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Thread: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

  1. #1
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    How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Hi,
    I was a farm machinery repair welder about 45 years ago using a Lincoln AC-225 buzz box.
    I am thinking about getting back into SMAW welding. I got thinking. If one were
    carefully thinking about fine adjustment of current setting, how much does the current flow
    vary from using a new 14" rod to using a 1" rod that is almost used-up? Since the rod
    presents some electrical resistance, there is probably a difference in current flow through a
    new 14" rod vs a nearly used-up 1" rod. Has anyone done testing or some calculations on
    how the current flow increases as the electrode rod becomes shorter?

    I now have a Miller AC/DC 225/140 and an old 1960's Ideal Arc AC/DC 300/250 both which have
    infinite adjustment of the current setting. Stated another way, if I were to set to a
    certain currently when I am starting out with a new 14" rod, how much do I want to decrease
    the current adjustment (of the welder) as the rod shortens down to 1"? Are we talking a
    current difference of 5 to 10 amps for a new 14" rod versus a nearly used-up 1" rod?
    Last edited by Orson_Yancey; 12-06-2021 at 05:16 PM.
    Orson
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  2. #2
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    I never gave it much thought. I guess with a clampon ammeter you satisfy your curiosity.
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  4. #3
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    All you've got to do is measure the resistance of a new rod and a stub. Should be very low, I doubt if it is significant for welding amperage variation.
    CG

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    A stick welder is a CC (Constant Current) machine, so it will do everything to keep the set current the same.
    Arc voltage varies with rod manipulation and arc length and could theoretically vary with rod length, but I doubt that the small resistance difference between a new rod and a stub will make much difference.
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Guys talk about the rod flowing smoother as the rod warms up. Maybe reduced resistance plays into that as well, but it's probably unnoticeable with the other factors at play. For a 1/8" rod, we are talking the difference in resistance between 1 and 14" of steel 1/8" in diameter... neither have a lot of resistance so it's going to be negligible.
    Last edited by whtbaron; 12-06-2021 at 06:48 PM.
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    The answer is probably close to zero change in current. More than likely the voltage changes while the current stats pretty flat. SMAW welders are designed to deliver constant current.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    I run a lot of 18", 7/32, 7024 rod and I agree with the others. There is no difference except the heat of the rod itself. A cold new rod will be exactly the same as a cold used rod of any length.
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Never found time to worry.
    You find more variation in power company voltage from morning to afternoon. Most welders do notice voltage drop.

    Dave

    Quote Originally Posted by Orson_Yancey View Post
    Hi,
    I was a farm machinery repair welder about 45 years ago using a Lincoln AC-225 buzz box.
    I am thinking about getting back into SMAW welding. I got thinking. If one were
    carefully thinking about fine adjustment of current setting, how much does the current flow
    vary from using a new 14" rod to using a 1" rod that is almost used-up? Since the rod
    presents some electrical resistance, there is probably a difference in current flow through a
    new 14" rod vs a nearly used-up 1" rod. Has anyone done testing or some calculations on
    how the current flow increases as the electrode rod becomes shorter?

    I now have a Miller AC/DC 225/140 and an old 1960's Ideal Arc AC/DC 300/250 both which have
    infinite adjustment of the current setting. Stated another way, if I were to set to a
    certain currently when I am starting out with a new 14" rod, how much do I want to decrease
    the current adjustment (of the welder) as the rod shortens down to 1"? Are we talking a
    current difference of 5 to 10 amps for a new 14" rod versus a nearly used-up 1" rod?

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  16. #9
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    A welder produces a series circuit. Power Ac Or DC flows from the welder through the work lead & clamp, through the table, workpiece, across the ionized gas produced by burning flux, & back through the electrode, stinger & its lead. The welder is designed to keep current steady. The rules of electrical theory are that a series circuit shares applied voltage. Resistance in each component of the circuit takes a bit of voltage. Ideally, the arc of ionized gas is the greatest resistor. Very tight arc, voltage decreases at the point of arc. Long arc, voltage increases.

