Mini J Head Nozzle

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Revision as of 22:34, 20 April 2012 by Reifsnyderb (talk | contribs) (Assembly)
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Mini J-Head Nozzle

Release status: experimental

Mjhn unfinished prototype.JPG
Description
Mini J-Head Nozzle, Thermal Barrier, and Mounting Plate based on the J Head Nozzle.
License
GPL
Author
Contributors
Based-on
Categories
CAD Models
External Link


Introduction

NOTES:

  • This page is under construction.
  • More pictures, descriptions, etc., will become available when they are ready.
  • Some of the current pictures do not show a finished nozzle tip as it will be identical to previous designs. When these pictures were taken, it was a proof-of-concept for the thread sizes, internal dimensions, fitting of the parts, etc.
  • An experimental unit has been completed and sent out for testing. Therefore, this entry has been updated to "experimental."
  • This page has now been marked as experimental and will be used for the 1.75mm Mini J-head.

This nozzle has been designed as a drop-in replacement for the RepRap Universal Mini Extruder hot end.

Advantages

  • Internally, the filament path is identical to that of an already proven design.
  • The design is simple as the number of custom machined parts is kept to a minimum.
  • If necessary, the PTFE liner can be replaced by using an off-the-shelf piece of PTFE tubing.
  • The PTFE is not stressed nor used to provide support. This reduces a point of failure that is part of other designs.
  • A resistor is used as a heater. There is no need to wrap nichrome wire or to bake a heater core.
  • Heat transmission is improved as there is no thermal junction where a separate heater screws onto the nozzle.
  • With most versions weighing in at under 25 grams, this design is very light.

Disadvantages

  • Considerable machining is required.

Parts List

Mk I

Quantity Part Description Part Number
1 Mini J-Head Nozzle (v1) Machined Brass Nozzle/Heater Combination, Version 1
1 Thermal Barrier (v1) Machined PEEK Insulator
1 Mounting Plate Insulator Machined Internally Threaded PEEK Insulator
1 Mounting Plate Machined Rectangular Aluminum Mounting Plate
1 PTFE Liner 4mm OD, 2mm ID PTFE Tubing McMaster-Carr 52335K32
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 100K B57560G104F


Mk II

Quantity Part Description Part Number
1 Mini J-Head Nozzle (v2) Machined Brass Nozzle/Heater Combination, Version 2
1 Nozzle Holder (v2) Machined PEEK Nozzle Holder, Version 2
1 PTFE Liner 4mm OD, 2mm ID PTFE Tubing McMaster-Carr 52335K32
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 100K B57560G104F

Sundries

Description Part Number
PTFE Insulation For Thermistor, 0.012" ID McMaster-Carr 5335K9
PTFE Insulation For Heater Resistor, 0.047" ID McMaster-Carr 5335K15

Machined Parts

Mini J-Head Nozzle

Version 1

Mjhn brass nozzle.jpg

Material: Brass Bar Stock, 5/8" Square Or 5/8" x 1/2" Rectangular, 0.875 Long

Note: 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.

  1. Cut a piece of brass bar stock 0.875 long plus enough to adequately hold the stock in the lathe.
  2. 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.
  3. Mount the brass bar stock in a 4-jaw chuck on a lathe. Adjust the chuck so that the nozzle axis is on center.
  4. Turn the threaded end of the nozzle down to 0.375 +0.000 -0.004. The threaded end will be 0.375, from the top end to the heater block section.
  5. Cut a relief groove to an OD of 0.305. This closest edge, of this groove, will be 0.100 from the heater block section. While the groove is about 0.040 wide, it's width is not critical.
  6. Thread the nozzle to 3/8-24 up to the relief groove created in the proceeding step.
  7. Using a 6mm drill bit, drill out the center of the nozzle to a depth of 0.375.
  8. Using a 4mm drill bit, drill out the center of the nozzle to a depth of 0.725.
  9. Remove the work piece and mount it by the threaded end so that the threaded end is centered in the lathe.
  10. Cut-off any excess material.
  11. Machine the nozzle tip to the desired profile.
  12. Drill the nozzle orifice.
  13. 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.)
  14. Using a letter size A drill bit, drill out the hole for the heater resistor.
  15. Drill out the hole for the thermistor.

Version 2

Thermal Barrier

Mjhn thermal barrier.jpg

Material: PEEK, 8mm Round, 0.775 Long

  1. Drill out the ID to 4mm.
  2. Turn down the end, that will be the closest to the hot end, to an OD of 6mm for a distance of 0.425.
  3. Cut a 30 degree taper on the tip of the hot end of the thermal barrier.

PTFE Liner

Mjhn ptfe liner.jpg

Material: PTFE tubing, 4mm OD, 2mm ID, 2 1/2 inches long

  1. Using a razor knife, cut the tubing to length.
  2. Cut an approximately 30 degree (or greater) taper on what will be the hot-end of the PTFE liner.
  3. After assembly, cut the tubing to fit the application.

Mounting Plate Insulator

Mjhn mounting plate insulator.jpg

Material: PEEK, 5/8" Round, 0.250 Long

  1. Cut a piece of PEEK to length plus enough to mount in the lathe.
  2. Turn down the shoulder to an OD of 0.500 -0.000 +0.0510. The shoulder will take up 1/2 the length of the PEEK insulator or about 0.125.
  3. Using a letter size Q drill bit, drill out the ID.
  4. Internally thread to 3/8-24.
  5. Cut off the mounting plate insulator so that it is about 0.250 long.

Mounting Plate

Material: Aluminum, 3/4 inch wide x 1/8 inch thick, 34mm Long

  1. Cut the mounting plate to the above dimensions.
  2. In the center (17mm from one end and 3/8 inch from the side) of the plate, drill a 1/2 inch hole.
  3. Drill both 3mm holes centered (3/8 inch from the side) 3mm from each end.

Assembly

Mk I

Mjhn unfinished dis.JPG NOTE: Mounting plate is not shown as it was not available when this picture was taken.

  1. Hold the nozzle so that the threads are up.
  2. Install the Mounting Plate.
  3. Screw on the Mounting Plate Insulator so that the shoulder is towards the mounting plate.
  4. Push the Thermal Barrier into the nozzle.
  5. Slide the PTFE Liner into the Thermal Barrier so that the tapered end goes into the nozzle.


Mk II

Notes

General

Testing

Future Modifications

Pictures