MIG pre/post flow gas modifications

Hi guys & girls.
I have an old BOC TransMig 110A 240V MIG. It's around 25yrs old but almost
does everything I require, mainly panel work.
However it doesn't do pre & post flow on the gas. This is making tacking
etc a wee bit difficult, causing porosity and a 'dirty patch'.
I have wondered about creating a delay cct to the wire feed motor so the
gas solenoid would operate ahead of the feed. This would mean that the tip
would be live though.
My old SIP seemed have a two stage trigger which was great ie
squeeze - gas on, squeeze more - feed. Also very handy for putting out
little fires ;-)
Any suggestions would be greatfully received. I don't want to buy another
machine, this one's brill.
Balders, based in the UK
Reply to
Balders
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You can do preflow using a "time delay on relay" and postflow using a "time delay off relay". You can buy those on ebay. It is actually very easy.,
i
Reply to
Ignoramus14280
Thanks Iggy, I knew you'd have the answer :-) I shall look for a couple then I shall be happy with my dinosaur ;-)
Reply to
Balders
They are kind of expensive on ebay (about $25 with socket, much cheaper than retail though), but you can look for misdescribed ones and find them cheaper this way. The downside is that it takes personal time.
i
Reply to
Ignoramus6056
Actually, for post-flow, you can use an electrolytic (DC) capacitor on the gas valve, cheaper than a relay and easy to fit. Just wire it accross the gas valve coil in parallel. You might want to experiment with different values, starting at , say a couple of hundred microfarads. Make sure the cap is rated at about 50VDC to allow for spikes. You'll still need a relay for the pre-flow.
Reply to
Potblak
Comments noted, cheers guys. I like cheap fixes too. It's the pre-flow that would be the most useful to me. Checked on RS websites etc and a time on relay is about £35 (60 USD), over half the price I paid for the machine!
Reply to
Balders
Look on ebay, I bought six TDRs for $18 plus $6 shipping.
i
Reply to
Ignoramus3756

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