What exactly does preflow and post flow do? I was reading through my book and it said for every 10 amps or so you want such and such time in the post flow.

I originally had my welder set to .5 sec of preflow and 10 seconds of postflow but it seemed like I was wasting a ton of gas for nothing.

What is the purpose of having the gas start before the arc starts then having it run after the arc has ended?

 

Preflow - Purges the gas lines and protects the weld pool from the very start.
Postflow - Protects and cools the weld.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by backpurge &raquo;</TD></TR><TR><TD CLASS="quote">Preflow - Purges the gas lines and protects the weld pool from the very start.
Postflow - Protects and cools the weld.</TD></TR></TABLE>

So do you normally have the preflow set for a very short period of time?

When you say protects the weld what do you mean? I thought it cooled the weld but did not want to post that and get flamed.

 

Usually you only need the preflow on for a second unless more is required by code. Postflow I keep around 7 seconds. Postflow protects the weld by making sure oxygen and other gases don't touch the weld until it is fully solidified. Some codes require you to keep on the postflow for a certain period of time.

 

I agree with Backpurge.

However, I figure you really don't need any prepurge, but if you do, half a second works fine. Many machines don't even have the option. Mine does, and I don't often use it. If I do, I set it so low I can't tell it's working anyway...dunno why I bother.

anyway, it's useless.