Setting up a spot welder

[B1N9S]

Hi guys.

I bought a Sealey spot welder recently for a car project I am doing. It is an old SR12 model 1+1 max with a separate timer box.

I have been doing a couple of test welds on new clean 0.9mm steel, but the welds don't seem to be very strong. I can 'pop' them apart with a couple of pliers.

I have it set to MAX time and the squeeze pressure to MAX, so why are they so weak ?

I am guessing the electrodes, but no experience of spot welders. I did strip the thing and gave it a really good clean, inc the arms and electrodes, so I don't think cleanliness is the problem ? I am thinking perhaps the electrodes need to be sharpened or set up differently ? Any suggestions ?

 

[Shox Dr]

You need to clean the ends, making sure they are the same diameter, (6mm ISTR), and parallel.

If you are using Galv, or zintec, you'll need to double tap the spot, the first boils the galv off, the second welds the panels.

As for testing you need to peel the parts apart, not twist, to see if they are bonded correctly.
So you are left with a tag stuck to one piece and possibly a small hole in the other, all the way to it tearing the sheet.

Fickle machines.

 

[Robotstar5]

The tips need to be dressed (filed) to a diameter of 4-5mm, making sure they are square to each other.

Handy link here

 

[Jim Davey]

The flats on the tips are way too big. The machine simply doesn't have the power to create a spot with such large surface area. Dress them down to the sizes mentioned, I'd go about 3mm myself and see where the arms flex to with the tips squeezed together with a piece of steel of the size you are welding between them (obviously with the welder turned off) so you can have a look and see if the tips line up well under pressure. Just bringing them together till they touch isn't a good indicator as they tend to shift slightly due to flex and play in the pivots will affect this too.
You are looking for a dead straight path for the current to flow between the tips otherwise material tends to get fired out of the joint causing sparks, crowning or both.

 

[B1N9S]

Thanks guys. I'll grind/file the tips to 4mm each and see if I can set them any better. They are cleaned with emery cloth, but the pic is just after use. To be honest, I am thinking of just selling it and plug welding, these machines seem to be more trouble than I can be bothered with !!!

 

[B1N9S]

The flats on the tips are way too big. The machine simply doesn't have the power to create a spot with such large surface area. Dress them down to the sizes mentioned, I'd go about 3mm myself and see where the arms flex to with the tips squeezed together with a piece of steel of the size you are welding between them (obviously with the welder turned off) so you can have a look and see if the tips line up well under pressure. Just bringing them together till they touch isn't a good indicator as they tend to shift slightly due to flex and play in the pivots will affect this too.
You are looking for a dead straight path for the current to flow between the tips otherwise material tends to get fired out of the joint causing sparks, crowning or both.

Sorry mate, you replied as I was typing my last reply !! I'll try 4mm then 3mm. Thanks again for the help, I'll let you know how I get on.

 

[awemawson]

If you have a lathe, shaping the tips is a doddle. I just bring a 45 degree tool up and clean them to shape. Alternatively there is a device you can buy that fits in a hand drill and works a bit like a pencil sharpener.

 

[Robotstar5]

If you have a lathe, shaping the tips is a doddle. I just bring a 45 degree tool up and clean them to shape. Alternatively there is a device you can buy that fits in a hand drill and works a bit like a pencil sharpener.

We had the air powered cutters at work to dress the tips, just had to remember to turn off the weld current or it scrapped the cutter!

 

[Jim Davey]

Those cutters are a bit beyond the budget of a home user I'd imagine.

 

[B1N9S]

I sharpened up the tips and hey presto, works a treat. Cheers.

Grinder with a flap disc in a vice, then the tip in a drill worked a treat !!! ;-)

 

[B1N9S]

Can anyone tell me if the electrodes are a special material, since they seem expensive for what looks like a bit of copper rod ?

 

[Shox Dr]

I believe that's all the are

 

[awemawson]

I've made many 'specials' from copper bar

 

[Wallace]

I have some info in an old PW spotwelder manual that had a recommended material spec for tips, I'll dig it out tomorrow night and have a look. SR12 was covered in this post too.