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Black Forest
11-18-2014, 03:40 PM
Would a starter solenoid work to break the connection on a tig welding lead? The reason I ask is when scratch or lift arc starting a weld when you finish and have to flick the torch up to end the arc you lose gas shielding. I know a mechanical foot switch will work but I have the idea to also incorporate a solenoid valve for the gas with a delay for post flow. This would be on a DC inverter. Now the gas is controlled with a knob on the torch. I also have a HF box I could use to start the arc.

Just curious.

djc
11-18-2014, 04:41 PM
Would a starter solenoid work to break the connection on a tig welding lead?

Probably it would with some thinking. You might need to put it in the earth lead as the torch lead is often integral with the gas pipe.

The only problem I see is that a starter solenoid is push-to-make, which means you'd have to keep it energised all the time you want the torch powered. For this, you'd need a latching switch (a broken guitar effects pedal might be a good source). What I don't know is if starter solenoids have a high enough duty cycle. Maybe get one from a lorry or tractor.

I had a vague idea of doing something similar but using a high amperage solid state relay such as those sold for electric winches. Also, there are quite a few (claimed) high-amperage knife (blade) switches from China on eBay. That might be another option.

Black Forest
11-18-2014, 04:51 PM
Probably it would with some thinking. You might need to put it in the earth lead as the torch lead is often integral with the gas pipe.

The only problem I see is that a starter solenoid is push-to-make, which means you'd have to keep it energised all the time you want the torch powered. For this, you'd need a latching switch (a broken guitar effects pedal might be a good source). What I don't know is if starter solenoids have a high enough duty cycle. Maybe get one from a lorry or tractor.

I had a vague idea of doing something similar but using a high amperage solid state relay such as those sold for electric winches. Also, there are quite a few (claimed) high-amperage knife (blade) switches from China on eBay. That might be another option.

I need it to be an electrical switch not mechanical.

hoof
11-18-2014, 06:06 PM
I've had some problems with starter solenoids with long duty cycles. They get very hot then melt. You might want to consider an electric forklift contactor. continuious duty, High current, and relativley inexpensive due to relative high volume production.

Just my two cents


Ray

Mike Nash
11-18-2014, 08:07 PM
You might want to consider an electric forklift contactor. continuious duty, High current, and relativley inexpensive due to relative high volume production.
Ray

I think, based on another active thread here, that the use of an inexpensive device for an application to replace a much more expensive (identical, but for labeling) device might possibly be immoral and/or illegal...




Oh yeah - hah hah hah :)

Doozer
11-18-2014, 09:06 PM
You need a vacuum bottle interrupter.
Made by Eaton-CuttlerHammer and there is Greenstone, a Chinese knock off.
Good for a bit more than 34.5 kV.
-Doozer

lakeside53
11-18-2014, 09:18 PM
It would be easier to just to add post flow - a delay-off relay timer would probably do that with very limited wiring changes. Just add it to the the existing gas flow valve.

macona
11-18-2014, 10:04 PM
You need a magnet blow-out contactor like what is used in Lincoln ln-25 and other suitcase wire feeders. They run off 12v. Standard truck starter contractors won't work for welding because of the high OCV, the arc will sustain in the starter solenoid.

CCWKen
11-19-2014, 12:06 AM
Geez! This thread reeks of "muffler bearings", "conudor valves" and "blinker fluid".

Is a "vacuum bottle interrupter" for real? :confused:

Yow Ling
11-19-2014, 12:43 AM
switch the welder off at the wall, that should kill the arc

LKeithR
11-19-2014, 01:37 AM
I think it's time to buy a decent welder. Get one that has post-flow built in and no more worries...

lakeside53
11-19-2014, 12:17 PM
Post flow has to be the easiest thing to add to just about any welder ;)

Black Forest
11-19-2014, 01:18 PM
Post flow has to be the easiest thing to add to just about any welder ;)

I agree the post flow is no problem. Killing the arc is the problem. I don't know if I kill the power to the welder from the mains with a switch if that will damage the welder. The welder is a …WM Pico 162 DC inverter welder. I would hate to tear up a 1000 dollar welder just to kill the arc! This little inverter welder is by far the best stick welder I have ever welded with in my life. It has a great arc and starts the arc really easy. I bought it to do repairs out and about on the farm. It is a 220v only welder so I can plug it in anywhere and weld. EWM is supposed to be the Rolls Royce of welders here in Germany.

ironmonger
11-19-2014, 01:35 PM
I have been tig welding stainless for a long time, and all the welding machines that I learned on were scratch start. The post flow was established by increasing the arc length by lifting the torch and rotating it to allow the gas to bath the joint until it cools to 600 degrees or so... not very long. You could also run an auxiliary line to flood the joint.

