RE: Maxnc Spindle RPM

Message: 1
Date: Wed, 13 Feb 2002 12:21:52 -0500
From: "Alex Canale" <alex.canale@...>
Subject: RE: Maxnc Spindle RPM

Hey everybody,

I have a 15 CL2, I just replaced the 1/5 HP Dayton motor for another
identical one due to the fact that the original one crapped out after it's
estimated 300 hours of use.

As I installed the new motor I made sure I left the belt in the same
position. That is in the smaller diameter pulley on the motor side and
naturally the larger diameter pulley on the spindle side. In other words I
have it set up for maximum torque.

It ocurred to me that I would measure the RPM with a hand tachometer. It is
a mechanical device (unlike the laser one that shoots a beam at a reflective
spot of a shaft.) It only reaches an RPM of 4000. Then I Manual Data Inputed
M03 S1000. To my surprie I registered 3500 RPM on my hand tachometer. My
question is why? I don't get it. I'm assuming it's a software issue. Does
anybody know how to fix it? I'm also assuming that the previous motor was
acting just the same, I simply didn't measure the speed before.

Hi Alex-

[What don't you get? The spindle on a MaxNC will achieve 10,000 rpm if it's
set up to run 1:1 (that's how fast the motor goes, flat out.) It's also
possible to go even faster, but that's not recommended, as it exceeds the
specs for the spindle bearings. (Motor life will also be reduced). If you
reduce speed, as you did, by running the small motor pulley to the big
spindle pulley, you get more torque, but at the expense of speed. The speed
commands can't take account of different pulley settings, but if you give it
a S10000 command you'll get the maximum speed it will produce. Here's the
result of some tests that Bryan Harries <gab@...> ran on a similar
setup:]

Here are the results of the "no-load" tests, per request...

MaxNC-15 O.L. (1/5 HP)
Motor speed 100% 50% 25%
Brush voltage 95.6 45.6 25.5 (?0.1 VAC over all tests)
Top pulley 13,575 9,056 5,207 (Spindle RPM)
Middle pulley 10,225 6,992 3,723
Bottom pulley 5,814 3,947 2,359

Note: belt tension was minimal for these tests (this is how I normally run
my machine)...
For an example of the difference it makes; top pulley (belt tight),
at 100%, the spindle speed is down about 1,000 RPM, and at 25% it's down by
1,500 RPM.


I am also wondering how much tension do I need to have on the belt? Is a
1/4" of flex on the belt enough?

Thanks,
Alex

[If you're actually cutting, rather than testing, run the belt fairly tight,
and make sure the alignment is right on, to avoid undue wear. We talk about
MaxNC-specific issues like this in Bryan's MaxNC Yahoogroup: "MaxNC-users"-
you're welcome to join...]

Andrew Werby
www.computerwsculpture.com