several folks (including me) reported problems with threading - namely oscillations of the spindle-synchronized feed (G33 and G76), mostly with homebrew encoders. Most people looked at their encoders and signal properties.
I've isolated the problem now with a *simulated encoder* - decoder pair - it looks and sounds the same like a real encoder with same PPR. After trying with various PPR values in this setup, it turns out the problem depends on PPR - if the PPR value is set high enough the problem goes away. Here's my observation points: PPR behaviour 2000 fine optically + acoustically 1000 acoustically not as clean as 2000, but fine otherwise 200 ok, but Z axis definitely sounds "rough" 70 Z axis oscillation clearly audible 50 heavy Z axis oscillation 45 same (that's my encoder disk :-/) 4 same I had the sim-encoder RPM fixed at 240rpm. The problem shows on both the threading.ngc and lathe-g76.ngc examples. -- Even if some folks have problems with encoder noise, I think the problems more likely stem from the fact that homebrew encoders tend to have a low PPR value - that might explain some of the observations. I dont fully understand the trajectory planner, but my gut feeling it's a control loop oscillation which gets excited with the encoder quantization/noise spectrum gets too close to the loop frequency. -Michael ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
