Tuesday 29 November 2011

Chapter 22 - In which I mount the hot-end, and find useful things in the garage

Firstly let me apologise for not posting in a while. Things have been busy here, and as usual the write-up get left until later. We resume our story just as I have built my DIY nozzle and heater block....

With the hot end assembled, it was time to mount the thermal barrier. It was a tight fit in the heater block, so I got it started by hand and then used a ratcheting clamp to squeeze it fully home.



I mounted a 2.5mm drillbit in a chuck for the electric screwdriver, and drilled and tapped the holes to hold the thermal barrier in place.


 Next I test fitted the heater resistor and its spacing sleeves into the battery clamp. As the following photo shows, there was still a gap to eliminate.


Remembering a tip from the forums, I wrapped the outer sleeve and the resistor with tin-foil, until they were a tight fit within the clamp.


Next I mounted the extruder body to the X-carriage and wired it up. I mounted a terminal block with cable ties through the fan mounting holes on the carriage.


I loaded up the feedstock and performed the E_steps_per_mm calibration for volumetric extrusion as found (prusa method: insert link here).


I performed the calibration with the hotend removed for ease. I ended up with a figure of (EDIT, May 2012:  I found my initial E steps figure during a tidy up - I worked it out to be 488.4)

I prevoius look around my Girlfriend's Dad's garage had provided me with a crimping tool, that I used to fit some PTFE wire to the resistor legs via a pair of bootlace ferrules. Isn't it funny that sometimes the right tool turns up at the right time?






I covered the outer nozzle sleeve in a thin layer of heat sink paste, and set about clamping it into place. I had thought this to be a fairly easy task, but it turned out to be much harder than I had anticipated. The outer sleeve wasn't really big enough and so there was a very large reduction to be made by the clamp's bolt. Eventually I had to resort to a pair of pliers, as the bolt was distorting the clamp too much. With the aid of a very patient girlfriend, it was eventually tightened up.


I fitted the sensor as far into the hole as it would fit, and held it in place with a small peice of wire.




I screwed the mig tip into the barrier, and tightened it up. Then I fitted the heater and thermistor wires into the terminal block, and competed the wiring to the board.



Next up: Will it actually work...?