voltage. Since few operators actually adjust arc voltage to compensate for consumable wear, consumables that are still useable are often discarded too early because of poor cut quality. If operators do make these adjustments, they can improve cut quality and be able to keep the same consumable parts for longer. Sampled arc voltage solves this problem by automatically adjusting arc voltage over consumables’ lives. Essentially, the system does this by going to a known cutting height and then “sampling” the arc voltage at that height. It then makes adjustments as the consumables wear, which improves cut quality. This system stops operators from having to do this manually and compensates for operators who do not adjust for voltage at all.

Adjusting the voltage of your plasma cutting can have great implications for your consumables. It may not seem overly-important to extend the life of your consumables, but over time the added life of these parts could save you thousands. Remember that the process of controlling voltage is slightly different for bevel-cutting and I-cutting. By taking these measures or implementing a sampled arc voltage system you can get the most out of your consumables and improve the cut quality of your CNC plasma.


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