On 09/25/2016 08:13 AM, Kirk Wallace wrote: > On 09/25/2016 05:47 AM, Robert Ellenberg wrote: >> Hi All, >> >> Recently, I found a way to reduce the acceleration / velocity jitter during >> threading and tapping motions (see this issue on github >> <https://github.com/LinuxCNC/linuxcnc/issues/164> and the >> feature/spindle-sync-jiiter-fix branch >> <https://github.com/robEllenberg/linuxcnc-mirror/tree/feature/spindle-sync-jitter-fix>). >> The effect looks significant on the HALscope, but I'm not sure how much of >> a difference it would make on a real machine. Is anyone interested in doing >> a before and after test on real hardware? > > I added tapered threading to G76 to my local 2.7.6 branch. I had > concerns that the transitions between up to three synchronized path > sections might not be handled well. My tests with 1/8 NPT and .25-20 > straight threads with end taper worked well, but these probably would > tolerate some variation. The end tapers usually don't mate with > anything. I wanted to see what HALscope might show at these path > transitions, but I didn't see any velocity HALpins, off hand, on my Pico > servo setup, and I haven't taken the time to go any further on this. I > would like to, maybe in the coming week. I can look at your issue while > I'm at it. > > http://www.wallacecompany.com/cnc_lathe/HNC/ > > http://www.wallacecompany.com/cnc_lathe/HNC/
Hmm... I found this which means I need to look a little closer at my pin list: "... (All float output) 'ppmc.<port>.encoder.<channel>.velocity - Velocity scaled in user units per second. On PPMC and USC this is derived from raw encoder counts per servo period, and hence is affected by encoder granularity. On UPC boards with the 8/21/09 and later firmware, velocity estimation by timestamping encoder counts can be used to improve the smoothness of this velocity output. This can be fed to the PID HAL component to produce a more stable servo response. This function has to be enabled in the HAL command line that starts the PPMC driver, with the timestamp=0x00 option. ..." -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
