OK so open my eyes to Linux CNC

[N2 Welding]

More than a couple mentioned some benefits of building a table based on Linux CNC and MESA hardware. Not sure what version of Linux is required. Mint? Ubuntu? I had another friend suggest at least installing Linux and giving it a try. His hang up was the file structuring and storage of saving and finding saved files. I have never used Linux outside of a live cd for cloning disks etc.

You have a very closed mind so its probably best you stick with Windows software. Just be aware external THC's cannot compete with ones embedded n the motion controller which is how linuxcnc works. That is because the motion controller knows everything going on and extenral THC's fly blind.

Mesa is a long standing company specialising in motion hardware, particularly for linuxcnc. The owner is a very active member of the linuxcnc forum and tirelessly offers support to users and is on hand to answer any questions about his hardware. Thousands of machines use Mesa hardware. Hundreds of rtrofitters breathe new life into old iron machines with mesa and linuxcnc. Tormach uses linuxcnc and mesa cards and CommandCNC also uses mesa hardware with their linuxcnc system.


For Plasma you need a 7i96s and a THCAD-2 as I said before. Building a plasma config using this hardware is supported by pncconf, the mesa configuration tool bundled with linuxcnc.

The price is not bad for both controller board and THC board. What type of software can be used on Linux based os? Do I create and edit my cut files in a Windows environment then convert and or transfer to the Linux CNC?

My plasma cutter TD 60i has a built in voltage divider machine board that allows me to select the divided arc voltage as well as iirc collision detection with Ohmic sensing. The TD 60i uses both non shielded and shielded consumables for Ohmic sensing. Once again iirc the non shielded consumables use a wire from the pip to sense Ohmictouch and the shielded consumables require the external wire to clip to the Ohmic clip. This is where I get confused. If I use shielded or non shielded, does my machine still only use two signal wires out to the THC unit. Trying to understand how it works.

Then with that in mind how does that work with the THCAD-2

[Rodw]

If your machine has the TD automation interface there is a circular connector at the rear of the machine. It outputs divided voltage, transfer or arcOK and an input for the torch on signal. You really should use the machine torch as there are sensors to disable the machine if a hand torch is installed. Ohmic sensing is not part of this connector.
ArcOK is an internal relay turns on when the machine has a valid arc and off if the arc is lost. Field power (24v in the Mesa world) is snet to this relay and back to an input. It is intended to tell the CNC controller if there is a problem so the machine will stop if the signal is lost.

I only ever used shielded consumables on my TD A120. Forget the unshielded ones. The ohmic sensor circuit is described in the documents at Linuxcnc. A seperate isolated power supply is connected to the ohmic clip and the material. When the torch shield touches the material, the circuit closes and contact is sensed to set the material height.

The THCAD-2 is a fast highly accuate voltage to frequency interface that can handle overvoltage of 500 volts. Each one is individually calibrated. It has 2 voltage ranges 10 volts or 5 volts. Use 10 volts for torch voltage and a 20:1 or 30:1 voltage divider setting on the plasma cutter to give a 200 volt or 300 volt full scale. The divided voltage is attached to the High voltage inout. The low voltage frequncy output is attached to an encoder input on the mesa card and linuxcnc converts the frequency back to a voltage in software (1000 times a second). Linuxcnc uses this voltage to control torch height internally via its sophisticated PID capabilities.

It is possible to use a THCAD-2 set on the 5 volt range and a software component I wrote to do the ohmic sensing. It can sense the rise and fall of the voltage as the ohmic clip makes and breaks contact with the material. Breaking contact is where its at as the probe makes contact then moves off slowly to get an accurate height. As soon as a downward trend is confirmed against a moving average, it turns the probe off so its very sensitive as it triggers at much higher voltages than a relay would.

If you know what you are doing, you can get probing happening super fast. Probing is time and time is money. We dont waste much in this video....

[N2 Welding]

If your machine has the TD automation interface there is a circular connector at the rear of the machine. It outputs divided voltage, transfer or arcOK and an input for the torch on signal. You really should use the machine torch as there are sensors to disable the machine if a hand torch is installed. Ohmic sensing is not part of this connector.
ArcOK is an internal relay turns on when the machine has a valid arc and off if the arc is lost. Field power (24v in the Mesa world) is snet to this relay and back to an input. It is intended to tell the CNC controller if there is a problem so the machine will stop if the signal is lost.

