Re: Which Software?

While back when I was confronted with this
confusing concept I went to a way to visualize
the scenario as follows.

visualize the weight of the machine Table and the cutting forces
involved as a Box of a certain weight sitting on a grit.

The guy in charge of moving this box is your driver electronics.

The effect of a step pulse given for a stepper motor causes
the guy to give the box a push suppost to send it into the
next grid field.
If the Box is heavier then the strength of the guy pushing the
Box will not move but remain where it is resulting in a missed
step that can not be detected by feedback less software.

Servo motor drivers go about this a bit different even so the
results should be the same.
Servos are controlled by target position.
So when given a signal to take a step the mover guy moves first
onto the next grid then he pulls the box towards him.
Again if the Box is heavier then the guy pulling nothing may happen.
However the step will not be lost it will go into a error register
on the driver. Additional step signals to the mover guy will result
in him moving farther away from the box trying to pull the box up.
His arms are sort of like a rubber string streching quiet a bit and
get stronger as farther he gets away from the box.
The larger the error register the more current is send to the motor
to catch up.

The size of this error register depend on the manufacturer of the
driver, on geckos is 128 steps I belive.

If the error register gets more steps than it can hold it will reset
to zero this means all 128 steps in case of the gecko are lost.

So called real feedback software monitor the error registers
constantly and desides what action to take if the error exeeds
a certain value. (syncronisation of all axes)

Hope this helps somebody out to make sense of it.
Good Luck


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "gadget_c <billsand@c...>"
<billsand@c...> wrote:

> Hello All,
>
> I have the milling machine sorted out, the servo motors, and the
> drivers, but the software is baffeling. I see most software venders
> explaining how it works with stepper motors, not servo motors and
> that's what is confusing. Please correct my assumption that the
> software will drive either type motor depending on the motor

driver?

> Looks like the feedback from the motor encoder 'regulates' the step
> and feed rate - now how does the computer know if there is an under
> or over drive - as if open loop, or does the feedback input into

the

> computer - closed loop?
>
> Also need a recommendation on the software - something worthy of
> spending hundreds for.
>
> Thanks much up front,
>
> Bill C.