Re: [CAD_CAM_EDM_DRO] Re: Servos drivers

caudlet <thom@...> wrote:

> [Non-text portions of this message have been removed]

The lowest cost for that application is the DeskCNC servo card at
$79 bucks sold by Fred


They do not have step multiplication. You would need step
multipliers if the line count of the motor encoders times 4 (in
quadrature) times gear/belt/leadscrew reductions are greater than
your max pulses per second to move the target distance in that one
second.

Try this formula:
V1 = target speed = max speed in IPS
Pr = pulses/rev = Encoder line count * 4
Pi = pulses/inch = Pr * (belt-gear ratio) * (leadscrew pitch)

PPS = pulses per second needed from PC = V1 * Pi

IF PPS > 45,000 THEN implement step multiplication

The line count of the encoder is a very big factor here because you
have to supply four times the line count to rotate the motor one
revolution (Pr). Then you have to multiple that by any gear rations
like belt reduction or leadscrews (Pi). If you do all of that and
find you need 45,000 pps or less then you DON't need a step
multiplier. As you can see you need to have all of the numbers to
make an accurate prediction.

Hi Tom,

Always enjoy your posts. The way I address this is issue is: Find suitable motors,calculate the high speed/torque in relation to the supply voltage and amperage, install encoders that allow the use of drives void of step multipliers, Calculate ratio between servo and ballscrew to attain the traverse rate desired. Is this just another path in which to arrive at the same point? Or am I missing something here?

Ron






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