I inherited an older, Chinese CNC router, and have used it on several projects, but I am now thinking of a major rebuild on the machine and am hoping to avoid some of the more common mistakes ,,🙂.

What I have is a 60 x 90 (cm) machine in pretty good mechanical shape.  Spindle is air cooled and it seems to be ok.  Spindle is controlled by a delta VFD controller  box.

There are 3 nema 23 steppers that seem to be ok, these are connected to an interface box which is ancient and has issues, this box is connected to a parallel port interface via a hand made isolation board which also has issues.   The parallel port interface board is connected to an xp desktop running Mach 3 which is on its last legs.  I use fusion 360 to generate G code which I load via USB thumb drives (networking on the xp machine doesn't work).

I am planning on replacing all of the electronics on the machine, moving to a more modern computer, and cleaner interfaces.   Questions that I am working on are Mach 3 vs Mach 4,  USB vs Ethernet (I assume that I use Ethernet as a direct connection with the controller, and connect the computer to the shop network via WiFi)
Should I replace the existing stepper motors or keep them?  What about the Delta VFD controller, should I be looking to replace that too?

Any opinions gratefully considered...

Just a couple of points to consider…

Although many still use the USB connection for their motion controllers, overall, Ethernet is considered better because of its electrical noise immunity.
The Chinese motion controllers rarely perform as intended, have no manufacturers support and many do not respond correctly to some of the special Mach G and M command codes.
When selecting a new motion controller choose one of USA or EU manufacture which does have manufacturers support. Caveat – Mach3 no longer has support from Artsoft / NFS and only very limited support from the motion controller manufacturers so Mach4 many be a preferable choice. Having said that Artsoft / NFS only provide full support for those holding the Industrial Mach4 license.
The computer running your machine should be considered as a ‘machine controller’ and not used for any other purpose. It should not have access to the Internet else Windows updates etc. are liable to screw everything.

Hope this helps.

Tweakie.