Re: [CAD_CAM_EDM_DRO] Z Axis feed control ?

washcomp wrote:

>I'm converting an old NC controller (and a Spindle Wizard) on a
>Bridgeport to CNC with the existing stepper motors.
>
>On the old control panel there are two potentiometers labeled "%
>feed" and "dwell".
>
>Does anyone know if I put the "% feed" pot in seriies the the DC
>voltage feed to my stepper controllers if this will allow me to
>manually control the top speed of the Z axis motor?
>
>

No, certainly not. First, the pot has a dissipation limit of 1 watt or so.
Secondly, the speed of the stepper is controlled by the rate the computer
applies step pulses to the drive. The % feed dial would have applied to all
the axes in a coordinated way. Most good CNC programs have some way
to control the speed, usually called a feedrate override.

>Also, does anyone know what the dwell pot is for and how it is
>supposed to be connected?
>
>

It would be used to adjust the time that a dwell command (is that G04?)
takes.

>There is also a 3 position rotary switch labeled "Rapid", "Feed"
>and "Auto". I assume the rapid setting bypasses the "% feed" pot and
>the auto setting goes through it. Don't know what the feed position
>does (unless it was originally for a manual feed capability with one
>of the many unmarked push buttons on this thing). Anyone able to
>confirm (or deny this)?
>
>

Feed may disable the feedrate override for operations that require
absolutely EXACT
feedrates, like threading. If the feedrate override were to alter this,
the threads would come
out with the wrong pitch. Most CNC programs have a G-code that
implements this
disabling of the override. Rapid may cause all G01, G02 and G03
commands to be
executed as fast at the machine can move, instead of the programmed
feedrate.


Jon