On Sun, 2012-06-03 at 21:08 -0400, Dave wrote: > buy one or two PID controllers.
The slicing software can produce different extrusion temperatures for different layers (or classes of layers), so the printer needs programmatic control over *everything*. You may as well integrate all that in LinuxCNC, where it belongs. The thermal time constants of small extruders seem to be on the order of tens of seconds, while my hunk o' steel requires minutes. The whole extrusion process is strongly nonlinear along many axes, which is something that's becoming more difficult to ignore as extrusion speeds increase. With XY speeds under about 30 mm/s, the linear assumptions work reasonably well. Moving faster than that shows the limits: oozing from a "stopped" extruder, nonlinear flow-vs-pressure, nonlinear flow-vs-acceleration, and (for my printer) unstable mechanical construction. The threshold obviously varies with printer design & implementation, but the high end of of DIY 3D printing has now collided with the low end of CNC machine control. The limits of the Arduino-class controller programming model are becoming apparent (at least to me, anyhow). LinuxCNC could implement a complex extruder model as a HAL component, with inputs from temperature sensors and motion control, far better than an Arduino-based controller. Handling multiple extruders with different material properties would be relatively straightforward in HAL. Doing all the soon-to-be-required toolchanging, height probing, and platform leveling in HAL / Classic Ladder makes a lot of sense (again, at least to me). Methinks anyone working on such a contraption would receive a visit from a nattily attired lawyer who would explain his employer's view of the US patent system... -- Ed http://softsolder.com ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
