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Old 03-06-2010, 03:22 AM   #1
Skippii OP
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Welding: Why is Electrode Positve called "Reverse Polarity"?

Probably a stupid question, but this bothers me.

Normally, I ground the workpiece and attack it with the electrode. So normal = reverse?
(Let's ignore the fact that I only have an AC welder for a second...)
It just seems like it should be that the workpiece would "normally" be grounded, not hot, and the active part you are using would be the hot part.

Anyway, I guess I could live be being told that it's just that way, but I just read something else...

I just read that the reason Reverse Polarity means a hot electrode is because electrons flow from the ground to (+). This is what actually bothers me:

No other engineering discipline in the world uses that convention. We all know it's true, but EVERY SINGLE OTHER FIELD uses a system that follows "hole flow". Even electrical schematics indicate diodes with arrows indicating the flow of positive current. Please, someone tell me that the weldors didn't decide to just be different from everyone else. Please tell me that there is no real reason behind the Reverse designation. Or maybe the first welding machines only did Straight polarity, and so they later designated EP as reverse. But please don't tell me that unlike every other mechanical or physics field, they decided to base welding on the direction of electrons.
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Old 03-06-2010, 06:15 AM   #2
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As far as the welding aspect, DCEP and DCEN are used for certain electrodes for certain penetration qualities.

As far as the rest of your er, question (rant?)....

I've always understood current flow is from negative to positive. Sink, source.
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Old 03-06-2010, 06:35 AM   #3
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Its not always like that, depends on the rod and material.
Heres some good info.
http://www.clovisusd.k12.ca.us/agcenter/arc_welding.htm

"
If the lead which has the electrode holder on it is connected to the + (positive) connection point on the welder, then you will be welding Electrode Positive, which is called Reverse Polarity ( DC+ = Reverse Polarity). If the electrode holder lead is connected to the (negative) connection point on the welder, you will be welding Electrode Negative, which is called Straight Polarity ( DC- = Straight Polarity).
"
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Old 03-06-2010, 09:33 AM   #4
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Quote:
Originally Posted by Skippii
I just read that the reason Reverse Polarity means a hot electrode is because electrons flow from the ground to (+). This is what actually bothers me:

No other engineering discipline in the world uses that convention. We all know it's true, .
So if it's true, then what's your problem????? Just because everyone else is wrong now we welders should be sucked in to what a bunch of engineers do?

I always think of it as if metal from the rod is following the flow of electrons in straight polarity and when you are welding reverse polarity, then the rod material flows against the flow of electrons.

When Heliarc (aka TIG) welding and the electrode isn't deposited into the weld, the direction of the flow of electrons is very important. When TIG welding aluminum, you us AC current and when the AC wave is in the negative phase you get cleaning action as contaminates flow from the base material to the electrode. Many TIG machines actually allow you to control how much time the flow is in the positive or negative phase of the AC wave with a knob that you adjust from more cleaning to more penetrating or more time spent in the negative or positive phase.

Miller and Boeing made a Heliarc machine called the Miller-Aerowave that allowed you to independently adjust the frequency and amplitude of each side of the AC wave yielding the ultimate in AC waveform manipulation. I digress.
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Old 03-06-2010, 06:52 PM   #5
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just cuz

that's why. I thught it oddd when I learned it in trade school 34 years ago
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Old 03-07-2010, 07:51 AM   #6
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Quote:
Originally Posted by Skippii
Even electrical schematics indicate diodes with arrows indicating the flow of positive current.
There is no such thing as "positive current" anymore than "cold moves to hot."

What "flows" in current are electrons...which are negatively charged, in the same way that heat travels from higher temperature to lower temperature.

Molecules at a higher temperature "vibrate" faster than those at a lower temperature...but by "bouncing up against" molecules of a lower temperature, molecules of a higher temperature cause the colder molecules to vibrate faster...raising their temperature.

I believe the reason they say that a positively-charged stinger in DC welding is "reverse polarity" is because when DC welding first was done, they traditionally used the negative side for the stinger...and then discovered that a positive stinger penetrated deeper.

Whatever...it's arbitrary. In my own conversations regarding SMAW welding, to avoid confusion, I just talk about "DCEP" ("DC electrode positive") or "DCEN" ("DC electrode negative").
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Old 03-07-2010, 10:31 AM   #7
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Well if electricity moves from negative to positive, and you have a positive stinger, that makes sense to me to call it reverse. It's 'pulling' current away from the piece instead of 'shooting' it at it.
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Old 03-07-2010, 11:03 AM   #8
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Electric current convention was established by physicists (specifically, Ben Franklin) before the polarity of electrons was known. Electric welding was invented after.

