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How shallow could a water table be and how far from the metal?

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AdrianH
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How shallow could a water table be and how far from the metal?

Postby AdrianH » Mon Jan 02, 2017 5:13 am

I never looked into a water table when building my table as it was just for my hobby, I tend to use it when the doors are open and sweep up a lot after!

I have 1 inch slats that the work sits on and these sit on a frame underneath, so unless I raise the slats that is really the only depth of water I could use.

So anyone know what the min depth of water is before it just gets blown away and has no benefits with regard to particle entrapment etc? I assume I could have the bottom of the work just in the water?

I have found ideas about getting water in and out of the table but no answers to this so far.

Cheers

Adrian

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Re: How shallow could a water table be and how far from the metal?

Postby SONIC » Mon Jan 02, 2017 4:09 pm

I don't know the exact depth, but as long as it's not so shallow you end up blowing a hole in the bottom on a pierce I imagine it would be fine.
A shallower table would likely splash a little more.

I would make the slats at least 1.5" if it were me but I think you'll be fine.
Most commercial tables i've seen are 3" or so deep.

Correct you can have the work piece in the water. I raise my level until it touches the bottom of the sheet, makes a world of difference for warpage.

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Re: How shallow could a water table be and how far from the metal?

Postby AdrianH » Mon Jan 02, 2017 6:29 pm

Thanks for the answer.

Adrian

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Re: How shallow could a water table be and how far from the metal?

Postby sawdust1 » Sat Jan 07, 2017 8:52 pm

My table by accident rather than intent is 5 inches deep. I used 2 x 6 aluminum tubing for the sides. Going down 1/2 inch from the edge you get to the top of my sacrificial supports. These supports are rings made from 1.5 inch steel strapping bent into hoops and spotted with my mig. The rings can be made any size, most of mine are about 20 inches in diameter. The torch cuts into them about 3/8 inch. The rings get thrown down, I try to avoid places where the cut will cross, this almost eliminates tip ups. A half sheet of metal can have 6 rings underneath it. The rings are supported by quarter by one aluminum bar that span the table and are on four inch centers, the center of each bar is supported in a notch cut in an angle iron that runs perpendicular. There is a couple or three inches of water under that support system. Pictures would be better I know. The aluminum rails are never damaged, the slag is cool enough that there is just dust and slag laying on them. The only issue I have is needing to add water all the time as it evaporates just sitting there.

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AdrianH
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Re: How shallow could a water table be and how far from the metal?

Postby AdrianH » Sun Jan 08, 2017 3:12 am

Hello sawdust1, I have seen a post somewhere about using rings before, so could well have been one of yours I have read.

The problem for me is height, when I built it I did not even consider a tray. Here is an early picture showing how simple it is made from 50 x 25 rectangular box section.
desktop2.jpg
early pic of frame


It was done like this to sit on a bench, has the H frame as you can see that the slats sit on, so my main concern is just blowing the water out of it, but the main part is trying to keep the dust down.

I am getting a tray done early next week, as as the maximum the tray will hold is around 30 litres, then it will be easy to fill and empty by lifting a tub on a stand and lowering again to drain. It may not provide what I wish, but worth a try.

Adrian
Last edited by AdrianH on Tue Feb 21, 2017 3:41 pm, edited 1 time in total.

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Re: How shallow could a water table be and how far from the metal?

Postby sawdust1 » Sun Jan 08, 2017 10:17 am

@AdrianH
I had no idea when I started! Mine holds about 240 L.
Smoke and dust are remarkably reduced by the water. I still wear a mask if I am doing any amount of cutting, I get a little bit of spray up against one of my side rails but only if I am cutting close. I found that the metal laying on the water prevents any splash or waves, the little splatter that I do get comes from the top surface of the metal after the water has bubbled up from the drop out holes.

I notice lots of people drain their tables, is this to fish out little parts?
I did weld a ball valve into the bottom and can garden hose it into the trees. The spruce seem to like that water.
I have a camera again and next time I drain I will take pictures.

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Re: How shallow could a water table be and how far from the metal?

