On 10/2/2019 7:18 AM, Gene Heskett wrote:
On Wednesday 02 October 2019 00:36:41 Brent Loschen wrote:
<https://www.ebay.com/itm/Mini-Peristaltic-Pump-Head-With-Tube-Small-F
low-Stepper-Motor-OEM-Package/273419600046?hash=item3fa91400ae:g:h1MAAO
SwMdZbe77a>
I sorta went crazy, ordered two kits of telescoping brass tubing to help
make better, smaller nozzles. I can solder up a 1/16 od, and redrill it
at #80 to get an even smaller tip. Then off this link, which takes a
short nema 42 motor with a 10mm shaft (no way do I have a motor that
big), but I did find a 12 volt rated peristaltic that looked usable at
$6.32/copy. So since even the silicon tubeing has a limited lifespan in
service of only a year or so, I bought 4 of those. But they're in china,
so a Nov 1 estimated delivery date. Spit.
If you check out the mechanical drawing of the pump in the link above
(last thumbnail to the right), it appears to have both 31mm and 47mm c-c
mounting holes which match NEMA 17 and 23 steppers respectively. Not
sure why they reference a 42 motor which has a larger bolt pattern (89)
than the overall dimensions of the pump (57)!
Although it would be nice to have adjustable spring tension on the pinch
arm to accommodate a wide range of pump tubing, it's hard to beat the
price ($13 delivered) for a 6 roller pump. Precise speed control of a
stepper should be a lot simpler than to PWM a DC motor. Would it be
possible to treat that pump/stepper as a joint and set the RPM via
feedrate in Gcode?
Brent
Now if I can write hal code to allow enabling a PWM module to drive this
for speed control, at the same time the m7 is on, and some more pyvcp to
dial the speed via controlling the pulse width, I should be set better
than I am right now. Enough air pressure to keep the work area clear,
and just enough fluid to cool things without soaking the neighborhood.
The stepper drive is a nice idea, and I may yet pull one of the 225's off
the remains of the hf and put it on this 6040's z drive. OTOH, unless I
start doing a lot of 3d woodworking, this is fast enough. Famous last
words...
==========
Speaking of PWM, is it possible we (meaning LCNC) have a means to detect
the rise in back emf as the motor starts to turn, effectively pulsing
the motor so it has enough power to overcome roller friction, but would
them turn it off after 2-10 degrees of rotation? Should make a much
more controllable low flow speed control.
Somehow, I doubt we could turn it off and sample the back EMF with one of
a 7i76's 12 bit A/D's fast enough to make that work, and the docs don't
say how long to a valid reading, but can you tell me, Andy or Peter?
That way I could use a solid 12 volts to bang it with, detect that the
motor is moving, extending the pwm's off time for speed/flow control and
that should allow flows that hardly wet a finger. Or have I let my
imagination out to play w/o a chaperone again?
Won't be the first time, and I hope not the last. :)
Thanks.
Cheers, Gene Heskett
_______________________________________________
Emc-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/emc-users
