Re: [CAD_CAM_EDM_DRO] Which Software?

gadget_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?
>

Not exactly. there are servo drives that emulate stepper drivers,
taking in step and direction
and moving a motor until the encoder give a number of counts equal to
the steps received.

This is really a half-servo system, as the computer has no idea where
the machine is. generally,
all it gets back is a fault indication, but it has no idea how close to
the commanded position
it really is.

A true servo CNC system has the encoders feeding back position
information to the CPU.
This allows for constant monitoring of following error, as well as
adaptive control, where
other axes are slowed when one begins to lag.

Also, with encoders fed back to the CPU, the computer always knows the
true position, even
after a crash or emergency stop. Without this, any emergency stop or
driver fault during
motion leads to loss of position information, and you have to re-home
the axes.

>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?
>
>

In most step/direction servo systems, the computer does NOT know - it
only assumes!

>Also need a recommendation on the software - something worthy of
>spending hundreds for.
>
>

I use EMC, the only low cost software I know that can handle most all
types of motion
control, including true servo.

Jon