Connecting to a CNC machine, pros and cons of USB vs PP vs Ethernet etc.

[Jess]

however nobody uses it as a communication method between a computer and CNC machine

Not on Mach 3; but that part of the conversation hasn't been about Mach 3 for several days now! And, of course, that ethernet motion controller is a computer, but that's not what any of us mean.

On the LinuxCNC side, whilst RS485 is more popular, there's definitely people interfacing their machines to their computers with CANbus.

The hardware's been available for years. There's plug in cards that provide the interfaces plus industrial PC motherboards that already have CANbus and/or RS485 on board.

but you're then into a very glorified parallel port like system.

Rather unfair and misleading. CANbus gives you something much closer to a PCI I/O board in function - you're not having to do software step generation, and you actually have the ability to read encoders.

To seque this into the topic of the thread:

Approaches that allow your computer to more directly control the machine is definitely of huge value if you've got some complicated/non-standard kinematics going on, but even on a standard perpendicular axis mill then there's a potentially a significant financial saving to be made.

The additional costs associated with Mach 3; Windows licenses, Mach 3 licenses and ethernet hardware motion controllers could buy you all the electronics you need to convert something like a Novamill or Triac, even once you've thrown in something like a Mesa Anything I/O.

LinuxCNC on BeagleBone Black? A back of the envelope calculation suggests that I can have my entire dedicated control computer as well as software and breakout for the cost of the Mach 3 license alone; that's a lot of difference.