Re: true closed loop vs. hobby closed loop

The software is informed by the G320 via the ERR/RES output that it
has "faulted out".

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "snagglexr650"
<snaggletto@c...> wrote:

> Hello,
> I work in a machine shop and we have several retrofitted
> lathes/mills using OpenCNC and various motors/drives including
> Yaskawa servo motors/drives, we also have a Haas VF4 VMC. These

are

> all high dollar, industrial level cnc controls, with "true" closed
> loop feedback from the encoders.
>
> It seems to be widely considered that true closed loop actually
> allows the computer control to self-adjust the motors if error in
> positional accuracy has occured. However, all the machines we

have,

> including the Haas (not a retrofit) have an allowable following

error

> (FE) on each axis. If that FE is exceeded, the drive faults out

and

> cuts power to the servo motor. If the positional error falls

within

> that FE range, then inaccuracy does occur, it's happened to me.
> Furthermore, this FE is used in axis crash situations. Say you

crash

> Z into your vice/part/table, as the axis stops moving due to

hitting

> a solid object, FE is exceeded and the drive faults. Attempted
> positional compensation via the control would simply drive the axis
> into the part harder and cause more damage to the machine.
>
> Now, with that in mind, compare the +/- 128 counts 'FE' on the
> Gecko drives. If positional error exceeds 128 counts, then the

drive

> faults out and servos stop.
>
> In either scenario, it appears that the same thing happens, and
> that even in the case of 'true' closed loop controls, there is no
> attempt to correct the positional accuracy, just a fault.
>
> My question is where is the difference? I know software is the
> key to closing the loop. Is it simply that with Geckos, your
> step/direction software will happily continue to run the program
> without knowledge of the drive faults, and that on the Haas
> control/OpenCNC software control the software is aware of the fault
> and stops running the program and displays an 'excessive following
> error exceeded' message?
>
> Is this true? If not, then please explain to me the difference
> between hobby closed loop via Gecko Rutex etc... and
> industrial 'true' closed loop via our Haas VMC and OpenCNC retrofit
> control.