Water table depth for submerged cutting?

[Knut]

RIGHT FORUM THIS TIME!

Looked at Graybeards pics of his water table on Yahoo. Didn't find much info on submerged cutting there or here. Lots of dead ends hits on cnczone, the search words bring back just about every thread. Most deal with water trays.

With 5hp of air pushing through the kerf, a great deal of air movement must be involved under the sheet. That will need some depth to handle the flow. Curious as to how much depth is truly needed as my table has to tip up for storage. No matter how deep, it would appear that six drop down support legs will be necessary to support the water and level the table with such a large load on it. The shallower the better for me. A 5.5" water depth would work well for construction IF that is deep enough to disperse the gases. That makes my tanks mounted under the table smaller also. That would mean making tanks of 2.4cuft/linear ft of table, about the max I can sneak in there.

My intention is to cut mostly thin materials, so a submerged cutting table is very desirable. After watching one work at the local collage I appreciated the dust and noise control also.

Thanks,

Alan

[Dale Heart]

The correct answer is to consult your power supply manufacture. But, in general 2-3" of cover is the range you are looking at.

[Knut]

Hi Dale,

Perhaps I was not descriptive enough. I was curious about the depth of water UNDER the sheet. Tom and others have noted that an ordinary plasma setup can only handle a easily blow away layer of water of the top of the sheet. I was hoping that meant 3/8" so that slightly warped sheets can be completely covered. Some of the 'home' videos I have seen appeared to have a 1/4" or so of water on top.

I didn't want the air flow disturbing a light sheet from below with its turbulence.

thanks,

Alan

[Torchhead]

Alan 4" to 6" of water under the table is enough. The air gets defused in the cutting process. It's not like standing with an air nozzle at 70psi and shooting it into the water.

Heck, put Jello in the water and thicken it Better yet soap and something like foto-flow soltiuon to make the water more "sticky" and you you can blow some impressive bubbles.

[jcc3inc]

Sir,

We had a customer in Oregon who cut thin SS, and his water table was about 2" deep. When the sheet was in place, the top surface was just barely covered with water. But this was enough to carry away the heat and minimize warping.

Regards,
Jack C.

[Dale Heart]

Knut, I really didn't pay enough attention to your post and just assumed you were asking about the depth of submerged cutting and 2 – 3 inches is generally in the ballpark.

You do bring up the problem of noise and dust. Personally, the noise isn't a problem… ear plugs are like a dollar. The big problem is the dust. It is seriously dangerous and will cause severe health problems. Underwater cutting (like a few inches) will solve that problem or a good filtration system… VERY good.

Seriously guys, I don't think many of you understand just how hazardous that dust is.

[Torchhead]

I don't think you realize the the normal torches we all use are NOT designed for underwater cutting....period. You can get by with having water over the surface of the metal but it has to be shallow enough that the air can blow it off as it cuts. Water to the back of the piece being cut is sufficient to stop most dust and smoke.

[Dale Heart]

I didn't imply that the torches you were using are good for underwater cutting... I didn't read the original post carefully enough. I just gave a range for a torch, which can obviously cut submerged. I don't even know what heads you are using. I'm just pointing out that the fumes generated are hazardous. I might post a photo of a couple of vials of what is thrown into the air from plasma cutting and it might shock you guys. I’ll do it tomorrow.


Also, having a thin layer of water on the top of the plate generally isn't enough to stop fine metal particles being thrown into the air... you generally either need to submerge cut, cut with a water shielding or have excellent ventilation and filtration.

[Knut]

Hi Dale,

I can appreciate that with only a 1/4" of water, blown away from the cut zone, it will allow a certain percentage of blow back from plasma cutting. Having spent an overnighter in the ICU for a breathing problem stemming from either aluminum welding fume or OSB dust I do not intend a repeat of that. The PAPR welding helmets and HEPA welding fume extractors are expensive but worth it.

Watched a water table at our local Votech and they only partially submerged with of course the air blowing off the top layer. It seemed to capture the vast majority of dust though, plus we could talk. I had planned on placing a hood like the router guys do right over the torch to capture some for filtration. I have a second PAPR helmet for soldering at metal sheetmetal shop which can be donned also.

Thanks, Alan

[Knut]

Hi Jack C.,

Your Post on your customers use of only 2" of water with light metals is very promising. That would reduce the number of supports I would need to setup and take down with every use of the table. But still would need a convenient way to hold the slats and replace them, and allow good drainage of the sludge laden water for filtration and storage. The smaller storage tanks would be great also!

Buy chance did this customer just use 1x2 angle iron tacked to the bottom of the water table? I do need to develop a low profile means of holding the slats securely that will still allow drainage. That would include the edge holders and the secondary supports midway on the slat. I have no need to support anything heavier than 10ga in a large sheet.

Thanks,

Alan

[Knut]

Hi Tom C.,

Thanks for the recommendation on water table depth (4"-6"). I would like to shoot for the 4" depth as a feasible depth for the installation of slat holders. Drainage would necessitate a shallow drain taper to perhaps 6" on one end, increasing table load some.

After reading jcc3inc comment about his customer using only 2" of depth (possibly overall) with which he was successfully cutting light sheet, would you be tempted to try this? With a shallow V to the table and a longitudinal slope to drain to one end, total table depth could be kept to 4" on just a portion thereof.
This would substantially deduce the load on the table, not a problem for most, but for a tipper a real boon. Especially if the water has to be stored underneath it.

I would get really worked up about cutting the bottom out of my frame/table if it were not deep enough!

Thanks,

Alan