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what eBay welder?
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miles&Jules
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Thanks for all the info guys.
So inverter stick welders are supposed to be able to do tig? So what would the parts that attach to make to do tig be called? Maybe we should try that first. Cheers M&J
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Post Sun Nov 22, 2015 8:38 am 
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miles&Jules
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needthis


http://www.ebay.com.au/itm/WP-17F-12Foot-Air-Cool-Tig-Welding-Torch-Complete-With-Flexible-Head-Euro-Style-/310988905035?hash=item4868621a4b:g:61oAAOSwoQ1ToTqq

and this


http://www.ebay.com.au/itm/TIG-foot-control-pedal-For-JASIC-WELDER-/140440300764?hash=item20b2e4ecdc:g:q9AAAOSwRLZT9FAj


and this
http://www.ebay.com.au/itm/Disposable-Gas-Bottle-PURE-ARGON-2-2-Litre-Combo-Kit-Hampdon-MIG-TIG-/121425859546?hash=item1c458b93da:g:k6kAAOSwEK9UBIEe
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Post Sun Nov 22, 2015 8:39 am 
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maddox



Joined: 21 Dec 2006
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Location: Belgium


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DO NOT USE A DISPOSABLE GASBOTTLE

It's way more expensive than a rental bottle, what in its way more expensive is than a owned bottle.

Also, an el cheapo Chinese DC/AC TIG welder, with some TLC will do the job nicely.
No need for extensive and expensive additions and adjustments on a cheap stick inverter.

I just converted my cheapy to a watercooled torch.
Feels funny, the pulsing of the water trough the handle...[/b]


Last edited by maddox on Sun Nov 22, 2015 6:46 pm; edited 1 time in total

Post Sun Nov 22, 2015 9:39 am 
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Nick
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I'm sure one of our welding experts will correct me if this is wrong - pure Argon is more expensive and only required for aluminium. It cools the weld puddle more than CO2 or a mix, so you have to turn up the welder power or move slower. I use BOC Argoshield, which is an argon / CO2 mix and I like the results on steel much more than using pure argon.

@ Mario: what is the advantage of a water cooled welder? is it really required for light-duty work on thinner materials? does the hand-piece feel much heavier or unwieldy? After the welding failure on Shiny, I am really thinking about learning to TIG weld.
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Post Sun Nov 22, 2015 10:15 am 
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Spockie-Tech
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Hmm, Argoshield is the gas normally used for Mig isnt it ?
I hadnt heard that you could use that on a Tig for steel work, interesting,

I might have to try that out until I get my AC Tig if it gives better steel results. In what way would you say the steel result is better ?

regarding Gas prices, shop around and play off the big suppliers against each other. I got my Argon bottle refill price cut nearly in half by telling SupaGas about a special deal that BOC was offering that I was thinking about and they matched and slightly bettered it, cutting my bottle refill from about $175 to $100 (for 6.8m3, Supagas run some sort of extra high pressure bottle that fits 6.8m3 (compared to the usual 4.0 to 4.2m3) in an E size), so its worth talking to them instead of paying sticker price.

Those disposable bottles are a complete joke. You get about 5 min of welding time out of them, dont even go there.

Converting an inverter arc to a Tig. I tried that, and it does work, but you have to "Scratch Start" the arc, just like starting a stick electrode.

The problem is, as a novice, I quite often scratch-*stuck the electrode trying to start it, which then requires panic'ed wiggling to break it free (since you dont have a power switch on the trigger with a converted arc welder, power is on all the time), destroying your tip point, sometimes breaking the tungsten off.

And if you mis-manuever the torch, the arc goes out, and you have to scratch again, which means either waiting until your weld puddle cools and starting again, which makes for ugly welds, or if you dont wait, you dip the tungsten in the weld pool trying to restart it, and get a big blob on the tip, requiring re-grinding your tip if you want to keep a nice arc.

After a few frustrating weeks, I gave up and bought a Tig with HF (High Frequency) arc start. you just press the button, and zap, it lights the arc with no contact at quite a long range. Accidentally get too far away with a wiggle and the HF automatically kicks in again, keeping the arc going while you re-establish a nice short arc length.

It also lets you "long arc" for a second to spread out the heat input while you change direction, or reposition your filler rod or something, without the arc going out.

Its probably a bit of a noob-crutch, since I got a stainless steel fuel tank professionally tig-welded back togther after mods, and I watch the guy do that with a simple scratch-start arc-inverter/tig rig, and he just lit up first go with a practiced flick of the wrist and motored on out without a problem.

"You make it look easy !" I said... "Yes, well, 15 years of experience will do that" he said.. OK, but Im not sticking electrodes for years, so I like the HF start Smile
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Post Sun Nov 22, 2015 12:54 pm 
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Nick
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I should have mentioned that the Argoshield is used on my MIG welder.
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Post Sun Nov 22, 2015 1:24 pm 
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maddox



Joined: 21 Dec 2006
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Hm, my gas supplier seems to be very friendly then.
I pay €25 for a filling of 2.5m³ pure argon.

Mixed gas (argon with a dash of CO2) isn't that much cheaper.
And as I weld steel, cast iron, hardox*, stainless steel, aluminium and titanium, most of the jobs require pure argon.

For normal steel and cast iron, mixed gas is an advantage tough, gives better burn in. But to change over the bottle each time, nah.

