I actually thought I was getting somewhere with this…
Managed to get one good print of something other than a box the other night, namely the knob for the display panel that will eventually be mounted on the front. Since then however its been a complete mess. Firstly there’s been no end of trouble getting the bed level, mostly this has to do with its design and the decision to have 4 mounting holes (one in each corner). Whilst this may be great for support its a right pain in the ass when it comes to adjusting them all. Secondly I wonder if the perspex that the heated bed is mounted on is too thin and flexes too much. This could explain why after I’ve spent 20 minutes leveling the whole thing when I go to print its sits too close to the extruder and appears to not be level again.
Tonight I also noticed an issue with the actual extruder. During another attempt at printing the knob I noticed that the large gear on the extruder seemed to be stalling at times that made no sense, i.e in the middle of a long pass (not near the end, when moving or any other times when you would expect the machine to not want to extrude material). Initially I thought that either the current limiting on the motor controller was set too low and the motor was stalling or that the limit was set too high and the controller was shutting down from overheating. Neither of these turned out to be the case, different current settings didn’t help and the heat-sink with the added fan was defiantly below the + 150 degree limit.
It turned out that the screw attaching the smaller of the gears to the motor shaft was slipping which left the motor still turning during these times but the gears and extruder stationary.
This was duly tightened.
I then gave the extruder a test, extrude 100mm of filament so I could check that it wasn’t slipping anymore and so I could reset the current limiting and this was when it all went wrong. Whilst fiddling with the motor controller I heard several clicking sounds coming from the extruder. I then noticed the brass lower section descending from the PTFE rod that attached the hot end from the extruder body. By the time I was able to hit the emergency stop button the brass section was most of the way out of the rod and only held on by the leads coming off the thermistor.
Needless to say this is a real bugger of a thing to happen, looks like tomorrow night is going to be spent ripping apart the x-carriage and extruder to see how bad it all is, hopefully the threads in the PTFE rod will be fine and the brass can just be screwed back in. At the moment the brass section is completely out of the ORFE rod and hanging from its power cables above the heated bed.
I’m not sure how to prevent this happening in the future however, I’ve had a look at the graph and the temperature never dropped below 183 so I know that it wasn’t an issue with the filament clogging up from being too cold. It looks like it just came down to too much filament being forced in the hot end and it not all being able to exit the nozzle quickly enough.