There was a push to convert to the electron flow convention during the vacuum tube era as it is much more intuitive, just like in welding. Once semiconductors took over it was dropped.

Tangent: in animal nerve cells, electric charge carriers are positive sodium ions.
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Old 03-08-2010, 07:18 PM   #9
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Maybe the beginnings were in England, you know those positive earth people.
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Old 03-09-2010, 09:02 AM   #10
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Simple answer: Because it's the opposite of 'Normal Polarity'.
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Old 03-09-2010, 05:12 PM   #11
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Skippi,

You asked.

In the early days of electric arc welding, carbon arc welding was widely practiced. Direct current was necessary for the form of the process then used, and the carbon electrode had to be connected to the negative terminal. Through custom, this common way of connecting the leads came to be known as straight polarity. In time, however, the covered metal electrode was introduced and shielded metal arc welding grew popular. Reversing the polarity by connecting the electrode to the positive was found to work better. Welders naturally referred to this newer system as reversed, or reverse, polarity.


With an AC machine it matters not.

Are you experiancing issues with erratic arc?
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Old 03-09-2010, 11:06 PM   #12
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Quote:
Originally Posted by gsweave
Skippi,



Are you experiencing issues with erratic arc?
I think they make a cream for that o_o
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Old 03-10-2010, 03:17 AM   #13
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Quote:
Originally Posted by gsweave
Skippi,

You asked.

In the early days of electric arc welding, carbon arc welding was widely practiced. Direct current was necessary for the form of the process then used, and the carbon electrode had to be connected to the negative terminal. Through custom, this common way of connecting the leads came to be known as straight polarity. In time, however, the covered metal electrode was introduced and shielded metal arc welding grew popular. Reversing the polarity by connecting the electrode to the positive was found to work better. Welders naturally referred to this newer system as reversed, or reverse, polarity.


With an AC machine it matters not.

Are you experiancing issues with erratic arc?
No issues, just curious. I had a feeling the answer might be something just like this.
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Old 03-10-2010, 03:58 AM   #14
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Quote:
Originally Posted by Skippii
No other engineering discipline in the world uses that convention. We all know it's true, but EVERY SINGLE OTHER FIELD uses a system that follows "hole flow". Even electrical schematics indicate diodes with arrows indicating the flow of positive current.

Please, someone tell me that the weldors didn't decide to just be different from everyone else. But please don't tell me that unlike every other mechanical or physics field, they decided to base welding on the direction of electrons.
The symbol on schematics isn't really an arrow, it's a triangle, or acute angle shape, used to represent a PN junction. The larger side, or open end of the angle shape, is the area of greater positive charge. The smaller side, or point, is the area of greater negative charge. Like the greater than >, or less than <, symbols. The symbology is based on charge.

Welding chose a naming convention based on electron flow, which is arguably more relevant to welding. As it happens that naming convention is inversely intuitive, so the names straight and reversed look backwards, but that's just a coincidence.

I suppose it's a little like the naming of airplane landing gear. There's conventional gear and tricycle gear. The conventional gear is a tail-dragger. The nomenclature is chronologically sequential, but from the perspective of in-use contemporary landing gear, it's reversed. But that's just a coincidence.

Welding's more contemporary use of DCEN and DCEP are an attempt to clear up the ambiguity of terms. Which has the somewhat predictable effect of causing more confusion.

That ain't nothing. Wait till we switch over to the metric system.



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Old 03-10-2010, 04:57 AM   #15
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Quote:
Originally Posted by Poolside

The symbol on schematics isn't really an arrow, it's a triangle, or acute angle shape, used to represent a PN junction. The larger side, or open end of the angle shape, is the area of greater positive charge. The smaller side, or point, is the area of greater negative charge. Like the greater than >, or less than <, symbols. The symbology is based on charge.

Welding chose a naming convention based on electron flow, which is arguably more relevant to welding. As it happens that naming convention is inversely intuitive, so the names straight and reversed look backwards, but that's just a coincidence.

I suppose it's a little like the naming of airplane landing gear. There's conventional gear and tricycle gear. The conventional gear is a tail-dragger. The nomenclature is chronologically sequential, but from the perspective of in-use contemporary landing gear, it's reversed. But that's just a coincidence.

Welding's more contemporary use of DCEN and DCEP are an attempt to clear up the ambiguity of terms. Which has the somewhat predictable effect of causing more confusion.

That ain't nothing. Wait till we switch over to the metric system.


The airplane thing makes perfect sense. So does gsweave's response. Some people say that weldors chose to use electron flow, but I strongly suspect that the real answer has to do with chonology as in gsweave's answer rather than trying to relate to physics.
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