Saturday, March 20, 2010

Plasma and BACON!

Well, no bacon but we did fire up the plasma cutter tonight and have some interesting results.

Aluminum bad.  The current supply doesn't seem to have enough power to cut through AL.  Seems the heat conduction is too much.  It cuts, but verry, verry slowly.  See photos.

Next up was 0.035" steel, cuts quickly and easily.  Clean on top but dirty on the bottom.  cut width is 0.030" with the head contacting the surface and 0.50" raised up 0.125".

Finally we tried the 0.075".  Slowest of all, but does give reasanable cutting action.  Tilting the work head up to 45 degrees seems to provide much faster and cleaner cutting.  Not sure how to make the CNC head do this.  Estimate 12" / min with the head tilted, slower with head perpendicular.  Higher air pressure might help this, but the available compressor can't keep up to much more than 60 psi continuous.

Arc needs to be started at 30 PSI, then raised to 50 for cutting.

Arc must be started by grounding the tip, which will start the plasma inside.  This could be problematic for the CNC version because we don't really want to automate the third axis if we can avoid it.  One idea would be to build a circuit that momentarily connects the outside of the tip to positive to start the arc.  This circuit can then be removed and the arc will jump to the material to be cut.

A general problem with flame cutting flat material is warping.  This may not be a problem with our setup because the heat input is quite low, but if it is we could add a caster to the cutting head and let it ride up and down with the material as the machine moves.

The wiring is pretty kludgy at this point, but we can clean it up a bit as we start to pull the system together.  It's in proof-of-concept phase now.

We'll need to get some shade 6 welding glasses.  The shade 11 welding helmet was just too dark to see much, and there's loads of UV and too much light to do without protection.


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