Hi Russel, I got exactly the same troubles describes with the VFDs creating a lot of perturbation. Aspiration was also making perturbation for me. Thankfully at my work place we have experts on EMI and Stephen advices are what you need to follow.
In my case, to solve it I had to shield the cable between the VFD and the spindle and physically separate them (away from the cable chain in my case). Limits and touch probes are now with shielded cables and ferrites. Also Shields are touching the metallic part of the connectors so as to be linked to the electronic rack. Between electronic rack, VFD generator and the machine I have metallic braids (flat and large). Linking the axis together with this braids might have helped also (and not relaying on the balls from the guiding rails). I also have a metallic plate which "shield" the control computer from the VFD. Good luck solving this, sometimes it work for 20 minutes without tripping a limit, but there is hope even with Chinese parts, now, for me the setup is reliable. Cheers, -- Yves Watier 2015-03-06 13:36 GMT+01:00 Stephen Dubovsky <smdubov...@gmail.com>: > 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, russ...@lls.lls.com 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: russ...@lls.com 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. 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