15m Industrial Plasma Cutter

there are lots of good cheep costructions online
let me upload mine Monster
sorry it is 15MB
its very cheep it uses TR20x4 spindles no mashining needed they fit the Block bearings UCP
ok the speed is limited to less then 3m/min
but on total mashine cost of 1600euros for 2x1m its ok
including s-Cutt 50 and watertable Tb6600 Bob5A 24V 2Nm

Looking into motors, I have heard that servos are better for this kind of size but am not really sure why, are they much harder to rig up than steppers?

Should the Z axis be steppers regardless of X and Y?

Also, assuming servos are being used, am I right in thinking that I can get away with: 7i77, 7i92 and THCAD - 10. Could these interface with steppers as well if steppers are used for the Z axis? I'm thinking the 7i92 could?

Is there anything else I would need (control panel kind of stuff) other than the motor drives? Any interface for controlling the torch? (current?)

Do I need anything when it comes to sensing?

I saw that Rod said he used ohmic sensing on another thread.

Ohmic sensing would be better for you but you still need a floating head with a floating switch in case the shield is dirty and does not make proper contact. To make one have a look at how Rod or TheFabricator and some others did it, there is plenty info on this forum.
My advice on motors, use steppers. It is your first machine so try to avoid complicated stuff as much as you can, you can replace them later if you see the need for it. You can also use servo motors with step/dir control as that would not complicate things more than normal steppers, but if you are willing to go the distance the 7i77 with analog controlled servos would be best and more complicated to setup/ tune and isolate properly from interferences.
And it is not a requirement to have a stepper on Z axis anymore, that was only for the toma_thc config before i also added support for servos on all axis and THCAD.

Jarman wrote: Do I need anything when it comes to sensing?

I saw that Rod said he used ohmic sensing on another thread.

You will definitely need ohmic sensing on such thin material as it will warp a tremendous amount.
Ohmic sensing is covered in the Plasma Primer which is part of the main Linuxcnc 2.8 & 2.9 docs.

But you also need home and limit sensors. With Mesa hardware if you use PNP proximity sensors it is pretty easy and you can keep all the wiring located on the moving gantry. My build thread shows the simple method I came up with on the first post. Just make sure the max limit sensor plate is mounted so the high side is on the inside of the limit otherwise if the home sensor is at that end it will think it is near home and move the wrong way and crash!

forum.linuxcnc.org/show-your-stuff/32029...a-cutter-build#84551

So back to material height sensing. Ohmic will be your primary method but you will need to also make a float switch on the Z axis in case it does not activate. This thread which predated my build thread shows some close ups of my Z axis design.
forum.linuxcnc.org/30-cnc-machines/31509...pinion-drive?start=0

The advice from the guys on this thread was really invaluable and this is an excellent design. By purchasing a prebuilt stage, all you need to build is the parts secured to the collar around the ballscrew nut in this photo



eg. the assembly held on by the large black screw.

The only other thing I would say is to be really generous with the Z axis travel. I used a 150mm long ball screw which gave me about 85mm of travel. I think I would use a 300mm long stage and make sure you have a minimum of 200 mm of travel to handle material warpage on thin stock

Also, these NEMA 34 reduction mounts will save you a lot of time for the Y axis. They come with a drive belt and have worked well for me with a 1.25 mod helical rack. Much better than the straight rack I used on the X axis
www.aliexpress.com/item/33038138992.html...0.0.0.c16c2e0e8i97dg