On Fri, 2012-10-19 at 20:37 -0500, Jon Elson wrote: > Greg Bentzinger wrote: > > > > My problem is this - with site 3phase power you can throw a motor running > > forward into reverse and it just does it. I'm sure the control has a ever > > so slight delay between relay actions to allow for mechanical times to > > prevent switching "shoot through" but I have no idea what this delay is. I > > don't think I can just switch direction on the VFD without first going > > through a breaking action. For any other action the machine would just open > > the relay, let the motor coast down for 6 seconds then apply a spindle air > > break to lock the spindle. E-stop drops the relay and applies the break > > instantly. > > > > I am using a Teco FM50-203-C and I also have the optional breaking > > resister. I would prefer to let the motor coast and just reverse it for > > tapping but I don't know if a VFD can take that kind of repeated abuse - > > lots of tapping. > > > > So - do I need to hook up the breaking resistor and have it set to break > > the motor in under a second? How would the VFD be setup under LCNC to do > > tapping? - I watched Ander's rigid tapping videos and it looks like it is > > reversing at full programmed speed. > > > > > Yes, you need a braking resistor or the VFD will fault when the spindle > is at high speed > and you ask it to stop. But, it still won't stop and reverse like plug > reversing a 480 V > motor. It will probably take almost a second to reach zero speed. If > the CNC control > expects it to act like a plug reverse, you may have a big problem, > depending on how > much slack there is in the tap holder. (Of course, if it is really > smart with the tach, > it may actually do a fine job regardless of how fast the spindle > actually reverses.) > > I do absolutely rigid tapping on my LinuxCNC Bridgeport with an encoder on > the spindle, and I actually had to have LinuxCNC slow down the reversal > a bit > to get the most accurate following of the Z axis. > > Once you've tried real rigid tapping, you'll be hooked. I figured out > how to adapt > a spindle encoder even to a machine that made a traditional approach pretty > much impossible. See http://pico-systems.com/bridge_spindle.html > for some pics and description. > > Jon
Jon, That is a really cool approach and I have the sensors but my project list is very long and due for some offset soon. Dave > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://p.sf.net/sfu/appdyn_sfd2d_oct > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_sfd2d_oct _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
