Posts tagged #plasma

CNC Plasma Dinosaur Project

I worked on a quick side project today as a wedding present.  I used my Grunblau CNC to plasma cut a dinosaur and then welded it together with the TIG welder.  It was a good chance to test some changes I made to the packaging of the torch height control electronics and the effectiveness of the water table.

I had some initial issues with the tip plunging into the material, but after replacing the consumables and fiddling with the THC settings a bit it ended up working quite well.  The cuts came out pretty clean:

Also, the water table worked very well for reducing the smoke and fumes.  Moreover the grate is still working well for supporting the pieces.  There is very little cut-through so far and the holes are small enough to prevent parts from falling through.

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I made a vide of the cutting and welding process:

And the end result turned out well:

Now back to the 3D printer project!








Posted on April 15, 2015 and filed under Projects, CNC Machining.

Plasma CNC Water Storage System

I finally had time to assemble all of the parts to the water storage system for the water table. I ended up using kegs as water storage containers since they're designed to handle the pressure. The system uses compressed air to force the water up into the table from the kegs.

The good news is that it works well! It fills in a few minutes and drains in about 10 minutes. I'll probably end up welding a bung for the drain to increase the water flow or modify the tap to increase the output diameter. But for now it's functional. And I definitely need to add a baffle on the outputs; the water splashes up when you start & end the filling process.

The bad news is that it only works with the kegs vertical. And unfortunately they are about 1/2" too tall to fit underneath the stand I built. I have two options: 1) cut big holes in the top sheet to fit the tops of the tanks, or 2) raise the whole table about 1". I haven't decided yet which approach to take.

Also, there were a few drops leaking from underneath the 2nd time I filled it. i'll have to check it again to make sure there's no additional pinpoint leaks I missed in my previous tests.

I made a video walking through how it all works:

Posted on April 13, 2014 .

Plasma Water Table

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.

Posted on March 29, 2014 .