Patrick Ferrick wrote: >Hi everyone, > >I'm happy to report that I now have my fourth axis spinning. Not quite >as fast as I was hoping for, but it works. Now the issue is getting it >to move a specified number of degrees via gcode. Basically what I'm >getting is much smaller changes in the A value than the actual number of >degrees it spins. > > Great that it's moving :)
>It probably sounds like the INPUT_SCALE setting in the ini file is >incorrect (and it probably is) but I've tried lots of changes to it >without success so I think it's time for a couple of hints! Here's >what the mechanics of the rotary axis are: > >200 step motor w/24 tooth sprocket --> 95 tooth. I make that out to >be a 3.9583:1 reduction. >Then, a 28 tooth sprocket on the same shaft as the 95 tooth drives a 145 >toother on the actual rotary axis. Another 5.1785:1 reduction. >[Sounds like a nightmare when you write it out that way, but it's smooth >and stiff and mechanically it works well, so....!] > > You don't mention whether you're using half-stepping, quarter-stepping, or some higher microstepping. The math loks good to me. >So the overall reduction is somewhere in the vicinity of 20.498:1, which >would translate into 11.387 motor steps per degree. >INPUT_SCALE is supposed to be the number of steps per UNIT (which is 1.0 >on the ANGULAR axis), but setting it to 11.387 or 11.0 makes things go >really sloooooooow and I cannot for the life of me adjust the >MAX_VELOCITY to anything that moves it at a decent speed without >immediate following errors. > > If you're using stepgen, then following errors are a software misconfiguration. >Note: with INPUT_SCALE set to 4100 (the approximate number of steps >needed for 360 degrees) I get a good spin speed but the A values are all >out of whack with respect to the rotary table. I have tried lots of >combinations of INPUT_SCALE, UNITS, [TRAJ}ANGULAR_UNITS and cannot seem >to get it right. > > About how far does it turn when you issue G0A360? Also, if you disconnect the motor and turn the shaft by hand, does it take 11.387 turns to move the table one turn? >One other thing: when I try to get rid of the UNITS tag for the 3rd >axis and use [TRAJ]ANGULAR_UNITS (as it suggests in the manual) I get this: > >Starting emc... > >iocontrol: machine: 'TOWS CNC' version '1.4.2.4' >task: machine: 'TOWS CNC' version '1.4.2.4' >emc/ini/iniaxis.cc 192: can't find [AXIS_3] UNITS, using default >Traceback (most recent call last): > File "/usr/bin/axis", line 2299, in ? > unit = float(inifile.find(section, "UNITS")) * 25.4 >TypeError: float() argument must be a string or a number > > Hmmm. It looks to me as though this isn't fatal, but Jeff or Chris will know better. The message "cant find ... using default" rells me that it did what you want, but the traceback line concerns me a little. (again, I'm not a python expert, so I don't know if it's of concern or not) ><sigh> sorry this is so long-winded...anybody have any suggestions? > >Thanks a lot. > >regards, >Pat > > Hopefully, those questions will point you toward the solution. If not, please post again with microstepping, actual rotary travel, and the results of crakning by hand. - Steve ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
