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Been playing around with my 225LX and decided to turn the pre-flow knob up to
2 seconds. After about an hour I noticed my tungsten was still sharp and contamination free (A first for me). I've had the post-flow set at 2 seconds but never bothered with the pre-flow.
So, I'm thinking I should have been using pre flow from the beginning.
Is 2 seconds about average.
Welding mostly stainless with argon at 12 cfh
Brian,
Preflow is one of those things you adjust until it works for you. There's not a complicated formula that I am aware of. In most applications where it is fixed, it is usually set at .3 to .5 seconds. Stainless though could benefit from a little extra flow. The biggest obstacle you face is having enough preflow for your arc to be stable when it lights. Having a "burst" of argon while starting a weld can destabilize the arc. Give it enough time for the flow to settle...that would be the best idea. IF you are using our flow meters, it isn't in cfh, but lpm...You only need about 6-7 lpm.
Yep, one or two seconds is good. When your machine has been sitting for a while the argon leaves the hose. The argon needs to be coming out of the torch before an arc starts, to shield the tungsten.
You can either set a few seconds of pre-flow, or get in the habit of bumping the pedal while getting your torch all set up, which basically turns post flow into pre-flow and gets everything purged while you are getting yourself all ready to start the arc.
Although, I've noticed on my 225lx, it doesn't seem to do the entire post-flow length if no arc was actually generated. Is that true, or did I just imagine that? Seems like it's just doing my couple seconds of pre-flow then shutting back off if I just bump it.
Like Mark says, it "really" is what works for you.
I use lpm at 8 and no pre-flow. I purge with the trigger, never used a foot pedal (other than to show how it works). Everyone has posted something different but what works for them.