I've gotten my Bridgeport BOSS 5 mill running fairly well. I'm using the Pico Systems USC board and LinuxCNC 2.4.6.
First off, I observed that the default acceleration values in the Pico-Systems sample configs were too high for reliable operation of the axes on the BOSS. Particularly, the Z would stall randomly. I suspect it has something to do with the microstepping on the Gecko 203V's, along with the high inertia and detent torque of the old NEMA 42 motors. First I dialed the rapid speeds, then the acceleration values way down and have had reliable behavior. I haven't touched the PID terms and have had no issues there once I got the Input Scale & Output Scale values set the same. Once I get the acceleration parameters tuned a bit better, I think I can turn the max velocity up to closer to factory values (120 IPM). Can anyone suggest a method for optimizing the acceleration values? Second, I have mounted my spindle encoder (512 CPR quadrature w/ index), wired it up, and copied the appropriate lines from the threading example config (from USC_motion.hal). I wanted to confirm that the 'scale' parameter in the line "setp ppmc.0.encoder.03.scale 6912" should be the counts per revolution, or in my case, 512 (or is it 4x512?). I'm looking for a way to confirm that the encoder is responding properly. I'd like to find a way to test the rigid tapping functions prior to actual use. Third, a series of questions relating to spindle speed control. By way of background, I have solid state relay control of the solenoids which operate the vari-speed drive air motor and the Pico Systems DAC board for adjusting VFD frequency. I plan on writing a component which will turn on the spindle, adjust the vari-speed drive as required, and trim with the VFD. At this point, I'm not sure I understand what I'll be getting for ppmc.0.encoder.03.velocity as I have not defined user units for the USC's 4th encoder channel because it doesn't correspond to a machine joint. I'm also wondering how I might be able to determine the direction of rotation of the spindle. Is the velocity pin negative when rotating counter clockwise and positive when rotating clockwise? I'd like to use this to determine whether the backgear is or is not engaged. Not that I've read through my hal files thoroughly on this issue, but I'm wondering if it would be feasible to make sure that motor rotation direction is automatically corrected for backgear engagement (to ensure that M3 rotates the spindle clockwise regardless of whether the head is in backgear or high range). I can see an instance where I forget to switch from/to backgear and break a cutter. If I can read spindle direction, then I can programmatically command a reverse in motor direction and prompt for a change to backgear if required (in theory). I suspect that none of this automatic speed setting & direction correction would work for the manual spindle start buttons in AXIS (at least not with a lot of reworking), but I can live with that. I think that's it for the moment ... Thank you in advance for your help! ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
