I wrote this up in chat gpt pretty quickly I think it just about covers all of the bases here of the project.

CNC Plasma Table – Electrical & Wiring Requirements

Project: Remote design of electrical system + wiring documentation for LinuxCNC plasma table
Client: TCB Metal Works

1. Project Overview

You will remotely design the complete electrical and control system for a custom CNC plasma cutting table powered by LinuxCNC.

You will create:

Complete wiring diagram set (schematic + physical routing)

Full Bill of Materials (BOM) with real part numbers

Wire gauge, shielding, grounding, and EMI mitigation plan

Bulkhead connector list + panel layout

Mesa board selection + full LinuxCNC I/O map

Integration notes for all components

Testing & commissioning checklist

This is a 100% remote engineering job — no physical inspection of hardware is required.

2. Available Power Sources

Near the machine:

220 VAC available

460 VAC available

No dedicated 110/120 VAC, which must be generated using a control transformer if needed

Engineer must design the incoming power strategy and transformer selection.

3. Motion Hardware
3.1 X & Y Axis – AC Servos (Provided)

3× A6 Series 1000W RS485 AC Servo Motor Kits

3000 rpm

3.18 Nm

17-bit absolute encoder

IP67 motors

Axis layout:

Y axis: 2 servos (dual-drive gantry)

X axis: 1 servo

Notes:

Motor-to-drive cables are already supplied by the manufacturer.

You do not need to design or evaluate those cables.

Engineer must:

Design AC mains wiring to each servo drive

Design control, enable, alarm, and ESTOP signal wiring between drives and Mesa

Include needed fuses, breakers, filters, and terminals

Provide cabinet layout and routing plan

Include proper grounding and shielding recommendations

3.2 Z Axis – Stepper Motor (Needs Driver + Cable)

PV267-D2.8AA stepper motor — Oriental Motor

Stepper driver not provided

Stepper motor cable not provided

Engineer must:

Select a compatible stepper driver suitable for PV267-D2.8AA + LinuxCNC step/dir

Define driver voltage supply requirements

Design:

Step/Dir wiring from Mesa

Motor wiring from driver to Z motor

Required cable shielding, gauge, and insulation

Connector type and strain relief

4. Control Electronics (Mesa + Power)

Engineer must select Mesa hardware capable of supporting:

3× servo axes

1× stepper axis

THC-AD

Ohmic sensing

All limit/floating switches

Plasma start / Arc OK

E-stop & safety I/O

Deliverables:

Recommended Mesa board combination (e.g., 7i76E, 7i96S, 7i85, THCAD, etc.)

Justification for chosen hardware

Complete LinuxCNC I/O mapping

Required DC power supplies (24V / 5V / others)

Proper AC distribution, fuses, breakers, and protection devices

5. Torch Height & Ohmic Sensing
5.1 THC-AD Integration

Engineer must design:

Raw arc voltage wiring from Hypertherm HT2000 to THC-AD

THC-AD signal wiring to Mesa

Required shielding and filtering

Scaling notes for LinuxCNC

5.2 Ohmic Sensing (Planned)

Engineer must:

Recommend a compatible ohmic board

Provide wiring diagram for torch → ohmic board → Mesa

Specify cable type and shielding

Document signal polarity & behavior

6. Hypertherm HT2000 Integration

Engineer must design wiring for:

Required signals

Torch start / trigger

Arc OK

Raw arc voltage (+/–) into THC-AD

Required protection

Isolation (if needed)

Surge suppression

Filtering

EMI protection

Routing rules

Arc voltage wiring must be kept separate from low-voltage control wiring

7. Limit Switches & Floating Head
X Axis

2 limit switches:

X-min

X-max

Y Axis (Dual Gantry Drive)

2 limit switches:

Y-min

Y-max

Engineer must propose a reliable gantry squaring / homing method for the two Y motors.

Z Axis

2 end-of-travel limit switches:

Z-min

Z-max

1 floating-head switch (touch-off)

Engineer must:

Select appropriate switch type (mechanical or prox)

Provide wiring diagrams to Mesa

Specify wire gauge, shielding, and cable routing

Provide LinuxCNC input mapping

Include any debouncing/filtering requirements

8. Wiring, Shielding, & EMI

Engineer must specify:

Wire gauges for:

AC mains

Servo drive feeds

Stepper driver feeds

Stepper motor wiring

Limit/floating/ohmic wires

Plasma signals

DC supply lines

Shielding requirements for:

Step/dir

Limits/floating/ohmic

Arc voltage

THC-AD lines

EMI considerations

Cable separation

Ferrite locations

Filtering recommendations

9. Grounding & Bonding

The engineer must design the grounding/bonding approach.

Important physical detail:

The water table, gantry, and control cabinet are three separate physical assemblies.

