Re: [CAD_CAM_EDM_DRO] CNC Servo motor gear ratio: overheating. EMC step rate. Table speed

Kim Lux wrote:

>> If so, you can make an attempt to see whether friction
>>and cutting forces (if any) will exceed this spec. Always throw in a fudge
>>factor for unanticipated drag. Anyway, if 25 Lbs linear force is required,
>>add a generous 20% fudge for the ballscrew and you get 25 * 1.2 = 30
>>30/1059 = 0.028, or 2.8% of peak torque. (I'm assuming the 620 Oz-In
>>is the peak torque, otherwise, this is a HUGE motor).
>>
>>
>
>What is the relationship between peak torque and continuous torque on a
>stepper motor ? I thought the torque curve was constant with RPM on a
>stepper motor.
>
>

Stepper? No, the torque of a stepper motor is rated as HOLDING torque,
and it falls off very rapidly as the motor accelerates. By 1000 RPM, most
stepper motors have lost more than half of their holding torque.

Unfortunately, there is NO fixed relationship between peak and continuous
torque on a SERVO motor. It depends on many details of motor design,
including wire resistance and heat conduction from the armature. The torque
possible is constant, but the time over which you can demand this torque
is not infinite. Above some value that takes serious effort to measure,
the motor will eventually burn up if not given a rest.

Jon