On 16.06.13 06:57, Ed Nisley wrote: > Bowden drives put the feed at the spool end of the guide tube, which > makes retraction less effective.
That's easy to believe. Is it perhaps feasible to retain feed control at the extruder, but add a simple DC unspooling motor and capstan, which puts e.g. 4 N force onto the filament in the Bowden tube? That would eliminate the (peaky) spool acceleration and rolling forces, and reduce the tube drag, while still allowing the feed capstan to retract the filament, as the unspooling motor would back up under increased pressure, given nothing more than a DC feedback loop from the force sensor. (I.e. One-transistor drive from an op-amp should just about do.) OK, there'd be noise on the force sensor (small strain gauge?) due to the filament being whipped about, but little of the acceleration would be axial, if the spool is high? (And filament mass in the tube isn't much in any case.) Dunno if any of that is viable, but it visualises nicely when I try to imagine it running. > The gotcha is that the filament loop thrashes around as the extruder > head zips back and forth. On the M2, that's only along the X axis, but > printers like the Ultimaker and Replicator move the extruder along both > X and Y. I'm not sure where the sensor would be happiest, because you > don't want to constrain the loop motion too much: pinning it to a board > at the top of the arch might be too confining. I'm imagining measuring the force applied to the filament at the stationary spool end of the Bowden tube. 3D printing is powerfully tempting technology and looks like a lot of design fun. Why can't they sell Round-Tuits, the same way as Bitcoins? I'd buy a boxful. Erik -- Was darf ich für sie bestellen? What may I serve you? Haben sie Schildkrötensuppe? Do you have turtle soup? Haben sie schon je Schildkrötensuppe gegessen? Have you ever eaten turtle soup? Nein, noch nie. No, never. Dann haben wir sie. Then we have it. (LHS snaffled from a post by Christian Brabandt on vim-users ML.) ------------------------------------------------------------------------------ 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