The engineer must account for this when designing:

Grounding/bonding layout

EMC/EMI mitigation

Plasma return path considerations

Ohmic sensing grounding

No grounding method (star, bus, single-point, etc.) is mandated — the engineer chooses the correct approach.

10. Control Cabinet & Bulkheads

Engineer must design:

Cabinet Layout

AC distribution, transformers, PSUs

Mesa boards

Servo drives

Stepper driver

Fuses, breakers, contactors

DIN rail layout

Ventilation/fans

Bulkhead Connectors

Used wherever practical for:

Servo cables (using glands or pass-throughs)

Z stepper cable

Limit/floating switches

Ohmic sensing

Plasma start / Arc OK

E-stop / operator controls

Ethernet access

Engineer must specify:

Connector type

Pinout

Panel cutout style

Labeling

11. Documentation Package

Engineer must deliver:

11.1 Wiring Diagram Set

Full schematic

Cabinet wiring

Field wiring

Power distribution

Grounding/bonding

Bulkhead connector pinouts

11.2 BOM

Complete list of:

Mesa hardware

Stepper driver

Transformers / PSUs

Switches

Connectors

Wire/cable

Protection devices

Cabinet hardware

11.3 I/O Map

All LinuxCNC inputs/outputs

Axis definitions

THC/ohmic mappings

E-stop & safety signals

11.4 Commissioning Checklist

Power-up verification

Servo enable/jog

Stepper test

Homing / gantry squaring

Z floating-head test

Plasma start / Arc OK

THC test

Ohmic test

EMI/noise checks

Hello community!
I have a Mesa 7i76e running, the wiring is correct except for the alarm loop. Using a Lenovo ThinkCentre M910q with i7 4-core, 256/GB NVMe SSD, i7 16GB RAM WLAN Intel Core i7-6700T 4x 2.80 - 3.60GHz with Linuxcnc 2.9.4, Probe Basic V.5 on Debian 12. No latency problems.

Once again, I'm here with a big problem. My DIY milling machine (1000x500x220 with aluminum profile frame, 20mm HGR, 1605 ball screws, 3 axes, 2x OMC Stpperonline 400W integrated servo, 1x JMC CL Stepper 3.5Nm, set 2000 steps/rev) is now mechanically finally assembled. I also got a lot of help from this forum in setting up LinuxCNC, eliminating latency problems and spindle control problems, but now I have a milling problem that I can't solve.

I have milled several test parts with drill holes, 2 circular pockets, and a rectangular outer contour, and have noticed that my circular pockets are becoming elliptical. The deviations in Y are approximately +0.35 mm at 45° and approximately -0.38 mm at 135°. The X values for the rectangular contour are perfect to within 0.01 mm in X and 0.09 mm in Y, X I consider to be acceptable, but Y is over tolerance. However, the circular movements contain deviations I cannot tolerate. I will show you a photo of the last test piece. After each individual test part, I made changes to rule out certain things.
The first change was to replace a simple Chinese C7 ball screw with a ground C5 spindle with double nuts. This reduced the originally even higher values by almost half. However, the deviations described above remained. After the next test part, I replaced the 400 W servo with a 3.5 Nm JMC CL stepper motor. The results remained almost the same. As a final attempt, a few days ago I replaced the spindle's fixed bearing with a new one, with 7002AC angular contact bearings in an O-arrangement with a 1 mm spacer ring between the outer rings. I inspected the previous fixed bearing and found no faults. There was a 1mm spacer also and the O arrangement was the same.  I had also taken measurements at the spindle end earlier and actually and found no backlash.

Yesterday, moving away from mechanical faults, I noticed a difference in the motor definitions for the X and Y axes in the .ini file. The Ferror and min_Ferror points differed by one decimal place. X was set to 0.1 and 0.01, while the Y axis was set to 1.0 and 0.1. After I corrected this difference, the motor on the Y axis went into alarm mode after a few position changes.

What could be the reason for this? How can it be that one motor runs perfectly with much lower tolerance values, while the other quickly goes into alarm mode with less load? The motor in question has the same power supply and is certainly less demanding in terms of starting currents than the servo on the X-axis. With the higher tolerance values, the Y motor runs without alarm, but has these deviations. Are these tolerance values in the .ini file responsible for these deviations?
The mechanics of the Y and Z axes are flawless, as checked with a dial gauge, and the repeat accuracy is also very good, less than one hundredth. 
Do you have any ideas about this? Where can I look further?
Thanks for your time and hints    

 

Hi,
i am currently trying to setup my Mesa 7i95T but so far i hit a wall.
Problem is even after following a video to set it up via pncconf using the 7i76e, i get no working results.
The video i am reffering to : 

Check the images to what im reffering to.

