Could someone please explain to me what excactly the "arc force" control on a Lincoln 355 TIG welder is for and what effect does it have on various processes, i.e. SMAW, TIG on SS and Aluminum. Also, I've never fully understood "pinch effect" in MIG machines, either. I would appreciate any input on these issues.
Thanks,
Dutch
on my miller syncrowave 250 arc force is used for smaw to help start an arc or make verticle or overhead welds. it increases short circuit amperage which lets you use a very short arc length without sticking the electrode. turn it off for gtaw.
The arc force knob changes the shape of the volt/amp curve that the machine puts out when SMA welding. A high arc force is associated with a "drooper", or a curve that drops off a lot when the voltage (arc length) is increased and a stiffer arc. Conversely, the curve, or amperage increases a lot when the voltage decreases. The high arc force is typically good for using with thick, or rusty metal where joint penetration is desireable. It can also be used for varying joint fitup because you can controll the amps just by changing the arc length. Low arc force is associated with a steep volt/amp curve and creates a softer arc. When the arc length is changed with low arc force, the amperage does not change very much. This softer arc is good for higher amperage weling, or welding sheet metal/low penetration applications on lower amperage. It is also more likely to stick to your work with a low arc force.
Hopefully this helps more than confuses.
G Roberts
Arc force/Arc control/Dig Control is additional amperage at a low voltage condition. Amperage is heat and heat/amperage has the greatest effect on penetration. Usually this low voltage is less than 20-24 volts. Watch someone GTAW (tig weld)and notice the voltage at 100 amperes on the machines meters. Change to SMAW (stick welding) notice the voltage.
Try this, without welding, turn on the machine, close contactor and notice the open circuit voltage on the voltmeter (on machine or voltmeter (make certain high frequency is turned off!) connected across out put terminals of machine). Turn amperage and arc force control to zero and shut machine off. Connect the electrode clamp and work clamp together (dead short) lay cables out on non-conductive surface (not a steel deck). Turn machine on notice the load voltage. Set 100 amperes on amperage control. Then increase the arc force control and notice the voltage and amperage. Additional amperage has been added to the circuit. This gives a "stiffer more penetrating arc"
The ¨Pinch effect¨. When you have a current passing across an electric conductor (electrode), it is generated a magnetic field around this conductor wich is circular and concentric. This electromagnetic field generate a force in radial direction wich strangle the electrode causing the detach of the filler metal (drops) from the tip of the electrode (from here the name of Pinch effect). This effect is also applicable to other arc welding processes like SMAW, SAW, etc., with consumable electrodes.
Jorge Giraldo
Medellín, Colombia
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