Re: [CAD_CAM_EDM_DRO] MaxNC Servo Upgrade

At 04:08 AM 11/1/2000 -0500, you wrote:

>Hi group,
>
>I have the MaxNC-15 Servo, (nothing more than a stepper with encoder
>feedback). I bought it to do a 1 tool production job and now that it is
>done, I would
>like to make it more useful. What I'm looking for is a bigger (ie: more
>torque) stepper
>motor.

I'd be careful here. I suspect the drive electronics don't have a lot of
extra current capacity so if you go to bigger motors, you might not get any
more torque. Pacific Science makes good motors and the only way to PERHAPS
get more torque would probably be a higher inductance (i.e triple stack)
motor that would have a slower maximum speed (for the same current). You'd
lose feedrate. If you replace the drive electronics to get more current,
you lose the feedback servo system (unless you want to spend big bucks on a
new servo system).

> Also I want to replace the cheap 1/10 hp AC/DC spindle motor with a 1/2 hp
>Sherline variable speed reversible motor. Their motor is run as AC with
>control thru
>the software, but no feedback as to the correct RPM.

If you have a MaxNC 15, it should have the 1/5 hp motor? The 1/10 hp motor
is for the MaxNC 10. The Sherline motor is not a 100% duty cycle motor
while the MaxNC motor is. If you run a Sherline motor at heavy load for
any length of time, it overheats and shuts off. That's how they can claim
1/2hp from a motor that's physically smaller than the MaxNC 1/5 hp
motor. The MaxNC 15 also runs 8500 rpm spindle speed while the Sherline
only manages 2700 rpm so some of that "power" is just gearing. Finally,
I'd think you have to be careful about weight. If you put something too
heavy on the non-counterbalanced Z axis, you're likely going to have
problems overloading the servo system.

>can I replace the spindle motor without too
>much modification to the electronics?

The Sherline motor is designed to be used only with the Sherline speed
controller. As I understand it, it runs on DC and is torque
compensated. This would not be compatible with the MaxNC speed controller
at all. If you go to the Sherline, use their speed controller and it will
not be under software control.

Hope this helps,

Mike