*hardox doens't have a real advantage with mix gas to my feeling.

@ Nick. Water cooled torch. The welder itself is a cheap chinese AC/DC TIG job.

The original torch overheats every time I go over 120 amp (160 on the readout), and that's regulary on welding long stretches of 3.2mm hardox or 10mm ali.
An overheating torch means the copper locking collar anneals and gets very soft deforming and pulling the needle out of center. Or even losing grip so the needle just falls out after a serious bit of welding.

I had the luck to know about water cooled torches due my experience as a photo-welder in the past, so it was logical to use a watercooled torch. (€90 via Aliexpress, including consumables) .

The watercooled hose is stiffer, but the torch is lighter than the gascooled one. So it cancels out.
The main disadvantage is the cheap set I made. I use 2 diaphragm pumps in parallel to push the water trough the 5 meter of hose. It's noisy and I can feel the pulses in the handle.

Post Sun Nov 22, 2015 5:05 pm 
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Valen
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HF start is a must for me.
If the tungsten touches the weld pool it'll get contaminated, your weld will be crap from that point on until you grind it clean. Lots of black carbon and crap everywhere.
Scratch start is probably ok if your quick, get the torch high before you get molten metal under it. Our welder keeps the HF running all the time (arc stabilisation)


AC on aluminium can be loud at high amps, I actually used hearing protection when doing kang (10mm aluminium all around, 200A welding current)

You can DC TIG Aluminium too apparently much aerospace stuff is done that way. You use the rod to break the surface layer.

We just use straight argon out of a purchased bottle, argon works with everything and having more than one bottle is too hard.
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Post Sun Nov 22, 2015 6:30 pm 
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DumHed
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straight argon for everything with TIG.

If you use a CO2 mix (MIG gas) you will end up with brittle welds that often crack on cooldown.
There is hardly any price difference in the gases in my experience.

I would not bother with the scratch start sitck welder with a TIG torch option.
You don't get adjustable ramp up and down, or automatic gas control - which will really waste your argon.



There are a few places these days selling argon bottles, which pays for itself vs renting after a couple of years.
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Post Mon Nov 23, 2015 7:37 am 
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Nick
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Mario: what is inside a water cooler that makes it so expensive? I figure there is:

Pump
reservoir
radiator (maybe a car oil radiator could be used?)
fan
plumbing and fittings
240V wiring

It must be possible to make a reliable unit for WAY less than the commercial ones.
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Post Mon Nov 23, 2015 10:26 am 
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Glen
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I've got one of those tweco tc900 welder coolers i was going to use for the laser if you wanna buy it Smile Its a bit too noisy for said purpose.

Remember you won't be welding the entire robot in one non stop session or it will warp up like a pretzel lol, So huge continuous current ability isn't the end of the world. the WP17s last a while before getting too hot to hold on 200A anyway.
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Post Mon Nov 23, 2015 11:04 am 
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Nick
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Interested! I figure that getting into inside corners of the frame will need a small torch and they don't take much current unless they are water cooled.
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Post Mon Nov 23, 2015 11:20 am 
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Valen
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@nick
You gotta look at the duty cycle too, if you can weld at 150A for 15 seconds, that is actually not that small a time when you are doing inside one of your bot frames. If you needed to wait a minute for it to cool off eh, you're going to spend longer than that moving everything around to get the next weld set up anyway ;->

What sort of current do you need on your thickness of Ti anyway? I'm guessing its somewhere between steel and Al, so like 120A?

@spockie, our torch has a dial on it, you aren't going to turn it when you are running it. It saves a little time when you are between welds but a foot pedal would be *so much* better.
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Post Mon Nov 23, 2015 2:05 pm 
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maddox



Joined: 21 Dec 2006
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@Nick,
My watercooling unit is actualy a recycled, huge industrial unit, and it contains what you list up. I added a cheap digital thermostat/relay from aliexpress, but I never have seen the watertemperature rise with 10° over ambient.
Before you heat up 15 liters of water, you're doing some serious welding tough


I'm planning to build a new welding table, and integrate the reservoir in one of the legs. No radiator or fan , the reservoir will be large enough to dump a lot of heat in it.

The pump should be capable of pushing 5 l/min @6 bar.
A rotary vane or gearpump sound the most realistic.

******************************************************************
On welding titanium. If you can do it in a glove box , you can keep it flooded in argon, avoiding any contamination of the welds or base material.
Otherwise, get a bigger regulator, make a splitter on the hose and keep the argon flowing around the welds, including the backside.

Ti also behaves differently than steel or ali. The welding puddle is a lot more viscous and the filler melts in slow fat drops.
The bad heat conducting qualities of titanium are another matter and makes for a different way of thinking about warping and handling.

Post Mon Nov 23, 2015 3:40 pm 
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Nick
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@ Jake: I'm not really sure - about 150 amps for the thicker parts seems to be a recommendation.

@ Mario: Finding a suitable pump that can deliver the pressure is harder than I thought, a replacement pump from a cooler was $200 USD on eBay. I like that idea of building the reservoir into the welding table - very clever! Smile

I read about converting a sandblasting cabinet into a welding glove box but I don't really have anywhere to keep it. Making a temporary fold up box might be an option. I'm guessing they really eat up gas if you need to open the box up regularly to reposition clamps & parts?
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Post Mon Nov 23, 2015 4:40 pm 
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