Hardware Reccomendations

Okay, so it looks like the 7i76eD is what I'll need, since I don't want to be rewiring the entire machine if I can help it.

Just to confirm the number of axis:

I have 2 X axis, 1 Y axis and potentially 3 Z axis (plasma torch, air scribe which has its own Z travel, and i want to add a milling spindle which will also have its own z travel).

Do the 2 X axis count as 1 or 2 axis for the mesa. Ie will 5 axis be enough, or do I need a board capable of 6?

Or does the THCAD-9 take care of plasma Z?

Your axis are called joints using from LinuxCNC 2.8, so if you pretend to use separated joints at your gantry (i recommend) you have 1 driver per motor, my background is 3d printer (toy from your perspective?) and there things are small compared here and we use in some designs at Z for example 2 motors per drive and the gantry just 1 motor but using belts to distribute the power.
i strongly recommend you to read the documentation at least, very well documented.
linuxcnc.org/docs/2.8/html/
linuxcnc.org/docs/2.8/html/plasma/plasmac-user-guide.html
linuxcnc.org/docs/2.8/html/plasma/plasma-cnc-primer.html

To me looks like the 7I76 isnt the best option for you but maybe im wrong and you can use some I/O from another place in the board.
Maybe 7I95 or 7C80 (this one is for RPI4) both support 6 axis and are S/S.
7C80 looks nice.

I dont know whats your specs but i think you know your spidle will act like a lever, this machine was designed for that?
at begin probably will work but over time will be consistently? after all you have one lever forcing it everyday in some design who made at begin dont have this force, something to check.

To me looks like the 7I76 isnt the best option for you but maybe im wrong and you can use some I/O from another place in the board.
Maybe 7I95 or 7C80 (this one is for RPI4) both support 6 axis and are S/S.
7C80 looks nice.

I agree, the 7i95 appears to be a bit mote versatile than the 7i76, but i would love to here some feedback from others. I wool be using an Odroid so I guess that rules out the 7c80

I dont know whats your specs but i think you know your spidle will act like a lever, this machine was designed for that?
at begin probably will work but over time will be consistently? after all you have one lever forcing it everyday in some design who made at begin dont have this force, something to check.

I am only aiming for a low power spindle. Something that can handle taking a very light cut with a 6mm end mill to clean up plasma cut holes, and maybe drill up to 7mm dia. I think the gantry will be sufficiently rigid to handle it, but I am still conscious of keeping weight and torque as low as I can get away with

Odroid, right, im with RPI4 in my mind last days.
You can open new thread and be more especific about Mesa card, you already know how many I/O you need and joints, maybe PCW (the head behind the mesa i think) see it and give you advice about which board is better for you. At Plasmac section and Show Your Stuff if you check there you can get idea what people are using.

Im not engineer and its just my experience, i know if something is long enough i can even bend with my hands.
Your Ø 6mm end mill if someone make mistake to adjust the length and the end mill crash into the table will be rigid enough?
The lm guides block use M4, if so its okay?
Maybe thats why we dont see many setups like the type you have in mind, something to check or loose customer if something crash.

I checked some videos and they use pneumatic to hold the material and drill.
And you can run process to check the proper tool length to avoid crash.
The sensor part isn’t difficulty but your table i think you cant...out side keep clean the sensor.
Just weight now.
High tech model:


More affordable model to make:

htdave wrote:

{...}
I am only aiming for a low power spindle. Something that can handle taking a very light cut with a 6mm end mill to clean up plasma cut holes, and maybe drill up to 7mm dia. I think the gantry will be sufficiently rigid to handle it, but I am still conscious of keeping weight and torque as low as I can get away with

Plasma and milling/drilling have quite different machine requirements - a machine with a big enough budget can be designed for both, but the plasma wants to be light, fast, quick to accelerate, and typically big, whilst milling/drilling wants to be heavy/stiff (and therefore biased toward small).

The typical 2.2kW Chinese spindle has a sweet spot around 6mm end mills, but negligible torque below about 6,000-9,000rpm, which is already fast for drilling to achieve the desired chip thickness. Their bearings aren't really up to milling steel. 7mm is also quite a big drill for this sort of spindle. Slower/torquier spindles are likely to have bigger (heavier) motors and/or gearing (and the aforementioned spindle is already a very heavy addition to a plasma machine). Also, plasma is typically for steel, which is much harder than the aluminium most people process on DIY gantry machines.

In my opinion, spot the holes and drill them on another machine. The spotting could be by scribe if you want to be easier on the drills (spotting with the torch will harden the steel locally). Regarding IO, the scribe likely doesn't need a driven axis - mine's just on a pneumatic actuator.

Well, I have ordered the odroid and a 7i76eD, so just have to wait now.

Is there a link to the Odroid iso?

The milling / drilling feature will come later on when i have a bit more time. I have a fairly heavy duty gantry so a small spindle should be okay

My main reasoning for adding the mill is less setup time/ manual labour and more accuracy - not relying on someone to correctly line up a centre punch.

I don't mind if it takes a long time to mill a hole, as long as it can do it by itself

Thanks everyone for your input. I'm sure I am going to have plenty mote questions when I start setting up

There is also a topic under "Installing Linuxcnc"
forum.linuxcnc.org/9-installing-linuxcnc...3-linuxcnc-odroid-h2