"I think that would come heartbreakingly close to working, because the feed rate depends so much on the effective diameter of the gear/pulley/wheel. A teeny difference in hobbing will eventually (i.e., over the course of a dozen hours) cause the filament loop to either vanish or spill off the table: gotta wrap some feedback around the filament coming off the spool."
I noticed that the A axis keeps track of total number of revolutions. I would think that the coding would not be that hard to do a diff between the A axis and the B-spool axis for amount of material feed. If you wanted to get fancy, linuxcnc could have virtual limit switches automatically trip if the loop difference is too small or large. Pause the machine, Hit an override to let out some more feed, or pause one axis for a set amount of filament feed. Outside that, I'd code the homing for the filament feed to have 40mm of feed slack available. (I am not thinking of a stepper to rotate the spool, but to draw the filament. Just making sure we're on the same page). On Sat, Jun 15, 2013 at 1:31 PM, Ed Nisley <ed.08.nis...@pobox.com> wrote: > On 06/15/2013 12:04 PM, Charles Buckley wrote: > > you could treat the spool feed as an > > additional axis whose feed rate is the same as the 4th axis. > > I think that would come heartbreakingly close to working, because the > feed rate depends so much on the effective diameter of the > gear/pulley/wheel. A teeny difference in hobbing will eventually (i.e., > over the course of a dozen hours) cause the filament loop to either > vanish or spill off the table: gotta wrap some feedback around the > filament coming off the spool. > > But it might be close enough. Do a coarse positioning at the start of > the print to put "enough" filament in the loop, then run the two motors > in parallel for a few hours without feedback. That would eliminate the > need to keep track of the filament while it flops around, which sound > like a Good Thing. > > > measuring the table temp for a heated table bed would also be good. > > The TC4 board also has four thermistor inputs... and I now have some 25 > A DC-DC SSRs on hand. [grin] > > -- > Ed > softsolder.com > > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by Windows: > > Build for Windows Store. > > http://p.sf.net/sfu/windows-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
