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

For a comparison.

Do a search for brushless on http://www.ebay.com.au (there seems to be a
good importer over here). They come in all shapes and sizes. I ordered one
of these:
http://cgi.ebay.com.au/4890-Brushless-Motor-for-R-C-Electric-Airplane-05AUP_
W0QQitemZ5990961964QQcategoryZ2563QQrdZ1QQcmdZViewItem
And a speed controller.

Some of the outrunner motors are very cheap. Lower speed and harder to mount
though, check out the dimensions of the unit above!

Shipping is from Hong Kong, so I don't think it matters where you are.
My only concern is heat. These things are designed to work in aircraft. I
suspect that they will be fairly lightly loaded (by comparison) in a milling
application though. Additionally, my spindle design has it thermally bonded
to an Al bar.
PK

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of baccus61
Sent: Thursday, 11 August 2005 8:53 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Brushless Motor Spindle with CNC desktop
machine

Hey Alan,
Thanks for the great post. I have a link here for you from Model
Motors in Sydney, Au that you may peruse. Instruction manuals are on
the site as well as a lot of info for the controllers. I opted for
the rotating casing/housing and fixed coils as I had heard alot of
people had blown windings from the high speed throwing them out. The
AXi has neodymium magnets with a very strong cogging effect when
turned by hand and a 5mm shaft size which is large enough for a decent
coupling. This was the motor I opted for as the price was about what
I was willing to pay for a prototype. There are bigger more powerful
motors that go way up to 75-80 Amps. WOW!!! Way too expensive though.
here is the link.
http://www.modelflight.com.au/axi.htm
hope it helps.
Warm regards.

> Hi Richard,
> Cc Dave,
>
> The RF format follows the "servo" format used in the R/C world. A PWM
> signal designed to control an R/C servo. The pulse width varies

around a

> center of 1.5 mS (.5 - 2mS), and the pulse is repeated at a 20 mS rate.
> There are PIC controllers to run R/C servos that can do this. The robot
> guys use 'em all the time.
>
> It would be difficult to control this R/C servo with Gcode, unless

it was

> the only thing the controller did! A special PWM signal (which

would have

> to run continuous) would be needed.
>
> A PIC controller could be devised to take step/dir signals and ramp

up/down

> a continuous PWM signal (1 "slot" in about 10). In this case, the CNC
> controller would generate an "up" direction and a few pulses to set the
> speed to the desired level.
>
> I like the idea of the high speed R/C spindle, just what I need for PCB
> work. I take it I can look for an "AXi 2826/10" motor at my local hobby
> store? How much?
>
> "continuous pulses" That's an oxymoron! The pulses are no doubt TTL

(.5V

> low, 4.5V hi) signals of sorts, it's the generation of them that is

a little

> more complex. And this stream of pulses doesn't start/stop like the

axis

> moves do. The "1 in 10" may be thought of as "time slots", if one were
> running 10 channels of servos (!), then the time allotted to one

servo would

> be similar to what's being described.
>
> Chuck, an old friend of mine from the "Homebrew Robotics club"

(Silicon

> Valley, circa '86) has a good write up.
>
> http://www.mcmanis.com/chuck/robotics/projects/servo.html
>
> Humm... That's a good circuit for an H-bridge, if the FETs are big

enough,

> (or half an H-bridge) ...could drive your motor. And the PIC code

could

> be modified to take an occasional step/dir command to set the spindle
> speed. COOL!
>
> Alan KM6VV

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