I only ever used shielded consumables on my TD A120. Forget the unshielded ones. The ohmic sensor circuit is described in the documents at Linuxcnc. A seperate isolated power supply is connected to the ohmic clip and the material. When the torch shield touches the material, the circuit closes and contact is sensed to set the material height.

I did purchase the TD SL100SV 180 deg 25' torch and it is sitting in a box waiting to have some fun

Ok going from the diagrams in the TD CM 60i and A60i manuals I am confused as to how the Ohmic works. Please look at these diagrams and confirm what you are saying is correct.

The info I read about Ohmic is the unshielded consumables still have Ohmic abilities and are used for 40 amps and less cutting, marking etc and anything more than 40 amps should be using the shielded consumables.

[Rodw]

Thats cool we don't get your machine in Australia.
Its cool!
So depending on the way you wire your machine, active high or active low (I use active high).
SO in my case I would take +24 volts field power from the control box, attach it to pin 10 common and connect pin 11 to a mesa input. (Check with TD if it will handle 24 volts first.) So when contact is made, the mesa card sees it.

Use 20:1 divider too (200v). It will likely be exceeded during piearcing but we don't look at what the voltage is at that point and the 500v overvoltage covers it.
Cutting will arely go over 130 volts so you are using the best resolution of the 10 v full scale.

I would probably set it up so there was a switch (could be in the GUI) so that you could also use conventional ohmic on the shield. In linuxcnc terms you would attach both to seperate inputs and you would use a mux2 component to select which input was used based on the switch position.

[Rodw]

This will involve hand coding of your hal file but worry about that later once you have a working system

Linuxcnc qtplasmac has custom user buttons and you could use one that toggles a hal pin attached to mux2.0.sel
button: http://linuxcnc.org/docs/2.9/html/plasm ... er-buttons
mux2: http://linuxcnc.org/docs/2.9/html/man/man9/mux2.9.html
each ohmic input would be attached to mux2.0.in0 and mux2.0.in1
and mux2.0.out wuld be attached to the plasmac probe input.
toggling the button will change the probe type

Its this sort of stuff that gives you enormous flexibility with linuxcnc that you can't get with other systems. Even though it might do your head in....

[N2 Welding]

yeah my head and eyes are already hurting :/ I can only do so much reading per sitting before my eyes and head feel like they are going to explode. I have had cataract surgery in both eyes in addition to procedures to stabilize Macular/retinal hemorrhaging so the less reading the better off I am. Besides I learn better when watching vs reading about the topic.

[N2 Welding]

This will involve hand coding of your hal file but worry about that later once you have a working system

Linuxcnc qtplasmac has custom user buttons and you could use one that toggles a hal pin attached to mux2.0.sel
button: http://linuxcnc.org/docs/2.9/html/plasm ... er-buttons
mux2: http://linuxcnc.org/docs/2.9/html/man/man9/mux2.9.html
each ohmic input would be attached to mux2.0.in0 and mux2.0.in1
and mux2.0.out wuld be attached to the plasmac probe input.
toggling the button will change the probe type

Its this sort of stuff that gives you enormous flexibility with linuxcnc that you can't get with other systems. Even though it might do your head in....

I’m thinking pins 10 & 11 send the signal to the THC unit for any unshielded torch consumables without Ohmic clip and pin 13 is used with the Ohmic clip and shielding cup to send signal to the 60i then back out through same pins 10 & 11. Trying to make sense of the wiring configuration.

Edit: I had to google what a Male Faston was for the Ohmic sense wire at pin 13. Turns out it is just a regular spade wire connector.

[Rodw]

Maybe. Same concept would apply but would work off the common so it would just be a wire to the ohmic clip. It would save you some wiring!

[Rodw]

Actually, it might be either or so instead of mux2 you could use an or2 component

[N2 Welding]

Actually, it might be either or so instead of mux2 you could use an or2 component

That is way over my head atm

[Rodw]

A bit wise or..... so if either pin goes true, or both are true, the output to linuxcnc probe input will go true