Re: breakout boards plus - hard choice

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <grezmos@...>
wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@> wrote:
> >
> I think Mariss' idea uses a step driver which has a
> > master current setting, so the controller can ramp the current
> > up as needed to drive the mechanical load. It might work with a
> > G201 or G203 drive without the pulse multiplier (which
> > complicates the phase relationship a lot). The motor would run
> > hotter as it runs at full current all the time. Then again, the
> > current modulation may be part of the key. I certainly have not
> > done this.
>
>
> I was under the impression that the "unstallable stepper drive" just
> slowed the feed down to get more torque (presumably it talks to the
> motion controller) and although the motor might come to a complete
> stop that isn't a real stall because the driver decided to slow it
> down to a stop. Obviously you are not supposed to try and push the
> point.
>
> All sounds very nice but I'm not sure what it will do to surface
> finishes, I cant help but think its better to stick the correct sized
> motor and use proper feeds and speeds people have done that for a long
> time perfectly well.
>
> Graham
>

I think there are some general presumptions that are taken into
consideration.

first, few people worry about surface finish when heavily loading.
usually that is the area of high metal removal and rough cuts.

second, presumably, the finish cuts are will within the limits of the
machine so one would not be approaching the override zone when finish
is important.

The idea as I see it, is more along the lines of you or the machine
did something wrong and under many circumstances the machine would
lose a step and the rest of the part would be toast. by slowing down
all axes to compensate for the one that needs more time (power) the
part is saved as is the location of the machine.

I think that no one would recommend a builder make a machine with such
a logic control and then use undersized motors. the work could take
hours longer to complete.

in my estimation, a properly sized drive system AND perfect tool paths
and sharp cutting tools will never need the feature.

Kinda like seat belts and air bags, one hopes they are never needed.

Dave