RE: [CAD_CAM_EDM_DRO] Re: servo board

I'd love to have a servo drive system that still controlled the servo in
a closed loop/step-direction fashion, but that had a USB connection to
each controller so that they could be queried for their position.

Why do I want this ? Lets say that we are operating our machine and
something goes wrong. We press abort. Lets say it is a software
generated abort and the controlling software immediately stops the pulse
train. Chances are the servo drive is going to error because the servo
can't immediately stop. With a simple step-direction system, we've just
lost our machine position. We have to reset our machine position before
we can resume our work.

The same thing happens only worse when we do a power abort when pressing
EStop. However, in order to the machine position to be maintained in
this instance the encoders and "quadrature counting circuit" must remain
powered.

Another thing I'd like to have communicated between a drive and the
computer is the power level the servo is operating at. This would allow
the software to do a smart "force sensing" abort, thus saving tooling,
crashes, etc. It would also give the operator a heads up on what sort
of cutting forces are being generated. As it sits right now, we don't
really have any feedback.

As far as putting the software in the control loop, I say forget it.
Servo controllers have PID loops and that is about all most machines
need, even when operated at high speed. One thing about having encoder
position feedback to the computer is that it could be a great, great
help when tuning the PID loop of the servo controller and when tuning
the speeds and accelerations of the software.

As far as software not supporting this functionality, I've kind of
soured on the software available to the public and taken to modifying
things as I need them. We've got 3 CNC machines now running our
specially modified TurboCNC software. We've added special canned
cycles, the ability to edit part files while running, etc. I had two
very experienced machinists touring the shop last weekend. I did a demo
and they were very, very impressed.

Kim

On Fri, 2003-11-28 at 14:20, Tim Goldstein wrote:
> > -----Original Message-----
> > Hi,
> >
> > As I mentioned earlier I'm NOT an expert on servos or servo
> > drivers BUT, Isn't it quite simple to setup the Gecko to
> > communicate with the computer to, if you so desire? I don't
> > know if its vise or not, but it's possible, I have seen it
> > somewhere on the net.
> >
> > Regards,
> > Eze
>
>
> Just feeding the encoder position from a Gecko to the computer only
> works if the program you are using accepts encoder feedback in a step
> and direction output mode. EMC does it with an encoder board that is no
> longer available. I am not aware of any others that handle it. Even so,
> you will not achieve the performance that you can get with a true
> software controlled servo loop. For many purposes the Gecko with an open
> loop step and direction control program will give tremendous performance
> for the money. But, they are different animals. It would be well worth
> investing some time into learning about the different servo setups and
> what they are all about before giving out advise on them.
>
> Tim
> [Denver, CO]
> Visual Mill 5.0 Basic at a price too low to post!
>
> Sherline & Taig products at Deep Discount
> Mach1 & DeskCNC with credit card ordering
> www.KTMarketing.com/Sherline
> Timg@...
>
>
>
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Kim Lux <lux@...>