Assessing the start types-high Frequency
There are two common start types that you should be familiar with. One is High Frequency, and the other is a Blow back start. The High frequency start is a simple, but effective method of starting that uses something similar to old fashioned ignition systems of automobiles with a coil, and points to generate a high frequency, high voltage spark at the tip of the nozzle to ionize the air and create a plasma arc that is focused and expelled through the tip of the nozzle. This type of start is efficient and fast but has two basic problems. The first is that it creates a lot of electromagnetic interference and is not suitable for use around computers, and electronic devices. The HF energy can create isolated and sometimes mysterious problems, which are hard to pinpoint and predict in surrounding electronic equipment. Also due to the design of the HF, some systems do not provide a pilot arc. Pilot arcs provide a plasma arc that is self contained without the benefit of a complete grounded circuit that routes power flow back through the work lead. Instead, the torch provides its own ground, and the arc is created against the consumables as a grounded point. The design of this pilot arc provides a softer, non cutting flame at reduced amperage to provide a steady arc that helps scour and prep the surface for full arc transfer. It makes cutting on irregular surfaces such as expanded metal, and on rusty or dirty metal a very easy task. No arc restarting is required, and continuous transfer back and forth of the pilot arc when needed is accomplished. The reduced amps are used in order to keep from blowing out consumables rapidly. In an HF system, the arc is started usually by having the torch in close proximity, if not touching the workpiece. Some HF systems do provide a grounded consumable, to create a pilot arc. These units can work quite well for a variety of applications, except for machine or cnc use.