Question about welding. Deformation.

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Hi. I am very new to welding. My girlfriend got me a Lincoln Electric 140HD mig fopr xmas and I'm looking to use it soon, to practice atleast. Anyways,.. I have a serious project I want to tackle sometime this year. I want to construct a CNC router out of mostly structural steel, A36. Here's some pics of what I would like to do:Now some friends of mine online asked about how I would deal with the deforming from welding. If I was going to send it to a machine shop to be milled straight and true. My question is,... much much deformation are we talking about if any depending on how talented the welder is?!?!? The structure will be made out of mostly 1/4" thick A36 steel.Any tips and tricks to keep the deformation down to a minimum? What type of deformation are we talking about?!?! And bending of the structure? I was told something about the weld points would deform the bearing surface area? If it is what I think it is that wouldnt be so bad. I'm more worried about bending and twisting. If thats even a problem how could I prevent that?!?! Maybe clampling the angle iron to some more angle iron as a straight heat sinking surface?!?! I dont know. Any help would be greatly appreciated
Reply:I'm no expert on this, but I do a bit of welding here and there.Any welded structure will suffer from heat distortion.  It can be flame straightened, but to the tolerances of a precision machine........................  Not to sure about that.Most precision tooling I've sees is either cast, and milled and ground to final tolerances.  Or it's bolted together.The ladder shape you got there will try to distort up and down, and not too much side to side.  If you weld in from the diagonals.  But it ain't gonna be perfect."Any day above ground is a good day"http://www.farmersamm.com/
Reply:1/4 might be a stretch for your machine"Any day above ground is a good day"http://www.farmersamm.com/
Reply:This really is a trick question, isn't it?You got to be kidding me.  I think deformation will be the least of your problems.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIThis really is a trick question, isn't it?You got to be kidding me.  I think deformation will be the least of your problems.
Reply:I would build the outer frame separate to minimize distortion.  Then build the grid work to set inside and attach with bolts or pins.Also, that 140HD is really not up to the task of welding 1/4" steel.Last edited by TSOR; 05-11-2009 at 12:10 AM.
Reply:I disagree that deformation needs to be a big problem.The frame will sit on a stationary bed, not be subject to great forces or vibrations so the many welds won't have to be large and full length to give the needed rigidity. The hard part will be getting the double-v insert pieces exactly the same length and maybe finding high-quality (straight and uniform thickness) angle iron to go on the outsides. Might have to modify the design to make up for slight deficiencies such as varying of width of the track, by making one set of follower wheels spring loaded.I'd guess you will need to do a fair amount of practice to get where you can do this, if you are of average abilities. Things like knowing the order of parts to be welded take time to learn, beyond just laying a good bead.
Reply:I am just going to skip out on this design for now and use wood instead. It will save me time. I'll start playing around with welding and figure it out myself. I'm pretty sure I can do it if I spent the time on it. Thanks.
Reply:Get rid of the angle.  You have too much welding going on.  Use tubing instead for all your running rails.  Keep the shorter angles for your carriage.  If this was a rail say four feet long it is unlikely you would need more than three vertical struts, one at each end and one in the middle.  Use tubing for the struts and do NOT weld up solid.  If the tubing was 2 inch square then each joint would need less then 3 inches of weld at each connection.  Fit your pieces with the minimum gap possible so that everything is touching with no gaps.  Otherwise when you weld the gaps will close up and pull the unit out of alignment.  If you were to use your design the welding and machining would be an impossible task.  The frame would first have to be stress relieved in a furnace before machining.  If it was not done when the machinist unclamped the frame it would spring to a new position.  Tubing is pretty straight to begin with.  I am not sure what level of precision is required.Last edited by lotechman; 05-11-2009 at 08:02 AM.
Reply:Why not bolt the critical pieces together, that way they can be shimmed and trued? Otherwise the whole thing would need to be precision ground after it was welded together.Like posted above, looks over complicated. Don't count on getting perfectly true metal stock to start with, else it will cost you $$$Lincoln PT185 TIGLincoln 175 MIGLincoln 240 amp AC StickLind Needle Arc plasma welderPlasma cutter, soon???
Reply:For the "Green Weenies" who see fit to comment:I made a statement that deformation (warping would be the least of his problems).Just so we understand, let me point out a few things.OP states that he received a 140A mig for Christmas.  Never even used the machine to practice with.Rather ambitious project even for an experienced welder with the right machine.Grossly overdesigned.Underpowered machine for the task at hand.No understanding of the effect of heat on metal.  Shown by the design.If the OP had even tried welding up a couple of pieces of angle iron, he'd have already answered his own question.Bottom Line:  OP has a lot to learn about WELDING before taking on a project of this complexity.  If you think differently, then you've got a lot to learn about welding also.Any of you smarta$$es want to find fault with my observations, fire away.How about learning how to stick two pieces of metal together properly (weld), before you start worrying about deformation (warping).Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:My previous comment (comment #11) was made to a poster who evidently saw fit to remove his posting or it was deleted by the mods because it was made by the same troll who has used about 10 different user names on this forum.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Make that three, but it doesn't mean what he said is wrong....just how it was said.Learn to weld first, then figure out what you can do with a new skill.If you forget all welding for a moment, that design has enough flaws that it should be scrapped and redone anyway.  Lot's of material without gain.....
Reply:Charles:   Another thing that came to mind was to do away with the framework you have drawn and go to a single tube.  I am not sure as to what you are mounting the frame to but a single four inch square tube eight feet long is quite rigid if secured at both ends.  For routing wood I think it would be rigid enough.  If it is not then the carriage could just ride on a second member freely and you could shim and adjust the second longitudinal to be true to the main tube.   As you can see designing something is ninety percent of the work.... at least you do drawings rather than a scrawl on the back of a cigarette pack.
Reply:Make me four.  I feel just the opposite about the position that the OP must learn to weld (in the sense that his skill satisfies the trolls on this forum) before trying to build a CNC router.  Go for it!  We're not talking about something that will injure people on the highway.  Either the finished product works or it doesn't.I have seen plenty of examples online over the years of people without previous welding experience who have set out to do things as complicated as this and who were successful.  Think TIG welding automotive intake manifolds, etc.The critics would have every idea reviewed and passed by a board of pessimists before ever metal is melted.  B.S.Back to the original question.  There are threads here and on several other forums about how to minimize distortion caused by welding heat.  Good fit-up, heavy use of clamps, a flat surface (welding table) to build on, tacking and cooling to keep heat to a minimum and most importantly, a well researched and thought-out design all come to mind as ways to succeed.  Do lots of practice, practice, practice on trial joints before tackling your project.ScottMiller XMT 350 CC/CV w/gas solenoid opt.Miller S-22A wirefeederBernard 400A "Q" gunMiller Spoolmatic 30A / WC-24C-K 200A torch/gas lensWeldcraft WC-18 watercooled torchHypertherm Powermax 30Victor O/A
Reply:It must be reassuring to newbie's coming on the board to find that some of the older members don't have a clue what they're talking about either.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Hey cvriv.charles, count your blessings that your girl friend loves you enough to get you that welder. Never be sorry you asked. The learning may be harsh, but it will serve you well in the long run, if you pay attention to the content and don't take it personally. It's just paying your dues to learn. If the welding bug really bites you there will be no stopping you.Start with the fundamentals and stay with them until you're knee deep in empty spools, you'll see first hand some of the effects of distortion. Engineering and design are whole different matter. Chances are, what you're looking for is already made, sitting on a scrap pile waiting for you give it a new life. Good luck, and let us know what rod you use if you make it from wood.....maniak