Spot welder

[KevJTD]

bought this spot welder last week, listed as spares or repairs. seller had fitted a "new" cable (check out the wiring, bad even by my standards!) which at least confirmed it worked!
not had chance to have a look at it until tonight, plugged it in down the shed which confirmed it still worked....but on second go it tripped out the breaker. once reset it did another weld...then tripped again.
i took the back off the unit and checked what i could, my electrical/electronics skills not being the best but nothing looked too out of place. old wires looked a bit crispy and aged but nothing drastic.
so i ground down the tips to a nice shiny point and put it all back together.
tried it again and worked fine, then by chance i felt the top tip, very hot indeed. to be expected really i guess, it is doing a weld!!
with the missing pipework leading down to the top tip it dawned on me that this must be some kind of cooling pipework, either an airflow system or maybe a fluid?
so i let the tip cool for a minute or so then tried again, worked great. let it cool then tried again, all good.
so it seems it was tripping due to overheating probbaly through lack of cooling from the missing pipework
tried the timer settings and it works fine even on the longest weld setting, as long as you give the tip time to cool between welds


so, my question is to anyone who may know;

what should run through the pipework? fluid or air?

also i'm guessing the arms can be changed for shorter, less awkward to use ones?


one thing though, it'll save a massive amount of time not having to use plug welds! having to drill or punch a hole, mig it up then spend time grinding it flush. takes an age to do a sill lip joint for example. with this it produces a brilliant little weld that is virtually ready to be primed over. just a clean up with a knotted wheel should suffice, and the bonus is it leaves a factory looking dimple.
incredibly strong welds too.

[vecchioalfa]

Hi Kev,
Looks a useful bit of kit mate. I would have thought compressed air would be the way to cool it but not 100% sure, water could be dangerous should a leak develop during use, what does everyone else think....

[KevJTD]

Hi Kev,
Looks a useful bit of kit mate. I would have thought compressed air would be the way to cool it but not 100% sure, water could be dangerous should a leak develop during use, what does everyone else think....

kind of what i was thinking mate, water flowing down to the tip that has high vlotage current running through it.....can only imagine what might happen!

i did wonder if a small bore pipe could be rigged up and a regulator so airflow could be fed through it, or maybe even a small computer fan (handy, being 240V) fitted to the unit with ducting into the pipe

it is useable as is, you just have to wait a minute or so between welds. hardly a big issue and the time saved is huge compared to the mig/plug weld method as i'm sure you'll agree mate

[PETROLHEAD]

Hi chaps

i think you'll find that those arms were once part of a large piece of kit, and that the arms indeed are water cooled.

if generally stationary rather than portable, and used in high frequency, they are often plumbed in to refrigerated chillers rather than just a general water circuit.

The tripping out you experienced will have been as a direct result of not being cooled. As the heat from the weld increases the temperature in the contacts and arms, the resistance of the material increases exponentially, so for example if the first weld took 10amp, the next one might be 20 or 30amp!

They're are equations for specific grade materials and their current carrying capacity according to temperature, but thats not really important right now, but thats definitely whats going on, and i suspect thats exactly what they should be,

water cooled mate.


lecture over lol!


i'm sure you could rig something up couldn't you mate

[Kegsti66]

Surely, water would be deadly, especially with that wiring
Like your thought Kev of the PC cooling fan. That could work well.
Our one at work has nothing like that on it.
Good ,clean metal and contacts are a must, or like you found it will kick out the fuses.
Maybe you could get some shorter arms as well.
Very handy bit of kit.

[KevJTD]

water cooled, that's interesting.
thought i'd be bound to electrocute myself!

so you reckon a small water reservoir with a pump to circulate the water around might do the trick....something like a sud washer bag perhaps...
pump & resrvoir all in one, just need a 12V supply.
if the pipes from the bag were long enough then it needn't be anywhere near the welder too so it wouldn't get in the way that much.


glad to know that my theory on it tripping due to excessive heat build up were right at least

brill bit of kit though, even if it has a phenomenal amount of dust in it

[KevJTD]

Surely, water would be deadly, especially with that wiring
Like your thought Kev of the PC cooling fan. That could work well.
Our one at work has nothing like that on it.
Good ,clean metal and contacts are a must, or like you found it will kick out the fuses.
Maybe you could get some shorter arms as well.
Very handy bit of kit.

so, that's one vote for water and one for air!

must admit that i find the thought of using air much safer...

guess i could try and rig up both ways...see if water runs out of every orifice...that'd make me worried!
also rig up a small fan, see if that cools it enough..

bit like mythbusters.....except nobody has ever wondered yet which way is best

[KevJTD]

and shorter arms would be nicer too.....would that change the overeating in any way? make it worse with less surface area to do the cooling?

