update on "dirty starts?"

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Doing an aluminum project today.  Did not get any dirty starts untill I started trying to do  an inside  corner.   The first 3/8 inch was really dirty- big plume if black soot arround puddle and puddle wouldn't wet together L-R.  A little farther down the puddle got clean and OK.   Then something occured to me.  Remembering someone said too much gas can causecontamination.   I have always noticed that on my miller dynasty (25 foot water cooled hose ck-20)  when I first trigger the pedal the gas pressure is too high for about 1 or 2 secconds and then it settles down to a steady flow.  I always figured that this was a backlog of gas between the selenoid and the tank acting as an compresses vollumewhich spewed out when pedal triggered.  After I got the sooty start - I wondered if this initial high flow might be the cause of the dirty starts.  Its about the correct length of time to match how the bead cleans up after about 1/2 inch or so. So I hit the pedal to bleed it but not weld.  it goes on however long the post is set for.So before the post stoped I started the new inside corner.  The arc was quieter and perfectly clean and the bead was beautifully shiney !Has anyone else noticed this and how did you get rid of the initial "big flow" I wonder if I could program the machine to do a pre-flow of about 2 secconds to bleed itdown before the arc starts ?   May have to be in 4 step mode - I'll have to read the manual ( NO- Not the manual !  )I am thinking this could be my problem all along ?What yall think ?Tim
Reply:I always tap my foot pedal and release to get the gas flowing for a couple of seconds before I start any weld. Gets a nice pre-flow going, and eliminates that blast effect.
Reply:Using a smaller internal diameter gas delivery hose between the gas regulator and the gas solenoid inside the welder reduces the rush of gas when starting.  Also, adding an orifice at the inlet connection to the gas solenoid helps.  You might want to check out this thread. http://weldingweb.com/vbb/showthread.php?t=40973Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:My peddle for some reason will purge gas before starting an arc within the top 1/4" of peddle travel. So I always roll into the peddle until the gas flows then keep rolling slowly in till the arc comes on.
Reply:I like the idea of an orafice between the hose and back of welder.ThanksTim
Reply:Originally Posted by jethroDoing an aluminum project today.  Did not get any dirty starts untill I started trying to do  an inside  corner.   The first 3/8 inch was really dirty- big plume if black soot arround puddle and puddle wouldn't wet together L-R.  A little farther down the puddle got clean and OK.   Then something occured to me.  Remembering someone said too much gas can causecontamination.   I have always noticed that on my miller dynasty (25 foot water cooled hose ck-20)  when I first trigger the pedal the gas pressure is too high for about 1 or 2 secconds and then it settles down to a steady flow.  I always figured that this was a backlog of gas between the selenoid and the tank acting as an compresses vollumewhich spewed out when pedal triggered.  After I got the sooty start - I wondered if this initial high flow might be the cause of the dirty starts.  Its about the correct length of time to match how the bead cleans up after about 1/2 inch or so. So I hit the pedal to bleed it but not weld.  it goes on however long the post is set for.So before the post stoped I started the new inside corner.  The arc was quieter and perfectly clean and the bead was beautifully shiney !Has anyone else noticed this and how did you get rid of the initial "big flow" I wonder if I could program the machine to do a pre-flow of about 2 secconds to bleed itdown before the arc starts ?   May have to be in 4 step mode - I'll have to read the manual ( NO- Not the manual !  )I am thinking this could be my problem all along ?What yall think ?Tim
Reply:Originally Posted by RojodiabloI will stab the pedal, then after a second I will strike the arc. Yes, it makes a difference.
Reply:Originally Posted by weldermickMy welder doesn't have a "preflow" timer, so I do exactly the same, before starting any arc I hit the pedal, get the gas flowing, then position properly and arc up. Clean, smooth start every time.
Reply:Rojo:Yes I guess that makes sense about the gas just siphoning out the end of the torch slowly.I am in the habit now if doing the same thing - i can tap the pedal and not start the arc but getthe post flow time.  That looks more likely maybe than just turbulance alone.  Often it is a big blackflower shaped blob of soot rite where the arc started.   But the other thing wich I havn't fully figuredout yet id I can do flat and its perfectly 100% clean and shiney and move the torch 1/2 inch to an inside corner and its dirty when the arc starts in the corner.  no changes in settings and 2 secconds from the flat weld.Just thought of this....Sometimes when I hang the torch for a moment between welds.... sometimes I hang it up high on thewelding cart and other times I lay it down on my lap or on the floor.   I bet just like water - having it lowerthan the welder is going to cause gravity to let it drain out and replaced with air.  So maybe I shouldmake a torch hanger thats a little higher than the welder to hang it on  to minimise that !Tim
Reply:Just replace the stupid reg and be done with it. There is likely some derbris on the seat which keeps the orifice open longer until it can lock up, causing a higher than desired lock up pressure. When it starts to flow it has to vent the built up pressure first before it gets to the set pressure.
Reply:good on flat bad in a corner sounds like to much flow try turning it down, you only need enough to much causes all kinds of weird drama.
Reply:Originally Posted by jethroJust thought of this....Sometimes when I hang the torch for a moment between welds.... sometimes I hang it up high on thewelding cart and other times I lay it down on my lap or on the floor.   I bet just like water - having it lowerthan the welder is going to cause gravity to let it drain out and replaced with air.  So maybe I shouldmake a torch hanger thats a little higher than the welder to hang it on  to minimise that !Tim
Reply:maybe I can rig a gague on the end of the feed hose to see if the pressure is inching up when no ga is supposed to be flowing.   I have another old reg on the mig welder I don't use anymore.  Maybe I will switch and see if that fixes it.  I would have before  except the old reg has a helium calibrated flowmeter.  The current one has 3 concurrent scales I can convert with...I bet it is siphoning when I lay the torch down.Thanks for the replys.Tim
Reply:Originally Posted by jethroI like the idea of an orafice between the hose and back of welder.
Reply:Thanks Kelvin - looks like JUST what I need.  I will see if my local has it monday !Tim
Reply:Jethro, I can honestly say where you rest the torch will mean nothing. I lay mine on the floor, hang it over racks, it is never in the sam place twice. If you weld well straight, yet corners have issues, it's a welding issue, NOT a gas issue. Angle you go in, how you point he tip, which way and how you feed the filler is more of an issue.Alum. filler rod WILL oxidize quickly, and right there near the puddle if your feed is not correct. You will see soot, grey, volcanic bubbles, all manner of crap. That is a trial and error thing, not a $13 fitting swap out. Try different cup sizes so you can either: A. Get wider gas coverage with the same flow. or B. Try a slightly smaller cup so you can see what you are doing better in the corner.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:I have had a similar problem when welding an inside joint on aluminum and in my case the solution was to actually turn the gas flow down.  The turbulence from the shielding gas bouncing off of the joint.
Reply:Make sure your regulator is working right.   If the regulator leaks, your pressure will creap up.As for the rest, I have a 2 second pre-flow dialed on my TIG and the 350P also has preflow (I really only use that on aluminum - its whatever the default is for steel).Default pre-flow seems to be .5 seconds, but on stainless, I saw brown rusty colors at the start of my welds.  1.5-2 second preflow took care of that.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX