Arc when on AC very unstable

[Dan T]

Hi

Recently been trying to set up my tig plant for welding ally. Did a couple of courses recently and seemed to get on fairly well with aluminium. However while setting up mine the arc is jittery, sounds like it's "spitting" and doesn't seem very stable. At 140 amps it's struggling to get a weld pool on 2mm.
Got it on ac obviously, HF continuous and using the right tungsten.

If anyone has any ideas the help would be much appreciated.

Cheers

 

[BrokenBiker]

do you have ac balance setting? or frequency adjustment? does it weld ok on dc? is the torch connected correctly?

 

[Tigman]

what model and make of machine ?

 

[Dan T]

what model and make of machine ?

It's a lincoln electric square wave 255.
Welds fine on dc. Only ac that is causing the problem. Believe the torch is fitted correctly and have tried diff settings on the balance. But doesn't seem to make it any better.

 

[Tigman]

Have a clean out of the machine inside with an air line and have a good look at your spark gap (HF) may be dirty and or need setting with a feeler gauge ! Dc wont be affected by this as HF only used at start thats why it welds ok when on DC ! I had this with my old Tig Uno Cebora once cleaned and set Happy Days

 

[Dan T]

Ok. That would make sense. Thanks! Will give it a go and let you know what happens

 

[Dan T]

So pulled out the electrodes and gave them a clean. Hasn't really resolved the problem. Then looked at the spark with machine on and it seems there isn't a spark across the whole gap. I assume I am lookin at needing some new electrodes? If so where should I look for them. Do I need to go to lincoln electric hq in the states or is there a uk division? Not finding anything easily online it seems

 

[shenion]

What type of electrodes are you using?

What shape are you grinding them to?

 

[Dan T]

I'm talking about the HF electrodes inside the machine. By the way the spark is flickering and not covering the whole gap in between the electrode I'm assuming that's my problem on AC?

 

[shenion]

They may need to be cleaned and the gap set.

 

[Tigman]

yeah I cleaned mine , took them out and used emery , then replace and set the gap ! should make a difference!

 

[hotrodder]

As above the gap is important, i posted a link to the manual for your machine in your foot pedal thread which says

Inspect spark gap spacing at regular intervals to maintain a 0.015 in (0.4mm) gap. (Smallest possible air gap consistent with good welding is
desirable to minimize R.F.I. problems.) Dressing or any refinishing of the spark gap contacts is not recommended. If the contact surfaces become
irregular or completely eroded, replacement of both electrodes is recommended.

on page 25. The don't clean or dress the points bit... if they're knackered you've got nothing to lose

There is a Lincoln Electric UK (in Sheffield) but they'll probably point you in the direction of your nearest Lincoln dealer http://www.lincolnelectric.com/en-g...ountry=GB&zoomLevel=5&doNotFlaglocations=true

 

[Dan T]

Yea I did pull them out, clean and set the gap but it hasn't improved. Looking like I need to replace the assembly. Thanks for lincoln details. Will get in touch with them Monday.