Tig Welding

[forteh]

Will stick with the No.5 for now, better to actually get the welder to work properly and get some more beads laid before changing around more parameters

With the arc flaring up, could it be that (suppose because of the wrong flow meter) there is insufficient gas flow, once the post gas quits, the tungsten is still hot enough to ignite the oxygen in the air and once ignited keeps burning? It's odd because there shouldn't be any current to the torch at all. Hopefully the new collet will cure my lack of apparent amperage getting to the peice.

[forteh]

Got my bottle of gas from work along with a regulator, a gas lens and No.6 ceramic to suit it and sharpened my new lanthanated tungsten. Got the gas set up and flowing around 5lpm (using my little flow meter attached directly onto the regulator as the scale is much finer) and all seems to work ok

Having found the torch with the button and heavy hose sleeve quite cumbersome I decided to strip it all apart and convert it to a foot operated switch toallow better torch control. Made a simple wooden hinged pedal with a pocket routed out for the switch to sit into, works an absolute treat - obviously not as good a proper pedal but it give far easier torch control.

Had a play around with the 2t/4t settings and couldn't manage to replicate the tungsten blowing itself to pieces again, it all seemed to work as intended. I have found that the 4t works the best, press and hold to strike the arc at low amps, release to ramp it up and press/release again to kill the arc. For some reason the 2t doesn't seem to ramp up to the same current as 4t does and acts as an on/off switch so perhaps something it buggered with it, either way the 4t seems to work out quite well.

All of these welds are autogenous as I haven't got any filler rods yet

Laid a load of plain beads, playing with various amperages to see the effects and penetration, also to guage how much heat I'm getting into it.

First ever attempts at a butt weld, these were done with 2t and it really struggled to get the heat into it (see above - I don't think it is ramping up as it should do on 2t) so was lingering far longer than I should have been with the torch trying to build the pool up.

Then went onto a lap weld, I orignally started this on 2t and was struggling with building the pool properly, I then found that the 4t was ramping up properly and went over it again (probably with far too many amps) and apart from the overheating (I think), I'm really quite pleased with it so far

Spent a couple of hours in the shed this afternoon and gone through about a sixth of the bottle, overall I'm pleased with the results but I want some critical input before I get through some more gas

Edited November 23, 2013 by forteh

[*gentlydoesit]

Your getting no real penertraition, I assume you were maxed out on the welder? Try grinding an angle down the edges of the stainless to form a v shape when butted together, then fill it with rod.

The but joint looks ok technique wise, were you pivoting on the ceramic. maybe cutting the edges off a bit(I do it a lot ), more rod will solve that.. but you said you didn't have any? So fair play if you didn't arnt the last three pics the same? No lap weld? Think I said before I always used 4t but couldn't remember why... maybe the same reason.

The foot switch idea was cool .

*guess you spotted the pic

Edited November 23, 2013 by f**megently

[forteh]

Aye there is no penetration to speak of on most of the welds, that was using 2t though and struggling to get heat in. All of it was free hand with no cup walking, also no filler rods used, just forming the pool in both pieces and getting it to run together and then forming the bead from there.

Now I've figured that the 4t is giving much more heat, much faster I will aim to be reducing amps and increasing speed

You noticed the sneaky edit then!

[*gentlydoesit]

Imo your doing pretty well. Especially free hand.

I see everthing

[i like cunning stunts]

When you say freehand are you completely freehand or do you have 1 fi ger on the workpiece, if you havent try it will help a lot.

Always best to use 4t as you can relax your grip when you have initiated the arc should only be holding the torch lightly.

[forteh]

Yeah, I'm propping the torch hand

[N.Wood]

Can you electrocute yourself doing this shit?

[i like cunning stunts]

Yup more of a belt that can hurt ive done it many times.

A few pipefitters who have had the misfortune of working with me have had a few shocks along the way too.

[forteh]

Yup, I tried an electrode positive weld on some aluminium and it shocked my torch hand through the leather gauntlet. Not significant shock but a definite tingling from my hand to elbow. Not sure why exactly it did, probably one of the settings wrong on the unit. I haven't had any shocks doing it electrode negative (which is how you weld steel).

edit: was welding at about 80 amps so wasn't a big one.

Edited November 24, 2013 by forteh

[*gentlydoesit]

I got a pisser at 80amps too, just the other day... made me throw the torch, shattering the ceramic on the floor.

I did have my elbow on the earth and a hole in the rod hand glove

[forteh]

So now I am having thoughts about converting the pushbutton (currently mounted in my foot pedal) into a true analogue amperage control pedal. In theory I would only need to wire a potentiometer in series with the existing microswitch and package it into an operable pedal. Any thoughts on using a pedal over 2t/4t?

[*gentlydoesit]

Lots to think about first bud.

Can the transformer in the welder cope with variable voltage/amperage. The plug on my foot pedal has loads of pins. The amperage/voltage controller in the welder may suffer as it only designed for the preset tasks.

