Hot end assembly

Goal

By the end of this section, you will have built the hot end, assembled it with the effector, and installed it in the printer frame.

Assemble the hot end components

The hot end melts the filament, and extrudes it, to build the 3D printed object.

Nozzle assembly

The nozzle is where the filament is heated and extruded from. You will need the following parts:

# Component Qty Type 1180 Brass nut 1 Hot end 739 Heater block 1 Hot end 1179 Threaded nozzle 1 Hot end 1136 Heatsink 1 Hot end

Screw the nozzle into the base of the heatsink by hand.
Screw the heater block onto the nozzle, again by hand. There is not need to use any tools at this stage. Take care to fit the heater block with the small hole nearest the nozzle tip.
Fit the brass nut. Using an 8mm spanner, gently tighten the assembly until it is just over ‘finger tight’. The constriction in the nozzle has a very thin wall, so care should be taken not to over tighten the assembly as it may result in snapping the nozzle.
Screw in the pneumatic fitting to the heatsink. There is no need to use a spanner, hand tightening is sufficient.

Thermistor

The thermistor is the temperature sensor for the hot end, and makes sure the hot end stays at the correct temperature. So it’s rather vital! You will need the following parts:

# Component Qty Type  430 Thermistor 1 Hot end  167 PTFE heatshrink 1 Hot end

This is how the thermistor should look with the PTFE shrunk onto it.

Test the cartridge heater

The cartridge heater provides the heat for the hot end. You will need the following parts:

Check the resistance of the heater cartridge. It should be around 7.0 ohms.

Thermistor wires

These wires connect the thermistor to the wiring loom.

Thermistor wires should each have the female terminal wrapped in heatshrink.

Assemble the hot end and effector

The hot end is mounted in the effector. You will need the following parts:

# Component Qty Type Hot end assembly 1 Assembled Effector assembly 1 Assembled 113 M3x25mm hex head screw 1 Fastener 242 M3x12mm cap head screw 2 Fastener 212 M3 plain washer 2 Fastener 368 3×2 Female Housing (3020-06) 1 Hot end 314 Cartridge heater 19v 1 Hot end 433 Thermistor wiring -160mm 2 Hot end Thermistor (insulated) 1 Assembled 1194 50mm blower fan – 160mm crimped 1 Electronics 133 Cable ties 2mm 2 Electronics

Pull the thermistor through the heater block. If you use pliers, use them on the PTFE heatshrink, NOT on the metal legs of the thermistor; you are likely to break the thermistor. Ensure the thermistor bead is seated centrally inside the heater block.
Push the hot end into the effector, orientated as shown. This may require a small amount of trimming of the printed effector part, but it is supposed to be a close fit. Do not trim the MDF effector plate; the hot end has a flange that sits on this. Bend the thermistor leg around the heater block; this ensures it can’t fall out. If the nozzle comes loose in the heatsink, taken the hot end out, tighten, and put it back in again.
This picture shows the lower flange of the heatsink sitting on the MDF effector plate.
Secure the hot end in place using the two M3x12mm cap head screws and M3 washers as shown. Take care to orient the heater block as shown, without loosening the nozzle in the heatsink, before tightening the M3 nuts.

Adding the heater, thermistor and fan

Connect the thermistor wires to the thermistor, and push the heater cartridge into the larger hole in the heater block. All wires should come out the same way.
Fit the fan into the printed effector. It should be a snug fit. Using the M3x25mm hex head screw, fasten it in place. This self taps into the printed part.
Secure the fan and hot end wires with the cable ties. Make sure the thermistor and heater cartridge are still fully inserted in the heater block. Try to cable tie the wires to keep them as close in to the effector as possible.

Hot end wiring

Wiring diagram

Put the pins on the ends of the wires into the six-way female socket. The wiring diagram, above, is looking into the back of the socket, where you insert the crimps. The little black rectangle is the locking tab, and the housing has small embossed ‘1’ and ‘6’ numbers on it, so you can orientate it as the diagram. The pins are crimped on one side, and smooth on the other. The smooth sides go downwards in the diagram.
Neither the thermistor nor the heater cartridge have a polarity so it doesn’t matter which way round their wires go. (Though the H+ and H- are the way that the machine will apply power – hence the labels.) Make sure to get the polarity of the fan right. This picture shows one of the fan wires being put into the housing, but it is not fully in yet; you can’t see the crimp easily when it is.
Check that the pins are all the same depth into the housing. The pins are very difficult to remove without damaging them, so check twice, plug in once! They should click into place, and then shouldn’t easily push further through, or pull back out.

Wire colours, related to hot end wiring loom

You can check the wire order by comparing it to the end of the hot end loom, which the hot end plugs into.

Mounting the effector

Orientate the effector so the fan is facing the open side of the printer. As you did when connecting the rods to the carriages, gently prise the rod ends apart, and slip them over the balls of the effector. Tighten the grip of the rods on the stainless steel balls, by tightening the M3x8mm cap head screws on the rods.
The printer so far.