J Head Nozzle

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J-Head Nozzle

Release status: working

Jhn mk5.jpg
Description
J-Head Nozzle and Thermal Barrier Based on a combination of ideas from the Makerbot Mk 5 hot end, The Inline Heater Variation, some ideas from Brian Briggs, and some ideas from me.
License
GPL
Author
Contributors
Based-on
Categories
CAD Models
none
External Link


Introduction

NOTE: All Research and Development on J-Head Hot-ends has stopped due to the availability of cheap chinese counterfeits that have been spammed throughout the online markets, don't work well, and have no support.


Jhn nozzles.jpg

This nozzle is a combination of ideas from other nozzle designs combined with a goal to reduce the number of custom machined parts to a bare minimum. By reducing the number of machined parts, it is hoped that the cost of this hot-end can be kept down while improving the reliability.

The use of a machined piece of round PTFE, as a liner, was requested in one of two designs by Brian Briggs.

The idea of using the PTFE tubing as a liner, from the Cold End to the tip, was borrowed from the Makerbot Mk V extruder design.

The PTFE tubing also acts to "bridge" the joint between the PEEK insulator and the brass nozzle/heater. By not having the filament in contact with this joint it is hoped that any possibility of leakage will be completely eliminated.

The use of a combination heater and nozzle was borrowed from ParCan's Inline Heater Nozzle Variation. However, instead of the heater resistor being mounted parallel to the path of the filament it is mounted perpendicular to the path of the filament. This was done to both reduce the length of the nozzle and to make it a little easier to run the leads from the heater resistor. Combining the heater and nozzle also helped to meet the goal to keep the number of custom machined parts to a minimum.

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 and the lightest version weighing in at under 13 grams, this design is very light.
  • Significantly more reliable at printing PLA than other designs. The set screw on the PTFE ensures even compression for a good seal to the brass. PLA becomes soft at very low temperatures and is also a very good adhesive. Minimizing crevices and using a long non stick liner path is ideal.

Disadvantages

  • Considerable machining is required.
  • Not suitable for high temperature materials.

Printing Instructions and Tips

  • The use of a cooling fan, for printing PLA, is highly recommended. If a cooling fan is not used, the chances of the hot-end jamming is greatly increased.
  • Do not obstruct the airflow through the cooling vents or, with the Mk III-B, around the heat sink.

Suppliers


Differences Between Real J-Heads and Cheap Clones


clones - removed see discussion page

Parts List

Mk I

Summary: First J-Head hot-end.

Jhn mk1.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v1.x) Machined Brass Nozzle/Heater Combination, Version 1.x
1 Nozzle Holder (v1) Machined PEEK Nozzle Holder, Version 1.x
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk II

Summary: Added a hollow set-screw to retain the PTFE liner.

Jhn mk2.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v1.x) Machined Brass Nozzle/Heater Combination, Version 1.x
1 Nozzle Holder (v2) Machined PEEK Nozzle Holder, Version 2
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk III

Summary: Added a heat sink in order to print PLA. To reduce weight, an aluminum nozzle is used.

Jhn mk3.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v2) Machined Aluminum Nozzle/Heater Combination, Version 2
1 Nozzle Holder (v3) Machined PEEK Nozzle Holder, Version 3
1 Heat Sink Machined Aluminum Heat Sink
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk III-B

Summary: Added a heat sink in order to print PLA.

Jhn mk3 b pic.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v1.x) Machined Brass Nozzle/Heater Combination, Version 1.x
1 Nozzle Holder (v3) Machined PEEK Nozzle Holder, Version 3
1 Heat Sink (v1) Machined Aluminum Heat Sink, Version 1
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk IV

Summary: Removed the heat sink and added a series of vents to provide cooling. To reduce weight, an aluminum nozzle is used.

Jhn mk4.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v2) Machined Aluminum Nozzle/Heater Combination, Version 2
1 Nozzle Holder (v4) Machined PEEK Nozzle Holder, Version 4
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk IV-B

Summary: Removed the heat sink and added a series of vents to provide cooling.

Jhn mk4 b.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v1.x) Machined Brass Nozzle/Heater Combination, Version 1.x
1 Nozzle Holder (v4) Machined PEEK Nozzle Holder, Version 4
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Support Washer Optional 1/2" Fender Washer McMaster-Carr 91090A114

Mk V

Summary: Reduced the size and increased the length of the melt zone. To reduce weight, an aluminum nozzle is used.