I now have lift start, and I love it, but the lift start circuit does not come into effect until the arc is extinguished by breaking the arc and then re-establishing contact to start up again. Breaking an arc abruptly can result in a pin hole when fusion welding light wall tube, and the standard manual process is to slowly increase the arc length, thus reducing the heat and 'dragging' the arc off the center line of the joint to keep the pinhole action away from the puddle.

If you are going to install a foot switch to kill the arc why not just purchase the foot pedal and use that to break the arc?

paul

macona
11-19-2014, 02:16 PM
Like I said, a magnetic blow out contactor on the lead will do it. There are also commercially available contactor boxes available too.

macona
11-19-2014, 02:17 PM
Yes, they exist. Very expensive though.

https://www.google.com/search?q=vacuum+relay&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=qexsVKHXA-LuiAL46ICYDA&ved=0CEUQsAQ&biw=1324&bih=1051

MrSleepy
11-19-2014, 02:33 PM
Like I said, a magnetic blow out contactor on the lead will do it. There are also commercially available contactor boxes available too.

Jerry..BF says he has a HF Box in his first post.

The only HF boxes I'm familiar with are by ESAB and Migatronic , but they both have internal contactors and gas solenoids etc ,along with HF protection for the source PSU.

BF... Bruce .. have you tried hooking up your HF box.

Rob

Black Forest
11-19-2014, 03:01 PM
Jerry..BF says he has a HF Box in his first post.

The only HF boxes I'm familiar with are by ESAB and Migatronic , but they both have internal contactors and gas solenoids etc ,along with HF protection for the source PSU.

BF... Bruce .. have you tried hooking up your HF box.


Rob

Yes I use the HF box. It only generates the HF to start the arc. It does nothing else. The gas connects to the HF box but it is just a pass through. I took the cover off the box to see what is inside. I also called the company and they said it only initiates the arc and will not kill the arc.

Here is a link to a vacuum relay on Ebay. Would this one work?
http://www.ebay.de/itm/Relais-Vacuum-ITT-Jennings-RB3-26D737-mit-2x-Um-Kontakte-Mod-1-/231305900103?pt=Elektromechanische_Bauelemente&hash=item35dae7f047

Jon Heron
11-19-2014, 03:22 PM
Is a "vacuum bottle interrupter" for real?
Yep, they are used for high voltage switches, with HV the air will ionize and become a conductor, the vacuum eliminates the ionization problem.
If you want a nice small HV switch SF6 (sulfur hexafluoride) gas filled bottles are all the rage now...
BF, a mercury contactor may do all you need (though I really have no experience with the demands of a TIG welder) they eliminate the issue of burnt contacts and will never weld shut. You see them frequently on ebay reasonably priced. http://www.ebay.ca/sch/i.html?_from=R40&_trksid=p3984.m570.l2632.R2.TR2.TRC1.A0.H0.Xmercur y+contactor&_nkw=mercury+contactor&_sacat=92074

Cheers,
Jon

macona
11-19-2014, 04:00 PM
Some HF boxes do not have contactors. It is usually an option.

macona
11-19-2014, 04:11 PM
Yes I use the HF box. It only generates the HF to start the arc. It does nothing else. The gas connects to the HF box but it is just a pass through. I took the cover off the box to see what is inside. I also called the company and they said it only initiates the arc and will not kill the arc.

Here is a link to a vacuum relay on Ebay. Would this one work?
http://www.ebay.de/itm/Relais-Vacuum-ITT-Jennings-RB3-26D737-mit-2x-Um-Kontakte-Mod-1-/231305900103?pt=Elektromechanische_Bauelemente&hash=item35dae7f047

Probably won't handle the current.

macona
11-19-2014, 04:11 PM
Mercury won't work either, you need some way to extinguish the arc.

MrSleepy
11-19-2014, 04:14 PM
Some HF boxes do not have contactors. It is usually an option.

Yes .. As BF said about his. The ones I've come across.. are internally.. like this crappy Stirling (http://www.ebay.co.uk/itm/STIRLING-300-DC-HF-TIG-WELDER-BOX-for-stainless-steel-welding-DC-Contactor-unit-/201216298012)

http://www.ebay.co.uk/itm/STIRLING-300-DC-HF-TIG-WELDER-BOX-for-stainless-steel-welding-DC-Contactor-unit-/201216298012
Rob

Barrington
11-19-2014, 04:56 PM
Just a thought...

