RE: [CAD_CAM_EDM_DRO] Re: breakout boards plus - hard choice

It may be possible to do this with a Grex, but that would require encoder
feedback to the Grex, which is not part of the unstallable stepper
philosophy.

The unstallable stepper just relies that if there is too much load, it slows
down and by doing so has more torque at slower speeds. There is no
communications method to tell what ever is driving the pulses to adjust
other axis accordingly.



Also at present for those using the Grex with Mach, even with encoder
feedback, if one axis slows, the others are not slowed to suit.

I have a G100 running servos with encoder feedback wired, it presently just
gives a count value in mach, that is not in a format directly related to
machine position because there are issues resetting it within the G100,
nothing is done with this info at present. I have been looking at building a
macro to count the errors per axis and adjust the feedrate should they go
above a threshold, but it is not yet implemented. We were offered/promised
many options for the G100, but further development has either ceased or gone
very quiet.



What ever happens if you want to work with the unstallable stepper board and
are machining with a high risk that it will drop the speed during machining
you are going to have to add encoder feedback and build something to work
with it. The only real area where unstallable won't cause a problem,
actually there are two, when machining along one axis only, or during
rapids, and if it gets used during rapids you will have to pause the program
before going into a machining move to allow the axis to catch up, or the
stored count in the card may reverse before you've got to where you need to
be.



Robin's board here is still the better option for the present.



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Graham Stabler
Sent: 19 July 2007 12:17
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: breakout boards plus - hard choice



--- In CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com, "Mark Vaughan" <mark@...> wrote:

>
> The worrying bit Graham is while one axis slows, what are the others

doing.

>
> To work they all need to be tied together, and by quite a complex set of
> formulae to maintain the shape accuracy.
>

Its done by the G-rex. The formula is no different than what is
already driving it really its just a matter of adjusting the rate to
match the slowest drive.

Graham





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