High Frequency starting is a high voltage discharge between the nozzle and the electrode in a plasma torch.....think of the spark on a spark plug in a gasoline engine. The plasma gas (usually air) passes through this discharge, causing the gas to increase in temperature to its ionization temperature. When air reaches ionization it become electrically conductive....and then provides a path from the negative electride through the nozzle (some call it a tip) orifice to the workpiece (material to be cut). Once the DC arc is started the high frequency voltage turns off. the high frequency voltage level is usually in the 15,000 volt rang in order to add enough energy to get the plasma process started. This type of voltage near sensitive electronic equipment can couple to low voltage signal lines (computer and drive electronics) causing computer crashes and even internal damage to electronics.
Blowback starting, developed and patented by Hypertherm (the worlds largest producer of plasma cutting equipment) completely eliminates the need for high frequency. This system uses a moving electrode (spring loaded) that creates a short circuit DC spark inside the torch, reliably and immediately ionizing the air to get the process started. Because it just uses the plasma power supplies DC energy output it does not create electrical noise that will disrupt computers, cnc machines and other sensitive electronics.
High frequency continues to be used on older technology air plasma cutting systems (and newer, low cost imports), as well as on high end industrial cnc plasma machines that are robustly designed to work with high frequency starting. (high frequency is needed on larger torches ....between 130 and 1000 amps for more reliable starting at these higher power levels).
Take a good look at the existing plasma cutting systems on the market. If this is a tool you plan to keep in your shop and use for many years it is wise to look at the major brands that engineer and build plasma systems in theri own factories, companies that have been in business for a while. Don't just look at the price, rather look at the performance (cut thickness, cut quality, consumable parts life), look at the operators manual. If the system comes with a legible manual with many pages of cut charts, cutting recommendations, detailed parts breakdowns and even multi pages of troubleshooting, as well as toll free contact information for the factory that built it.....then you know you are getting a good product that will be supported and hav parts availability for many years to come. These units will prove to be less costly over time.
By the way...the operators manual for the Hypertherm Powermax45 is about 100 pages long....about 12 pages of cut charts with cut speed, cut height, arc voltage information that will help you cut with precision and long consumable life. All Powermax45's from Hypertherm are equipped with Easy to interface CPC connectors for CNC macine wiring, and have quick disconnect torches for both hand and machine cutting.
Jim Colt Hypertherm
What is the difference between high frequency and blow back? Does the HF on the PP100 cause interference?
So what do you value?