Postby AdrianH » Mon Feb 20, 2017 7:03 pm

Just an update, I finally got around to putting the water tray on my home made set up.

Only done the one cut with it so far but apart from water vapour and a bit of steam, it seems to keep the dust down a great deal, no blowing black stuff from my nose!

I do believe it is too shallow really as I know the air pressure from the nozzle is displacing the water from underneath the work to the tray. So the tray gets peppered with the grit. It must also mean that the metal tray gets hot then is quenched by water as the jet moves away, so over time I think heat distortion and even possible cracking could be an issue. Time will tell.

I had the water to approx 3mm under the work piece, so was easily blown onto the work to cool it. I saw no signs of heat distortion on the work piece so that is also good to have.

Think I may have got to the limit of improvements to my CNC Cut40 system.


Adrian

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Re: How shallow could a water table be and how far from the metal?

Postby BTA Plasma » Tue Feb 21, 2017 2:22 pm

We have a customer that cut 1/2" material for 6 years on a 3" deep water bed with a 200 amp plasma. Deeper than that for less amperage means wet hands and shirt cuffs and really adds nothing but a deeper pool to pick your parts from.

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Re: How shallow could a water table be and how far from the metal?

Postby AdrianH » Tue Feb 21, 2017 3:50 pm

Well my depth is around 28/29mm I can raise to probably 32mm or 1 1/4 inch but suspect that is my limit without the water escaping from the tray when cutting.

But thanks all for the comments.

Adrian

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Re: How shallow could a water table be and how far from the metal?

Postby Gary Anderson » Mon Feb 27, 2017 9:08 am

I have both water and down draft setup on my 5x5 table and get almost no smoke in shop . Have pan about 8 inches smaller than table leaving gap all around for air flow, water is about 6 inches below work 1 1/2 to 2 inches deep. I closed in table legs , put a squirrel cage blower from Surplus Supply and 4inch flex drier duct out the door and cover all open areas around work with pieces sheet metal. I realize this is not very sophisticated system but works great. Still wear dust mask. Hypatherm 65 cutting 1/4 inch and under.

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Re: How shallow could a water table be and how far from the metal?

Postby SONIC » Tue Apr 11, 2017 10:00 am

with the water 6" below the work why even bother? There's no way it's catching anything, just making your slag wet and harder to clean out.

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Re: How shallow could a water table be and how far from the metal?

Postby tmks » Sat Apr 15, 2017 9:27 pm

SONIC wrote:with the water 6" below the work why even bother? There's no way it's catching anything, just making your slag wet and harder to clean out.

Jim colt recommends about that distance
"Here are some things to consider:

Water 6" under the plate (so no water splashes the cut edge).....or no water at all will produce the best cut quality (smooth finish, minimal dross, softer edge) on most materials."
http://www.millerwelds.com/resources/co ... over-water
and as wih SS "raise it to about 1" or so over the slats (stainless cuts best submerged"
CancCNC PlasPakIII 4*8 table
HyperTherm PM1000gs

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Re: How shallow could a water table be and how far from the metal?

Postby jimcolt » Sun Apr 30, 2017 4:26 pm

With the water 6 to 8" below the bottom of the workpiece you will catch about 60% of the hot metal pieces (heavier particles).....then you can also pull a downdraft (smaller fan, less flow because you have already removed 60 percent) on the rest of the particles (finer, they rise in air as smoke). This makes for no splashing on the mechanical parts of your machine and easy removal of the smoke. I call this a hybrid fume control, and in my experience provides the advantages of both downdraft and water.

If you are using water to combat warpage, then you are cutting with too much power or cut speed too low. Matching the correct power and speed when cutting usually will eliminate warpage, though there are exceptions to that!

When water splashes on the cut edge, expect more dross and a rougher edge. Air plasma does its best job when the plate is dry.

Jim Colt Hypertherm

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Re: How shallow could a water table be and how far from the metal?

Postby RyanS » Tue Oct 10, 2017 4:48 am

Jim, I like the idea of hybrid fume control. I can't visualize how the ducts are positioned above the water pan. Do you have pictures that show how its constructed?


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