KES-1600 / HBS Stud Welder

[awemawson]

Years back I had a project that would have been SO much easier if I had a 'Stud Welder' ie a specialised welder that welds a threaded stud onto a piece of structure, so not only giving you a solid fixing, but a fixing that hasn't pierced the structure, not damaged the surface finish on the 'other side', and is still therefore watertight.

(Not to be confused with the lighter duty Stud Welder used in car bodywork repairs for pulling out dents)

So I've had a 'search' set up on ebay telling me when they are listed - and they fetch HUGE amounts of cash. Well this one popped up as a 'buy it now' and was at a VERY modest price  In fairness the seller couldn't be sure it worked - it had come in in a job lot of kit and he hadn't dared try it. Well there's a challenge if ever there was one 

A deal was struck, and when the holidays were over transport arranged. This is what arrived:

[awemawson]

Now in anticipation of managing to get it going (how hard can it be ......... ) I also bought a job lot of 8.5 kG's of suitable welding studs ranging from M4 up to M8. So really no excuse not to jump in at the deep end 

Well an inspection showed that it was by no means perfect but just a little neglected. The rear case was hanging off exposing the large bank of capacitors.

As I understand the operations of these things - the box of tricks charges up a bank of capacitors, then when the stud is in physical contact with the structure they are discharged, presumably using a solid state switch, melting the end of the stud and where it is pressing. As the stud gun holds the stud 'spring loaded' the two fuse together

[awemawson]

So lets give it a go! There happened to be a 6mm stud in the gun when it arrived. I found a bit of 1.5 mm galvanised steel, set the tweaker to about 3/4 and pulled the trigger. Result, a HUGE bang and flash from the work piece and a stud not attached at all.

Two thoughts went through my mind. Firstly possibly the galvanising is causing a problem, and secondly perhaps too low a setting for this size of stud.

Here is the result

[awemawson]

Well a bit of experimenting showed I was wrong - the setting was too high, and the melted metal instead of fusing together was being blasted to kingdom come out of the joint.

Reducing the setting produced some excellent welds that are not only well fixed, they are strong enough to be able to bend the stud without breaking. Picture is of M5 stud on 1.5 mm galvanised

[awemawson]

Now I assume that the tweaker on the front panel (setting dial) is adjusting the voltage that the capacitors are charged up to.

Then I tried it on some 4 mm plate just to prove the mass of the metal didn't draw the heat too much for fusion, and also that it would be tough enough to try breaking the stud. Sure enough the weld is easily strong enough, and the stud breaks before the weld

[awemawson]

So it looks like it's just going to be a case of cleaning up the grubbyness, making a suitable box and trying to find an instruction manual (Google hasn't shown anything other than a users guideline in their particular application)

[John Stevenson]

Brilliant bit of kit.
Don't need tee slots on a Bridgy now, just weld studs where you need them and grind the old ones off.

Magic.

[vtsteam]

Now THAT looks like fun!!!!

Congratulations on that score! (I know If I just received it there would be welded bits of rod and all over every piece of scrap I could find! )

[vtsteam]

The thing I would avoid, though, Andrew is sticking your tongue across the terminals of those capacitors.

[awemawson]

Nice one John 

Not so much the Bridgeport, but I can see it being used to hold things down on the welding table sometimes.

Steve you can bet more studs'll be used up playing than in earnest 

As I said at the beginning this is really solving 'yesterdays problem' - that project was finished years ago, but it's just another weapon in the arsenal, and I can see it occasionally getting me out of the do dah

[awemawson]

The thing I would avoid, though, Andrew is sticking your tongue across the terminals of those capacitors.

Well the missing screw from the back panel was a self tapper, and it points straight into the can of the rear (of three) capacitors - I had to make careful measurement to make sure it wasn't going to pierce as it's only a few mm away 

[vtsteam]

So is that 66K UFd total?

thinking nasty thoughts like how complicated can that be to build?

Is there a step down transformer on the output of those caps or does the output just go directly to the stud contacts?

Seems like it would develop too high a voltage without some kind of reduction, since I'm guessing the actual welding is at low V and huge A.

[awemawson]

Steve,

I've not pulled it apart, but as far as I can see there are three of those capacitors, all the same physical size. The thing is quite light so no 50 hz transformer though probably some form of chopper / inverter arrangement for charging them.

