Warped Grating

[yeomansjon]

Hey everyone! I have been using my Plasma Cam (DHC) for about a year now, purchased from someone that had it for a few years but didn't use it very often. I've had great luck with it however lately I have been having issues with the machine sensing the surface when it comes down to touch the metal before the cut. I kept 'shimming' the plate thinking that a little warping might cause the issue. I kept frying tips when it would not back off far enough even ensuring the plate was touching the grating before the pierce. What I found was that the grating itself was moving up and down when the cutter would touch. I pulled all the grating out, cleaned and stripped the metal slag off, cleaned the entire machine, put it all back together, and sure enough the problem was still there. I suspected the grating to be warped but found it hard to believe given how thick the grating is in the z direction but sure enough when I sighted down the grates I could tell they all had a small bow in them.

Has anyone else encountered warped grating like this? I know any warping in the x or y direction is no big deal because the lattice holds itself together straight enough for what we need to accomplish. But warping in the z-direction can definitely cause issues if one is using a DHC model with the tips contacting the metal before piercing.

I have seen dxf files for new grates in the file sharing post, but now that I have realized how critical it is to have solid grating, i'm thinking the $250 to buy a set of grates (4x4 table) is worth the money to not have that headache anymore. Any thoughts from those that may have run into this before?

[mdwalker]

Yes, the grating just like any other metal will warp with heat over time.

[Francisco]

I'd recommend getting the new grating. Then, to extend its life, turn it over every month or so.

You don't have to disassemble the 4' x 4' PlasmaCam grate to do this. Lift it by hand (four hands - it's a two-person job)and flip it over.

[yeomansjon]

This is a dead issue at this point, but for anyone considering changing the grates, i think it's well worth the $250 it costs to buy the Pcam grates. When i put them in, the grid was SOLID. And I don't mean solid as in it can hold a lot of weight, I mean it was SOLID. Locked in place, does not move in ANY direction and will not deflect when the z-axis motor comes down and pushes on it. If the plate is flat and touching the grates, it will be solid too. I'm not sure that anybody can plasma cut a set of grates to such an exact dimension consistently to get the same super tight fit. The added cost to buy vs. cut your own IMO is well worth it.

Problem 1 fixed. Very happy with the new grating. Now on to other issues!

[BrianMick]

If your setting are correct you can cut anything with great(grate) accuracy. I do it all of the time.
Sure It took me 3 times wearing the grates out before I got the files tweaked to fit just right, but it is worth it in the end
the prices plasmacam charges for those things is ridiculous........

Brian

[geo4932]

The z-shift setting is important for the pierce height. The way you set it is to bring the torch out over the metal then jog the Z-axis all the way UP. Then jog down until the torch just touches the metal. Open the Settings and click the ZERO by the Z-shift. You will get an offset number. Click OK on the settings page and then reinitialize.
You should set the Z-shift every time you change the sheet metal.
The Z-axis speed works best at 45ipm.
Use "Stall on material" with over travel for stall between .05 to .100

The biggest advantage of the DHC2 is that it has an available ohmic sensing to set the pierce height.

George