[motoadz]

Hi everyone,
Long time reader first time poster.

I'm seeing if anyone can shed some light on my situation. We are making a new gantry for our 2.7m x 1.5m plasma table ill attach afew photos of the design.
The problem we are having is with cutting the 100mm x 1.8m long x 5mm thick parts for our beam. They bow like a banana during the cut.
We have never noticed this before on anything else we have cut but this is the first 100mm long rectangles that we have had to cut.
Ive tried letting it cool right down before i cut the other side and also tried submerging it in water which did help abit.
Im cutting at 2000mm @ 45A. Would like some advice before i waste more steel.

All 4 pieces bow the same amount and the same way ruffly 4 mm to the center of the pieces. I think its from the heat during cutting because if i stop the cut after the first side is cut and check it, it is straight.

Any help or ideas would be greatly appreciated. Im pulling my hair out here.

Thanks

[Torchhead]

Heat can cause warping but so can stress relief. Here is a couple of ideas:
Preheat the metal with a torch and see if it starts to bow Sometimes you can do stress relief before you cut the piece
Do not cut the slots out that are close to each other . Either let them cool or make you cut file so they get cut at different times.
Rig up a spray mister and air to cool the metal as it cuts.
Try clamping the edges an make all of the internal cuts first . Maybe leave in tabs on the outside cut to let the clamps keep ti down and cut them out with a saw or cut-off tool
Those a large pieces of thinner material and have lots of cut outs. Its not easy to keep something like that perfectly flat of straight

Good Luck!

[BTA PLASMA]

Your drawing looks neat but to get efficient you should move your center of mass between the trucks. Cantilevering over like that may give your bearings a short service life.

[motoadz]

Thanks for the advice. We are going to cut again in afew days.

We thought about the bearings aswell. Problem we have is we need to counter leaver out that far as we didn't make our table big enough so this is the only way we will be able to reach both ends on the machine to cut a 1220x2440 piece of steel. Our old gantry can only reach around 2200 down the sheet. Bit of a bummer and we have worked with it for about a year now, we are going to try this before we consider building a new machine. Our rails are 30mm supported rails hopefully the bearings will cope for the mean time.

[mactec54]

Thanks for the advice. We are going to cut again in afew days.

We thought about the bearings aswell. Problem we have is we need to counter leaver out that far as we didn't make our table big enough so this is the only way we will be able to reach both ends on the machine to cut a 1220x2440 piece of steel. Our old gantry can only reach around 2200 down the sheet. Bit of a bummer and we have worked with it for about a year now, we are going to try this before we consider building a new machine. Our rails are 30mm supported rails hopefully the bearings will cope for the mean time.

Putting the slots in the top edge is what is causing the distortion, do worry about you Linear Bearings, the Bearing are most likely rated for a few thousand pounds loading, they will only wear out with there normal life cycle, the loading that you will be using they won't be affected in any way, this is quite a normal way also to build the gantry