A couple of years ago I bought a 200amp dc tig from r-tech and taught myself to weld. Fairly good at it now and reasonably neat. The welder is awesome but now I'm building a kit car, I can't help but think I need to be able to weld ally. I could probably just about stretch to the 160 amp AC/dc unit if i sold mine but does anyone have any practical experience of moving from steel to ally? Is it unreasonable to think I will be able to make header tanks etc with a bit of practise? Fairly confident I could do a decent job if i made a stainless one. Any advice welcome!!

If you are okay with a DC unit welding steel, then I would have thought that with a bit of practice that AC ally would be achievable after some practice. Some things to consider is that material prep and cleanliness is more important with ally welding and because aluminium absorbs heat so well, for thicker stuff it takes more power to weld it.

Since AC is used for aluminium for a cleaning action, there will be some settings that you are not used to like AC balance, frequency etc. but easy to get the hang of, once you find a setting that works it becomes your standard.

Look up weldingtipsandtricks on youtube, excellent welder and teacher with the best 'behind the mask' shots out there which makes it much easier to learn.

Upgrade your RTEC and you will be fine

Have a look at the special deals and shop soiled, I got a 200amp for 160amp money and could not find any reason why it was considered shop soiled.

Ali needs a really good clean immediately before welding, apart from that it's not light years away from steel with a TIG.

Yeah I've got my eye on a shop soiled 160; I'd like the 200 but I really can't afford it. I've only ever been up to that kind of power when I did some 10mm plate on my landrover and I've never reached the duty cycle so I think the 160 would be ok. It's obviously not going to be 10mm thick on the kit car either!

We sell r-tech and parweld ac/dc units, we've used a parweld unit in our workshop for just over 12 months with no problems it's a really nice unit.
If you like I'll get some prices next week, we get some good deals.

thanks for the offer; I have been really happy with the DC unit so I've stumped up and ordered their ac.

Anyone want a second hand 200 amp dc before the credit card bill comes!?!

It turned up today, twice the size of the dc but very similar. Blasted a couple of heavy dc welds to try it then went for some beads on a bit of ally. Got some decent lines down fairly quickly. Haven't used a pedal before so that will take a bit of getting used to but well happy with my first go! Just need to practise practise practise now!!

Is the best thing with the pedal to set max amps on material thickness then ease off as it warms up or set the machine to max and do it all through the pedal?

Set the current to the material, as the work heats up you then back off as you progress or you risk blowing holes.