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

[Jess]

There's No Seems about it. Ethernet is much better than USB for Motion control and I'm going thru experience using Both for CNC from several companys products not Theory or what some Spec sheet says should be better.!!

The danger of relying on experience in this way that find yourself reaching conclusions that your experience does not - and cannot - support. To put it another way; lifting 6 tonnes on rope specified for a safe working load of 1 tonne is a bad idea, even if you've 'done it before lots of times'. In fact, it's increasingly poor idea even as you gain more 'experience' that the rope you're using is 'much stronger than the spec sheet said'.

Why I'm objecting is that, whilst you have a lot of experience, 'Ethernet is much better than USB for Motion control' isn't a statement of your experience - you've extrapolated it into conjecture. You can tell it's not experience, because the existence of even one solid USB motion controller is sufficient to falsify your claim.

...plus, I've had enough 'memorable experiences' with Ethernet to know that Ethernet gear is plenty capable of being 'erratic and unpredictable'!

. . . . BUT . . . . We are moving away from OP problem so lets get it back on focus.

A little off but experience and theory and the spec sheet all seem to indicate that if you've got a USB motion controller and a laptop then that combination might be a source of problems. If the planned for desktop PC happens to be lying in a box somewhere, then it'll surely be worth trying with that; given it'll eliminate using a laptop as a factor.

A useful thing to do is to try to split the problem up; perhaps, it's possible to run the machine with the motor drivers disabled, so we're only exercising up to the motion control board? If that's reliable, then the laptop and inputs to the motion controller are less suspect, if it's unreliable, then we can look harder at the laptop and motion controller.

Other problems could be as simple as the connection to the board being poor - so it might be worth trying other USB ports. This is especially true for older computers where the ports may have got worn - especially with laptops which tend to get more connections and disconnections. Sometimes, a different cable might fix things; worth trying as it's easy; although IME cabling problems are fairly uncommon with USB -I've only had it on bus powered gear and extremely cheap cables). If you do have a cabling problem (or even a wonky device) then you might be able to find messages about usb connections/disconnections/resets/errors in the Windows Event Log.

Trying other ports could also help with a problem that occurs with few older computers is that some equipment has an expectation of USB 2.0, but the USB ports are USB 1.1 (or only one of the USB ports is USB 2.0).