Speak to an electronics engineer first or you could do some damage. in beginner chat about a bad maggy thread somone said they were an electronics engineer, maybe he can help? Or post a wiring diagram and ill see what I can do

[forteh]

It's an inverter set so in theory it's only a low voltage/current control and the torch switch is basically mounted to bell wire, adding the pot in series with the microswitch will just vary the control voltage driving the inverter which actually handles the welding current.

Spoken to our panel builder at work and he says that it should work fine, just a case of finding out a suitable pot and making it work within a pedal. I've got a wiring diagram but it doesn't really show much info unfortunately

I've dropped an email to Stel in italy and they have referred it to their technicians to see if it might negatively impact on the unit itself. Will see what they come back with

[*gentlydoesit]

Ahhh.. I think... so the voltage goes through the microswitch? I wouldn't have thought that to be honest, more that the microswitch controls a voltage regulator inside the machine. And it would be that needing modifying/replacing.

All that being guess work though as ive no knowledge of the welder at all. If it works the way you planned it'll be genius

[forteh]

To the best of my knowledge the inverter handles the entire of the welding current, all the dial on the front of the box does is regulate a control voltage (a couple of volts with milliamps) that tells the inverter what to output.

Hopefully it should work, the potentiometer is only a variable resistor which will alter the voltage of the inverter control

[*gentlydoesit]

http://www.hobartwelders.com/weldtalk/archive/index.php/t-32945.html found this, it seems to have a few useful links in one of the posts. By 'celtic warrior' (I didn't actually look at them though ) Edited November 26, 2013 by f**megently

[forteh]

Got a response from Stel technical, he said that they use a 10k pot in their pedals, he didn't say that it would blow it up at least! Going to do a quick and dirty wiring diagram in autocad tomorrow and email it back to him for confirmation that it should work as planned.

Maplin do 10k linear slide potentiometers for 1.09 each, they have 45mm throw so shouldn't be hard to translate pedal motion into that with a short cam arm and linkage - time to raid my box of old RC car bits and peices

[*gentlydoesit]

Was there any worth while info in my link? I still haven't looked, that dude seemed to know what to do though.

[forteh]

What he seems to be doing is replicating the pot in the front panel with another seperate pot, effectively having to isolate the unit one if you want to use the pedal - in effect he is just turn the knob with his foot whilst welding. He mentions that you need to have exactly the same pot as the one in the unit.

I will see what the Stel tech comes back with once I've sent my sketch over

[*gentlydoesit]

I love twiddling my nob while welding

Can't wait to see if it works

[forteh]

Here is the circuit diagram for the unit, now I'm a mechanical design engineer with rudimentary electronics knowledge but here is my footpedal design

I believe that RV1 is the main amperage control potentiometer on the front panel of the welder, by using the existing torch microswitch in series with a 10k pot it should vary the voltage of the circuit feeing into the logic control which in turn tells the inverter what to output. The main dial (RV1) should set the peak welding current whilst the 10k pedal pot should ramp up the amperage as needed.

A colleague at work suggested re-purposing a hole punch for a pedal and then proceeded to hand me an old worn out one, god only knows why he had kept it! This thing is made like the eiffel tower, solid cast aluminium throughout, really smooth action and good solid springs. It's an old perforex 450 and looks a bit like this

Fits perfectly as a foot pedal and there is plenty of room to get the switch and pot in there. I love homebrewing stuff that would normally cost a fortune

[*gentlydoesit]

After staring at that for a while... i don't see it not working.

im not sure, but i think you won't be able to set the main pot half way and use the full stroke of the pedal pot, as once the 10k has been achieved at the foot it'll be over the 5k for example that the main one is set at. Basically you'll need to turn it to max and leave it there forever.

[forteh]

I'm not 100% either

Adjusting a pot will vary the current passed by the circuit, basically I will be using 2 variable resistors in parallel; what this might do is reduce the current shown on the dial.

Example: -

Main dial pot = 10k (100%)

Foot pedal pot = 2k (20%)

Resultant resistance = 1.6k

Main dial pot = 10k (100%)

Foot pedal pot = 10k (100%)

Resultant resistance = 5k

Basically it will be halving the current flowing through the control circuit, exactly how that would affect welder output I'm not sure. Like you say, I might need to leave the dial maxed out and just rely on the foot pedal to control the amperage - if it does indeed half the welder output then I wouldn't be able to put more than 80 amps into it.

Using a 100k pot on the foot pedal (also a quid each from maplin)

Main dial pot = 10k (100%)

Foot pedal pot = 20k (20%)

Resultant resistance = 6.6k

Main dial pot = 10k (100%)

Foot pedal pot = 100k (100%)

Resultant resistance = 9k

So only dropping 10% of the resistance which gives a a much closer representation of the output relative to the pedal position and the front panel dial.

edit: this is assuming that the pot in the machine is 10k!

Edited November 27, 2013 by forteh

[*gentlydoesit]

Just looking through some old stuff.. that symbol in the circuit where your putting your pot is a thermistor not a pot, are you sure its the main amp control? I think p1 is the main pot?

Edited November 30, 2013 by f**megently