I've just got my self a New 250A AC/DC Tig welder with pulse and I love it for just this reason as the heat is kept very isolated to small area. Fact I can weld thick Aluminium plate as well as thin Aliminium plate is lovely as well.
Any chance of some advice on best welding strategy for welding novices like me? Starting with the assumption that we are welding box section (I'm probably talking 50x50x3 in my case), what's the best way to get an accurate frame that's not going to distort as you add bits on? I'm starting to hear things like tack welds to hold it all together, then add more tacks/spots for strength, but continuous welds at the joints are not needed.
Specific example - you are welding two pieces of box section that meet as a Tee. Couple of spots on the "internal" corners so that you don't pull the pieces out of plane, then tack the sides, then add a few more spots for strength?
I'm guessing that all this is blindingly obvious to an experienced welder but I get the feeling that a lot of people cut their welding teeth for the first time building a router!
Erm, I don't have vast practical welding experience, but I'd say two decent 30mm long 3 or 4 mm leg fillet, i.e. one in the middle of each of the 2 flush butting sides of that joint should hold it good, for strength - just weld through (over the top of) any tack you've put down. I don't see any point welding round the corners or trying to fill the whole void in where the square cut end doesn't meet the radius edges of the mating member - doing this is just adding loads of extra heat and metal that isn't doing anything. The important point about tacking together is to set and maintain the WHOLE assembly geometry before laying heavier deposits down, so if you have any gussets orbraces supporting the ends of your T assembly, IMO they should be tacked in after the T is tacked together but before putting the structural welds down.
I'm no expert (I seem to weld every 4 years or so) but what I did was cut the pieces to length, dry assemble the uprights and the main frame outer pieces then put either one tack or a couple of tacks on each piece.
Then I got a square and spirit level and made sure all was as good as I could get. I then tacked in the bed braces..
I then checked all was square again before starting to add the angle braces...
I then checked that the uprights were still square and all was good and then started welding the uprights. Now here I confess I didn't do it in small short runs spread out round the frame like I probably should have. I just did it in one or two runs per weld (50mm long welds as using 50x50x4 box)
I then checked to see if all was still square (otherwise the angle grinder would have to come out!) and then proceeded to weld up the rest of the welds. I didn't do it in any particular order (it was pretty random) and then after finishing the frame (but without the X axis rails welded on) I checked all the frame was still level and the uprights were still 90° to the bed.
I then offered one X axis rail up, clamped it with F clamps roughly level and then referencing off the frame rails and tacked it as parallel (using a digital bevel box) as I could. I then put lots of tacks on it, checking in between that it hadn't moved, and then once cool I welded over the tacks in one go.
I then did the same for the second rail checking for parallellness (is that a word?) in both directions with the first rail as a reference but also checking the second rail against the frame to make sure it wasn't out. I then did the same weld procedure for the second rail and it turned out pretty square and parallel....probably more from good luck than skill!
The Following User Says Thank You to njhussey For This Useful Post:
All pretty obvious, then - the kind of "obvious" you only see when someone's pointed it out!
Thanks for the idiots' guide (and I'm the welding idiot, just to make it clear!).
Last edited by Neale; 07-02-2014 at 02:48 PM.
Last edited by njhussey; 07-02-2014 at 03:09 PM.Neil...
To be honest it's not rocket science but the Welder your using does make a difference to some degree.
Arc or MMA welders put a lot more heat into the steel than Mig or Tig so it's a good idea when using Stick to keep runs shorter and spread them around but keep balanced. By balanced I mean if you weld Left side of material for 1 " then weld right side 1" at same time before moving to another spot.
For general steel work then Mig is best has it's relatively quick and easy to learn but it's not has cheap has stick to buy equipment.
Tig is best for controlled heat but it's slow and more specialised and expensive so I wouldn't use it for steel frame work. (unless using MMA option)
Just for building a one off frame and keeping costs down then MMA(Stick) is best has it's cheap to get setup and not too difficult to learn.
Just remember bird shit can be scrubbed away so tis is true with welding and grinder is your best friend. . Lol
Welding and Epoxy leveling make steel frames very easy and cheap to achieve.
Last edited by JAZZCNC; 07-02-2014 at 06:18 PM.
The Following User Says Thank You to JAZZCNC For This Useful Post:
I would like to point again that the further i go building the machine, the more discover how important and later time saving was to weld the whole machine with under 1mm, even possibly under 0.5mm precision.
I would like also to remind you that i welded the machine fully, but it took like more than a half of day, due to waiting things to cool and the having in my left hand the IR remote thermometer, controlling that the overall temperature of the frame and gantry stays under 60C. So any change of dimensiones was successfully avoided.
So if you don't have thermometer at hand, just wait untill cool to the touch. And no more than 2 inch at once, always mirroring.
Here is some more progress in details.
The Hiwin are wide 20mm, i made the epoxy 40mm wide, hence-10mm each side. Thats should be the proper way. The meniscus took like 3mm at least.
So how i dealt with the meniscus? I decided i would not waste time on it, so i glued sand paper to a stick and started sanding it off. Not completely. I decided i will mount the rails and then continuing with epoxy leveling the gantry rails and side supports.
In other words dealing completely with the meniscus is a waste of time. The process took me 20 minutes, the epoxy sanded like a snow flakes. 20 min more for the end of the epoxy, where the end of the rails would be. here i checked with straight edge and scraped a bit the last cm.
It is a very good idea to stuck a tape over the middle of the epoxy, where the rails would be, as not to scratch it!
Well, it seems it worked as supposed. The epoxy i mean
Buying the precise 1m straight edge and precise square was a very good idea. In a matter of minutes i placed and aligned the rails. I would say that its crucial .
Both cost around 100 euro and a week research , see here: http://www.mycncuk.com/forums/tool-t...-straight.html
Once in place and squared i rechecked them using a long steel ruler made from 2 rules and magnets, which i fitted inbetween and checked at both ends. Tight fit as expected. I supported it with alu beam so it would not bend/ like in the picture, while i was making the shot/
Just a side note here. Forum is ok, but read the frigging manuals. Hiwin rails have direction, also the carriages/ its not seen on the pic, but the letters should be at the side where the arrow points to/ . have that in mind, is buried somewhere in the long manual.
I was tired and working after work. But i wanted and started to feel a kind of satisfaction not being in a hurry and doing things right. So instead of drilling through the clamped hiwin rails, i used a hole transfer tool lightly using the hammer. And a torch, to see better.
And as i started to feel that satisfaction, i decided to continue accordingly the process, drilling first 3mm holes, using the very handy tool to keep them vertical.
The torch helped again to see things , illuminating the epoxy from below.
Some holes and here is what happened. I had to go for a new drill, as it seems if the drill is not perfect, it adds heat and the epoxy lifts around the hole. Not a big deal, will scrape it with a small straight edge. The epoxy scrapes nicely, as i said-like snow flakes
Now i am waiting for a new brand M5 tap and the bolts for the Hiwin to arrive. I wouldn't risque with the cheap tap i have. I bought them from internet as it seems that screws are quite expensive locally.
Thats all for now.
Last edited by Boyan Silyavski; 09-02-2014 at 11:43 PM.
Coming on nicely nicely now, looking very good, but I wouldn't expect any thing else having read your build log and your obvious attention to every detail. Great stuff. G.
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