Upgrade of CNC Plasma Cutting Table with Mesa 7i96S, THCAD-2 And MyOhmic PRO

Hi all and thank you for checking this topic!

Little intro to my project and why I cam here.
I'm here asking for help with upgrading my table. I've bought a CNC plasma cutting table with the hope of starting my own thing and because it looked like a lot of fun. Couple of months down the road it turned out that the table is more on the hobbyist side than I would like. So I decided to start upgrading it in order to have higher quality cuts that I can be proud of.

My current setup.

PLASMA SOURCE

• Unit: Sherman CNC 130 (CNC variant).
• Divided arc output: 1:20 divider present on the machine (available for THC feedback).

CONTROL

• Unknown motion  control board
• Unknown THC controller

MOTION, DRIVES, AND POWER

• Motors: stepper-based system in use - Nema 24 - 60bhh86-300e-24db 
• Stepper drivers: 3 × CW-5045 in use for X, Y1/Y2, Z. (
• X/Y motion: rack & pinion, 
• Z motion: drive type ballscrew.
• Installed Power: 400VA transformer labeled “230V / 12A” and “SMT 400VA”. This is a step-down transformer: it takes the 230VAC mains in and produces about 30VAC (at up to 12A) on the secondary. After a bridge rectifier and filter capacitor, that 30VAC becomes roughly 42VDC.

CONTROL AND SOFTWARE

• CAM: SheetCam (current workflow).
• Machine control (current): Mach3.

TABLE

• 3.5 × 2.0 m with water bed.

My plan.

• Move to LinuxCNC with QtPlasmaC.
• Move to Mesa 7i96S: Ethernet motion interface
• Move to Mesa THCAD-2: for 1:20 arc-voltage THC input
• Move to MyOhmic PRO
• Install limit switches
• Use 18 AWG (0.75mm2) shielded cables for the up to 24V connections
• Use 16 AWG (1.5mm2) shielded cables for the connections that are more than 24v

In short: to replace the controls, cables, add limit switches and keep the rest

The diagram.
I've reused a diagram from the forum (I believe that it's LOWRIDER3) which turns out to be immense help, I'm not sure I would be able to come up with anything useful if it wasn't for it!

I'm adding the diagram itself so that you good folks can make comments, recommendations, critiques. Thank you all in advance!

I thought the THCAD can do the job of the Promo Ohmic sensing system?
Or perhaps one need an additional THCAD arc-voltage reader.
Plasma-guys, you know this.

Looks great. I will be interested in how you go with the My Ohmic Pro. I was sent an evaluation one and its beautifully engineered. I just had nothing to try it out on. The THCAD for Ohmic struggles on Water tables so hopefully it proves a more robust solution. Lukaz at Proma said he was very proud of the water handling of the  My Ohmic Pro

Be sure to add an EMI filter on your mains input to avoid electrical noise. You can get them built into an IEC connector. even with a power switch and fuse built in.

If using a THCAD for ohmic sensing has issues with water. the most likely issue
is that the sense  resistor is too high a value.

Thanks everyone for the feedback. I’ll keep you posted as things progress.