Re: MaxNC modifications

I don't know if your problem is the same, but I had the same thing happen to
me as I increased the amps I started getting problems with lost steps on
curves. It was particularly bad with about a 1/2" radius and moving around 7
ipm. The step loss was quite consistent on the parts with curves, but I
could do slow or rapid moves along an axis all day long and the moves were
perfect with no steps lost. It ended up being a shielding problem. I thought
the interference was coming from the mosfets & heatsinks, but Jon made a
post and thinks it is from the circuit board (with his knowledge and
understanding I don't have much reason to disagree). Dan Falck posted about
having a similar problem as he upped the juice on his system also.

The fact that your loss of steps increased as you upped the amps makes me
think you are experiencing the same type of thing. When I was lossing steps
I also would notice that the motor was running very ragged. More shielding
caused my step loss to go away and the motor started sounding much smoother
running.


Tim
[Denver, CO]

> -----Original Message-----
> From: Jon Anderson [mailto:janders@...]
> Sent: Wednesday, June 16, 1999 11:46 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] MaxNC modifications
>
>
> From: Jon Anderson <janders@...>
>
> Tim,
>
> The only that that has remained the same since I first ran into lost
> steps is the MAXNC ways and thrust bearings on the leadscrews.
> Everything else has been swapped or scrapped at least once. We've even
> tried swapping drivers to different axis' and moving motors around. To
> be sure, it's a LOT better than it was. Initially we were getting some
> pretty random lost steps. Sometimes a little, sometimes a lot, this with
> the MAXNC software. Ah-ha reduced lost steps a lot and at first we
> thought we'd licked it. MAX software would lose 4-5 steps just
> interpolating a single circle. Ah-ha lost steps didn't surface until we
> tried running real world parts. All the little test routines I'd written
> for debugging the MAX passed muster with Ah-ha. I should have made that
> distinction up front.
> We've cranked the motors up to 5 amps and they just get noisier.
> Can't recall, but I think it did change the lost step amount for the
> worse. I can do single axis linear moves at 60"/min all day and not lose
> steps, running at 3 amps.
> Did have someone mention quite some time back that I ought to put some
> large capacitors between each driver and the PS to help reduce current
> draw during sudden acceleration. Does this sound like something I ought
> to try? I should have made notes then and there, but I don't recall how
> I was to size the caps.
>
> Jon
>
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