Perhaps there are files out for the 7i95T.

And yes i did check the forum and tried to update the pncconf but it wont let me.

Kind regrads
Ringardy
 

I am looking to buy a "firewall" PC with 4 ethernet ports to have one ethernet port for my mesa 7i76e one for ethercat and one for LAN.
Do you have recommendations for that currently I am looking at this system on amazon:  amzn.to/4nEujde it has 4 x i226-V 2.5Gigabit Ethernet ports and seems to be fine for a linuxcnc build what do you think.

Or do you think I should rather get a normal big pc and get pci-express lan cards?
 

So werde ich es machen.
Vielen lieben Dank!

I would probably add a series resistor so so if you accidentally ground the ALM- output you do not damage the optocoupler

so:

+12V --> 1K resistor --> ALM+
ALM- --> 7I76EU input

I read the  Which Mesa Card Should I Buy?  post and it was super helpful.

I wanted to buy a Mesa 7i76EU card today but they are out of stock. They are also out of stock on the 7i77 daughter card.

So, I hope to buy a  7i96S today, but I need to know what daughter board I can use to increase the number of inputs an outputs?

Can I use the  7i76U ?

I am doing a manual lathe CNC conversion. I'm eventually going to be adding a 12 tool ATC turret.

I have not finalized all the required I/O yet, so I wanna make sure that I have enough I/O for future updates to the lathe.

If I can use the  7i76U , I think I will have plenty of I/O for future updates, that may include​ ...

• a third MPG
• an encoder on the ATC turret for tool location/identification,
• a "Y" axis, three motor, four gang live tool option with an MPG (this last addition is way in the future if at all). 

Thanks,
Chris​​​​​​

@PCW, @tommylight,
vielen Dank für die Tipps.
Wenn ich meine 12V direkt auf den Alarm des Motors geben kann, wäre das natürlich das einfachste.

@PCW
In der Beschreibung des Schrittmotores habe ich nun auch die richtige Stelle gefunden.
 
Was meinst du, ist der Vorwiederstand bereits im Motor verbaut, oder sollte ich da einen vorsetzen?

Danke und Grüße,
2tinker

The drive manual shows that the alarm output is an optocoupler
This can connect directly to the 7I76UE field inputs


+24V --> ALM+
ALM- --> 7I76EU field input

 

Meinst du ein mechanisches Relay?

Wenn das Alarmsignal des Steppmotors nur 5 V liefert dann schalte doch mit dieser ein Relais das die 12 V Ein und Ausschaltet
und lege die 12 V auf den PIN

Juergen

Ich habe das Support Manual.

"The 7I76EU field inputs have a nominal input resistance of 10K Ohms to field power ground. 7I76EU inputs sense positive input voltages above a preset threshold. For best general purpose use, default input threshold is 50% of the field power supply voltage with 10% hysteresis. That is with a 24V field voltage an input must be brought to 60% of 24V= 14.4V to be sensed as high and then brought to 40% of 24V = 9.6V to be sensed as low.These accurate thresholds and hysteresis allow high speed field signal detection whilemaintaining excellent noise immunity."

So wie ich das verstehe müssten bei 12V mindestens 7,2V anliegen um ein "High"-Signal zu erhalten.
Damit komme ich ohne eine kleine Verstärkerschaltung nicht weiter.
Richtig?

Als Schrittmotor möchte ich gerne diese verwenden...
www.omc-stepperonline.com/ess-series-2-2...vdc-1000cpr-ess23-20

Do you have the drive manual?

Is this a 5V push-pull output?

 

Dank Hilfe aus diesem Forum bin ich jetzt ein Stückchen weiter.
Den I/O-Bereich meine 7i76eu (TB1) habe ich an einen 12V Ausgang meines ATX-Netzteiles angeschlossen. Ebenso den P4 (mit 5V).
Die Näherungssensoren für „Home“ liefern entsprechend ein verwertbares „True“ auf der Karte.
Ein SSR, dass das 48V-Netzteil für die Schrittmotoren einschaltet funktioniert auch.
(Netter Nebeneffekt ist, das ich mir das Enabled der Motoren sparen kann)
Jetzt stehe ich vor der Frage, wie ich das Alarmsignal der geplanten Closed-Loop-Schrittmotoren (die ja nur 5V liefern) in die Software bringe.
Die „Input’s“ der Karte scheinen nur auf die 12V zu reagieren.

=11.0ptMuss ich da einen Transistor zwischenschalten, der mir aus den 5V ein 12V Signal macht?
=11.0ptWenn ja, was sollte ich da am besten nehmen (Transistor/Schaltung)=11.0ptOder gibt es noch eine andere Möglichkeit?

Grüße, 2tinker