Aluminum setup question???

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All you aluminum gurus out there, I have a job next week, welding a bottom in an 8000 gallon Aluminum fertilizer tank.  I was contracted to do the job, by another local fab shop, and will be using there equipment to complete the job.  Here is my question, I will be using a miller CP300 with a #1 spoolgun (same as a profax) The material will be 1/8th welded to 3/16 thick.  I am not familiar with this machine or gun, so I am going to play with it over the weekend to get familiar with it.  What would you suggest starting at with volts/wire feed.  I haven't run a spool gun much in the past few years, since i got my Tig machine and I usually tig my aluminum.  I originally was going do the work with a tig, but I have approximately 80ft of weld and figured it would take forever to complete.   Also any idea as to how many 1lb spools it will take to complete this job?  Thanks in advance for the advice.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:From the hobart website: 1. The best feeding of wire for aluminum is done with a spool gun. If you can't use a spool gun, use the shortest gun possible and keep the gun as straight as possible. Use Argon only for shielding gas. Only use a push gun technique when welding aluminum. 2. If you are having feeding problems, one thing you can try is a contact tip that is one size bigger than your wire. 3. The most common wire type is ER4043 for all-purpose work. ER5356 is a stiffer wire (easier to feed), and is used when more rigid, higher-strength weld properties are needed. 4. Clean the aluminum before welding, to remove the oxide layer. Use a stainless steel wire brush used only for cleaning aluminum. 5. Fill the crater at the end of the weld to avoid a crack. One way to do this is to dwell in the weld pool for a second at the end of the weld.
Reply:I weld 1/8" and 1/4" 5052 with mig and tig everyday and have made about every mistake you can with it. Wire size will make or break you but so will the WFS and Volts. I recomend .035 wire. The following chart might help you dial in your machine too;http://www.esabna.com/EUWeb/MIG_handbook/592mig8_8.htmAlso, you did not mention what type Al you are welding.I can't tell you how many spools you will use but plan on using a lot of wire.Best of luck -
Reply:Thanks for the link i think that should come in useful.   For the past five years 90% of my aluminum has been done with a tig.  So I am just not sure what amount of linear weld I will get from a 1lb spool.  ~JacksonLast edited by Hammack_Welding; 09-22-2005 at 09:10 PM.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Just found this site, it has the answers you need.http://www.airgas.com/documents/pdf/...hnicalinfo.pdf
Reply:Sorry, it is 3003 aluminum sheets.  all will be welded in the flat position.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:I would say start out at about 25 volts on a test plate of like thickness if possible. I would suggest 3/64 5356 wire. and at around 80' with a standard bead width you should consume no more than 6 spools unless more than usual fill up is needed. Machines run different and its hard to guess at the voltage I have used the exact same machine both being brand new and have one run much hotter than the other. I am using a delta weld 452 with the profax and I run around 25 for 1/4 on up to around 3/8 I would guess the cp300 would run a little colder so I say start with 22-25 volts for 1/8 to 1/4. Please let me know how close my guess was on voltage and spool usage.
Reply:Robby T.      I will let you know, I am going down to their shop in just a little bit to set up a machine and run some test welds to try and get everything ready to go for Monday morning.  I have 8 rolls of  L-tec 5356 3/64  So I will know this afternoon what settings it takes to run it.  Thanks for the advice.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Robby T, I went and played with the machine this afternoon, I was quite suprised.  I wound up with the best results set at 17-18 volts on the .125 but welds, and about 20 with the 1/8 to 3/16 lap joints.  The machine and gun were very tempermental.  I never could get into a spray transfer without burning through, and I was hauling azz with the gun.  I ran varying technique from straight line, to weave, to small circles, Working the seam in small circles produced the best looking welds.  I will try to get some pics of the job as we progress.  Thanks for the advice.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Hammack, I've been doing outside fillet welds with 3/64 4043 and I've been getting about 150 inches of weld out of a spool.  I'm using a mm250 and a spoolmatic and using way less voltage than I thought I'd need-about 16-17V to weld 3/16" to 1/4". As for a pattern, try a stringer bead but shake it forward and back a tiny bit, just a tiny bit, like you've got the shakes; this gives the puddle a chance to cool off a little bit.  The 4043 flows better than the 5356.  Good luck.