Instead of trying to break up to a max of 160A DC (non trivial...), how about simply shorting the welder output?

This sounds brutal, but would only have the same effect as dipping the tungsten, and the current should then drop to a low level. (As this is a lift start machine, perhaps to the normal sense current of a few amps ?)

Operate the shorting switch, arc extinguishes, hold the torch in place for shielding, then pull away, then release the short circuit.

Cheers

.

ironmonger
11-19-2014, 05:41 PM
What on earth are you welding that is so sensitive to post weld oxides?

I'm still curious why just breaking the arc as hundreds of thousands of tig welders have done as manual welders for ever won't work.

If you need shield gas stick this in the line after the flowmeter:
http://www.weldfabulous.com/p-71121-inert-gas-y-valve-argon-western-411.aspx
stick a hose on it and use that to purge the surface...
We never found this necessary, but if you must...

paul

macona
11-19-2014, 06:25 PM
Just a thought...

Instead of trying to break up to a max of 160A DC (non trivial...), how about simply shorting the welder output?

This sounds brutal, but would only have the same effect as dipping the tungsten, and the current should then drop to a low level. (As this is a lift start machine, perhaps to the normal sense current of a few amps ?)

Operate the shorting switch, arc extinguishes, hold the torch in place for shielding, then pull away, then release the short circuit.

Cheers

.

Still need a magnetic blow out contactor. When you open it an arc will start in the contactor without it.

garyhlucas
11-19-2014, 07:14 PM
I think this is getting way out of hand here. An inexpensive 200 amp battery vehicle contactor will work just fine here. On start of the arc you press the button, the contactor picks up, no arcing because you haven't struck an arc yet. When you release the button the contactor drops out extinguishing the arc. The contactors are internally double break across two terminals with a round disc that is free to rotate and spread the wear around. It is designed to disconnect a highly inductive DC motor with lots of back EMF and do that over and over again. A weld arc is pure resistance and in relative terms easy to extinguish. I'd get one and get on with the welding.

macona
11-20-2014, 12:21 AM
Engines are 12v to 24v max. Most stick and tig welders have 80v open circuit. That difference is pretty significant. Now there might be a possibility of placing a magnet in the right place on the solenoid cap if it is bakelite and getting the arc to blow out, I am not sure how you would test it though.

EVguru
11-20-2014, 05:12 AM
An Albright SW200 or even SW180 contactor would do the job and is readily available new or used. You can always fit your own magnets for blow-outs if the example you find doesn't have them. One trick is to make yourself a high current solenoid by winding a few turns of your welding cable around a Steel or Iron rod and use that as your blowout magnet.

MrSleepy
11-20-2014, 05:15 AM
Before HF start and Lift TIG etc , often they used to scratch start the arc on a sacrificial piece of copper bar..then move the arc onto the weldment.

In your case BF.. you could use copper bar to finish you weld on.. ie move the arc onto a copper bar and then extinguish it.

Rob

Black Forest
11-20-2014, 08:01 AM
Before HF start and Lift TIG etc , often they used to scratch start the arc on a sacrificial piece of copper bar..then move the arc onto the weldment.

In your case BF.. you could use copper bar to finish you weld on.. ie move the arc onto a copper bar and then extinguish it.

Rob

That wouldn't solve my shielding gas issue if I move the arc away from the puddle. I like shiny welds! Actually this set-up is for my 12 year old daughter. She really wants to learn to weld and of the three processes that I do she likes TIG the best. So I told her I would set her up a welding desk that she could work at whenever she wanted. She is a little hesitant to use my good TIG welder. She is afraid she might break it! I told her not to worry about it but she does anyway so I will let her use this one that I set up for her. After she gets the hang of it I will probably lose my good welder to her and get the jurry rigged one for my use!:cool:

macona
11-20-2014, 01:36 PM
As a guy who used to work on these machines there is pretty much nothing she could do to break it.

Black Forest
11-20-2014, 01:49 PM
As a guy who used to work on these machines there is pretty much nothing she could do to break it.

I told her that several times but she still doesn't want to use my good one. It was probably a bad move on my part I told her what it cost when she asked me.

