Re: [CAD_CAM_EDM_DRO] Re: Gecko + Servos + Taig Mill

lasernerd@... wrote:

> Ok. So I need a servo that's rated for about 5-15W (although higher
> couldn't hurt). With a 5000RPM servo I'd need an ~8:1 gear ratio.
>
> Where can I find such a motor on the surplus market? And where would
> I find the gearing?

Do not use gearing. Delivering power through anti-backlash gears is
a nightmare. Use a toothed belt instead. It is vastly easier to do that,
and it automatically takes care of the small misalignments in mounting
the motor.

> Should I make it myself, or buy one? (I have
> access to a HAAS VF-2 along with a number of lathes including a
> Hardinge HVL, Colchester Master 2500 and Harrison M250.)
>
> I've seen that some servos have brakes on them. Is the necessary?

Generally a good idea. A servo can run away, due to transistor failure,
computer crash, broken wire, etc. If most of the system is still functioning,
an E-stop might be signalled at the beginning of the runaway, and a
braking resistor could then bring the machine to a stop, rather than
permitting it to sail into the mechanical end of travel. A manual
e-stop actuation should also cause braking to occur.

There are several ways to hook up relays and resistors to provide
braking.

Jon