Re: [CAD_CAM_EDM_DRO] encorer feedback

R Rogers wrote:

>
>Jon Elson <elson@...> wrote:
>
>
>
>But, Mach2 doesn't actually USE the encoder information, except to
>display it on the screen. If a motor stalls and it is a whole inch out of
>position, it pays no attention, just displays where the machine actually
>is, while blindly continuing to ruin the workpiece. What's the purpose
>of encoder feedback, if not to keep track of machine position?
>
>Jon
>
>Ok. I'm confused here. I understood that Geckos after a 128 pulse/count dicrepancy between encoder and drive will fault. At 800 counts per revolution and 2.5 :1 reduction on the drive would only allow about .020" positioning error before faulting. If I understand this correctly. Incidently, I've used a Mach2/Gecko setup on a Bridgeport and have not lost a step/ruined a part due to lost position nor ever lost position in a year and a half under normal operation. To term it a "Hobby" or not a "Real" control software is a bit unfair. It reliably does what it is supposed to do. Without the "Real" software price and they do nothing more than hold position like Mach2. A software that monitiors axis position via encoder feedback is only required when the axis actuator is inadequate for the task at hand i.e. insufficient torque etc. Who wants that anyway?
>

Well, the difference is that with Gecko drives you don't know WHERE in
that +/- .020" region the machine
actually is. (Normally it is very close to the commanded position, but
you don't know for sure.) As
the velocity increases, the following error increases. For some
applications, a .020" error is
totally unacceptable. For others, it would be no problem.

Obviously your bridgeport setup satisfies your needs, and that is
great. Mach2 and Gecko
(or Xylotex, Rutex, etc.) drives are making a lot of parts for a lot of
people.

EMC costs LESS than Mach2, and does offer encoder feedback to the PC.
One thing this
allows is a sliding scale of acceptable following error. You can permit
a larger following
error at rapid traverse speeds, but a very small following error limit
for low-speed
cutting moves. Also, you can switch back and forth between CNC and
manual movement
(on machines with handwheels) with the same coordinate system. I don't
know if it works that
way in Mach2.

Jon