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Grahame Collins
20th Dec 2005, 01:05 AM
Would you like a series of threads on the above ?
I have tried to to avoid it but you all reckon GMAW (not bloody MIG)is the Go

What do you lot reckon about these topics ?
Why would you choose the GMAW Process?
Advantages and disadvantages - Cost versus versatility – what it will & will not do

Various Types of GMAW machines - gas , gasless multiple step voltage selection

Choosing a value for money GMAW machine – what to look for-what to avoid

Safety when using the GMAW machine

Setting up your GMAW machine for the first time – the components, what they do, where to start
Consumables for your GMAW – what the hell are they ?

GMAW Techniques and Procedures

Have I missed something
your comments please
Grahame

redwood
20th Dec 2005, 01:43 AM
whats a GMWA?:confused:

Edd
20th Dec 2005, 07:39 AM
whats a GMWA?:confused:
Gas Metal Arc Welding, AKA MIG. As opposed to MMAW (manual metal arc welding) or GTAW (Gas Tungsten Arc welding). These names are correct, as Tig and Mig's middle letter stands for inert and so if you have oxygen or something with argon, it's not technically inert. All in all, in the real world it's easier to say Mig.

Edd
20th Dec 2005, 08:20 AM
multiple step voltage selection
This made me think of Lincoln welders. Australians can buy an SP170T which has a 5 position switch for voltage (click, click). Americans have an SP175T which is infinitely variable with voltage control. I've always wondered why they don't just sell one or the other.

These are all good topics in this thread, one thing to add might be a Glossary of Terms:
Alternating Current (AC) -A flow of electricity that constantly changes direction of it's path.
Arc -The physical gap between the end of the electrode and the base metal. The physical gap causes heat due to resistance of current flow and arc rays.
Current -Another name for amperage. The amount of electricity flowing past a point in a conductor every second.
Direct Current (DC) -A flow of current that always travels from negative to positive and never changes direction
Duty Cycle -This refers to how much a welder can be used in a 10 minute period. For example, a welder that specifies 70% duty cycle @ 200 amps means it can be run at 200 amps for 7 minutes, then left for 3 with the fans running.
Flux Cored Arc Welding (FCAW) -An arc welding process which melts and joins metals by heating them with an arc between a continuous, consumable electrode wire and the work. Shielding is obtained from a flux contained within the electrode core. Depending upon the type of flux-cored wire, added shielding may or may not be provided from externally supplied gas or gas mixture. Consumables: contact tips, flux cored wire, shielding gas (if required, depends on wire type).
Ground Lead -This can refer to the clamp on a welder, but Workpiece lead is preferable and more correct, as it can be positive or negative.
Hertz -Cycles per second. Our AC here in Aus is 50Hz, meaning it changes from Active to Neutral or Neutral to Active 50 times a second.
High Frequency -Covers the entire frequency spectrum above 50,000 Hz. Used in TIG welding for arc ignition and stabilization. This means you can push the button to start instead of touch or scratch starting.
Hot Start™ -Used on some Stick (SMAW) machines to make it easier to start difficult-to-start electrodes. Used for arc starting only.
Inverter -Power source which increases the frequency of the incoming primary power, thus providing for a smaller size machine and improved electrical characteristics for welding, such as faster response time and more control for pulse welding. Many machines are inverters now.
Lift-Arc™- This feature allows TIG arc starting without high frequency. Starts the arc at any amperage without contaminating the weld with tungsten.
MIG (GMAW or Gas Metal Arc Welding)-An arc welding process which joins metals by heating them with an arc. The arc is between a continuously fed filler metal (consumable) electrode and the workpiece. Externally supplied gas or gas mixtures provide shielding. Common MIG welding is also referred to as short circuit transfer. Metal is deposited only when the wire actually touches the work. No metal is transferred across the arc. Another method of MIG welding, spray transfer moves a stream of tiny molten droplets across the arc from the electrode to the weld puddle. Consumables: contact tips, shielding gas, welding wire.
Pulsed MIG (MIG-P)-A modified spray transfer process that produces no spatter because the wire does not touch the weld puddle. Applications best suited for pulsed MIG are those currently using the short circuit transfer method for welding steel, 14 gauge (1.8 mm) and up. Consumables: contact tips, shielding gas, welding wire.
Pulsed TIG (TIG-P) -A modified TIG process appropriate for welding thinner materials. Consumables: tungsten electrode, filler material, shielding gas.
Semiautomatic Welding -The equipment controls only the electrode wire feeding. The welding gun movement is controlled by hand.
Shielding Gas -Protective gas used to prevent atmospheric contamination of the weld pool.
Spatter -The metal particles blown away from the welding arc. These particles do not become part of the completed weld.
Squarewave™-The AC output of a power source that has the ability to rapidly switch between the positive and negative half cycles of alternating current. If you graph this with the x axis as time and have a middle line with active (or negative) above and neutral (or positive below) it will have square shapes where the line changes direction, instead of rounded.
TIG Welding (GTAW or Gas Tungsten Arc) -Often called TIG welding (Tungsten Inert Gas), this welding process joins metals by heating them with a tungsten electrode which should not become part of the completed weld. Filler metal is sometimes used and argon inert gas or inert gas mixtures are used for shielding. Consumables: tungsten electrode, filler metal, shielding gas.
Tungsten -Rare metallic element with extremely high melting point (3410° Celsius). Used in manufacturing TIG electrodes.
Voltage -The pressure or force that pushes the electrons through a conductor. Voltage does not flow, but causes amperage or current to flow. Voltage is sometimes termed electromotive force (EMF) or difference in potential.
Workpiece Lead -The conductor cable or electrical conductor between the arc welding machine and the work, clamped to complete the circuit.
These were gathered from some google searching and some info I had in my head.

