What is the water tank for?

[ClarKent101]

I'm about to build my first CNC plasma table and looking online at different builds. I'm wondering what the large reserve tanks are for under the tables usually? Do people not fill the table with a water hose and then drain with a hose? What's the purpose of a water tank under the table?

[SegoMan DeSigns]

it allows you to recycle the water, after the parts are cut the smaller ones fall in between the slats so you drain the table to find them. Always go approx a 1/3 bigger than the water tray holds, My tank is 350 gal the water tray is 250 gal. You either use a pump or sealed air system / bladder to move the fluid back up to the tray.

[ClarKent101]

Ah I see, is there any online information on how to get the bladder working? I googled sealed air bladder but not seeing much?

one other follow up question to the water tray. What's the reason for curved slats? They are in tension I presume - just to stop any rattling or movement while cutting?

[SegoMan DeSigns]

Search this site for water tank, air bladder or pump system, keep in mind eventual the tank will need cleaned when designing your system.

Slats are curved like you say for rigidity so the metal don't jiggle around and create a bad cut, the curve also prevent the slat from being split if you do a straight cut on that axis

[adbuch]

I'm about to build my first CNC plasma table and looking online at different builds. I'm wondering what the large reserve tanks are for under the tables usually? Do people not fill the table with a water hose and then drain with a hose? What's the purpose of a water tank under the table?

I build a water tray for my Plasmacam table, but I don't use a tank. For me personally - I think it would be more trouble than it's worth. I'm not knocking others who use this approach, I'm just saying in my particular circumstance I don't really see any benefit to me with my cutting system. I have a diamond mesh screen installed into my water tray - about 1" below the water level. This is very convenient for catching small parts, and I just use a magnetic stick to lift them out of the tray. In general, I try to leave small tabs on my smaller parts so they don't fall into the tray. It is easy enough to break them off when finished cutting.

By the way, I use a draft system in addition to the water tray. This is very effective at removing any residual smoke which would not be eliminated by the water tray alone. My water tray is situated so that the top of the water is below the cutting grates, and this works well for me. I have seen others who run their water level right up to the bottom of the material being cut. I have been told that this can be very effective for helping to control warping when cutting very thin materials, and in particular thin aluminum.

If you are interested, you can see my water tray build below.

David

https://photos.app.goo.gl/h8LHufi6frttfGNQA

[SRdesign]

Ah I see, is there any online information on how to get the bladder working? I googled sealed air bladder but not seeing much?

one other follow up question to the water tray. What's the reason for curved slats? They are in tension I presume - just to stop any rattling or movement while cutting?

It’s not an actual sealed bladder. If you have a tank full of water, then add pressurized air to the tank, the water will have to leave the tank via the outlet at or near the bottom of the tank. That would be how you fill your water table. Then to drain it you would open up the air fill valve to let the air escape, causing your water to empty from your water table into the tank via gravity. I think I explained that right.

[SegoMan DeSigns]

Ah I see, is there any online information on how to get the bladder working? I googled sealed air bladder but not seeing much?

one other follow up question to the water tray. What's the reason for curved slats? They are in tension I presume - just to stop any rattling or movement while cutting?

It’s not an actual sealed bladder. If you have a tank full of water, then add pressurized air to the tank, the water will have to leave the tank via the outlet at or near the bottom of the tank. That would be how you fill your water table. Then to drain it you would open up the air fill valve to let the air escape, causing your water to empty from your water table into the tank via gravity. I think I explained that right.

Actually some do (click on the Bladder link):

https://ldrmotionsystems.com/cnc-plasma-table/

[SRdesign]

I was unaware of that. Does the water on the LDR table go into a reservoir when the bladder is deflated or does it just lower the height of the water?

[adbuch]

I was unaware of that. Does the water on the LDR table go into a reservoir when the bladder is deflated or does it just lower the height of the water?

I would assume the bladder is located in the tank. So depending on the size of the tank (and size of the bladder) it could all return back into the tank. I can see where a tank/bladder setup could be very handy for both draining the water tray and adjusting the water level under the cutting grates (or perhaps the ability to raise the water level right up to the material being cut. I'm not familiar with the LDR table, so I am only speculating here.

David

[SegoMan DeSigns]

This is the pic from LDR. I use a beer keg on my 2x2 table as it was cheaper than building new and pressure rated to 60PSI, one thing you have to watch is when the water level drops from evaporation you will blow air as you filling the table (that is why I told superman to go 1/3 bigger on his tank)

One of my metal suppliers uses the bladder system in their 20x50 table. Bladders can be custom made for just about everything (Wing tanks in air planes etc). I choose water over a draft design as the winters here get down to -40 and I don't want heat getting sucked out of the shop.

LDR.png

My 2x2 setup:

IMG_0358.jpg

[dhelfter]

Can not speak for all systems, but ours and all others like it that I am aware of do not have a "bladder" material. The bladder is the air.
It is simply a tank inside a tank with slots cut in the lower portion between the two. When compressed air is applied to the lower tank the air pressure forces the water to the upper tank. There are no moving parts and nothing to wear. As for pressure it takes .433 psi to raise water 1 foot at sea level, in our system we are raising it around 7 inches. The total pressure inside the tank is less than .3 psi.
All though not advantages to every user, there are many advantages to an air adjustable water table
1. lower tank holds 200% of upper tank, so requirement to add water from evaporation decreases in time
2. there is less evaporation loss when not in use as the water is stored in lower tank that has very little area exposed to atmosphere.
3. The water level can be changed quickly for different cutting jobs, and can be completely lowered to cut aluminum.
4. Water can be lowered so you do not have to fish in the murky mess to find small parts

Thanks
Dan
LDR

[tnbndr]

I thought I posted this sketch on another topic but will post here also.
This is a sketch of how the LDR Water table works. It has no physical bladder and works flawlessly. When I was shopping tables and Dan explained to me his water table system, I was skeptical and thought it couldn't work. Let me tell you it works well and I really don't understand how other manufacturers have not grabbed onto this simple but effective design.

Plasma Water Pan Sketch.jpg

You have to have the air outlet valve open when filling the water tank or adding water after evaporation.

[SegoMan DeSigns]

Here is how I "tapped" the keg, the line is 1/4" off the bottom and sealed to the keg with a plumbing boot. The SS line on the right is the air line. I installed the u shape to work as a metal trap.

P6061014- LR.jpg

When you need to clean the tank you shut the valve to the tank and blow out the keg through the fitting on bottom of the trap. I have a 1/4" regulator set at 5psi and it fills the tray in 20 sec. Control handles / levers attached to valves:

P6081051- LR.jpg

I attached the line to the tray with a bolt on flange as it has to be removed in order to R&R the water tray:

P6061020- LR.jpg

[adbuch]

Nice clean installation! Thanks for sharing.
David