Plasma table support

[Rambozo]

I know most tables use a slat system to hold the material. And the slats ideally are curved or at an angle to avoid having square cut parts potentially line up a cut right over a slat. But I was thinking of going with a bed of nails approach. I little searching shows that I'm not the only one that thinks this might be a good idea, but I haven't seen it done. Can anyone shoot some holes in this idea? I know after some use the slats tend to become a bed of nails type support anyway. I was thinking I would attach the spikes to some kind of drop in bars under the water level to make replacement easier. Then I could mount a cutoff disc on a small motor attached to the Z, and write a CNC program to have the table cut off all the spikes at a perfect level to the axis. I could also run this program from time to time to clean up the spikes making them a little shorter each time before they needed replacing. Since the machine would do the final trimming, replacing the spikes would not have to be precise at all. Am I missing anything?

[EmptyNester]

Very cool idea.

Some of the drawings I got when I bought my carriage kit from Precision Plasma show slats that have a profiles with multiple points on the top so that the material is above most of the top surface of the slat.

[geezer]

Spikes and slats with points seem like a cool idea, however in the real world, ordinary slats rule, they are cheap easily replaced and can be taken out and turned over to use the other side, some people curve them a bit or use a herring bone layout,, but the simple slat is still the cheapest and most convient support device...the spacing to avoid tip up's is an important thing to think about no matter what you use.

[Rambozo]

For production and commercial setups I think that is true. In the hobby area some things work that would never make it in a commercial environment. Cheap is relative, in actual material costs, slats would be more expensive than spikes. Of course the labor totally skews that the other direction if your time has any value. It also depends on if the machine is making you money or not. I have some equipment that brings money in while others are large holes I pour money into.

Something I hadn't considered at first, is that with modern CAD/CAM systems, it would be easy to automatically arrange parts on a sheet so that no cut would ever hit a spike. This would make lifespan a non-issue. This is done all the time in machining to avoid fixtures and clamps. I have seen some software that has features to guard against tip ups, by adjusting part placement and start and stop points. Probably out of my budget, but it's all math to a computer. I have read about people that because of the kind of parts they cut, have had to go to 1" slat spacing. That borders on the ridiculous. I know lasers and waterjets will often leave parts tabbed to the sheet, but this is not as practical with plasma, nor as precise. I'm still in the planning stage, so I have time to figure out the downsides.

The more I think about it, the more I realize that I can use the table to build itself. What would be tedious and difficult to do manually, will be trivial to program the machine to do, itself. There would be a substantial weight savings as well. However, loading heavy material by hand would be virtually impossible, and would have to be lowered from overhead. Not a show stopper, as I would probably always use a crane or forklift for anything heavy.

[sportbike]

I think the points could be a good idea, but I lean towards the slats with points on them. Kind of a combo of the two.

[acourtjester]

Best of two is get a slat (3" X 1/8" flat) and plasma cut a spike pattern right down the middle and make 2 spike slats with 2" points each

have fun
Tom

[dawjr32223]

A little late on this thread, but I think you would be fine - except for the heavy loading as you mentioned. Essentially it's simply support of the material and of no consequence if the torch passes overhead. I've got slats on mine, 1/8"x2" I can flip them over and end for end so I can get a lot of life out of them. I also think one reason people "bend" or put them in some stress is to keep the stock from "quivering" on straight slats while the gantry is jumping around.