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Jolt & friends - Team Overkill - NSW
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Out of gas (again!):

Mr T's frame is almost ready for welding and I cut up some scrap for practising, then found the TIG welder's gas hose was missing. A quick trip to Bunnings fixed that, then I found the tank was all but empty Crying or Very sad. A refill tank won't arrive until Tuesday or even later so the new plan is to rent a small tank from Bunnings.

While I was at Bunnings, I grabbed a mains powered Dremel - the cordless one needed a recharge too often and was slowing down progress.



This 4200 model is awesome - heaps of power and the quick-change chuck is very handy; until I can get more argon, I am having fun fitting Mr Mangle's new frame together with it.
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Post Sat May 20, 2017 8:32 pm 
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pilleya



Joined: 31 Mar 2016
Posts: 91
Location: Sydney


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If you have any spare time you should 3D print one of these guys. Finally a good use for a cordless dremel.

http://makezine.com/projects/make-38-cameras-and-av/dremel-devil/

Post Sat May 20, 2017 9:39 pm 
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Nick
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Ha Ha, I am totally doing it! I saw this a while back and then lost the link, so thanks for that.
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Post Sat May 20, 2017 10:19 pm 
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Nick
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Progress:

Bot building was hit n' miss over the weekend. I got a new argon tank from Bunnings, only to find that the fancy dual regulator had a leak on the high pressure side (which helps explain the lack of gas in the old tank Rolling Eyes.) That's now fixed although the soft solder job may not last long.



I am definitely out of practise with TIG welding and gas coverage is a bit dodgy but more practise will improve things. At the current rate, its going to take most of the week to get Mr T welded up.

Mr Mangle's new frame is also progressing; just the top panels need fitting:



Its definitely not getting welded until Mr T is all finished - I need the welds on this one to be super strong.
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Post Mon May 22, 2017 6:28 pm 
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Nick
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All day welding:

The replacement E size argon tank arrives and just as well - with three gas lines going the combined flow rate is 40 litres a minute Shocked anything lower and its oxide city. This is the set-up for some small brackets; its virtually all to get the part even partly shielded on all sides:



At least the brackets came out fairly well:



Here is a cut-away view of the pneumatics before the sides are welded on:



It mostly fits OK but I found a problem with bulkhead that supports the buffer at the front; it needs a couple of mm ground off to allow the arm to lower further and scrape the floor.
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Post Tue May 23, 2017 1:03 pm 
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maddox



Joined: 21 Dec 2006
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Hmm, why not using the bulkhead as the endcap?

And your valve is reversed in the setup. I hope this was a quick put together for showandtell.

For small parts as the brackets, I use a big box and fill that with argon, as argon is heavier than air (not much and any disturbance will make it "slosh out")
I have a 4 liter/min flow with a diffusor to keep the box filled.
The flow on the torch is 6 liter:min, giving me a combined flow of 10 liter/min

Idealy, that should have been a glovebox, but I don't have the space for that atm.

Post Tue May 23, 2017 3:34 pm 
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Nick
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Joined: 16 Jun 2004
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I never thought about using the bulkhead as an end cap - great weight saving idea! I was thinking of giving a prize to the first person to notice the valve was reversed, guess I will have to promise you something now Smile. Everything is just thrown together for now, most joints have no sealant & are just finger tight.

I don't know how you get away with using so little gas (other than just being a good welder). On my torch with a HUGE cup and a gas lens, anything under 20 LPM gives me a really oxidised weld. I started out at around 10 LPM on test welds and kept turning the gas up until the weld was clean.
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Post Tue May 23, 2017 4:09 pm 
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miles&Jules
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Looking great nick👍
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Post Wed May 24, 2017 1:03 am 
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maddox



Joined: 21 Dec 2006
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I can't say what goes wrong with the welding over there.

Except that your open setup allows for increased intermingling with atmosphere.

Just boxing the sides in will limit that a lot. No "firestorm effect" on the gasflow, as the draw in from the bottom is cut off.


On the valve thingy. Don't worry, I had an unfair advantage.

Post Wed May 24, 2017 5:59 am 
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Nick
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When possible, I have two shielding strategies: for larger parts that join at 90 deg, I use one or two aluminium blocks as in this mock-up.



They work really well and only need a low gas flow. I only have three different shapes; when I get the mill set up again I will definitely be making more. They don't work on small parts or in confined areas so I also make little enclosures from aluminium roof flashing:



This works fairly well but not always as you can see. It needs way more gas and even when the flashing is carefully fitted around the part there are always leaks. The flashing has to be kept away from the TIG arc or you get a real fireworks display.

The biggest waste of gas is that the back shielding lines are continuous flow, not solenoid controlled. The time it takes to turn on the gas at the tank, walk back the to job, drop my helmet, pick up the torch & filler is longer than doing a short weld
Rolling Eyes. After the Vivid event, I want to make an flow control accessory with a couple of extra gas valves.
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Post Wed May 24, 2017 10:18 am 
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maddox



Joined: 21 Dec 2006
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Maybe use a pedal to control the extra valves?

I was thinking about using another inert gas to improve the "staying power" of the gas shield. But some research and digging up memories from school and work did give me the answer I dreaded for.

For an heavier noble gas, you're looking at krypton, xenon or radon. That last one is suicide, due the radioactive nature of it.
The other 2 are WAY to expensive to be used as a shield gas.

Maybe there are studies about the use of those for welding, but not even in my guide to weld uranium there is any mention of the use than something else than argon and helium.

As I mentioned earlier, ideal would be a glove box, pre-vacumed and then filled with argon. But the next best thing is an open top box (maybe a big ceramic square flowerpot thing?)

Avoiding fast gasflows, as those can create turbulence and draw in the gasses we want to stay away from the weld.

Post Wed May 24, 2017 3:11 pm 
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Nick
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Joined: 16 Jun 2004
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A gas solenoid and some plumbing will run less than $100 - about the cost of a D size refill, so there is a really short pay back time to making a gas controller, slaved off the main solenoid in the welder. The box idea is good for smaller parts but full chassis will need a large container and I would be giving up all the handy features of the steel welding table. Making more of the aluminium manifolds is a good long-term option; they always work and are fairly cheap to make.

The Ti welding was a disaster today; everything went wrong and even my helmet broke! It pissed me off so much that I decided to take a break from bot building for a while to finish off the workshop, get at least one CNC project finished and learn to weld Ti properly.
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Post Wed May 24, 2017 8:38 pm 
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Nick
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Welding table:

The welding table has some upgrades: A new shelf allows the MIG and TIG welders to fit under the table tap and an outrigger holds the gas tanks so that everything can be wheeled around:



The frame is now finished in hammertone paint (still need to slap some paint on the outrigger). The big bench vice is just temporary until I make a proper work bench for it. The next upgrade is to fit the torch water cooling system; it will be hidden under the shelf to save space. Fitting most of the welding gear under the table really saves floor space; getting rid of a separate welding cart saves almost one square meter Smile.
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Post Tue May 30, 2017 3:12 pm 
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miles&Jules
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Like ya tig holder-printed?
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www.wombokforest.com.au

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Post Tue May 30, 2017 4:22 pm 
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Nick
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No, its all steel. I picked it up from eBay while I was getting the last gas refill. You can get the same thing from Hare & Forbes - they have a magnetic base that is super convenient
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Post Tue May 30, 2017 4:36 pm 
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