Early Plasma Cutter Experiments

 

What makes a quality CNC Plasma Cutter

Here are a list of requirements I came up with for a quality CNC plasma cutter.

  • The CNC needs to achieve .3Gs on both the X and Y axis.
  • The CNC needs to achieve a feed speed of at least 300IPM.

In addition to the above feed specs, the plasma cutter will also need the following:

  • Some sort of touch off for arc start and cut height settings.
  • Curved slats for stability.
  • Good quality compressed air. (Clean and Dry)
  • Down Draft or water table
  • THC for larger thinner cuts

You don't want any kind of wiggle or vibration during the cuts.  And while the plasma cnc does not add a cutting load, moving a large torch with cable can add to the stress of the machine.  For this reason the machine must also be super rigid at the above feed speeds. 

Early Plasma Cutter Experiments

A couple years ago, I started serious research into designing and building a quality plasma cutter CNC.

Here you can see one of my prototypes.

This particular one used belts on the X and Y carriages. It was only after my full speed tests that I realized a belt drive system on a plasma cutter will not yield quality cuts.

 

Belt drives stretch, especially during fast acceleration and deceleration. This caused little wiggles at the end of high speed movement.  

KRMx02 as a CNC Plasma Cutter

I converted converted my smaller KRMx02 build to a plasma cutter a while back and was able to perform a multitude of experiments.

Here its connected to my Hypertherm Powermax 65.

It has an Ohmic sensor as well as a floating head that is used to stop the machine if the Ohmic sensor fails.

The machine has its own down draft system venting outside the shop. 

I experimented with both an Everlast 50s plasma cutter and a Powermax 65 and both performed very well. The Powermax 65 has more features and its documented settings for various materials is a plus. It is a Air hog though, and I had to upgrade my compressor.

The Everlast 50s cut very well and will be the unit I will be initially testing on the CNC Construction Set plasma build. Note that I don't have a machine torch for the 50s, but the design of the torch makes it very easy to mount.

The KRMx02 was able to exceed the acceleration and speed requirements I was looking for.

When my testing was complete, the KRMx02 plasma cutter worked so well that I use it for a lot of my steel fabrication projects.

I made some fixtures to hold steel angle and bar stock.  It only has a 18 x 14 cutting area but, works very well for most of my fabrication needs.

 

Here is the KRMx02 cutting some steel motor and bearing mounts for the original Titan CNC.

You can read more about my KRMx02 plasma experiments here:

KRMx02 Plasma Experiments

 

 

I never had a THC on the KRMx02, but since most of my work was on steel angle using my fixtures it was not needed.  For the CNC Construction set, I plan on testing both capacitance and voltage based THC's.