So, I have these nice, straight metal slats. I want them bent to mild curve for the plasma table (curved slats resist having lengthy burn damage their tops).
They are not hard to bend, force wise. But getting them all bent consistently with matching curve, seems to call for a bending fixture or some such.
Anyone have ideas or experience on this? Tips? Suggestions?
PS: these are the ones I bought: Steel Slats for CrossFire or CrossFire PRO – Langmuir Systems
for these you could easily make a bender made like a pipe bender - I’m thinking an mdf wheel of the correct diameter and maybe even an mdf roller on the lever - it only has to last as long as the job after all!
What diameter is the bend or bends?
Pretty big diameter. For an already done example, here is @kd2018’s plasma table:
However, his table is a square, 48" x 48", while mine is smaller, 30" x 48.6" — and my slates will be going across the 30" span, so I don’t know if that means my slats will be bent more acutely or would be OK with the same curvature as his.
There’s the right way (rollers) and the way that “might” work! I’m not a metal guy but I’ve made heaps of curved boat beams. Can you make an MDF form and spring them into place while you weld?
Like this only you’d only need a clamp each ends - you might end up with an almighty spring pushing out the sides of your table though! 
you know you want to do it properly…
I can definitely do a form like that. These are sometimes (often?) not even welded. Often there is a little tray on each side with slices in it, and the slats just drop into the slots. Slats in slots. 
Re: possible spring force: these slats are made of metal that is very malleable. Once bent, the metal holds the bend.
Thanks for the idea!
Re: mold form versus roller,
For this I think form is the way to go.
Water table depth = 2 3/8"
Slat width = 1 7/8"
(This means my slot holder things will need to elevate the slats by at least 1/2" or more, as I think the slats should be proud just a bit (protrude up above the side walls of the water table).
Water table inside width (for the distance to be spanned) = 29 3/4"
Slat length = 33"
A quick bit of calculations courtesy of my CorelDraw vector illustration program yields a couple of possible radius options (I thinking the more acute one could be the form, and the less acute one could be in case the metal “springs” out a bit after bending:
Regarding slots, those are usually used for straight slats. Since my slats would be curved, I think I would not need slots, just strips that the slats could rest on. Three strips, 1/2" think, one on each edge and one down the middle… would do it I think.
Hmm, but spacers would be helpful to keep the slats from sliding out of proper spacing.
One more vector calculation, with an even more acute form (right side) with a circle radius of 25" — as I am thinking the metal slats might spring back a little more than the first illustration above.
I always assumed these tables were made by just bending them during assembly. You would cut the stock to the same length and then bend them into a box of a specific length and they would all bend exactly the same.
Doug,
I repeatedly built forms to bend curved metal strips. We used to make curved bars and table edges for the
Industrial antique look. We would cut a male/ female curve die from two thicknesses of 3/4” plywood. It’s cheap and you just have to experiment with cutting the curve a little aggressive to account for the spring back. We put the male/ female die in an hydraulic arbor press but you could use a car pump jack or pipe clamps. The material bends easily.
Rand
Blackington Furnitue custom made .com
The issue there is they won’t bend uniformly unless you have used a form to force them to.
In looking at the needed work to make curves — coming up with equipment or else making equipment to get them uniform — I’m thinking of another approach that may possibly be workable. Instead of avoiding the risk of long run burn damage to top edges of slats by way of curving them, what if I did it by way of slanting them. My slats are longer than the span that has to be covered, so I could angle them on a diagonal, and not have to bend them.
Here is another vector calculation on using angle instead of curve to resist long-run burn damage to tops of slats:
They wouldn’t bend 100% identical, but as long as they started off the same length, they’d bend pretty close. You’re not talking about a huge curve or bend. Are you looking for perfection, or are you wanting to finish the project?
Personally, I’d weld in vertical pieces where I want the slats to go, Then I’d just bend the pieces to snap them into place.
I already did a test bend without any form. This metal is very malleable. It can bend into a corner “here” and a straight away “there” pretty easily. Anyhow, I’m still pondering. I was not planning to weld them at all, as they are a long term consumable and I like the “slats in slots” replaceable approach. But I tend to lean toward angling straight slats over the curving. It also makes it easier to replace them whenever that becomes a need.
I left mine straight, I had plans to bend them but it just adds complexity that I did not feel was necessary.
You can flip them over or end to end, it is fast and easy. I don’t think a bend will really make a big difference. I do find myself lining long straight cut up between slats so in the end I think I miss them more than I would if they were curved.
I was going to curve them with a offset middle end point.
Oh and as for the length. Don’t bother calculating it. Mark it and snip the end off with your lightsaber sitting conveniently at the table as you install them.
Just grab a slat by each end and put a bend in em! I spend about 5 seconds max on each one. They’re consumables, they don’t need to be perfect or pretty. And they won’t be pretty after the after the first few cuts and you start burning through them and throwing slag all over them.
Edit: I’ll elaborate on what I did. There were three slat holders tacked on to the tables support beams, perpendicular to the direction of the slats. These holders are just 1/8 strap that I put slits in about half way through the strap with a chop saw on something like 3" centers. I offset the slits for the middle slat holder by an inch or two relative to the slat holders on the ends. With the slats them selves just give them a quick bend until they fit in the slits.
Sounds easy. Don’t overthink it.