Jhn mk5.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v5) Machined Aluminum Nozzle/Heater Combination, Version 5
1 Nozzle Holder (v5) Machined PEEK Nozzle Holder, Version 5
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Flat Washer 1/4" OD Flat Washer McMaster-Carr 98032A436

Mk V-B

Summary: Reduced the size and increased the length of the melt zone.

Jhn mk5b.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v4) Machined Brass Nozzle/Heater Combination, Version 4
1 Nozzle Holder (v5) Machined PEEK Nozzle Holder, Version 5
1 PTFE liner (v1) 1/8" ID, 1/4" OD PTFE tubing, Version 1 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 1 EPCOS 100K B57560G104F
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Flat Washer 1/4" OD Flat Washer McMaster-Carr 98032A436

Mk V-BV

Summary: As the old thermistor was discontinued, the Semitec thermistor was substituted.

Jhn mk5bv.jpg

Quantity Part Description Part Number
1 J-Head Nozzle (v4.1) Machined Brass Nozzle/Heater Combination, Version 4
1 Nozzle Holder (v5) Machined PEEK Nozzle Holder, Version 5
1 PTFE liner (v2) 1/8" ID, 1/4" OD PTFE tubing, Version 2 McMaster-Carr 5033K31
1 Heater Resistor Axial, 5.6 ohm, 1%, 5W UB5C-5.6-ND
1 Thermistor 5 Semitec 104GT-2 or 104NT-4-R025H42G
1 Hollow-lock socket set screw 5/16-24 hollow-lock socket set screw McMaster-Carr 91301A150
1 Flat Washer 1/4" OD Flat Washer McMaster-Carr 98032A436

Mk VI-B

Not released due to cheap chinese counterfeits of J-head hot-ends. The innovation and production of new J-Head hot-ends has stopped due to chinese counterfeits that do not follow the specifications and have ruined the reputation of the product.

Mk 7-B

Not released due to cheap chinese counterfeits of J-head hot-ends. The innovation and production of new J-Head hot-ends has stopped due to chinese counterfeits that do not follow the specifications and have ruined the reputation of the product.

Mk 8

Only available through special order at http://www.hotends.com

Summary: Improved J-head with a better internal seal, axial thermistor, heater cartridge, and a fluted PEEK nozzle holder design. No kapton tape is required.

This design will not be publically released due to cheap chinese counterfeits of J-head hot-ends. The innovation and production of new J-Head hot-ends has stopped due to chinese counterfeits that do not follow the specifications and have ruined the reputation of the product.

Sundries

Description Part Number Notes
PTFE Insulation For EPCOS or Semitec Thermistor, 0.012" ID McMaster-Carr 5335K9
PTFE Insulation For Heater Resistor, 0.047" ID McMaster-Carr 5335K15
20 AWG High Temperature Wire McMaster-Carr 8209K11

Note: *A good drill-chart for anyone with plans to make one can be found here http://whatisacnc.com/index.php?cID=241

Installation

Using the Mounting Holes in the Wade Extruder

Wade Extruder

  1. Insert the nozzle holder in the 5/8 inch (16mm) hot-end socket.
  2. Using a sharp instrument or other object, mark the 4 hole locations on the nozzle holder.
  3. Remove the nozzle holder.
  4. Using a round file, file the mounting grooves in the nozzle holder in order to create 2 grooves for the mounting screws or bolts to pass through.
  5. Install the hot end.


Using The Support Washer

Note: The support washer cannot be used for hot-ends starting with the Mk V.

  1. Prior to installing the optional support washer, mark and drill the appropriate mounting holes on the support washer.
  2. Install the optional support washer in between the J-Head Nozzle and the nozzle holder.
  3. Use the support rods, screws, and/or washers to hold the hot-end in place.

Using Wire With The Support Washer

Example

  1. Cut 4 evenly-spaced slots in the support washer.
  2. Run the wire into the channels.
  3. Tighten the wire vertically and diagonally. Then wrap wire around the middle tightly, tightening all of the vertical and diagonal runs.


Using A Mounting Groove

Use a nozzle holder that is machined with the optional mounting groove and a cold-end that is designed for using a mounting groove or an adapter plate adapter plate for a mounting groove. In this configuration, a mounting groove is normally required.

Wildseyed Simple Hot End Mounting System

Note: Ensure that the cold-end either has a 5/8" mounting hole or can be drilled out to 5/8".

Follow the mounting instructions for the Wildseyed Simple Hot End.


