Hot End

This component is the one that does the printing. You can print with one filament per hot end that's installed on your printer. Software can generally accept multiple hot ends but the limiting factor is the number of motors that your Arduino/Ramps 1.4 board can control seperately (the 2 Z-axis motors count as 1). Here are the main types of hot ends: 
Hot Ends                                              Filament Dia.           Nozzle Diameter
- Single (e.g. J-Head or E3D)              1.75mm                     0.25mm      High precision low speed
- Double (e.g. Chimera)                     3.00mm                     0.30mm
- Tripple (e.g. Diamond Head)                                              0.35mm
- Quad  (e.g. Kraken)                                                              0.40mm      Balanced
                                                                                                  1.20mm      Low precision high speed
We are using a "J-Head Mk V-BV" single hot end with a 0.50mm nozzle and 1.75mm filament. This gives great results and a great place to start as its more reliable as well. But you can easily change this by simply switching the hot end (or nozzle only if you prefer) and changing the settings in Slic3r and in Repetier-Host. (should be black not beige in picture below)
The Extruder
This is the device that takes the filament, heats it, and then places it exactly where needed to make your 3D print. It's main parts are:
  • The hot end                    ... melts the plastic 
  • The extruder                  ... grabs filament from the spool and pushes to hot end 
  • The mounting                ... holds the extruder and hot end in place
There are all kinds of different looking extruders on the market but they usually fall into one of two types: Direct Extruders or Bowden Extruders. 
Bowden extruders allow the extruder motor pushing the filament to be away from the hot end. It grabs the filament from the spool and pushes it through a PTFE tube to the hot end. This reduces the weight of the printing heat (package of hot end, extruder, and mounting) which can help increase print speed and reduce vibration, but its more prone to problems.
Direct extruders, like we use below, are more reliable or at least easier to trouble shoot and a little simpler. With a single hot end like we use, not much is gained with a Bowden.
Step 1.  The 3 plastic parts 
The photographs contain modified parts to make viewing easier, so they are not exactly as the 3 parts that we will use. 


Add the left and right fans holders as shown below by screwing in the two small M3 x 25mm screws with M3 nuts. Tighten them sufficiently so the fan holders can remain in a chosen position. Once done, carefully place the 40mm 12v fans in each one.  


The Hot end kit contains:
  • Brass nozzle         (screws in heating block)
  • Brass heating block
  • Cooling tower      (beige in the picture)
  • Heat resistor        (heating element)
  • Thermistor           (tiny thermometer)
  • PTFE linner           (helps guide filament)
Heat Resistor opening in Heating Block
Thermistor opening in Heating Block
Brass nozzle
Heat Resistor goes here
Fitting in the parts is simply, but it is important to minimize the space or air between the heat resistor and the heating block. If its too lose, then wrap the heat resistor in foil before inserting in heating block. 
The thermistor is very small an finky, but critical to your printer. Make sure the small wires aren't crossed (short circuit) as that will give a false reading that tempurature is very high. You should look to tape in in place using Kapton tape.

Parts for this section

  • Plastic parts 
  • 1 Nema 17 stepper motors                          ... 1.8 degree per step and ideally 4800 g/cm holding torque
  • 1 fan 30mm 12v
  • 2 fans 40mm 12v
  • Mini hyena v2.0 for 5mm shaft                    ... little wheel with groove and teeth to grab filament
  • 1 screws M3 x 25mm
  • 4 screws M3 x 40mm 
  • 2 screws M3 x 30mm
  • 3 nuts for M3 screws
  • 10mm Spring
  • Idler bar 5mm diameter
  • 605zz ball bearing
  • J-Head MK V-BV kit:
           - cooling cylinder
           - brass nozzle (0.50mm dia.)
           - brass heating block
           - Heat resistor (heating element)
           - Thermistor
           - PFTE tube for thermistor leads (wires)
           - PFTE tube for heat resistor leads (wires)
           - PFTE tube to guide filament into hot end
30mm fan mount
40mm fan mount-right
40mm fan mount-left
Extruder idler
Extruder body
Extruder flange
Insert and hold  M3  hex nut
Insert the Mini Hyena v2.0 on the 5mm shaft of the stepper motor and tighten the lock screw to the shaft. The rest of the assembly will scew into the 4 holes on the stepper motor.
Extruder body
Extruder idler
Extruder flange
Place the idler bar through the center of the bearing, and then place these pieces in the slot as indicated.
Next, place and hold the M3 hex nut while you insert and screw an M3 x 25mm screw from the opposite side. Place spring on the foot of the screw which comes through the nut. This screw will be used to tighten the grip of the hyena on the filament.
Once the extruder body is in place, adjust the position of the mini hyena to align it with the filament's path to the hot end below.
Next, place the extruder idler and hold in place and set the 10mm  spring into position. The fimalent must slide between the mini hyena and the bearing. Do no insert screws yet !
Finally, place the extruder flange and insert the four M3 x 40mm screws. In reality the extruder flange would cover the extruder idler and hold the top of the hot end in place.
The top right screw serves as a center of rotation. The spring pushes the extruder idler away to tighten the grip on the filament.
Similarly, by compressing the spring, the extruder idler moves away from the filament which releases the grip the mini hyena has on the filament 
Here's the dynamic with the filament in place.
The complete extruder assembly including the hot end held in position. The fan for the hot end can be seen here as well.
Next we need to mount or attach the extruder assembly to the X carriage that was previously assembled and assembled on the X-Axis v-slot rail. This is easily done with two M4 x 30mm screws with two M4 nuts. One screw is postioned at the top center of the X-Carriage and the second is positioned bottom center.
The screw slides in and can then be fasted tightly into place. Now the extruder assembly is fastened to the X-carriage.