> 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. It's easy to see you're losing steps if you're paying attention, but that's not always the case. I turned it to 10, and it wasn't enough. Finally, 5, and it worked perfectly for a machining run I did. But now I'm considering turning it up a bit. Perhaps instead I'll just restore the velocity values. I doubt the limited accel will have TOO much of an impact ... > It should be 2048. Use halmeter to read ppmc.0.encoder.03.position, > turn the > spindle exactly one turn and see if the value changes by 1.000 +/- a > small amount. > It should count up or down one integer value per turn if scale is correct. > > For final sanity check, make it run a tapping cycle in air with a tap in the > spindle, and put your fingernail lightly in the grooves of the tap. If > the whole > operation works right, your nail won't move up or down. You may also be > able to see this with a light shining behind the tap. Great advice, thank you. Better than trying to tap some soft material as a test! > This is using one variable (the S word) to adjust two things. It is > possible, but with the varispeed, there's > no need to change motor speed. Precise spindle speed is rarely > important, +/- 100 RPM won't make > much difference except at the lowest speeds. There are some things on > the wiki about closed-loop > speed control components. 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. 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? While I'm certain that the vast majority of my cuts are well below the horsepower limit, I don't know how to verify that. In order to get closer to maximum power, I envision a function with high and low limits for spindle speed error (say 75% to 150% of commanded speed). If outside that range, adjust the varispeed drive until I'm within the range. Then adjust the VFD to the appropriate value (say 45 Hz to 90 Hz). That way we're not running the varispeed drive too much, we always see at least 75% of peak power, and we don't overheat/overspeed the motor beyond reasonable limits, while still getting the full range of speeds (or more). Perhaps my concerns about power are overstated, I'm looking for your thoughts. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