Don't know for sure, but I suspect the discharge is direct from the capacitors through whatever switches it, and I expect that they will be special high current low internal resistance types.

I used to spot weld tags onto NiCad cells years ago just by charging a big capacitor to about 150v and letting it wack the tag - very effective

[vtsteam]

Oh, I just noticed two leads going to the gun -- maybe things are more complicated ???

[vtsteam]

Well maybe one is a local gun shield ground....maybe those vise-grip ground clamps only partially supply the ground -- or maybe they are for a different job situation.

[awemawson]

There is a welding style lead to the gun via a 'dinze' plug, then also a multi-pin plug / socket. The gun has a trigger that is obviously just a switch. The main box lights up a lamp when the spring loaded gun is pressed against the work, so that's just detecting an earth on the shroud.

So again just assumptions, but the only active thing coming back from the gun is 'trigger pressed'. There is a light over the setting dial that goes green when ready, but if you move the dial up or down it takes a few seconds to go back to green from the red it shows as you move. So I assume it is measuring the volts on the capacitor bank and comparing with the 'set point' from the dial.

[vtsteam]

I see, and I guess the caps are probably charged to a relatively low voltage, so that would solve the puzzle to me of the need for a step down transformer on output. If they are never charged very high, no need. But they do need to be huge to store enough power and supply the instantaneous welding current. Well 66 thousand microFarads, is a respectable capacity!

Fun to pick this stuff apart...

[vtsteam]

Oh, just noticed you attached the manual -- now RTM'ing...

[vtsteam]

Looks like the limit is 6m x 20 mm studs. The chuck is special, as are the studs -- copper coated, and they have a small pin at the tip, which probably sets up the resistance needed for the initial melt. The weld pool (if you could call it that) then probably eases further melting of the larger stud, and it's now high temperature continues to provide enough resistance for the larger area melt. This is all taking place in an instant.

There's spring loading, is it a continuous pressure or is there a momentary hit? They refer to an "impact pin".

btw, I definitely wouldn't want to build one (kidding earlier) but do love to understand how things work. This is a particularly fascinating tool! 

[awemawson]

Steve, that's not really a manual, more a guide written by some firm that are using one for only two sizes of studs. I think it'll actually do 8 mm.

Stud is just mild steel, as you say copper plated and with a pip on the end. It is held in a simple four fingered collet made from copper, and the fingers are held together with an O ring. Up the back of the collet is an adjustable 'depth stop' to adjust for different lengths of studs. If I get a chance I'll pull the back off and measure the voltage on those capacitors - I suspect it's not going to be that low - 150v is my guess but time will tell. My guess is based on them being 200 v rated. To last they need to be under rated, but no manufacturer is going to pay for higher voltage caps than they need as I bet that they are rather special and pricey.

[lordedmond]

Andrew
and you thought lipo's were bad news  those caps will hold a fair amount of energy


great bit of kit when you need one


Stuart

[vtsteam]

Oh, thanks, Andrew.  Does anything "impact" the stud when you pull the trigger (like the way an automatic center punch works)? Or does it just remain uniform pressure when you press it against the base metal?

[awemawson]

Stuart, yes loads of energy stored potentially (pun intended) 

Steve, No the only force on the stud is a spring. The stud projects at rest forwards of the shroud and when you put the stud to the work you compress the spring - it is adjustable by a tweaker at the rear of the gun

I have downloaded the manual of a similar capacity stud welder by a different manufacturer (Lynx) and they calibrate the oomph in real world volts from 50 - 200 and include a circuit diagram.

I've attached this Lynx manual to this post as although a completely different manufacturer the studs are the same AND SO ARE THE COLLETS - now there's a co-incidence. It also has the SAME 66,000 uF CAPACITORS !! The volts must be similar to deliver the same energy requirements I'd presume

[lordedmond]

Wonder how many Joules that thing discharges


Stuart

[Manxmodder]

Brilliant bit of kit.
Don't need tee slots on a Bridgy now, just weld studs where you need them and grind the old ones off.

Magic.

I laughed when I read that,but I'm certain we've all witnessed the type of philistine who would do something very similar. .....OZ.