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 ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