Clinton1
20th Dec 2005, 09:13 AM
Good topics and talking points. I'd hope that after the GMAW you do the other systems as well.

One problem might be created through:

Why would you choose the GMAW Process?
Advantages and disadvantages - Cost versus versatility – what it will & will not do


If you want to focus on the pro's and con's of one system over another you might need to be fairly objective.

You will have your opinion, someone else will disagree - and I'd hate to see the thread turn into a slanging match of people trying to prove their point over someone elses.

A bit of objectivity and a few "I think" or "My opinion" sentences and you might avoid this.

One thing I learnt when teaching adults (and maybe you have seen this as well) was that someone will come out of left field with a bloody good idea that I'd never thought of and change my point of view.
If they expressed their points calmly and clearly it would be great, others would just leap out with a "Bull....." and rant on and turn a lecture into an attack, the others would just turn off when the attack was going on, which wasted everyones time.

glock40sw
21st Dec 2005, 07:41 AM
G'day Grahame.
I think it would be a great idea.
Iv'e been playing with aluminium welding for the last few days.
Making chrissy light frames out of 6.35mm Ali rod.
0.9mm wire with straight Argon 20 l/m flowrate running thru the Transmig 165.

There has been a fair amount of welds that look like pidgeon poop.

I have a project for the holidays.
To make a puppy barrier gate.
16x16x1.5mm Ali square tube frame with 12mmx1.6mm round tube for the bars.

Any tips for Ali miging would be welcomed :rolleyes: .

Hooroo.
Regards, Trevor
Grafton

Edd
21st Dec 2005, 09:23 AM
I've been playing with aluminium welding for the last few days.

There has been a fair amount of welds that look like pidgeon poop.

Any tips for Ali miging would be welcomed
A quick search indicated your welder is only DC. Hmm...(1 google search later..) I guess I just learned you can in fact weld Al with only DC with mig. Maybe because the current goes the other way to the wire it almost simulates AC. Have a look at this (http://www.lincolnelectric.com/knowledge/articles/content/compactmig.asp) article from lincoln.

Grahame Collins
21st Dec 2005, 02:10 PM
Trev , it may be that your mig is a bit underpowered. Alimunium needs the correct deposition mode to avoid the bird poop appearance. It means to achieve the arc pool operation and weld bead appearance the arc should have a smooth sounding hiss to it. It won’t run too well at all, set at the short arc ( dip transfer mode ) –this sounds like a crackle or a tearing noise.

To achieve the spray mode in a smaller capacity machine one needs to use a smaller diam wire say .9mm diameter to maximise heat input on the small diam wire.this in turn leads to a new problem. Aluminium GMAW wire by its nature is soft, really soft. Without an absolutely straight cable, friction (as would be caused by a curved or coiled handpiece cable) against the internal liner causes a pressure. Remember the drive rolls are pushing this soft stuff against a resistance. Increase the resistance and the soft wire grabs in the liner,stops fowards motion while the drive wheels are still going and a birdnest is the result. Dedicated Ali mig welder handpieces are built with the drive roller in the handpiece. One brand I am aware off would cost more than some welders - $1600 in the 90’s

Next problem is that if your metal thickness is under 2mm burnthrough is likely.
Minimise it by standing the weld face up and down vertical and run a side to side wash- this is a weave from side to side while moving downwards- pause slighty on the edges.

Finally if you really want problems use an angle grinder meant for steel. There is a wheel available for aluminium but I have no idea where to get them.Best bet is to scuff up the area to be welded with some coarse sand paper.
nearly forgot
.Set your flowmeter at no more than 15 lpm and that means your not wasting exensive argon.
Is your liner a plastic or teflon liner - it needs to be. Your contact tip if say .9mm should be drilled out to 1mm. Aluminium expands in diam during the arc process and that may cause a jam and bird nest.

I will include this later in the notes about mig generally
Cheers
Grahame

Big Clint
21st Dec 2005, 03:53 PM
Glock

the other option (which will depend on how big the gate is) would be to hire a Tig from a welding supply shop. i built a aluminium framed outdoor table a couple of years ago, 50mm box with a 2mm wall. i didnt think my mig could cope as it was only 150 amp and i had had a few people tell me that i would need to replace the rollers when using the ali wire. in the end i hired teh tig, which including rods and gas cost me around $100 for the weekend from memory.

I had not used a tig before, but manged to pick it up as i went plus i got a few tips from one of my dads friends. probably the best tip he gave me was to practice butt welding thin plate together without filler rods, which taught me a lot about when to tell when the ali is plasticising. i did use a heap of filler rod as i kept blowing holes in the tubing, but it was easy to fill in and once sanded and polished doesnt show up.

but if i was to need to weld ali again i would probably look at hiring a mig again.

Clint