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 Hello everyone,This is my first post here on the LinuxCNC forum, and also my very first CNC build — so please forgive any mistakes or lack of experience on my part. I'm doing my best to learn as I go.I'm building a plasma CNC machine and using a Mesa 7i92 card. For my setup, I’ll be connecting two 5-axis breakout boards — one on P1 and one on P2. I’m looking for a suitable firmware that would allow me to:

• Use 4 or 5 encoder inputs (for THCAD and potentially other uses)
• Have at least 10 inputs and 5 outputs for general machine control

I’ve checked the Mesa site and the firmware list, but I’m not sure which bitfile would suit this configuration best. If anyone has a firmware file that fits these needs — or could point me in the right direction — I would be very grateful.Thank you so much in advance for your help and patience. I really appreciate the knowledge and support shared in this community.Best regards,

Hello All, I'm using this post processor (PlasmaCv2.1) in Fusion 360. My issue is that my first round hole in the gcode cuts no problem, machine come downs and probes, makes a perfect cut and then the Z axis rises 1-2inches and continues along the path in the gcode but doesn't come back down to start the plasma arc, it just runs the whole program without coming back down to initiate arc and cut the material. I don't get an "arc okay" error which is odd .I went back into Fusion360 and set my retract height and clearance height to 0 to see if that would help and maybe the THC via THCAD through a MESA 7i76 board would work but it just gave me an error. "Safe Traverse Height has been reduced to 0.23in"


Images attached of my cut parameters ,material properties , gcode from Fusion 360 and some misc info. 

The machine cuts simple parts using the conversational in QTplasmaC no problem, and my THC works so I've isolated it to the Fusion 360 Gcode and unsure how to fix my issue. Possible bug maybe?

I feel like I'm doing something really dumb and overlooking something really simple, in an effort to not waste another couple days going in circles, could anyone point me in the right direction, i greatly appreciate it!
 

Daan96 wrote:

Are the following components suitable for making a voltage divider? My plasma has a 1:1 arc output.
 

Yes.

Daan96 wrote:

I'm using a TH-CAD2 in combination with two resistors in series and a 0.1uF capacitor to absorb the voltage spikes. Am I doing this correctly?
 

Yes, but wire one resistor to each side of the arc voltage, not both on the same wire. That makes it much safer in case the cable is kicked somewhere on the way to electronics and lowers the interference caused by plasma source.
And you can skip the capacitor as it does work without it, but i like to have it as it smooths the voltage readout and subsequently the torch motion up/down while cutting, but it will limit a bit the reaction speed.

Daan96 wrote:

What happens if a voltage spike does occur? Will the capacitor fail?
 

Usually nothing, if the polarity is correct.

Daan96 wrote:

Can I connect the start arc and arc OK signals directly to the Mesa board, or is it better to use a relay to protect the mesa board?
 

Yes you can, 7i96S has two fully isolated outputs ( 4 and 5 i think, double check that), so no need for relay.

Daan96 wrote:

Can I route these signals to the plasma cutter through the same cable as the THC?
 

Yes, if the resistors are mounted inside or outside the plasma source, but close to the plasma source.

@tommylight
Sorry for the questions, but I'd like to get it right the first time. I'm not yet that good with various electrical components at a detailed level.
I've read through your other threads and I think I found the right info, thank you very much!!
Are the following components suitable for making a voltage divider? My plasma has a 1:1 arc output.
I'm using a TH-CAD2 in combination with two resistors in series and a 0.1uF capacitor to absorb the voltage spikes. Am I doing this correctly?
What happens if a voltage spike does occur? Will the capacitor fail?
 

I have another question.
Can I connect the start arc and arc OK signals directly to the Mesa board, or is it better to use a relay to protect the mesa board?
Can I route these signals to the plasma cutter through the same cable as the THC?
 

For now, I think I'll test it this way.
Later, I can make a support from cut aluminum plates.

I've also ordered the plasma source.
Any other tips and tricks? 

 

 

I've decided to immediately apply a 1:3 reduction ratio, which translates to 25mm (15T) or 20mm (12T) of displacement per revolution.