Notes

General

  1. In the Mk1 version, the cold-end of the PTFE liner will need to be retained in order to prevent it from backing out of the hot-end. With some extruders, such as the Wade Extruder, the PTFE liner will easily be retained by the socket that retains the hot-end. If the liner is not properly retained, there is a high probability of the nozzle developing a leak.
  2. While printing ABS, if the nozzle clogs due to crystalized filament the temperature is most likely too high.
  3. Either black or tan PEEK can be used for the nozzle holders. Black PEEK is usually used as it looks nicer. However, sometimes suppliers are out of black PEEK and tan PEEK has to be substituted.
  4. When using a hot-end, with a vented PEEK nozzle holder (i.e. Mk IV-B), it is critical that the milled vents are not obstructed in any way. These vents are used to cool the hot-end by both removing as much PEEK as possible, to prevent the liner from being insulated, and to allow air to blow through and cool the hot-end. If these vents are obstructed (i.e. taped over), it is quite possible that PLA will jam in the hot-end.

Nozzle Orifice

Drill bit sizes and conversions

As drill bits usually drill holes slightly larger than their rated size, the following drill bits are used to drill out the orifice of J-Head nozzles:


Rated Size SAE Drill Bit Used Actual Metric Size
0.25mm 0.0098 0.2489
0.30mm 0.0118 0.2997
0.35mm 0.0135 0.343
0.40mm 0.0157 0.399
0.50mm 0.0189 0.480
0.60mm
0.70mm
0.75mm
0.80mm
0.90mm
1.00mm N/A 1.00

Notes:

  1. More sizes will be added as they become available.
  2. Smaller drill bits are used in order to keep the orifice size within the rated size and to increase the lifespan of the nozzle by ensuring that the orifice size will "wear to size" in the event that the orifice is slightly enlarged for any reason. (i.e. by cleaning with a piece of thin wire).

Nozzle orifice length

  1. Mk IV hot-ends (up to the middle of May 2012), and earlier models, had a nozzle orifice length of approximately 1.25mm.
  2. Mk IV hot-ends (after the middle of May 2012) and Mk V hot-ends have a nozzle orifice length of approximately 0.50mm.

Note: Due to the nature of 5c collets, the nozzle orifice length can vary as much as 0.25mm.

Troubleshooting

  1. PEEK appears to have a maximum temperature of 248 degrees C. If the nozzle pushes out of the PEEK nozzle holder, this temperature was most likely exceeded.
  2. If the nozzle is leaking, between the PEEK nozzle holder and the brass nozzle, check to see if the hollow set-screw is snug. This set-screw is located at the cold end and retains the liner. Wrapping PTFE tape, around the brass threads, will help to eliminate leaks as well.
  3. It is possible for the PTFE liner to impede the filament path if the hollow set-screw is too tight. This is because of the taper at the hot end of the PTFE liner.
  4. Ensure that the thermistor value is set to "1".
  5. In the event that the extruder is not feeding correctly, loosen up the pinch wheel and ensure that the filament can be fed by hand. Also, if possible, independently verify the temperature of the hot-end.
  6. If a cooling fan is blowing directly on a non-insulated nozzle, it is possible to have an uneven temperature on either side of the brass nozzle/heater. Under the right conditions, this can cause a condition where the temperature is correct, on one side, and too high, on the other. To resolve this problem, either insulate the brass or direct the airflow away from the brass.

Testing

Prototype

  1. While this nozzle is experimental, initial tests have proven to be very positive. At the time this note was added, the prototype had printed for well over 20 hours.
  2. Further testing indicates that it is critical that the internal gap, between the brass and the PEEK, is completely eliminated. If there is a gap, the PTFE will tend to "flow" into the gap and create a place for the filament to form a plug.
  3. Since this nozzle, internally, is similar to the Makerbot Mk V, testing indicates that it is probably a good idea to taper the PTFE at the hot-end of the nozzle.
  4. Testing of units with the internal gap, at the joint of the PEEK and the brass, have resulted in early failure. Replacing the PTFE liner would allow the nozzle to continue printing.
  5. Even with the internal gap, after two weeks the the initial prototype nozzle is still working.
  6. After almost a month, the initial prototype nozzle is still working. Due to the gap problem, it needs to have the PTFE liner replaced around once a week.