    Heat is measured in watts. Watts are the product of Amperes X Volts. A long arc gives more heat, but that heat isn't where you want it. In comparison, I doubt length of rod will measurably change Amperage. And the machine will modulate to keep it steady.
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    The only reason a rod seems to burn better after an inch or 2 is because the unburned rod is preheated. Same reason rods fresh out of an oven burn nicer on start up. Some large diameter Innershield wires calls for 4 inches or more wire stick out. This is to preheat the wire and gives vastly improved deposition rates.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Thanks for many good replies. I am hoping to provide the needed electrical service
    so that I can get out there and burn some rods--more fun than just thinking about welding.
    Orson
    Portsmouth, NH

    Lincoln AC/DC 225/125 flat top tombstone buzzbox Mfg. 2018
    Lincoln Idealarc 250 Code 5825-C, Mfg. 1966
    Dayton 240 volt spot welder
    Oxyacetylene torch

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Hook up the Idealarc. It is a superior machine to the others.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    prorbaly more change due to the way ur leads coil/unravel as u move around

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Quote Originally Posted by Welder Dave View Post
    The only reason a rod seems to burn better after an inch or 2 is because the unburned rod is preheated. Same reason rods fresh out of an oven burn nicer on start up. Some large diameter Innershield wires calls for 4 inches or more wire stick out. This is to preheat the wire and gives vastly improved deposition rates.
    I've never heard it, but my brain goes there. Evaporation of water has a big cooling effect. Near every electrode is wet in the sense of taking water from the air. Theoretically, "new" 7018 is "sealed" Maine Oxy & Airgas "seal" packages of 7018. The new packages I buy have scotch tape on the joint. No way in Hell that keeps humidity out.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    I suspect the current stays the same, but the rod "flows" better because it, and the workpiece, are hotter by the time you get to the end of the rod.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Quote Originally Posted by Willie B View Post
    A welder produces a series circuit.
    Ideally, the arc of ionized gas is the greatest resistor. Very tight arc, voltage decreases at the point of arc.

    Long arc, voltage increases.

    A long arc gives more heat,
    I was taught that the long arc gives more heat when I was in the US Navy,,

    I have always used this fact when welding, if the base metal is getting too hot, cram the rod into the weld, and keep the arc short.

    If the arc is short, the voltage is lower, and, the watts will be lower (the machine is trying to keep constant current)

    Right , or wrong , this short arc, and less base metal heating has always seemed to work ,, for me.

    A short arc, and less heat, seems to be the case, whether the rod is long, or short.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Quote Originally Posted by SweetMK View Post
    I was taught that the long arc gives more heat when I was in the US Navy,,

    I have always used this fact when welding, if the base metal is getting too hot, cram the rod into the weld, and keep the arc short.

    If the arc is short, the voltage is lower, and, the watts will be lower (the machine is trying to keep constant current)

    Right , or wrong , this short arc, and less base metal heating has always seemed to work ,, for me.

    A short arc, and less heat, seems to be the case, whether the rod is long, or short.
    Less arc length, less resistance, less voltage. Amps should remain the same if the welder functions. End result, fewer watts. And the jetting action of the rod exploding drives the heat deeper into the workpiece, where the transfer of heat causes the molten filler to more quickly freeze.
    Another benefit, less heat input reduces distortion as it cools.
    Last edited by Willie B; 12-08-2021 at 01:41 PM.
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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Good weldors can vary the arc length to control heat when doing root passes on pipe.

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    Re: How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

    Quote Originally Posted by Kelvin View Post
    I suspect the current stays the same, but the rod "flows" better because it, and the workpiece, are hotter by the time you get to the end of the rod.
    In theory, hotter metal (rod) would have higher resistance. I doubt the change is going to be significant in measurement of ohms in the rod unless you are talking about 1/16 rod. The hotter rod tip will be more effective at making plasma in the arc. Wild guess here, but I'd say the hotter the rod, the less voltage wasted in the jump from base metal.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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