Re: [CAD_CAM_EDM_DRO] converting Bridgeport powerfeed to CNC DC servo

Doug Fortune wrote:

> Considering the relative ease to add, and low cost
> that a Bridgeport table powerfeed costs (both X & Y &knee),
> has anyone taken one apart to see what kind of motor is
> in there? Probably AC.
>
> Can it be replaced with a similar size DC motor,
> and then be run from a G340? An encoder needs
> to be added, obviously.

Most of the later ones are almost certainly DC motors. but, the
problem is that the power feeds have GEARS in them, thus
backlash. If you put the encoder on the motor, the system will
be stable, but the backlash will be huge.

If you put the encoder on the leadscrew, the backlash will cause
the motor to continuously hunt across the backlash range,
driving everything crazy.

I have to tell you, don't even try this, you will be very sorry.
The only way to do it is to use a direct drive motor with LOTS
of torque, or a somewhat smaller motor with a toothed belt
drive, with the belt tightened up quite snug. A reduction
ratio in the range of 2:1 to 4:1 is usually the best.

Jon