Matthew Herd wrote: >> With an open-loop system, there is no measurement available other than >> your ears or a dial >> indicator. As long as it doesn't lose steps, you are OK. When first >> starting to machine >> actual work, watch out for missed steps. >> > > Thanks Jon! That's what I was afraid you'd say ... The default accel of 15 > caused intermittent stalls. 15 inches/second-squared? No surprise. I usually use between 3 and 5 on my machines. My Bridgeport snaps timing belts at 5, so I have to keep it below that. (The belts are too narrow.) > This was not a concern about precision so much as having adequate spindle > power and prevent premature failure of my ~1980 vintage 2HP motor. I was > wondering what range of speeds is recommended for a stock motor, as I know > that the horsepower will drop linearly from 60 Hz. Since you have the varispeed, I'd just set the VFD for 60 HZ and use the belt drive for speed control. But, generally, don't go below 50% except for short duration. I do sometimes go below that for light work with no heating in the motor. > I presume that it will also drop due to back EMF above 60 Hz, but at a much > less substantial rate. Is there a good way to observe used spindle > horsepower to know if I'm getting close to the limit, or do I have try it and > see if it stalls/faults? If your VFD has a current monitor setting, you can watch the motor current.
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