On Thu, 26 Aug 2010 18:51:13 -0500, Ignoramus29468
wrote:

On 2010-08-26, Jon Elson wrote:
Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

I am positive that it is a limit switch error.

So have you individualized them yet, Ig? If not, do so and try the
same cut. Let us know if it still errors out.


I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

Twisted pairs will certainly limit noise transmittal.


I'm waaaay behind you.
My sister got the -other- book for me on the re-purchase, and I think
I'll be happier with it. I'm just getting into it now. The info is
very basic (so far), but that reinforces info I've learned here. It
does not follow the programming style "cookbook".
http://fwd4.me/b47 _The CNC Cookbook_, E Hess.

I'll be getting Overby's book when it releases, too.
http://fwd4.me/b46 _CNC Machining Handbook: Building, Programming, and
Implementation_, Alan Overby (of Custom CNC, Inc. fame, high-perf
ShopBot controllers)

--
Not merely an absence of noise, Real Silence begins
when a reasonable being withdraws from the noise in
order to find peace and order in his inner sanctuary.
-- Peter Minard