Another struggling beginner... :(

[David_17]

Hi all.

I'm new to the site so be nice

I've just started a kit car project, and i'm learning to weld before making the chassis.

I've bought a Sealey 150A mig welder, which i'm running off a 6.5kva generator.

The problem i'm having is penetration - I've tried running the welder on 2 max & about 5.2 wire speed, with co2 disposable gas and 0.6mm wire. No matter how long i hold the torch in one place, the weld gets bigger but won't penetrate, even on full power.

Using 2mm steel plate by the way. Here's a few pics...

Cheers

Dave

 

[David_17]

oops... just realised i've posted in the wrong section. Could a mod move it please??

 

[W4yne]

Hi Dave,

If you are on the maximum power setting the machine has experiment by increasing the wire speed a bit more at a time, possibly between 5.5-6?

Here is a calculator that may help?

http://www.mig-welding.co.uk/calculator.htm

Hi all.

I'm new to the site so be nice

I've just started a kit car project, and i'm learning to weld before making the chassis.

I've bought a Sealey 150A mig welder, which i'm running off a 6.5kva generator.

The problem i'm having is penetration - I've tried running the welder on 2 max & about 5.2 wire speed, with co2 disposable gas and 0.6mm wire. No matter how long i hold the torch in one place, the weld gets bigger but won't penetrate, even on full power.

Using 2mm steel plate by the way. Here's a few pics...

Cheers

Dave

 

[David_17]

Hi.

Thanks for the reply. I tried as you said, but it just pops and splatters all over.

 

[malcolm]

Weird that - your welding looks OK and 150 amps should nuke 2mm plate. Something else must be going on. At a rough guess you are running 70 amps there, and that's not much for a 150 amp welder.

The obvious one - is the generator giving you 120V? That would do it. Try the welder at home and see if will do any better.

Failing that if the welder was secondhand from eBay it might have a failed diode in the rectifier. That would reduce the voltage by the same amount.

And the obvious again - can it be turned up a bit more (3 max or something like that?)

 

[rich74310]

Whats the input ampage of the welder?

6.5kva works out to about 25amps at full tilt.

 

[David_17]

Thanks once again for the replies.

Not sure on the welder's input voltage without checking, but when buying the generator, i checked and all the numbers seemed to add up.

The only thing i can think, is that if i haven't got the wire tensioner tight enough, could the wire be coming out faster than the welder thinks. So the current it's giving out isn't enough for the ammount of wire??

I've read that the current increases slightly as you increase the wire speed, so this would make sense.

 

[paulmowers]

This may be way off the mark, but when welding from a genny the rating of the genny needs to be twice or 2 1/2 times the load of the welder, or something like that. so if the welder draws say 3kva you need a 6 or 7.5kva genny to cope, otherwise you will get poor results and an overloaded genny.
probably way off, but just a thought.

 

[brightspark]

check the output voltage of the generator before and while u are welding u may be getting voltage drop .also try welding on a mains power supply at same settings and thickness of plate that will answer your questions

 

[the snooper]

paulmowers has the answer the genny isnt big enough an add to that the fact unless you can test it it may not be producing full power.
and to find out all you need to do is measure the output frequency under full load if its anything less the 50Hz its running slow 50Hz = 3000 rpm on a 2 pole altenator.
the govenors dont always work that well.
you need to first try the welder on the same steel but using the mains at home
also if your wire tensioner isnt tight enough you will get less wire out not more

 

[TBC]

This may be way off the mark, but when welding from a genny the rating of the genny needs to be twice or 2 1/2 times the load of the welder, or something like that. so if the welder draws say 3kva you need a 6 or 7.5kva genny to cope, otherwise you will get poor results and an overloaded genny.
probably way off, but just a thought.

Exactly so, I often think genny manufacturers are smoking large pipes when they plate there genny's lol.

The output of the genny is often times the peak output, since a welder is continous power and surges at twice that power then the genny requires significant overhead from its plating rates. Personally i wouldn't dream of using less than 10KVA for any welding purpose and even that is not adeqaute for more than 4mm thickness of material imo.

tbc

 

[David_17]

Tried it at home today, plugged into the mains. And although it made a nicer sizzle noise, with less popping, it still doesn't seem to penetrate deep enough.

I bought the welder new off ebay, and have contacted the seller.

Is there any way i can test any parts that could be at fault?

Thanks

Dave

 

[malcolm]

The only test I can think of is measuring the steel thickness. If it's 2mm there is a dead diode in the rectifier. The weld is less than you would expect from a Clarke 90 - You are getting half voltage on that. Was the welder cheap?

A dead diode would give a sine wave with half of it cropped. Would that reduce open circuit DC voltage? Worth measuring that - it's the voltage between the contact tip and the earth while you pull the trigger and send the wire off to free air (don't arc). Clarkes are normally a bit high on OCV so expect 30V DC on full power, maybe 20V DC on low power. Much less than that would pin it down.

Genny doesn't seem too far out to me. Works out as 27 amp supply which is more than double the requirement, and especially with a test on 240V unlikely to be the issue.

 

[David_17]

Thanks for the advice. I'll try that in the morning.

Could the generator have damaged the diode? Or is it a factory fault?

Cheers.

 

[series2]

Looks familiar!

I've got a Clarke 90 that I keep for small jobs, and that is about what it will manage on 2mm ish plate with 0.6 wire and full power. If I use 0.8 wire, I can get full penetration on 3mm, if I go slowly.

It is worth checking the earth clamp, if it is getting warm where the cable connects, your problem could be there. Also, not wanting to insult your intelligence, your not using a 0.8 tip with 0.6 wire?

The open circuit voltage test is not very conclusive, unless you can get your hands on a true R.M.S. test meter. A better test would be to use an oscilloscope, if you have a local tv repair shop or similar, they would be able to tell you in seconds if there is a rectifier fault.

The welder is probably over rated by the manufacturer, not uncommon with far eastern stuff. Might be worth trying to recover your money, and talking to Weldequip.

 

[David_17]

Looks familiar!

If I use 0.8 wire, I can get full penetration on 3mm, if I go slowly.

Also, not wanting to insult your intelligence, your not using a 0.8 tip with 0.6 wire?

I'm using 0.6mm wire and tip, although i do have some 0.8 and 0.8 tips which i haven't tried yet, may give that a go.

The welder has a 12month warrenty, so should be easily replaced. (fingers crossed anyways)

 

[series2]

Unlikely that the diodes would be damaged by the genny, unless there was a major fault with the genny.

You could try loading up the genny, 2 or three electric kettles would do the job, listen to engine speed as you load it up. It should not change speed, but sound like it's working harder (louder).

 

[David_17]

A dead diode would give a sine wave with half of it cropped. Would that reduce open circuit DC voltage? Worth measuring that - it's the voltage between the contact tip and the earth while you pull the trigger and send the wire off to free air (don't arc). Clarkes are normally a bit high on OCV so expect 30V DC on full power, maybe 20V DC on low power. Much less than that would pin it down.

It gets 29v dc on full power, so does that mean it's not the diode?..

 

[Drains]

Dave, a couple of things (as your voltage seems to be Ok) -
1) adjust your wire speed up and down as you're welding (torch in one hand, control knob in other), until you're happiest with the smoothness of the weld sound and feel
2) leave a gap between the two pieces to be welded - a "prep". Experiment to see what gap works with your settings and speed - it'll be less than the thickness of the steel. Don't necessarily expect the weld to penetrate unless you do that.

 

[outofthefire]

The wire acts a bit like a resistor you get more current down it the bigger it is i'd give the .8 a go and see what happens.