So what does a tig welder use to terminate the arc? Maybe the best thing to do is go to my LWS and get one from them.

lakeside53
11-20-2014, 02:20 PM
Usually there just some low voltage logic internally that turn off what controls the current drive (often just SCR's in a bridge). If I wanted to interrupt the output current, that's where I'd start.

macona
11-20-2014, 10:13 PM
I told her that several times but she still doesn't want to use my good one. It was probably a bad move on my part I told her what it cost when she asked me.

So what does a tig welder use to terminate the arc? Maybe the best thing to do is go to my LWS and get one from them.

In old machines there were contactors on the primary of the transformer. When they moved to square wave they generally just used the SCRs that control the current to turn the output on and off. With inverters that is all in the logic of the machine, there is no real way to go in and add output control unless it is there and just not connected. Many early generation mini inverters were always hot on the output. The IGBTs are controlled by the microcontroller and believe me, you dont want to mess with that. Screw something up and get shoot-through on them and POOF!

Welders are designed to be as idiot proof as you can get and are full of protections. You could short the output directly to ground and leave it there and all it is going to do is deliver the selected current and make heat. If it is over the duty cycle it will eventually trip an overtemp sensor somewhere inside the machine and the machine will shut down till it cools.

The HF boxes with a contactor option use the same contactor as I mentioned. I checked the price for the replacement contactor for a miller suitcase feeder and they are around $400. Ouch!

ironmonger
11-21-2014, 05:22 PM
<<snip>>So what does a tig welder use to terminate the arc? Maybe the best thing to do is go to my LWS and get one from them.

As far as hurting it, +1 what maocna said. In my own experience the worst thing you can do is interrupt the mains and turn them back on quickly... thatís how I got the free one that required repair. :>)

As far as terminating the arc, as I said before, simply raise the torch until the arc goes out. As long as you are using scratch start or lift start all is well.

I tried to talk my wife into tig welding 30 years ago. If she had learned that she would have 4 times as much income and we both would have retired even sooner... Oh well. Best to your daughter. I'm sure she will do just fine.

paul

ironmonger
11-21-2014, 05:29 PM
BTW, these are pretty well thought of:

http://www.weldingtipsandtricks.com/tillman-welding-gloves-tigfinger.html

paul

Mike Nash
11-21-2014, 06:52 PM
BTW, these are pretty well thought of:

http://www.weldingtipsandtricks.com/tillman-welding-gloves-tigfinger.html

paul

I am considering one of those. It's amazing how hard it is to get my pinky into the glove when that finger got too hot and the leather drew up. I was really glad I had a thick glove on after I realized where I had had my hand.

Black Forest
11-21-2014, 07:01 PM
As far as hurting it, +1 what maocna said. In my own experience the worst thing you can do is interrupt the mains and turn them back on quickly... thatís how I got the free one that required repair. :>)

As far as terminating the arc, as I said before, simply raise the torch until the arc goes out. As long as you are using scratch start or lift start all is well.

I tried to talk my wife into tig welding 30 years ago. If she had learned that she would have 4 times as much income and we both would have retired even sooner... Oh well. Best to your daughter. I'm sure she will do just fine.

paul

I am using HF start.

ironmonger
11-21-2014, 07:46 PM
I am using HF start.

I should preface this by asking if you are welding DC?
Can you disable the HF automatically it after the arc starts? I dislike HF start personally, prolly comes from having been bit a few times. :mad:

If you are going to teach your daughter to weld, my thought would be to teach so that she would be able to weld with the simplest and most primitive methods. Moving up from scratch start, the first way I was taught in the piping industry, I will say that my personal preference is lift start. I still donít like continuous HF. When welding in position it is near impossible to use a foot pedal, and as position welding often involves many different 'holds' on the torch, trying to operate a trigger would be nuts.

I understand this begs the original query you made, but in light of your intended purpose for this machine, I would still teach a newbie the most basic methods first. I made hundreds of stainless steel and monel welds on socket weld 1/4"OD tube fittings for high purity gas in a chip lab, all the joints were pressure tested and helium leak checked. This was all done with scratch start. It's all you need and would be the best training before using lift or HF start IMHO

paul

danlb
11-21-2014, 09:21 PM
Probably it would with some thinking. You might need to put it in the earth lead as the torch lead is often integral with the gas pipe.



I would avoid doing anything that breaks the earth connection. Without the earth, your hand arm or belt buckle may become the best path to ground. That will not be fatal but it is NOT something that you want a neophyte to endure if you want her to persevere.

If a foot pedal switch will work, then there is no reason that you can't add a switch to the torch so that you can start/stop the arc from the there.

Dan