In for repairs

It has been a bit quiet here lately, as I have had to make some repairs to the Morgan. The areas giving problems are the hot-end and the extruder.

After many hours, the extruder small gear gave up the ghost. This was an ABS gear working on a PLA large gear, which Quentin warned me would wear out one of the gears. I quickly installed another small gear, but within an hour or two it actually broke the large gear. By this time I had printed half another Morgan, including the extruder, so I assembled a completely new, bright yellow, extruder. Different stepper motor and everything.

The swop was quick, but did not last long. I then assembled another extruder on the old body (PLA gears both, and all holes on the body drilled out to allow the gears to fit without strain, i.e. very slight play). This is running on the Morgan now.

Looking at the yellow extruder, I found that the filament on the OUT side of the extruder had jammed internally. There is a hollow in the extruder body. My Bowden tube (tube inside a tube) fits inside the hole in the extruder, but only about 3mm. This creates a cavity and if the extruder exerts enough pressure, it kinks the filament inside this cavity. I will have to cut back the outer tube to allow the thin tube to fit deeper into the extruder body, sealing off the cavity.

The second area of attention is the J-head. Somehow or another I got the J-head temperature up to 350 degrees and jamming the plastic inside. I disassembled the J-head, but cracked the plastic body when screwing out the nozzle (I had to clean up the PTFE liner inside). This caused molten PLA to ooze out over the heating body, and under-extrusion through the nozzle. But thank goodness for Holts Firegum (exhaust fixing paste). As the tube says: "Self sealing, heat setting". Seems to work so far (OK, that's only half a print).