On 7/15/25 15:47, Viesturs Lācis wrote:
trešd., 2025. g. 9. jūl., plkst. 23:31 — lietotājs andy pugh
(<bodge...@gmail.com>) rakstīja:
On Wed, 9 Jul 2025 at 20:13, Viesturs Lācis <viesturs.la...@gmail.com> wrote:
I will rephrase my original question - can anyone suggest ANY place
where I can get a 8i20 drive?
Would the updated STMBL be an option? (I have no idea what availability is like)
https://forum.linuxcnc.org/27-driver-boards/53752-new-update-on-stmbl?start=0
Thank you very much for the link!!! I was looking at STMBL drives as
well last summer when I started this retrofit but I could not find
anywhere to get them so I chose 8i20 drives. I sent him a message in
Element chat, hopefully I will get some response. I would prefer not
expanding nomenclature of servo drives that are installed in the
machine but that is optional. Getting machine to work properly is
mandatory.
This is something I might be able help with.
Q: do these servos have a nema type motor mount? So you can just bolt
on a nema-xx motor?
There are over the last decade, a new tech version of stepper/servo's
coming out. These new "closed loop stepper/servo's" have a 1000 ppr
encoder on the back end of the motor that is not fed back to LinuxCNC
but to the driver so the driver knows very precisely where the motor is
so the driver gets data as steps/dir from the trajectory planner. Based
on the comparison between this encoder and the the steps/dir received to
move the motor, the driver can reverse the motor in case of overshoot or
just boost the current during lag while accelerating, so the motor is
driven to make the two match. But that is not the full story. Normal
steppers run hot because they run on the programmed current full time.
Now the drivers we used to run on 24 volts suddenly get drivers that can
run on much higher voltages. This allows a stepper to move very
precisely as the inductance that limits a stepper to maybe 2000 revs at
reduced torque, but can now be driven to several thousand revs faster.
Nema-17 drivers are now rated for 90 volt supplies while nema-23's can
use 110 VDC.
The error detected by the step input and the encoder controls the
instant current thru the motor which in well constructed machines
generally reduces the motor heating and the motor runs much cooler as
its only fed enough current on a microsecond by microsecond time scale
to get the move done, a difference in power consumption the busy shop
can see in a reduced power bill and 60C cooler motors.
Now assume the motor hits a tight spot and the error goes up, the driver
will use as much power, up to the psu's current limit, as it takes to
get the motion done, doing it on a dynamic basis for a millisecond or
two which is so fast the motor doesn't heat. And the driver has an error
output if unsuccessful in reaching the commanded position that can be
fed into the e-stop to stop LCNC in the next millisecond. Tested to
distraction in 3 of my machines, just one common problem, this shutdown
has not yet occurred running gcode.
These new motors and higher voltage drivers are made by Hanpose in
China. I have to get them thru aliexpress. They have a web page to order
from, whose shipping and aftermarket support are a far distant thing
compared to amazon. Cost differential compared to normal steppers is in
the $50 per axis range for nema-23 stuff. drivers and motors cost a bit
more but the higher voltage psu's are getting a bit cheaper as time and
demand increase. The machine can be run more precisely and considerably
faster, at less power draw.
This might not be the best cure for the present dilemma, but should be
sold as a machine improvement for the next conversion.
Viesturs
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Take care of #1.
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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