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Author Topic: Spindle orientation on a Bridgeport...  (Read 2520 times)

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Offline Davek0974

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Re: Spindle orientation on a Bridgeport...
« Reply #20 on: February 22, 2018, 04:33:22 AM »
That 16mm tool at 6mm deep in steel - was that profiling or slotting, only asking as there is a big difference in power used.

I have read something on field weakening but nothing further, i would have doubts about pushing these cheap import servos too far.

The setup is HTD belt drive now at 1:1 so going 1:1.6 would just be a new pulley/belt.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: Spindle orientation on a Bridgeport...
« Reply #21 on: February 22, 2018, 05:49:40 AM »
Hi Dave,
that was profiling, probably 25% step over. My machine starts flexing before the power limit of the servo is reached.

The essential concept of field oriented control is that the  applied field is calculated and phased such that it is 90 degrees to the magnetic field of the rotor
and therefore produces the highest torque for a given current. If instead the applied field is at a greater or lesser angle then a fraction of the applied field
will either reinforce or oppose the rotor field. Should the rotor field be weakened in this manner then the motor will produce a smaller back EMF at rated speed
or alternately a greater speed for the same back EMF.

A servo operated in this fashion might produce 10Nm at rated speed of 2500rpm but with field weakening produce 7.5Nm at 3500rpm, ie you can trade torque
for speed, very clever. You may have noted that some industrial machine specifications might list a maximum traverse speed of 36m/min but a max cutting speed
of 20m/min. What they are referring to is that with field weakening its possible to get higher speeds but not retain the torque and thrust to cut.

I'm not sure you aren't doing the cheap imported servos a disservice by suggesting they are not capable. Commonly you'll see a servo with a maximum speed limit
well in excess of its rated speed. Such a servo has the capacity to use field weakening. I suspect that the quality and reliability of the drive will come under pressure
well before the servo wilts.

Craig
My wife left with my best friend...
     and I miss him!

Offline Davek0974

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Re: Spindle orientation on a Bridgeport...
« Reply #22 on: February 22, 2018, 06:48:29 AM »
Interesting stuff.

Yes quite possible the import can take it but I just don't like pushing the envelope on that stuff. :)
Somedays your'e just happy it turns on - Huanyang VFD's for example ;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.