Re: Digest Number 315

Well said Ron.
What is needed for us stepper hold outs is a G code that would allow us to
have the program ramp the steppers up to speed and then not ramp down and
back up between moves until a G code is given telling the control to begin
ramping again.
What this would allow is servo like motion for moves like a tool path that
is a square with the corners radiused so that the path is a line followed by
a tangent arc followed by a line tangent to that arc etc.
It would also work with the situation where the G code is a large series of
very short segments that have a very small direction change such as an arc
that has been interpolated into line segments. All that would be needed to
make it work in this case would be a lead in and lead out move long enough
to get the steppers up to speed before starting into the short segments.
Bridgeport BOSS 5 and 6 have just such a G code called Deceleration Override
so it must not be that hard to do.
Darrell

----- Original Message -----
From: Ron Ginger <ginger@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Tuesday, January 18, 2000 11:24 AM
Subject: Re: [CAD_CAM_EDM_DRO] Digest Number 315


> From: Ron Ginger <ginger@...>
>
> I think this servo vs steppers is getting a bit nuts- It is a fact that
> there are many thousands of systems in service with stepper motors that
> do a very good job. This ranges from tiny motors moving ink jet printer
> heads to big ones movnig industrial size tables under big machines.
>
> If the motor is run within its design limits, it does NOT loose steps.
> PERIOD.
>
> Jon described the situtation where a servo system 'hits the wall' and
> breaks a tool or some such and says the servo doenst loose it positon-
> so what, the tool is broken, the work is likely ruined anyway.
>
> Trying to take a stepper and make it into a servo is a waste of time and
> effort. If you want a system that can be built within the design limits
> of a stepper, it will be considerably cheaper, simpler, more stable in
> operation and probably longer lived than servos. Just use good steppers
> and carefull enginering and strt making parts.
>
> If you want the highest possible speed, then the job equires servos, so
> bite the bullet and buy the servos and amps and controllers and get on
> with it.
>
> Trying to make a stepper into a servo is about like trying to make a
> flying automobile, sure it could be done, but why bother.
>
> ron
>
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