I want to listen to the advice of  rodw and  tommylight

This will change the design somewhat. I think I'll place the linear guide directly on the underside of the tubes to reduce contamination.

Slowly, all the parts are arriving, and I've started welding the table. Unfortunately, I have limited time

I use mode 0.
I connected the divided arc voltage to the thcad and now the machine moves when it cuts, but it also goes on and of very often. You can see it here:



Could it also be a grounding-problem as the part is very small and I attached the ground clamp to the aluminium box where a steel grid is inside.

And why does it dive down in the middle of the part ? It seems to stop when the float switch is activated. 

The resistor(s) go in series with the plasma voltage  to the negative THCAD input
Safety wise the resistors should be in the plasma source itself.

Thanks a lot for your replies.

The stahlwerk-plasmacutters look good.
 
I already have a THCAD10 that I use for my hypertherm powermax 1000g3, but the cut quality on the hyptherm is not the best because there is a thermal dynamics-torch mounted on the machine and it doesn't cut without an angle at 10mm steel (2mm bevel to the other side). I already changed most of the parts exept the starter cartrigde, and if I can't get it to work properly I need to buy another plasma-machine. 

So I could change the Plasmacutter and still use the THCAD-10 if I add series resistors.
Maybe you can explain which exact resistor(s) I need and how exactly the resistors should be added to the plasma-cutter ? I
Somewhere I read that the THCAD should not be placed inside the controller-box ? Is that right ? So where should I put the THCAD 10 and the resistors ? 

Thanks

You can use a THCAD2 or  THCAD-10 with a series resistor
or resistors, for example  2.4M will give a 250V full scale range.

Mesa has a set of three .4W  1M .1% resistors for this purpose, when used
with a THCAD-10  or a THCAD2 set for 10V you get:

1 = 110V full scale
2 in series  210V full scale
3 in series  310V full scale

Note that lower voltage ranges improve resolution so the 210 V range is fine for most
plasma systems as it will accept continuous inputs over 1000V without damage
and voltages over 200V are not typically useful when cutting.

www.stahlwerk-schweissgeraete.de/Plasmas...ider-CUT-50-SThtml_1
www.stahlwerk-schweissgeraete.de/Plasmas...er-CUT-60-Pilot-IGBT
www.stahlwerk-schweissgeraete.de/plasma-schneidbrenner-p60
-
www.stahlwerk-schweissgeraete.de/plasmas...-cut70-pilotzuendung
www.stahlwerk-schweissgeraete.de/zubehoe...r-p-80-cnc-edelstahl
Kein divider, und kein ARC_OK, aber
noch 2 mal die 1MOhm/2W resistors und ein "reed switch/reed relay" ist alles notig, etwa 5 Euro total
dan die THCAD2 von Mesa
www.welectron.com/Mesa-Electronics-THCAD...n-A-D-Accessory-Card
sehe
linuxcnc.org/docs/devel/html/plasma/plas....html#_arc_ok_signal
forum.linuxcnc.org/plasma-laser/52203-th...able?start=30#299935
forum.linuxcnc.org/plasma-laser/52203-th...able?start=30#299958
linuxcnc.org/docs/2.8/html/plasma/plasma...ide.html#reed-arc-ok
-
forum.linuxcnc.org/plasma-laser/35349-op...ea-and-a-lot-of-info

That should pretty much cover everything... i hope!

Hi,

i'm looking for a good plasmacutter that works with plasmac.

What if the plasmacutter doesn't have an internal voltage divider ? Then the THCAD 300 would be good, but its out of stock everywhere. What is the alternative if I want to use THAD 5 oder 10 ? 

To buy a Proma voltage-divider or is there another professional-looking alternative ?
And maybe you can recommend a plasmacutter for plasmaC ?

Thanks.

Master is 2.10

So you would need to build from source or get a snapshot from the buildbot
to update to master.

BUT... you should be able to just replace the current pncconf pieces with these:

forum.linuxcnc.org/39-pncconf/56464-mesa...thcad-pncconf-screen

( Thanks kworm )


Another option is MesaCT which has had 7I95/7I95T support for a long time.

 

possible solution

forum.linuxcnc.org/39-pncconf/56464-mesa...thcad-pncconf-screen    

thnx kworm