Day 7 - Finishing the extruder

The stepper motor's shaft needs to be shaped rectangular to fit the small cog wheel.

I first taped the shaft inlet (not shown on the picture) to protect the motor from dust. Then I tried both a rasp and then a Dremel to get it into shape. I found that the rasp was the most effective tool to use.

You need to get down over half the shaft to be able to align the cog wheel with the bigger one later. Be sure to not take away too much, the cog wheel should be press fitted and still, not crack when you attach it.

Then it's time to put it all together, except for the hotend that is not quite finished yet.

Start with the PTFE sheet (bottom), load spread plate (top) and filament guide. Then mount the stepper motor and finally slide on the feed mechanism.

Adjust the small cog wheel so it easily connects with the bigger wheel. Here you can also see the rectangular shaft coming up from the small cog wheel.



The silicon sealant has hardened into a rubber like material now and we can continue to wire the hotend.
Assemble the nozzle, PEEK barrier and heat block. Attach the black (or red) wire to the thermistor wire as shown below. You can't solder them together, unless you use a highly specialized solder tin that melt above 300c. The easiest way here is to crimp them together with a ferrule. DON'T FORGET to insert the wires into 15mm (or so) high temp heatshrink. The common heatshrink usually only goes up to a 180c or so.

Also notice that these wires are made for high temperature installations, not the ordinary stuff you find in the local shop. Use the Kapton tape we left on the other thermistor wire to insulate the ferrule. Repeat the process for the other thermistor wire and the heat resistor. Use the Black & Red with the smaller ferrule to the thermistor and the Yellow & Gray with the larger ferrule to the heat resistor. Cut away excessive wires and legs, apply the high temp heatshrink and use a heat gun to shrink them in place. You should now have something that looks like this:

The colours Camiel have chosen doesn't make any sense to me. Usually Red & Black are used for main power and Yellow for small signals. However, the colours are not important but the pin numbers in the connector are. 1 & 2 for thermistor and 3 & 4 to the heat resistor.

Check the resistance on the thermistor again and the heater resistor. The heater resistor should be around 6 ohm or so.

As the next step I wrap the cables together with another piece of Kapton tape to hold them in place.

Then mount the studs and tighten. I guess the Nylock can't take the heat and that is why we lock them with two ordinary nuts.

All together it will look something like this:

As you can see the extruder is already mounted on the X-Sled, mainly because I had to rip it apart to press fit two nylocks I had forgot earlier. The Gray wire is nicely placed in a small slot behind the bearing.

Check the resistance again, both thermistor and heater resistor.