Sturdy and Fast all Steel CNC , my first build

[CharlesJenkinson]

Very interesting build, and good research for me. A weld bead causes shrinkage where it is deposited, so weld induced distortion is not so much due to the 'heat' that goes into the part, but is due to the fact that a weld, when solidifying, pulls on the adjacent parent metal. Apart from looking nice, I'm not convinced these types of bed frames, with massive members, need to be fully welded at the joints, from a stress point of view anyway - stitch welding would be perfectly adequate - having said that, the effect of inducing bending due to weld shrinkage is possibly only noticeable on smaller dimension square hollow section, less than 70mm say. The effect of weld shrinkage induced distortion may be mitigated where possible by welding to the perpendicular plane of the material, if that plane isn't as critical for flatness, and the design configuration suits it - I don't think it applies in this particular build case though.

Sorry to theorize in your build thread - being a noob, I guess I'm eager and this seemed an appropriate, and reasonable relevant place.

[JAZZCNC]

Apart from looking nice, I'm not convinced these types of bed frames, with massive members, need to be fully welded at the joints, from a stress point of view anyway - stitch welding would be perfectly adequate - having said that, the effect of inducing bending due to weld shrinkage is possibly only noticeable on smaller dimension square hollow section, less than 70mm say.

Charles Very true regards Stitch welding being plenty strong enough if done correctly but even larger dimension SHS will distort if the heat put into it is too great. Spreading the welds around and keeping the bead length down to a minimum is very much needed with any size material if distortion is to be kept to minimum.

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.

[Neale]

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!