When a flashback occurs, the flame burns rapidly ‘upstream’, generally causing a loud explosion. If un-checked it can continue through the torch into hoses, regulators and gas bottles/cylinders.
Scratch start is a very basic and rudimentary process, usually found on low cost inverter welders that have been essentially designed for Stick (MMA) welding.
The TIG tungsten electrode is scratched on the job to initiate the arc, and must be quickly lifted off the job to try prevent it sticking, but not lifted too far to avoid extinguishing the arc. Not a very user-friendly process!
Whilst some machine suppliers advertise their scratch-start machines as TIG (or stick/TIG), at Weldclass we believe that scratch-start machines are not suitable for TIG use. All Weldclass "TIG" welding machines have either lift-arc or HF ignition.
With Lift-Arc Ignition feature, to start the arc the tungsten electode is touched on the job and lifted off. The start-up current is very low and therefore the tungsten barely sticks to the job and the sharpened point is not damaged. The tungsten is then easily lifted off the job. The machine senses that the contact is broken and begins supplying full welding current.
Lift-arc offers great operator appeal as it is user friendly and very controllable. It can, however, challenge manufacturers as the electronic processes must be carefully calibrated to achieve good results. If the start up current is not minimised it will cause the tungsten to stick excessively to the job.
In the case of Weldforce welding machines by Weldclass, the amperages and processes have been carefully refined to ensure optimum operation of the lift-arc process.
It is important to be aware of the difference between the ‘Lift-Arc’ ignition system and the ‘Scratch-Start’ ignition system.
Often DC inverter welding machines will be advertised as having TIG capability when they are a ‘Scratch-Start’ machine only.
Be warned! Scratch-Start is not a user friendly process: the tungsten must be very quickly touched on the job and can very easily stick (which means the tungsten electrode must be removed and re-sharpened each time this occurs).
In comparison ‘Lift-Arc’ is very user friendly and very controllable.
HF (high frequency ignition) allows the operator to position the tungsten electrode near the job, and simply press the torch trigger to start the arc.
HF is typically found on professional TIG welding machines with AC/DC function, such as the Weldclass 201T or 202T. On these machines, often the controls will allow the operator to chose between Lift-Arc or HF start.
The TIG Welding Process - your questions answered
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