CNC Plasma - Moving Gantry vs Moving workpiece?

Hello all,

I am at a conceptual stage of a CNC Plasma build. The main application will be automotive flanges and small brackets - so i am planning to make something relatively small compared to typical designs - 1x1m.

A suggestion was that the quality of the cuts might be better if the torch was stationary whilst the workpiece moved underneath.

I can only find examples of moving gantry type machines.I am thinking about building a jig to test the theory - but obviously don't want to reinvent the wheel.

Any thoughts? Given that my biggest part I will want to make might be 300mm x 500mm I could probably afford the lack of economy in building a moving workpiece (what is the correct terminology for this?) CNC.

The type you are talking about would be a moving table in the mill or router counterpart. That isn't the way to go with a plasma cutter though.
Consider this.
It is much harder to move a table with all the material and table weight than it is to move a gantry and small torch. Sometimes plasma needs to move pretty fast. Your bearings would also need to be under the table at some point and that is directly where all the sparks and debris fly. Also many like to use a water table to capture as much trash as possible. Can't do that easily on a moving table. Moving tables also require a larger footprint.

These are just off the top of my head. I'm sure there are other reasons as well.

While the gantry on my plasma cutter build is a little beefier than some, it will do some rotary cutting too at some point. That really isn't needed with plasma only, so you can get away with a very light weight gantry. It needs to be rigid enough not to bow under it's own weight, but really not much more than that.
Take a look through this section at some of the plasma designs. I don't recall ever seeing one with a fixed gantry and for good reason.