EMI. VFDs generate lots of it. You're likely getting lots of noise coupled into your limit switch cabling. Shield the vfd wires if possible. Running in a shielded single cable is probably best. Separate the motor and switch cables as much as possible too.
On March 6, 2015 6:56:08 AM EST, [email protected] wrote: > >I've just fitted one of them there 'Chinese' 2.2kW watercooled motors >with a Huanyang VFD as a second spindle on my mill. > >Last night doing some pocketing, when the cutter got into the 'meat' of >the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with >Axis 2 limit switch. > >This was unexpected as I was nowhere near the Z-axis limit switches so >I >checked the connections and started the job again.... and it did >exactly the same thing again in the same place! > >Just for fun, I reduced the DOC, tried again and the same thing >happened >in the same place (about 20 seconds into the job). Hmmmm.... > >The VFD is 1 foot away from the limit switch wiring, and the connection >from the VFD to the motor is shielded and grounded at the VFD end. I'm >controlling the VFD with hy_vfd over RS485. > >The limit switches (normal microswitches bolted to the column) are >wired >to a Mesa 7i76 with 12V field power and have not played up before. > >I did an 'air-cut' and that ran well past the place it was consistently >failing. > >I commented out: > >#net both-home-z => axis.2.home-sw-in >#net both-home-z => axis.2.neg-lim-sw-in >#net both-home-z => axis.2.pos-lim-sw-in > >in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits >were left unchanged. > >I ran out of time to experiment much further but I'm struggling to see >how the VFD could trip a simple limit switch when it's getting a bit >loaded up (the spindle was only pulling ~1amp according to hy_vfd and >it's rated for 8). > >I don't think it was simple vibration as I'd been fly cutting with my >normal spindle shortly before and that didn't trip anything. > >Any ideas what might cause this? > >-- > Regards, > Russell > -------------------------------------------------------------------- >| Russell Brown | MAIL: [email protected] PHONE: 01780 471800 | >| Lady Lodge Systems | WWW Work: http://www.lls.com | >| Peterborough, England | WWW Play: http://www.ruffle.me.uk | > -------------------------------------------------------------------- > >------------------------------------------------------------------------------ >Dive into the World of Parallel Programming The Go Parallel Website, >sponsored >by Intel and developed in partnership with Slashdot Media, is your hub >for all >things parallel software development, from weekly thought leadership >blogs to >news, videos, case studies, tutorials and more. Take a look and join >the >conversation now. http://goparallel.sourceforge.net/ >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