[vecchioalfa]

Shrew is right about this being part of a larger piece of equipment, I have seen and worked on industrial welding machines back in the day when I was a maintenance engineer on production machinery, these were indeed water cooled but obviously not hand held machinery as this is intended to be used for now, I think its not safe now to be cooled with water, it only takes a leak and you could become part of the circuit!

[PETROLHEAD]

Pah!

Where's your sense of adventure?


Shorter arms will of course mean less material and therfore less resistance to begin with, so could help a bit, but, you also run into the by product of that, in that you also then have less matetial to dissipate the heat build up,

Tough one, maybe we're gonna need that math afterall! Crikey!

I haven't had those books out for a while!

[KevJTD]

well, i've just ordered a small computer fan. only about 70mm diameter so easy to make fit some ducting down to the small bore which should then increase airspeed. 12V so i have a good plan for how to power it.
£1-70 delivered so not like i'm risking a fortune to try it

[Alfasixnut]

Way to go Kev! I'm sure the air cooling will be good for your use. What is next on your shopping list?

[Johnboy]

If you can get enough air in movement on it then it should work as you said you haven't blow your budget

[KevJTD]

bigger compressor next on the spend list phil, shrew coming over this sat affy hopefully to look over the electric supply, see what we can come up with.

find myself looking at ebay now with all these project cars.....

[PETROLHEAD]

Invaluable!

as you know Kev, i've been quite into that side of workshop equipment recently, and managed to teach myself quite a bit about it too.

my advice so far would be not to buy anything until i suss out what size leccy supply we can dedicate to a compressor feed, and then get absolutely as big a possible for that given supply.


buying too small is a very costly mistake, it will only mean spending much more down the line, and cost more in the meantime!

[KevJTD]

took it to work today to blow the comwebs (literally!) out of it......
thought i'd try it with the airline running through the pipewrok to see if
a/ airflow would circulate through it
b/ airflow would be enough to cool it

happily both answers were yes

dusty/rusty air came through it to start with which confirms it did indeed run with water through it, the staining inside the chopped off pipes kind of gave it away too
with a workmate holding the tyre inflation airline on one pipe i was able to do 3 or 4 welds in very quick succesion before tripping out, far quicker use than would ever be seen in real use, and with our hyper sensitive trips at work which struggled to even allow one weld before. guess the 'leccy supply my nephew installed in my shed is a bit more robust as i told him i'd be welding in there when he asked what i'd be doing

so at least it proves that a simple circulation of air through the system is enough to cool it down

actually thinking now it may be just easier to connect to the airline with a regulated airflow?

little 12V computer fan arrived today, neat little thing. only problem is it has 3 wires black, red & yellow. easy to confuse an idiot, what's the yellow wire for assuming the red and black are pos and earth....

[PETROLHEAD]

Glad the airline cooling worked so far mate, very encouraging.

as for the computer fan, well, you'll probably find that black indeed is your ground/negative, but the yellow and red are probably both live inputs, but at different voltage requirements.


PC power supplies have loads of outgoing wires, mostly yellow, many reds, then the occasional other colour. They vary between 12v down to about 3v i think, some can even be dc-! and if i recall correctly, its the yellows that are your desired 12v+, so use the yellow and black for your + and - respectively.

Assuming the fan you have requires 12v dc yes?

I'm not sure its going to adequately cool much though mate, they are normally ok just blowing across a channeled heatsink, but not much more, and not weld temperatures to begin with!

how were you thinking of rigging it in?

[KevJTD]

yes, think you're right that the little blower won't have enough urge to cool sufficiently.
as the airline on a regulated flow worked ok and will be very simple to rig up i think i'll do that instead.


£1-70 down the pan

[PETROLHEAD]

Ha ha!

Fit it in side your welding helmet, have yourself an Air Conditioned Brow!

Never mind eh...