Mini J Head Nozzle
- Internally, the filament path is identical to that of an already proven design.
- If necessary, the PTFE liner can be replaced by using an off-the-shelf piece of PTFE tubing.
- A resistor is used as a heater. There is no need to wrap nichrome wire.
- Heat transmission is improved as there is no thermal junction where a separate heater screws onto the nozzle.
- The brass nozzle requires considerable machining.
|1||Brass Mini J-Head Nozzle||Machined Brass Nozzle/Heater Combination|
|1||PEEK Insulator||Machined PEEK Insulator|
|1||PEEK Support Plate Insulator|
|1||Heater Resistor||Axial, 5.6 ohm, 1%, 5W (UB5C-5.6-ND)|
Material: Brass Bar Stock, 5/8" Square Or 5/8" x 1/2" Rectangular, ? Long
Note: These instructions differ from the machining example displayed in the above picture and are only one example of how the nozzle can be machined. The machining process can vary depending upon available machinery and tooling. The minimum machining requirements are a metal lathe with a 4-jaw independent chuck.
- Cut a piece of brass bar stock 1.125" long plus enough to adequately hold the stock in the lathe.
- On the brass bar stock, find the center of the axis of the nozzle. This can be done by various means ranging from using a milling machine to using marking fluid, a height gauge, and a surface plate.
- Mount the brass bar stock in a 4-jaw chuck on a lathe. Adjust the chuck so that the nozzle axis is on center.
- Turn the threaded end of the nozzle down to 0.375 +0.000 -0.004.
- Thread the nozzle to 3/8-24 up to the shoulder of the heater section.
- Drill out the center of the nozzle using a 6.5mm drill bit.
- Turn off the last 3 threads, at the end of the nozzle, and cleanup the threads.
- Cut a 30 degree taper on the very end of the threaded end of the brass nozzle. This is to completely eliminate the internal gap between the brass nozzle and the PEEK thermal barrier. This gap would exist due to the internal taper created by the cutting edge of the drill bit.
- Remove the work piece and mount it by the threaded end so that the threaded end is centered in the lathe.
- Cut-off any excess material.
- Machine the nozzle tip to the desired profile.
- Drill the nozzle orifice.
- Mill or turn off the excess material in the heater section. This can be accomplished by mounting the nozzle in the 4-jaw chuck sideways so that the excess material is presented for machining. If available, a milling machine can also be used. (If a 5/8" x 1/2" piece of bar stock is used, this step will be skipped.)
- Using a letter size A drill bit, drill out the hole for the heater resistor.
- Drill out the hole for the thermistor.
Material: PEEK, 8mm Round
Material: PTFE tubing, 4mm OD, 2mm ID
- Cut an approximately 30 degree (or greater) taper on what will be the hot-end of the PTFE liner.
See also: Extruder Nozzle Variations