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Long time since I've been here looking for help with project

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Platinum

Sun Jun 25 2017, 10:15AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Hello everybody haven't posted here in a long time, but I am looking for some help with an upcoming project after I move into my new house, its not very complex. I'm a fabricator welder by trade and me and a friend are starting to do jobs at his unit so I'm about to buy a Parweld XTS 142 arc welder, I've got about 5 years welding experience and I also worked in automation and control for 6 months making custom high powered electrical panels and I was brought into fabricate the buss bars things like 100 by 10 flat copper etc I then went back to my old job to go back into fab and welding. So like I'm looking to buy a Parweld XTS 142 arc welder which is 140 amp output far more power than what I intend to use it for and that is TIG welding stainless, so I need to also buy a TIG torch with a valve. So the help I need is because it's an arc welder the circuit is also live on the welding electrode now TIG is switched, can I use an SCR on the electrode terminal on the inside of the welder to turn it into a switched welding supply as in a hand operated switch on the gun? Also I have a small high voltage circuit off eBay which is an enclosed voltage multiplier I think and need to run from 1 or 2 18650 which I have already tested so I was looking at a small mains transformer on RS UK for 8 pound with a output of 6vac I intend to rectify that and add that to the high voltage unit and also add a another small switch on the torch and then the switch for HV start would be where my index finger would be to press momentarily and a thumb switch to maintain the arc via the SCR, would and SCR work? Would the little HV unit destroy the inverter welder?

Any help welcome thanks

Also anyone willing to help me and if possible trade a HF start circuit or SCR I will give a SSTC driver board the exact same one here, left the board and coil at s friend house while I pack thing for my new house told him not to use it and now is not working status led is green but 2 ICs are missing and one possibly failed you can get the information needed to repair it here

look for SSTC 2

hen918

Sun Jun 25 2017, 11:32AM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

I would recommend just buying a TIG /Arc / Plasma Cutting hybrid. It might cost another Â£100 but you would really be risking it with high voltage around an inverter welder not designed for it.

Edit: If you were to use the cheaper welder, could you not tap-start the arc as you would when arc welding? You could also use a beefy Solid-State Relay on the input to stop the arc on command, however I'm not sure how the welder would like the power being cut whilst arcing.

Platinum

Sun Jun 25 2017, 11:45AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Unfortunately a plasma, TIG/MMA welder will cost in excess of a good thousand pound except those Chinese ones which I won't take the risk even a half decent manufacturer I'd struggle to get one for 700 pounds. A well known manufacturer will give a good warranty and use reputable manufacturers for their semiconductors and accessories such as troches and cables and consumables as obviously they don't last for ever. Thermalarc make a 175 AMP arc welder which has the same insides as the same welder they sell as their 175AMP HF/HV start TIG welder I think they are priced around 340 for the TIG set up. Surely someone would recommend a HV choke, I will look into the relay though thank you

Also yes I can scratch start the TIG welder but this would include tungsten inclusion in the weld and contaminates, and in turn will not make the tungsten last very long. Also it would make a world of difference if I could make or break the circuit myself with a simple switch and HF start would make a big difference in weld and tungsten quality,

Finn Hammer

Sun Jun 25 2017, 04:31PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Platinum,

With regard to the chinese welders, I also had my reservation, but after buying this unit:

I feel different.
It immediately enabled me to weld alluminium, and stainless of course.
Quality is not so bad, and I recommend it.
I have had several years of welding experience, on shipyards, but that was 30 years ago.

Cheers, Finn Hammer

Platinum

Sun Jun 25 2017, 06:42PM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Unfortunately my budget is not that high but could stretch a little to about 600 pound, but would like to spend as little as possible for now(as most other would), I do TIG at work on a regular basis, my intent is custom exhaust manifolds and other small jobs, I don't need aluminium capabilities or atleast not yet. The machine you linked could I ask what quality are the components like? Thanks

Also I only need about 100amps max but more is obviously more versatile, does anyone know or have a schematic to a HF start circuit in a welder or know the basics/fundamentals of how they work

Thanks

hen918

Sun Jun 25 2017, 07:57PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Platinum wrote ...

...
Also I only need about 100amps max but more is obviously more versatile, does anyone know or have a schematic to a HF start circuit in a welder or know the basics/fundamentals of how they work

Thanks

The high voltage across the output terminals is caused by a high voltage pulse from a charged capacitor discharging via a spark gap and the primary of a coupling transformer with the secondary in series with the output.

This website will tell you mare about it:

Platinum

Sun Jun 25 2017, 08:34PM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

hen918 wrote ...

I see thanks for sharing that, it's a relay switched neon transformer circuit with an output on the one of the welding terminals, I have a very small ignition transformer which by the sound and size is a simple IC controlled voltage multiplier, intact the arc characteristics are very similar to HF that welder use if anything the output is higher on my small ignition device, although 3.6vdc would drop the power of it but still be very suitable for HF start, I assume a simple filter would protect the welders inverter circuit, that only leave a switch for power to be made and subsequently interrupted, I have yet to find a suitable relay to do this though, and an SCR would not work?

Thanks

johnf

Mon Jun 26 2017, 09:18AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

Buy a cheap tig welder
They get down to US$400 here in NZ ie 180amp hf start Chinese

adding hf start to an ordinary DC arc welder will vaporise your rectifier diodes unless you know how to stop the HF getting back into the welder. I did this to my big 500A DC arc welder and the replacement 900amp 1200PIV diode cost more than a cheap Chinese TIG welder when I added an aftermarket HF unit made by lincolln.

Platinum

Mon Jun 26 2017, 09:47AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

johnf wrote ...

Buy a cheap tig welder
They get down to US$400 here in NZ ie 180amp hf start Chinese

adding hf start to an ordinary DC arc welder will vaporise your rectifier diodes unless you know how to stop the HF getting back into the welder. I did this to my big 500A DC arc welder and the replacement 900amp 1200PIV diode cost more than a cheap Chinese TIG welder when I added an aftermarket HF unit made by lincolln.

Okay it looks like the better option is a Chinese welder, I'll see if I can find one with a good warranty

Finn Hammer

Mon Jun 26 2017, 09:53AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

In the case that you don't want ac welding current for alluminium, you can get a much cheaper unit at the same shop on german ebay. Just get a foot pedal too, so you can adjust current on the fly.
The quality of the tig torch looks like it is on par with the Parweld unit. It is the better end of chinese semi pro gear. Not quite as refined or roboust as Migatronic and Kemppi, but at a fraction of the cost

Cheers, Finn Hammer

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