mhackney wrote:dpmacri wrote:Yeah, they're tough little buggers . But perhaps the skipping is due to an overheated mosfet and so the motor loses all of it's holding power momentarily while the mosfet shuts itself down for a split second .mhackney wrote:Have you ever tried to move a stepper that is powered up? You have to overcome the holding force which is quite high on these little buggers. The "retract" that I observe is a lot more than the spring effect of compressed PLA could provide. It's an odd thing!
Well, I've been running 100% reliably now and feel confident (after some confirming tests) that I know the root cause of my and probably other's EZStruders skipping steps. The culprit? heat! My attempt to install a heatsink on the extruder driver was almost a disaster but luckily I did not do damage to my RAMBo. But, I did remove it. I then installed a 40mm fan in the cutout LCD opening in the door in the chamber when're the RAMBo resides:
[img]http://mhackney.zenfolio.com/img/s10/v9 ... 8937-4.jpg[/img]
This fan is wired to my E3D barrel fan on a switch so I turn it on when I start up and leave it on all the time. The fan is simply glued into the slot, it is almost a perfect friction fit. Now with the fan directed at my RAMBo, the board stays cool and I've printed for 100s of hours with many looooong 16+ hour prints with no "tat, tat, tat"! And, just to verify my hypothesis, I switched off the fan part way through a print and in about 10 minutes I started hearing the "tat, tat, tats" again. I flipped on the fan, manually assisted the extruder until the RAMBo cooled and I was back into flawless operation.
Now I think the symptoms make sense, I was seeing the stepper/extruder reverse during these skipped steps. Probably the thermal shutdown shuts off power from the stepper coils allowing the compressed filament to push back, thus reversing the rotation a few degrees.
Printed all weekend including 2 12hr prints with the grey filament with no issues. This seems to have solved my skipping extruder issue , I will ALWAYS have fans running on the board. THANKS!!!