Gantry oxyfuel / plasma type machine from scratch

NWE wrote:

For slow cheap I/O I used to not like modbus, but tried it some more recently and am pleased how it is performing. This would not do for limit or homing switches, for those you'll want ethercat or Mesa for sure.
 

Thats interesting. I never thought of this either. If you look at this diagram in the docs. it clearly shows what can be run in non-real time mode
linuxcnc.org/docs/stable/html/code/code-...rchitecture_overview

So spindle, coolant and auxillary devices could be modbus and I can see modbus I/O modules locally for < AUD $50 for 16 inputs and 16 outputs. I'm might also play with some now there is good modbus support in hal
 

I wrote about Modbus, because Ethercat I/O is expensive.
Configuration Mesa+Ethercat is more expensive and you need two network ports (some mini computers are enough powerfull but you can't add any cards).
Modbus need only USB port.
You can find cheap Modbus I/O cards on Aliexpress (for example 4 analog and 4 digital inputs less than 10 US dollars).
Of course Modbus is slow so suitable for slow signals.

tommylight wrote:

Yes you should leave them out, as noted above the only usable way for DMM drives is in Position mode as they have a delay in position signal outputs.
Also the encoder input will be used for THCAD if you want plasma.

By "leave them out" I meant to not connect them at all. But then how the linuxcnc will know where it is at certain point ? I will probably loose a part of precision with not connecting the encoders feedback.

tommylight wrote:

Yes there is, Mesa 7i85 or 7i85S should have 4 encoder inputs.

I see this card has a DB25 connector to connect it to the computer I suppose, or does it gets connected to the
7i96s ? Sorry for dumb questions.
Is the DMM Dyn4 encoder output supported by the Mesa 7i85 ?

tommylight wrote:

No, not per se, but LinuxCNC can be programmed as you need it, so a simple G04 P1800 will make the machine wait for 30 minutes at the first cut to preheat the material.
Same for outputs and solenoids, everything can be automated and even add a side panel with settings and buttons and stuff.

OK for this, I will take a look better on it once I install it in a virtual machine.

rodw wrote:

Linux-CNC is the Ethercat master. You just need ethercat slaves. Have a look at the Beckhoff EK1100 and the many various modules that attach to it. Many of these modules have native support in LinuxCNC. There may be other brands of modules available but you would need to write the driver and you'd need to be sure they have 500v or so over voltage protection in case something goes wrong. Beckhoff and Mesa have that.

I took a look at the EK1100 and various modules, thanks. I also checked the Isolation of TrioMotion FlexiSlice coupler P366 and they state it as 1 kV. So this should be ok.

saxa wrote:

By "leave them out" I meant to not connect them at all. But then how the linuxcnc will know where it is at certain point ? I will probably loose a part of precision with not connecting the encoders feedback.

Yes, do not connect the encoder output from DMM drives to Mesa board, see below

saxa wrote:

I see this card has a DB25 connector to connect it to the computer I suppose, or does it gets connected to the
7i96s ?

It gets connected to Mesa board, and yes it looks like parallel port, and yes there are adapters that connect to Mesa 7i96S (and other Mesa boards) that work as parallel port but at much, much higher pulse speeds, and no 7i85 can not be used with a normal parallel port.

saxa wrote:

Is the DMM Dyn4 encoder output supported by the Mesa 7i85 ?

Yes it is, and yes it works fine, technically, in reality the DMM drives have some strange latency/delay issues that make them useless for real time feedback.
But they do work fine (from what i read here) when used as normal stepper drives with step/dir control, and yes the precision will be out of LinuxCNC reach, but if the drives are tuned properly that should not be an issue.

Oh yeah, no need for virtual machines, this is Linux, so download the ISO, write it to USB using Balena Etcher or DD or image writer on Linux, boot from it in Live mode, test as much as you like, reboot and remove USB, it does not write nor change anything to existing hard drive.
And also you can actually run machines while in Live mode.