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Thread: Old vs New Arc Welders
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4th February 2011, 10:57 AM #1New Member
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Old vs New Arc Welders
I'm a learner welder and have grabbed my old mans arc welder which would be 40 years old. I'm going ok with it - but I was wondering whether new arc welders are easier or better to use. Is there any benefit in an upgrade? thanks
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4th February 2011 10:57 AM # ADSGoogle Adsense Advertisement
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4th February 2011, 02:00 PM #2SENIOR MEMBER
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I have a (very) old, massive, copper wound (AC) welder. My little BOC 130 inverter (DC) weighs about nothing by comparison and is *much* nicer to weld with.
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4th February 2011, 03:00 PM #3Engineers are qualified to make claims
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Hi,
The older machines use a transformer and have a straight output, in other words they are an AC welder as they do not rectify the output current into DC. This makes them harder to weld with as the arc is not stable until the the flux melts and ionises which then helps maintain an arc, while the electrode is cold it is hard to start an arc but once the electrode and weld are hot it will be easy to restart and maintain the arc.
On top of this they are AC so the arc is turning on and off 100 times a second whilst the AC wave changes polarity (off once for zero crossing on positive and again off for zero crossing for negative) AC waveforms are constantly changing so power transfer is variable at all times in the curve.
I won't go into explaining the inverter as there are many posts on that already however as they rectify their output into DC and do it at a high frequency there is negligible ripple so they are more or less 99% DC. This means the energy is on all the time providing smooth arc once ionised and the current can be supplied at any level.
For this reason inverters are very easy to weld with.
What you could do with yours is install a 300 amp stud diode and add a bunch of 150volt capacitors of decent micro farad size in parallel on the output. This would provide a very smooth arc but you would not have the low current stability as found in inverter machines.
John
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4th February 2011, 04:27 PM #4New Member
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4th February 2011, 05:44 PM #5Engineers are qualified to make claims
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You can get more info here
Converting a welder from AC to DC
John
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5th February 2011, 06:59 PM #6Pink 10EE owner
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The opposite side of the coin is this.... You will never kill your current welder... The inverter ones are going to be fragile and have a limited life in comparison.
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5th February 2011, 08:37 PM #7
In the 74 floods the shop where I did my apprenticeship went under.All they did was hose the muck off the the welders and dried them in the sun.
I won't work that way with the other ones.
Grahame
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5th February 2011, 09:12 PM #8
Hi Newby
Hey I'm a newby too! I have also welded with the old transformer type AC welders but many years ago. I bought a BOC 130 amp inverter welder and it really is chalk and cheese. I can do nice smooth welds with the BOC that I had no hope of achieving with the tranny welder. In fact a mate of mine bought one of those $99 el cheapo welders from Bunnings. I had a go at it but kept either blasting holes in the metal or getting the electrode stuck (and it comes unstuck with a flash just as you lift your welding mask!!!)
What are you working with? I can say with confidence that these blokes really know their onions and to my way of thinking; their advice is to be followed.
Best wishes
Peter
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5th February 2011, 09:16 PM #9
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5th February 2011, 09:53 PM #10Intermediate Member
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DC has always been easier to weld with, but providing you have good mains power the older AC 130/140 amp are OK. Have seen a decent size stock crate built with one.
My preference has always been a tractor or engine driven DC, although to-day most of my welding is done with a WIA 140 amp (22 years old) still have the engine driven DC Lincoln if the job warrants a 4mm rod.
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5th February 2011, 10:25 PM #11Pink 10EE owner
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They are a bit more complicated then just a bridge rectifier...
I have limited experience with the inverter welders but logic says that a basic transformer welder from the 80's with no electronic components inside is still going to outlast anything with electronics.. How much computerised equipment from the 80's do you still see in use today?
I probably see more old pre-electronic cars on the road then cars with electronics from the 80's and newer..
But of course your inverter welder is a lot easier to use and may be considered a disposable item..... If it dies after five years you go out and buy a better model for probably less money..
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6th February 2011, 01:01 AM #12Senior Member
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Inverter welders generally use high power semiconductors like MOSFET's or IGBT's to generate welding voltages. Like all semiconductors they are inherently fragile and susceptible to damage from power spikes, static, corrosion, mishandling etc. Their lifespan is also directly related to their operating temperature. Heatsinking high power devices is tricky at the best of times and I would guess that most welders (particularly cheaper ones) are not built well enough (cooling wise) to deliver a long life... Add to this the fact that the efficiency of the heatsinking will generally tend to decline with time and I don't think it bodes well in the longer term for these welders. At least in comparison to the transformer type of old.
Its probably also worth mentioning that it not so much a case of air flow across the heatsink thats the problem but actually getting the heat out of the component and into the heatsink that is the hard bit. If you google heatsinking for high power audio amps there are a few sites that go into the detail... Its pretty interesting if you like that kind of nerdy stuff.
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7th March 2011, 06:55 PM #13New Member
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new or old
oldschool all the way mate, an old cigweld compact 2 or transarc junior would be a good investment. newer models are of questionable quality unless you are willing to pay through the nose, my little welder (cigweld compact 2) is older than me by a longshot, but no matter what it goes through it still runs strong.
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8th March 2011, 07:35 PM #14
Also not mentioned as a major health hazard to electronic based welders is metal grinding dust which the pesky machines are inclined to inhale.
Any who owns a welder will need to grind at some some and to some degree.
With the deposition of enough nasty dust the way is then clear for the electrons to lose their way and the result is that the blue smoke will escape from your machine.
The school has 4 Off -400 I s which are well over due for a blow down. I need to consult the electrical welder speciallist but expect him to say strip and blow out.
Being school machines its more than more career is worth to DIY and I am not allowed to take the covers off.
I was present when a Thermadyne Stick tig went poof,very early in its life and let a very large amount of blue smoke out.
Maybe Rappy might make a comment as to how industry deals with the problem.
Grahame
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8th March 2011, 10:10 PM #15Member
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- Melton
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Hi all
NO blow outs with compressed air now,
MUST use a vac to remove dust and dirt NOW.
Vaccum out check all leads ect ect, test and tagg
Before put back into service.
No compressed air to be used as cleaning tool .
Work cover...............................................................
Tony
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