RE: [CAD_CAM_EDM_DRO] Advice on moving forward

OK. I'd always thought of microstepping as something you did to increase
resolution, but I can see how it tackles resonance.. I'll implement it and
test.
Many thanks for the responses. I certainly wouldn't have thought of this
myself.

.....

We'll I implemented 10step microstepping. No difference :-(
I'll pinch a fast cro from work and take a closer look.
If the problem is a resonance I should see motor impedance decrease as step
rate approaches the resonant rate of the motor yes?

Cheers

PK

> -----Original Message-----
> From: Jon Elson [mailto:elson@...]
> Sent: Sunday, 13 July 2003 6:01 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Advice on moving forward
>
>
>
>
> paulk6158 wrote:
>
> >Hi folks, I've spend some bleary hours tolling the archives (LOTS of
> >good stuff there) but haven't found a directly applicable post so, if
> >I may ask.
> >
> >I've spent about 3 months tinkering with stepper drivers designs
> >based on pic micro's. With acceptable results.
> >Recently I bought a larger (400oz) motor rated at 3V 4A.
> >I just can't seem to get this thing to work at more than 150PPS!
> >At 100PPS it's fine. Really good torque, no problems.
> >
> >
> This sounds like a typical resonance problem. If you have no electronic
> damping, you are going to get a strong resonance, and 150 PPS on an
> unloaded motor is right where I might expect the first one to pop up.
>
> The first thing to try is see if the motor performs a bit better if you
> wrap a rag around the shaft and hole it tightly. This is providing
> mechanical damping, which will also absorb the resonant energy.
> If so, that confirms the diagnosis. You can try developing a simple
> RC damper, with a few Ohm resistor in series with a pretty large
> capacitor. I come up with something like 10 Ohms and 2.6 uF
> These values are VERY rough, anything within +- 50% would produce
> strong damping at this speed. (I'm calculating based on 150 pulses/sec
> in full step mode = 37.5 Hz on the actual pulses on each winding.)
> You would put the dampers between the far ends of each winding.
> This should work for both unipolar and bipolar drives.
>
> Most modern stepper drives use more advanced electronic methods
> of providing this damping. I've used the Gecko G201A drive, and it
> has adjustable damping, which works AMAZINGLY well!
>
> Jon
>
>
>
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