RE: [CAD_CAM_EDM_DRO] Re: Brushless Motor Spindle with CNC desktop machine

Interesting, I'm building a little gantry mill and have ordered an RC
brushless motor and controller for the spindle. They'll run on 12V drawing
about 100W and at 4200rpm/v should really scream. Total cost for motor and
controller is about $AU60.. If it works out (I'm a bit worried about
temperature) then I'll be building a driver circuit to generate the 1-2ms
servo pulse, probably from a serial command, but buttons would be easy..

I should have some results in about 3-4 weeks. I'll post 'em.

PK

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of turbulatordude
Sent: Wednesday, 10 August 2005 9:22 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Brushless Motor Spindle with CNC desktop
machine

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "baccus61" <richmcm@a...> wrote:
> hey everyone,
> I am building a small desktop 3D milling machine and needed a
> brushless motor for the main spindle. I got sick up and fed of
> changing brushes on the prototype I built, and a brushless motor will
> also be much quieter for indoor use and last a whole lot longer.
> I purchased a model aeroplane motor - AXi 2826/10 motor (rotating
> outer housing for better torque and the rotor doesn't throw off it's
> windings) with an "easy 25" 25amp controller and I need to know how
> the controller signals are sent from the RF module to the controler
> and the type of pulses. In the "easy 25" instructions it lists
> positive pulses at 1.5 ms with a period of 10 - 30 ms. What voltage
> would these be. "3v - 5v"? and are they continuous pulses. If this is
> the case then I think it would (maybe)be a case of programming the
> software to use the 4th axis as the speed controller and inputing the
> appropriate commands into the G-Code
> These motors spin around the 10K-20K revs at 12V(and faster) and pull
> up to 40 amps so the power is there for a small Miller but I am not
> sure how they would react to a filtered DC power supply with the BEC
> (Battery Economiser Circuit).
> The best case scenario would be to just have a switch to turn the
> thing on and off and if anyone out there has a way of doing this
> (small circuit board with a pulse module?) then that would be great if
> they could contact me about doing this or better still post here.
> If anyone else has any ideas Idea about controlling a brushless motor
> with a CNC spindle then I will be forever, eternally greatful if you
> could let me know how you can do this.
> I haven't found anyone else doing this sort of thing with radio
> controlled stuff on CNC machines so maybe this will be a first and if
> it works the we can tell all the other CNC people out there how to do
> it and I know they will be greatful as brushed motors just aren't
> cutting it when it comes to running a CNC/engraving job for 9 hours at
> a time. The brushes wear out after a very short period of time and
> usually halfway through a job and I know you can all sympathise with
this.
> Please help.
> Warm regards
> Richard.


Hi Richard,


I think the hobby motor is still being overlooked by most of us.

A RC car motor can spin at 25,000 RPM and uses about 9.6 volts. Of
course, the ones I've seen use brushes, so that is a problem as you
mentioned. replacement is a PITA.

But, I opted for a simple DC motor controller (brushed) instead of
trying to use the RC variety. first, because it was less than $20.00
and second, I just didn't want to fiddle with making a circuit to
interface with the RC stuff.

ON Semi has a decent data sheet on the chips to make a controller.
https://www.onsemi.com/pub/Collateral/MC33033-D.PDF

I think that there is so little data on motors and the prices are so
high, that they are still not prime for this market. I just can't
imagine spending $85.00 for a tiny motor, and then another $85 for a
speed controller and still have to do something to make it work. I
currently think there are easier solutions, but will be happy to be
shown where I'm wrong.

Dave





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