Hi. I have diy plasma cnc (3000x1500mm) using cncrouterparts rack and pinion running on Hiwin LM guide. It is 3 years old now. It has more than 7000 pierces by Powermax 65. I want to build the next plasma machine using OX base with the same size as the old one. I am interested what you do, but in my opinion you should place the both y motors on the outer side. The plasma sparks during cutting will destroy or at least malfunction your motors, and if you use water table the situation will be worse. The idea to hide the belts from plasma torch is good.
Your idea with C beam on y gantry is great, belt driven and tight Z axis mount. I really want to know how perform the gt3 on long axis..

 

Maybe I can help you. I am using sheetcam since 3 years ago, it is great for plasma. Sheetcam can not do zeroing Z axis, the cnc controller does the job. We can program the sheetcam to slow down on corners, how lead in and lead out go, inside or outside cut direction, feedrate etc.
The THC controller like Neuron THC ( mine is Neuron Lite) receives the float head signal or Ohmic sensor sensing the top surface of a metal sheet that will be cut during Initial Height Sensing (IHS procedure), this signal talks to Neuron how height the zero Z. Neuron retracks the Z to a pierc height (according to plasma manufacture manual), piercing, then Neuron sends commands to cnc controller like UCCNC (mine is UC ETH400) to move the x and y axis. During cutting THC controls the Z height up and down to maintain cut height about 1,5 mm above the metal sheet. Sheetcam commands the THC to off on all corners to prevent torch dive, including on small circles, but it is done before by path programming in sheetcam.
As far as I know the Torch Height Control (THC) measures the zero Z, if there is no THC the cnc controller does the job. All serious plasma cnc builders use THC, THC IS A MUST for plasma cnc.

 

Hi there
I am a newbie as well in cnc and I am currently building my plasma cutter but haven't yet found a legit THC that I can trust.
Could you maybe recommend a brand ?
Thanks