Push/Pull for AL Castings

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At our aluminum foundry, we have parts that require welding after the casting process.  The parts are water-cooled, exhaust manifolds for marine engines.  We use the lost foam casting process.  Slots are intentionally made in the patterns to allow sand to get inside the to form the water jacket.  When the casting is complete, we weld the slots closed.  There are 12 slots on each casting.  The slots are about 1/4" wide and 3" long.  We have always used TIG to weld the slots, with 3/16" filler with a Synchrowave 350.Monday, the LWS is coming to demo a MIG set up with a push/pull wire feed system.  I'm curious if any of you guys have any experience using this set up on aluminum castings.  Any and all feedback, good or bad, is appreciated.  This will be a production job, processing about 300 castings per day.TurkeyLincoln Idealarc 250Millermatic 250Miller Synchrowave 250 Miller Synchrowave 350Thermal Arc PlasmaHH140Miller Diversion
Reply:The push-pull mig will certainly save alot of time over using tig for that kind of production volume.  I have used push-pull pulsed mig extensively on aluminum extrusions in production and it's great but I haven't used it on castings.   The castings may need to be pre-heated before you go to it with the mig, since with mig the start is always cold.  With tig  you can sit there and heat it up with the arc till it puddles then add the filler.  Mig just shoots the filler in right away while the metal's still cold.  Some machines have hot-start and run-in speed features to help reduce the cold start (my Millermatic 350P has these) and it does help but I don't know how well it would work on a thick, cold casting.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:MIG - speedTIG - finesse and controlEither process can most likely do the job.  But like DesertRider33 said, MIG -can- have issues of cold start.  Also with MIG, you can't taper off the amps as the workpiece heats up as the weld progresses.btw, why are you using sand with the lost foam process?    ... made in the patterns to allow sand to get inside  ...
Reply:Thanks for the replies.  The Lost Foam Casting process is a type of sand casting process.  The pattern, made from EPS (Expandable Polystyrene), is coated with a liquid refractory, the coating is dried, then the pattern is placed in a flask.  The flask is filled with sand while it is vibrating.  The vibration helps the sand flow into the internal cavities and also serves to pack the sand.  Liquid aluminum is poured in through a sprue.  The heat from the liquid aluminum causes the EPS to evaporate and the space the EPS occupied is replaced by aluminum.  Hence the name Lost Foam.  The process is better explained on our web-site, americanfoamcast.com.  You can also see it on Vulcan Engineering's web-site.  I believe it is vulcangroup.com.TurkeyLincoln Idealarc 250Millermatic 250Miller Synchrowave 250 Miller Synchrowave 350Thermal Arc PlasmaHH140Miller Diversion
Reply:If you  are just filling a slot I would think that cold start would not be as much a problem...especially if the part was preheated slightly on a hotplate or similar production heating device.  Now if you were laying a fillet on a thick casting then the cold start would be more of an issue. In fact the spray arc may even be a little hot for filling a large slot and may want to over penetrate. The pulsed systems may be nicer for such an application in that regard. As far as welding the dirty casting the wire is the same and the process runs on reverse and is essentially cleaning the whole time, so as long as you have good argon flow I would expect results close to TIG.