On 07/20/2020 07:04 PM, Gene Heskett wrote:
I think I'd drag out one of my 100+ MHZ scopes and look for noise of the
type one might get from lack of a single point ground.
Right. if the indexres test of the diagnostics shows the
position resetting multiple times/rev
(may only happen when spindle drive is on) then there is
noise on the Z. The A and B have digital filtering that
only accepts valid state transitions of the quadrature wave,
that hides a lot of really nasty garbage that some systems
have. There is no way to digital filter the index pulse, it
is edge-triggered, and a 10 ns pulse could trigger it.
But, noise on the index will only affect the place where the
spindle sync motion starts. Once the spindle encoder senses
an index pulse, then everything is counted from there. So,
a noisy index pulse should NOT cause the Z axis to behave as
the videos show. OHH, wait a minute! One thing that COULD
cause this behavior is if the move exceeded the Z soft
limits. Z would freeze at the most extended part, and then
pull back when the spindle count brought the position back
within the soft limits. That's exactly what it did in the
first video.
So, Matt should check what his Z soft limits are set to in
the .ini file, and then home the axis so
it won't be exceeding the soft limits.
Having just spent about 3 weeks solving a ground loop issue
on a PWM servo system remotely, they
can cause an amazing array of crazy symptoms. Having the
user shorten up all the wiring fixed it.
Jon
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