question about a spool gun problem

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I have a lincoln 100sg spoolgun.  It welds well. However, I have a problem when I begin a weld, occasionally the wire stick.  A gentle tug and it welds fine, again.  The problem is pretty much isolated to starts.  When I pull it out the is a small arc mark on the wire about where it would enter the tip.  Remove the tip and there is an arc mark on the tip.It does not how long I weld, just randomly sticks. Metal shavings don't appear to be a problem.Thanks
Reply:I am not really familiar with the particular gun you are using,however I have had similar problems with my profax gun. The "old stlyle" tip and nozzle set up was famous for doing the same exact thing you are describing. After upgrading to the "new style" tip and nozzle set up it seemed to help,but not elimate the problem. The one thing that seemed to really help was to use the next size larger tip. For example when welding with .035 wire I use the .047 tip. Also make sure you have enough tension on the wire so that you cant stop the spool from spinning with your hand, but not so much that you are overloading the motor.             Hope some of this info helps.
Reply:Thanks busyman.I have considered larger tip. I will locate some tomorrow.
Reply:You need to have the tip of the spool-gun about 3/4" away when you mig Aluminum.  Not so close as when welding steel.
Reply:Thanks TSOR, I noticed that does help a lot, though doesn't eliminate.  I wondered it the shape of the wire (balled vs. freshly cut)  contributed to the problem. By the way thanks for the photo of the angle finder in the other thread.
Reply:Seems like increasing the contact tip to work distance worked prior to pulling the trigger.  Starting about 3/4-1 inch from work surface.  I got some .045 tips today, haven't had reason to try them.  Thanks for your input guys.
Reply:Dunk the tip in tip dip/ anti spatter dip.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 am welding aluminum.  Spray. The thing that helped most (in addition to wire tip distance) was to start the wire feed, then bring it into contact with the metal though not the tip of the wire.    Now I recall a guy telling me to curl the wire before beginning the weld.  Since I have many corners to weld I just burn the wire off at the beginning of the weld, things start and stay much smoother.
Reply:The gas arrester...at least I think that what you call it...  The one I use to use had to be replaced. Spray aluminum after so long warped it slightly.You probably checked it already weld it like you own it
Reply:Would say the arc mark on the wire you seen is due to worn tip or tip size too large, creating a small contact area. The contact tip should be as required for the wire diameter. You need good contact between tip and wire to transfer the welding current well to provide enough resistance heating along the wire, (stick out portion), to assist arc initiation. This is why the increased CTWD is working, the longer wire stick out assists resistive heating.
Reply:Yeah,  the mostly tip wear.  I just replace them frequently.  The larger tip didn't improve things, though I didn't feel I was worse off either.  I only tried one oversized tip.  Start technique made the largest difference.My project is almost finished now about 70 contact tip later and 150 bucks worth of argon.   Thanks for the info. guys.
Reply:It could be a burn back, mill scale, or arc force issue as well
Reply:Hmmm, aluminum wire in the spool gun you say?You -are- using Lincoln's tips for 0.035 aluminum, right?  Not the 'standard' 0.035 tips, but the 'slightly-oversized-from-the-factory-to-be-used-with-0.035-aluminum-wire' special tips for aluminum.The part number on the 'standard' 0.035 tips for the Magnum 100 guns (regular gun or spoolgun) is KP2039-3B1 (pack of 10), while the p/n for the tip for 0.035 aluminum wire is KP2078-1B2 (pack of 10).  The 'new' p/n's are KP11-35 and KP2078-1B1, respectively.  The "Bx" code in the p/n seems to be additional/optional info, maybe related to 'bulk' packs (of 10).And spray mode will go through tips faster than short circuit, because it's 'hotter'.  And aluminum is also a bit trickier/fussier than plain steel as well.Also, maybe just snip the end of the wire after you stop a bead or before you start the next bead.  Inch some wire out, snip it, inch out another ~1/2" so you get your 3/4" CTWD/stickout, hold gun tip at 1" stickout (gap from wire tip to workpiece), pull trigger and move in to the 3/4" CTWD as the arc starts.  The best laid schemes ... Gang oft agley ...