Since the last attempt at printing, several problems arose. I wrestled with the Makerbot over Canada day trying to get it to work, but with no luck. For the sake of documentation, here are two major problems we're having as of now:
1) Weird Temperature Spikes
The Makerbot we're lent is from batch 9, which means it uses the 1mm thermistor. and as Eric pointed out in the previous post, that means we have to set the extruder temperature to 240C. However, around 230C, a series of weird spikes occur:
At first, we had no idea what these spikes were. It seemed impossible that the real temperature would just change like that. It also didn't seem like these spikes were caused by the PID feedback loop; after all, the temperature was kept stable at 200C (as shown in the screenshot above).
We spent searching the Makerbot website for several hours to no avail. It seemed like we were the only one with this issue. All out of options, Eric suggested me that I document the problem on this blog for future reference. Halfway through typing the first paragraph, it came to me:
"Hey! It's the signal from the nichrome wire!"
Indeed, LED6 on the extruder board cycled on and off exactly in sync with the spikes on the temperature graph. Suspecting a short between the nichrome wire and the thermistor, I measured the continuity between one of the heater wires and one of the thermistor wires. No continuity.
Puzzled, I started measuring continuity between two terminals, and as it turns out, the resistance between the "B+" terminal and the top thermistor terminal measures to be less than 100KOhm. Well, that's what happened 30 minutes ago. Now, there is no continuity between terminals, and I can't seem to replicate the continuity between any combination of two terminals. (The issue persists, though.).
2) Extruder Motor Refuses to Stop
This issue is just as weird as the first one. We were able to stop the extruder motor on command until today afternoon. However, for no particular reason I can't think of, the motor decided not to follow the stop command. Upon pressing the stop button on ReplicatorG's control panel, the motor briefly pauses, reverses (which is normal), and then starts going forward again.
I have tried resetting the board, swapping the ethernet cable, and even reloading the extruder firmware, but the problem seems to persist.
Well, I got a good (bad?) news. Issue #2 decided to resolve itself. I'm not sure if it's a good thing or not.... Probably not.
All in all, we're stuck pretty deep. I'm starting to suspect a faulty extruder board, but I asked about these issues on Makerbot Wiki nonetheless.
Hopefully we can figure out what's wrong with the Makerbot before this weekend ends. :D
Until next time,
David
Watrapter Team Co-Lead
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