Saturday, October 10, 2009


One step forwards

G'day all.

I've been quiet recently - I had packed everything away into the garage as we were planning to move. Plans change, we're now not moving so I unpacked the RepRap and fired it up.
From ResistorHeater

First problem : blocked nozzle, due to a broken thermistor - overheated - and set the ABS solid.
Cleared down and drilled it out.

I replaced the thermistor with a spare 100k makerbot one - my last spare.

Interestingly enough, I soldered in a 100k thermistor from Maplins into a spare circuit, connected it up, and the temp read about 20C at room temp, and 34C while holding it - pretty good without any change in configuration. It might be a suitable replacement for the 'official' ones.

Replacement thermistor in, I warmed up the heater and 'let rip'
From ResistorHeater

It works! Extrusion is pretty slow (232mm/minute) and wide (nearly 1mm diameter through a 0.8mm nozzle) but it comes out reliably and pretty consistently. Temp was about 225C and power (screw thread/servo) at 180/255.

Now I have something working, I can refine the nozzle size ( I should be able to get some 0.6mm B&Q nozzles) and the original BfB 0.4mm nozzle, plus I have some small drills.

I now need to get my settings and speeds right in the host software - my current version is months old, maybe I should update. I've been thinking about upgrading to version 3 electronics, too, but with the excellent Mendel design out with a much smaller footprint, I quite fancy that. It might be time to build a Mendel using my Darwin....


Did you mean 23.2 mm/s or 2.32 cm/s because 232 mm/s is not slow.
My mistake.
not per second - as stated.

oops- only a factor of 60 out...

3.8 mm/sec? Are you sure?
yes, I think so... I cut the thread off, then let it run for exactly 60 seconds, and cut it off again.
This is a 0.8mm nozzle though, so the thread is nearly 1mm diameter.
Makes sense,1mm thread means that 4 times the volume of material is pushed out vs .5mm. If the only thing limiting extrusion speed was the feed of 3mm filament this would be equivalent of about 15mm/s which is a pretty standard speed for my BfB machine.
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