Anders Wallin <[EMAIL PROTECTED]> wrote: > > Hi All, > > I have a 750W induction motor on my spindle and a cheap open-loop V/f > variable frequency drive. > > As I am converting the rest of the machine to closed-loop I'd like to > have a closed-loop spindle drive also (think rigid tapping!). > > A DIY way of closing the loop would be the following: > -Control the VFD using its 0-10V analog input (use the 4th DAC on the > m5i20 card) + direction input. > -Fit an encoder to either the motor shaft or the spindle > -close loop in EMC using PID > > > Has anyone done this ? What problems have I not thought about ? > The only thing I can think about is overheating of either the VFD or the > motor when running at low rpm and high torque.
Hi Anders: The Mazak at the CNC workshop has a DC motor, and a DC spindle drive with a 0-10V speed reference. We fitted a 360 ppr (1/4 degree per count) encoder to the spindle for doing spindle orientation prior to the toolchange. I used a PID loop, as you discussed. In this case tuning was a pain, because: 1) The encoder resolution is very low 2) The encoder is on the spindle, not the motor, and there is several counts of backlash in the gearbox that connects the two. If you can fit the encoder without spending too much time or money, I'd at least give it a try. Regards, John Kasunich ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
