avoiding heat warping......a call for your collective wisdom

[Country Metals]

Patience!

This plate is too small to deal with restraightening. Just tack the pieces in place, then jump/scatter weld it 4 times, go get a beer and drink it slowly, then come back and weld 4 more times, then go get a glass of water, then weld 4 more times, and get another beer......

And 3/8" welds aren't really welds, they are big tacks and prone to breaking if these bars are really necessary.

Also make sure you weld on both sides of the flat bar to keep that straight as well.

[monte55]

Just a thought. You could drill some holes through top where the braces will be..maybe two or three per brace. From the bottom, weld the braces on the ends only with short welds and then spud weld through holes in top of plate. I would also use thicker than 1/8 " for braces

[Cgotto6]

You guys are funny, the guy has not even said what this plate is for and you are already saying his design is insufficient. How the heck do you guys know that 1/8 x 1 bar is too small for the task?

[Cgotto6]

How many bars? You could per crown the plate by clamping it down with some spacer bars on the opposite side you are welding the 1" bars. If you clamp it to a flat surface it will still warp. As stated, do not air cool with compressed air it's just not a good idea weather it's critical or not!

Oh have you not been able to keep a welded piece flat using air to speed the process? Why would this not be alright to do on a non critical piece?

[ampedtech]

The overall project is a cnc device.

It is my intention, once this frame is assembled, to Blanchard Grind the surfaces (so that they will be in the same plane) that the linear bearing rails will be attached to.

although, I do not need this robust design to accommodate the operation of this device (can't hurt though) I do need to have the sides stiff to accommodate the grinding process.

Please see the rocker indicators (in blue) in my sketch. This is the motion that I am trying to avoid.

stiff2.jpg

[ampedtech]

by the way one of the most important things that I have learned is that I must drink beer when waiting for stuff to cool!

Not only can I do that, I can do it well.

beer22.jpg

[elvis]

by the way one of the most important things that I have learned is that I must drink beer when waiting for stuff to cool!

Not only can I do that, I can do it well.

beer22.jpg

I must agree, but there must be better beer where you're at? Maybe some big sky IPA or Arrogant B@st@rd or my local favorite: Lost Highway BIPA (http://www.motherroadbeer.com/our-beer/)

Sorry, this isn't exactly helping you keep your project flat. And now I'm thirsty!!

[aametalmaster]

I don't even drink beer but that Alaskan looked pretty good ....Bob

[Steve83]

Drawing heat away won't help. Welds warp because the WELD goes on at ~3,000degF, solidifies almost instantly at that temperature (locking the pieces together), and then shrinks as it cools rapidly to ~200degF. Due to steel's natural properties, this causes the WELD to shrink by about 2%. The longer the continuous weld, the larger that 2% becomes. Making it cool faster won't change anything but the speed at which it warps.

So the 2 ways to minimize warping are:
1) preheat the steel so it's already expanded close to what the weld will be as it goes on, and as they cool together, they shrink together, and don't warp;
2) weld in VERY short passes scattered across the length (AND on both sides, if possible) of the joint so that no one weld is long or strong enough to warp the base material, and so that the structure becomes locked together at many points along the joint before it has a chance to slide & bend.

Try it on some long straight scrap to test it.

[dkennett]

Strong attachment at the outer ends of the crosspieces is all that is required to attain maximum rigidity. Continuous or many short welds would in no way add rigidity and would serve only to warp the flat plate.

Apply how you tighten a cylinder head to this problem.

Try beginning the weld at the center on each 16'' strip with a small weld, 1/2" on each side. After all center welds cool, ziz zag 1" welds at the ends of the 16" spars, every other one staggered side to side, let cool and repeat beginning at opposite end from first run of outside welds. I would add a linear spar centered on the 16" spars and rather than welding, attach it by cutting slots for each of the 16" spars to fit into & then lightly spot weld it only enough to keep it from falling out.

Actually, by using the slotted linear strip, the center weld could be omitted. The outer welds are all that is necessary to achieve maximum rigidity.

Another method would be to slot the cross braces so as to arrange an overlapping XXXXX and weld only the center intersect points to the plate. Be sure to leave enough space in the intersecting slots to avoid distortion of the flat plate. This is only a general idea that undoubtably can be improved upon.