You can reverse with a VFD, no problem. You need to have correct ramping parameters set and probably brake resistors also.
i On Fri, Oct 19, 2012 at 9:47 PM, Greg Bentzinger <[email protected]>wrote: > > > I am converting a cnc knee mill from 3 phase to single phase. > > The spindle is 3hp (2.2kw) and I am fitting a VFD in place of the HD > relays that just turned the power on in FWD or REV. > > Speed will not be controlled directly by the VFD, only direction. The mill > (Hurco KM3P) uses the common Bridgeport style variable drive pulley system > and has a motor to adjust the pulleys while reading a tach for > verification. After speed is set it is not monitored. This is how the > current control (Hurco Max32) was designed, and for now I am retaining this > control and NOT doing an LCNC conversion. > > Others have done this with the KM3 model which does not have the > programmable speed function and it has worked great for them. I only have 1 > burning question. This machine can do near rigid tapping. I have floating > holders that only have about .09" total movement. The machine now taps by a > G84 type action and the control reads the tach and spots the zero crossing > point of the spindle reverse and ramps feed by the tach. Not perfect - but > close and great for its age. The regular KM3 does not have the tach > function and needs a float holder with more travel. > > 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. > > I'm trying to be as gentile and least excessive waste heat generation in > the components as I can while getting the usable function. > > BTW - I've been dying for a chance to make it over to MPM for a visit, I > am committed to a trip to the left coast in early May but I sure hope I can > escape again in June. I'm just next door in Colorado. > > ------------------------------------------------------------------------------ > 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
