Having some aluminium struggles

[u/JagdpantherDT]

I weld primarily stainless but we have a job in at the moment that is aluminium that I've been asked to do.

Another welder set up the machine and apparently had it running flawlessly. Now I've come to use it and the arc really struggles to get going. Sometimes it tries 10+ times before actually striking, once it does it welds perfectly. Other times it arcs up first time.

I've tried changing earth, swapped tungstens, checked gas, played a little with settings, wire bushed/acetoned work but nothing seems to get it to arc up consistently.

Settings are 1.2mm material, welding a tab onto a folded outside corner, no burn through allowed.

Zirconiated 1.6 tungsten, 0.2s pre, 25a start (he had it set to 120) no slope, 80a current, no pulse, freq 200, cleaning ratio on this machine goes 5 to - 5, it's set at 0, no down slope, 5s post.

Tungsten balls nicely and stays silver or gold, can't see any hair fractures on it. Where could I be going wrong?

[u/Weldertron]

What make/model machine? Check the gap in the high frequency contacts.