Planning your weld patterns....

[B_C]

I have been putting these Stainless SPIDERS together for the last year for
my Inventor customer. I usually get 200 bucks worth of time doing them..
They move so much when welded that they NEVER fit back on the fixture...
Making me spend some time adjusting the tubes with a bender I had to make.
I figure that tacking the flanges in three spots is not going to stop the tube itself from "TAKING OFF" when I weld them up...The four tubes have to be dead on or they won't fit. Is there a way I can plan my welds so that it will still move around but be where I need it to be after cool down. Or am I going to always need to TWEAK the tubes?


BC

[84ZMike]

Pictures...we need pictures.... I know stainless likes to warp way more than mild but it can be "tamed". I'd say lots of experiments would help....pull it were you dont want it then weld the other side to "bring it back"...or can you weld them up and heat them up to form them how you want / need them ?

[B_C]

The problem with heating them up to move them is they can't be discolored
a lot (Semi-Conductor parts) and being clean on the inside is crucial...
That's why I cold bend the tubes to get the fit back (.003 or .004 thousandths )

http://img.photobucket.com/albums/v93/billcalicura/DSC00001-35.jpg

http://img.photobucket.com/albums/v93/billcalicura/DSC00002-36.jpg

http://img.photobucket.com/albums/v93/billcalicura/DSC00005-22.jpg


There are two different styles of this part...when the legs get longer that's
when it really gets tricky...

[partagas]

Can you make a jig to told it down like pic 2. Then tac in the four spots. Then weld 12-3, then weld 6-9 then 3-6 then finally 9-12. That should help with the warping..

[TEK]

Its always going to pull towards your last weld. Do you weld out in the jig? or just tack and weld on the bench? If you weld out in the jig and its all clamped down, and you cool it completely before unbolting, it shouldnt move. Not always possible in a production situation. Which way is it easiest for you to tweak it? Legs in, out, or sideways? That will determine where your last weld would be.

Is this some kinda test? Anyone doing what you do, as long as you've done it, already knows this...

[B_C]

I can weld half way around the leg (flange top) and then let it cool and remove it to finish the other half of the weld...It always has to be pulled apart to fit back on the fixture. (sucks in)

Shaky hands BC

[whateg0]

If I was to try that on a regular basis, I think I'd try to make the fixture so that you could get to the whole thing, or maybe make another fixture that would allow the piece to be flipped and welded from the bottom.

Just my 2.4¢.

Dave

[Rocky D]

BC, I welded that type of tubing in some really weird configurations, of all sizes shapes. What you are doing is typical...you can't be 100% positive it will stay...it will always move. Welding it in quarters is good. Welding tubes circumferentially like you do, you notice the tube will rotate in the direction of travel. With that in mind, you cause the pull to pull against itself to minimize rotation. Flanges will always have to be straightened after ward, and it sounds like you have that figgered out. Bottom line..it is guaranteed to move, so you're going to have to cold straighten it after. In aircraft, they beat the crap out of the tubes to get 'em straight.

[B_C]

Ha Ha Ha that sounded funny :D I kinda wish that I would have pursued the aircraft deal when I got out of the Navy. Especially since I was stationed at Alameda CA NAS. during my reserve years...As I think back being a overhaul and repair facility I probably could have made all the right contacts...
Funny how hind sight is always 20/20 huh?

[chenry]

i have seen fixtures made where the " warp" is designed in the fixture so that upon removal the part moves into tolerance. but these were robot welded
with cold tig wire and not stainless.

if possible you can do like others have said and weld in quarters or thirds

weld completely in the fixture ( will have the most effect )

use vibratory stress relief in the fixture before un-clamping ( may or may not help and is time consuming )

[dsweld]

i do simaliar work sometimes and cool it with air or use a little water.this seems to help with the warpage.is there anyway you could use a kicker or brace tacked to the bottom side? stainless sometimes has a mind of its own

[DAD]

BC, Do you assemble all four legs together and bolt them down, before you start welding? If so, you could make a fixture for the underneath that clamps around each tube and ties in together; kinda like a "+" shape with a muffler clamp/tubing clamp welded on all four ends to clamp onto the tubes . Maybe that way, it would hold it when doing each side, then let cool and unclamp your "+". Let us know if you find the magic solution. Pretty good looking work you did.

[B_C]

Yeah I clamp all the legs down in the fixture.....See video...
http://www.youtube.com/watch?v=19xv64DH80g

[fillncap]

how about puting a packer under the middle !!! or bolt two of the spiders together back to back once the been tacked,agein brace and clamp the middle so it minimizes flexing in that ares.

fnc

[Bob]

You said: "It always has to be pulled apart to fit back on the fixture. (sucks in)".

Some thoughts.

A) Mount some spacer blocks between the base plate and the dogs. Slot the holes used to mount the spacers to the base so you can move them outward. I'd start with the outward offset equal to how much you have to bend them inward. Once you get the position right, drill and add alignment pins to the spacers.

B) Cut away the center of the base plate so you can flip and weld while still in the fixture. Do 1/2 of all the tops, then the opposite 1/2 the bottom, then the rest of the top, then the last of the bottom. Maybe mount the base plate on a stand that will make the flip easier.

C) Once the legs are tacked in place and you have done the tops of two adjacent legs, remove the outer dogs and let it expand while you do the other two tops. Trick here is probably how much of the tops you do before taking off the dogs.

Bob

[katswelder]

I have had some success with back welding the joint. weld from right to left then go back and weld another section ending at the start of your first bead. for me that helps with the inevitable movement of stainless. Good luck

[JoeS]

i'd say if you are getting distortion on the order of .003-.004" than that is pretty darn good for stainless steel compared to the dimensions of the piece you are building.

I think I would try taking the middle out of your jig, so you can get to the complete weldment, and then start your tack welds in the bottom, or inside of those tubes first, followed by the top side tack, then left and right. And by tacks, I would run maybe a 1/4" bead or so, then proceed to weld in quarters.

that's probably the best you are going to get without post-processing.

the only other way, would be as suggested previously, preload your typical distortion into your jig, and weld as you normally do.

[Phewzer]

Is there a way I can plan my welds so that it will still move around but be where I need it to be after cool down. BC

nope,
but you already knew that.:)