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Hi folks.I have a U shaped piece of aluminum that i'm TIG welding together. The pieces are made up of 6061-T6, 1.5" square tube with a 1/8" wall thickness. The ends are mitred together. Here are some drawings that may help describe what i'm talking about.This first one shows the general layout and dimensions (35" x 15.5")This second one shows that the pieces are square tube, and that the ends are mitred together. I plan on welding 3 of the four sides: the two sides (butt welds, and the inside corner (fillet weld). I am NOT going to weld the outside corner as I want the outside to look like a "sharp" point.I actually performed this piece of work a few days ago, but due to warping/bending (not sure what you call it), the bottom ends are bowed together so the distance between the bottom ends is about 1/4" less than the top ends. I need this piece to be exactly the same distance apart on the top as on the bottom.When I welded this, i used four corner clamps (http://www.homedepot.com/p/Pony-3-in...6-K/100180604#), two on each side of the corner. I also used a scrap piece of aluminum that was exactly 32" long clamped in between the bottom ends of the "legs" as a separator. I did the welding by having the piece standing straight up and tack welding each of the two sides then pulling the clamps off (leaving the separator in place). Then i laid the piece down on a side and ran the butt welds on one side, and then on the other side. Lastly, i did the interior fillet welds. I'm using a Lincoln Precision 225 AC at about 160A.I left the separator on the entire time as I thought that would help reduce the chance of the legs bowing inward. Apparently that didn't work. Can anyone give me any hints/tips on how to do this?My original thought was to build a complete rectangular frame/jig out of aluminum or steel (welded together). The frame/jig would have an interior set of dimensions exactly the exterior dimensions of the part i'm trying to create. Then i'd clamp the part to be welded into the frame/jig in multiple places and try again.I'm a decent hobbyist welder, so i can do aluminum relatively well normally. An instructor at the place where i do my welding (TechShop), mentioned to use the pulse setting to reduce heat input especially on the fillet, and also to do the sides first and let the piece cool completely. I'm looking for any other tips for how to do this, so i figured i'd ask y'all. Thanks!
Reply:One possibility is to add some positive angle to these so that when they pull, they pull straight vs pulling in too much. If they have all pulled in 1/4" total, make your spacer 1/4" larger ( 1/8" to each side to stay even) and try that.Sounds like you are already welding the sides 1st and the fillet last. That would have been the other major suggestion..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Normally on this joint the fillet will pull it together.To limit this effect, weld the sides, then the outside corner, last - the inner fillet. If this is not possible, just weld the sides. Or tack with the open end too wide, then the shrink will pull it to spec.Time for Mr. Shrink Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Here's another possible way to think about it:The first time, you did the fillet last, and it warped inward. Doing the fillet last the second time will yield the same result, unless something else changes. Tack the frame near where you will do the fillet, then put a spacer the correct width at the far end where there is no tube, then weld the fillet. THEN spread the structure if needed to get to specified width at open end, which should be easy since only the inside corners are welded. Tack near outside of corner, check for proper geometry, then weld sides. That way, you finish with welding the sides, which should cause less warping in the plane you are concerned about. Just a thought.Miller Dynasty 200 DXMiller CP-300 with 30A feederHypertherm Powermax 900Oxy-fuel w/Harris torchesScotchman Glide-in bandsawMonarch 10EE latheEmi-Mec Autoturn latheDeckel FP2NC milling machinePro-Tools 105 Bender
Reply:We do this kind of joint quite often.For a starter don't bother with the corner clamps, as you already know it's pulling in 1/4" overall so you have to allow about 1/8" per side at the open end to allow the frame to pull to where it wants to be.I set mine up on a flat steel bench set up with a couple of angle fences to sit the square alloy section against and clamp the pieces to the bench and as I want the outside corners welded I weld these 1st I usually linish the sharp corner back on each piece and weld this outside corner vertical down while it's all clamped to the bench.I then weld along the flat face from the outside corner to the inside corner.I usually work from one corner of the bench so I'll release the clamps then do the same the other side to form the completed frame and weld also.I'll then turn it over and put some packers underneath so the weld clears the bench and clamp over the packers. As the frame has already pulled in I'll "convince" the frame to sit back against the fences and as it's Aluminium it's pretty easy to move and weld the other flat upward faces.The inside fillet weld is always last.If you've got about the right amount of set to allow for shrinkage you can pretty consistently get 90 degree joins.Regards Andrew from Oz.We are Tig welders, gravity doesn't worry us.Miller Dynasty 350. 350 amps of awesomeness.OTC AVP 300 hybrid wave AC/DC inverter tig. (now retired)Kemppi MLS 230 amp for home, a sweet little AC/DC Tig
Reply:Originally Posted by MinnesotaDaveNormally on this joint the fillet will pull it together.To limit this effect, weld the sides, then the outside corner, last - the inner fillet. If this is not possible, just weld the sides. Or tack with the open end too wide, then the shrink will pull it to spec.Time for Mr. Shrink
Reply:Originally Posted by pbungumHere's another possible way to think about it:The first time, you did the fillet last, and it warped inward. Doing the fillet last the second time will yield the same result, unless something else changes. Tack the frame near where you will do the fillet, then put a spacer the correct width at the far end where there is no tube, then weld the fillet. THEN spread the structure if needed to get to specified width at open end, which should be easy since only the inside corners are welded. Tack near outside of corner, check for proper geometry, then weld sides. That way, you finish with welding the sides, which should cause less warping in the plane you are concerned about. Just a thought.
Reply:I dont understand why you cant tack the pointed outside corners, you can sand them back when your done? This way you tack up the whole frame before welding anything.... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Originally Posted by B_CI dont understand why you cant tack the pointed outside corners, you can sand them back when your done? This way you tack up the whole frame before welding anything.... |
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发表于 2021-8-31 22:38:13