The second step in preparing the Grunblau Platform CNC was designing a water table insert. I wanted something fairly light that I could take in and out to clean by myself, but sturdy enough to handle a significant chunk of steel sitting on it. I chose to build a water pan out of 18 gauge steel. The pan is supported underneath by the cross braces on the Platform table.
I started with a flat sheet. I cut the corners out with the plasma torch by hand, and then I bent up the sides using a metal brake I built attached to my jig table:
Next I test-fitted the bent-up bed into the Platform CNC to make sure I had it the right size. I determined that I had to trim a bit off of the top edge of the table, but otherwise it fit well.
I then took the scrap bits I cut off to form corners to weld in. This is the first time I welded 18 gauge steel, so I chose to double weld both the front & back sides of the seams. This ended up making the task harder than necessary:
And then I had to test the table for leaks. I took it outside and filled it up with water. I found a couple of leaks that were easy to fix with a second pass of the Tig welder:
The next step was fabricating the support braces to fit inside the table. I chose a simple design based upon material I already had available: I cut slots in three angle-iron pieces, and trimmed 2" wide slats out of the remaining 18-gauge steel sheet. Then I bent the slats to go between the slots. This makes it very easy to replace the slats as they get damaged with the plasma cutting:
Finally, on top of the insert I added a sheet of 9-gauge expanded metal. The theory of this is the expanded sheet has raised points minimizing surface contact area that the plasma can cut, while at the same time providing a great support structure for the material to be cut. Moreover, this expanded sheet helps protect the underlying slats extending their lifespan. And when the expanded sheet gets too damaged, it can be very easily removed & replaced:
I am still running tests, but so far this configuration is working very well. In the next article I will describe the water storage & air pressure forced feed system used to fill/drain the table and show some of the test runs.