Dear Andy,

This will be the cost-sensitive solution for industrial applications with Mach4.

I will be awaiting the product release.

The other options (Galil, CS-Lab, Vital) are very expensive. More expensive than industrial grade CNC such as SZGH.
https://www.aliexpress.com/item/32972757912.html?storeId=1540064&spm=2114.12010612.8148356.4.5a9020edC870WU

Congratulations for the initiative.

Felicio

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If your axis is coupled to a ballscrew then the rotational position MUST be directly linked to the linear position. Thus the encoder of the servodrive (or closed loop
stepper dive) performs identically to a linear scale attached to the axis and can signal a fault if the commanded position deviates from the actual position.
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Craig

Identical? Ahhh, not quite. Closed loop motor position is being read prior to the drivetrain, (and most significantly before any slop that drivetrain contains, couplers, ball nut, thrust bearings, wear) unlike linear scale position which is being determined after the drivetrain and so is a real measurement of the actual rather than hoped for travel of the carriage.

Hi,

Identical? Ahhh, not quite. Closed loop motor position is being read prior to the drivetrain, (and most significantly before any slop that drivetrain contains, couplers, ball nut, thrust bearings, wear) unlike linear scale position which is being determined after the drivetrain

Quite correct, however you need a controller that can close the loop about a linear scale and that is not possible with an ESS. As has been pointed out Hicon
and CSMIO/A can do so....at greatly added cost and complexity.

There are two other alternatives:
1) Use a better quality preloaded ballscrew which reduces backlash to zero and lost motion to nearly zero....or
2) Use a load sensing servo drive, for example A2 series Delta servos.

To explain this last option somewhat better: all AC servos absolutely require a close coupled rotary encoder on the servo shaft so the 'Field Oriented Control'
algorithm can work. Any effective 'slop' in the rotary feedback will cause major and unsurmountable instability with the Field Oriented Control loop.

Thus, and for example, the Delta B2 series has a 160,000 cpr encoder built into the servo and that connects directly to the servo drive and it uses it to close
the Field Oriented Control loop and incidentally the load position via the angle-to-linear drivetrain. There is no opportunity to close the loop about a linear scale say.
The A2 series however can. It has a second encoder input and the position loop is closed on that encoder, which could be a linear scale.
The A2's built in encoder ( 1,280,000 cpr) is still required and used for the Field Oriented Control loop. You get the best of both worlds. The A2 series servos are about an
extra $50 by comparison to the B2 series.

This idea of a 'load sensing' encoder channel is not new nor is it restricted to Delta, almost all of the top end manufacturers offer the same or similar thing.
Neither is the secondary load sensing encoder limited to a linear scale. You could use an LDVT or even an interferometric sensor. Both of these devices are used to
'fine' control semiconductor processing equipment which has accuracy demands in the nanometer range.

For my new build mill I elected the first alternative, that is high quality preloaded ballscrews. They a re C5 ground, double nut screws by THK. I estimate that any
inaccuracy or lost motion will be smaller than my machine resolution. Such screws are not cheap, but then neither is the premium you pay for load sensing
servo drives and the linear encoders necessary to drive them.

Craig

Hmm, for my second machine, a mill conversion, I went to linuxCNC and a mesa card which has been able to do just this since its infancy.  And at a much lower price point than an ess id add, I run one of those on my router.

Hi,
yes, that is indeed possible with LinuxCNC because the Linux distro on which it runs has realtime extensions, and can therefore be a realtime controller.
The Windows OS precludes realtime operation and all Windows CNC solutions must be buffered (hence not be realtime). To get closed loop performance
with a Windows OS machine requires an external hardware controller, like a Hicon or CSMIO/A, to provide the realtime processing loop.

There is another exotic solution for deterministic realtime on a Windows PC....but is rather getting away from the point. If you are interested you will
find some great videos by IntervalZero  about it. It is by use of the this solution that Mach4 is able to run Ethercat, which is by definition a deterministic
realtime communication protocol. A very worthy and interesting development in Mach4 and available from Automation Solutions, a complete CNC system
without need of a motion controller or BoB.

Just as a side note Linux with RTE (RealTimeExtensions) on most PC hardware has a runtime jitter of about 4us, pretty respectable but it is not deterministic,
also called 'hard realtime'. By this I mean that while on average the jitter is 4us the system cannot guarantee it.There is an industrial standard which requires
absolute determinism and the system MUST be able to respond within a certain time frame. This standard is often applied to safety systems, medical equipment,
automotive and areospace systems. Linux with RTE does not (quite!) satisfy that standard.

Craig