Plasma Cutter Gen 2 - Part 16: Water Table
When you build a CNC plasma cutting table, you generally have three options for how to deal with the fumes from the cutting process. These options are as follows:
1. Do nothing. If you don't like your lungs, or the lungs of your operators, or no one is around while the machine is cutting, just cut over slats and the fumes go where they want. I wouldn't recommend this route unless the plasma cutter is outside the building, or it's in its own room with heavy airflow.
2. Downdraft table. An downdraft table is essentially an enclosed area beneath the slats, but open up top, kind of like a hopper. There is airflow in the downdraft table that sucks the fumes down, and away from the table and usually outside from that point. This is effective with enough airflow (it requires a lot of airflow, dependent on the size of your table, length and size of ducting, etc.
3. Water table. This is basically a large pan that holds water, and has slats integrated into it. The fumes get thrown straight down from the plasma cutter into the water, and it absorbs most of the fumes. It's cheaper and easier to build a water table than a downdraft, because of the need of such a high flow fan. Another great side effect is that the water cools your part as it's cutting, reducing warpage and making the part cool to the touch once it's finished cutting. The downside is that the water can get pretty dirty over time, and can stain your parts. Washing with a brush or scotchbrite and soapy water does a good job of cleaning, but aluminum is stained very easily. Doing regular water changes, and cleaning of the table will minimize the staining, but it's a dirty job and takes a lot of time to do often.
With all that said, we like the water table, and it works well for our needs. When our Gen 2 table was up and operational, we initially used our 4 x 6 foot water table from our first gen. Well, a 5 x 10 foot table is pretty unusable with a table half the size needed, so we finally found the time to build a new table at the proper dimensions.
We cut slat holders in a certain shape, using the 4 x 6 foot water table, that allow water to flow over, under, and through them, once full of water and plasma drops. We had to cut them in shorter sections and weld them into longer sections, since we only had 6 feet to work with on the old water table. We used 3"x3"x3/16" steel angle for the framing of the table, and welded a 5 x10 foot sheet of 10ga steel under it. We used 16ga on the first table, since it's main goal is to hold water and not support any weight. However, it warped all over the place from welding, and it made draining the table difficult, so we just used the thicker 10ga this time around.