Mk I

  1. Initial testing of a nozzle, with the internal gap problem resolved, is very positive.
  2. A nozzle has been successfully tested extruding PLA.
  3. Some reservations have been expressed regarding the mounting of the nozzle. (Maybe the fender washer should be the recommended method or another method should be devised?)
  4. Extruding PLA can result in an early failure of the PTFE liner. This failure has been prevented by both increasing the feed rate of the filament and using a cooling fan. This is to keep the filament from getting to hot too high up in the liner. A heat-sink may be required in order to provide a more adequate solution.
  5. Due to this nozzle successfully printing both ABS and PLA, this entry has been updated to "working".

Mk I with Heat Sink

  1. Nozzles, with the experimental heat-sink, have been printing successfully. At this time, none have been reported to have printed PLA.
  2. The experimental heat-sink has shown to help considerably when printing with PLA. The configuration, that worked best, had the heat-sink with a fan providing active cooling. The air, from the fan, was directed to blow over the heat-sink and not the nozzle itself.
  3. When printing 3mm PLA, the heat-sink has proven to be very consistent and reliable.

Mk III-B

  1. PLA has been printed with a 0.70mm nozzle. However, there isn't enough heat provided by the heater resistor so the print speed has to be kept down. As a result, there is not advantage using a 0.70mm nozzle over a 0.50mm nozzle when printing with PLA.

Mk IV Original Prototype

  1. The version 3 nozzle, with a 6.8 ohm resistor, was used for testing.
  2. PLA has been printed with an airflow directed through the milled vents.

Mk V-B

  1. PLA has been printed successfully.
  2. ABS has been printed successfully.
  3. Some leakage has been reported when printing PLA. However, as long as the hollow set-screw is very tight, it isn't a problem. As "insurance", it is recommended to seal the brass threads with PTFE tape.

Experimental Light-Weight Hot End

  1. An experimental hot-end was built with a fluted nozzle holder and an aluminum nozzle (v2). A 1.75mm liner was installed and it was sent out for testing.
  2. With a fan, to provide cooling, this nozzle has successfully printed 1.75mm PLA.
  3. The light-weight aluminum nozzle should be insulated in order to maintain the proper temperature.
  4. This nozzle leaked. This was most likely due to the lack of a retainer for the 1.75mm liner.

Thermally Fused Hot-End

  1. An experimental brass nozzle was machined that would accommodate a thermal fuse.
  2. If a heater resistor were to be wired in series with the thermal fuse, the theory is that the thermal fuse would break the circuit to prevent the PEEK from melting. This would be ideal in the event of a thermistor failure.
  3. A static test was successful, however, thermal fuses are not yet readily available in the required temperature range.

Possible Future Modifications

Implemented Or Working

  1. If the extruder will not retain the PTFE liner, it may be possible to install a 5/16-24 hollow-lock socket set screw (McMaster-Carr part number 91318A550 or 91301A150) in the cold-end of the nozzle holder. (This has been implemented in the MK II.)
  2. Using 5/8 x 1/2 inch rectangular brass bar stock, instead of 5/8 inch square bar stock, will eliminate 1 machining operation, slightly reduce the cost of the raw materials, and may reduce the machining time for other operations as there will be less material to remove.
  3. Either the total length should be increased or two versions should be made available. The longer version would have a 50mm thermal barrier and the liner (for the MK I) should have an initial length of 3 1/2 inches.
  4. A groove-mount design could be created. However, a hollow-lock socket set screw (above) or a custom hollow set screw would have to be used to retain the liner. (The nozzle holder blueprint has been updated to include this option.)
  5. Add a starting taper to the cold end of the PTFE liner. (This has been implemented in the MK II.)
  6. A heat-sink option could be added to the nozzle holder.
  7. It may be possible to convert this extruder to 1.75mm by replacing the PTFE tubing with a piece of 1/4" PTFE that has been drilled out to 1.75mm. (This has been proven to work.)
  8. Use an aluminum nozzle made out of a high-strength aluminum alloy, such as 2024 or 7075. This should lighten the nozzle as well as improve the thermal conductivity of the nozzle. (Depending upon the alloy, the thermal conductivity, can be more than twice that of brass and an aluminum nozzle should be around 1/3rd the weight of a brass nozzle.)
  9. Turn the center of the nozzle holder down to 12mm and add fluting in order to provide cooling and weight reduction.
  10. Change to the 6.8 ohm heater resistor. The 6.8 ohm heater resistor has a smaller OD and, as a result, the heater block size could be reduced. (A prototype has been machined. Since it fits in a 13mm x 13mm piece of bar-stock, it is worth pursuing. The prototype weighs 3.1 grams.)
  11. Cut grooves in the nozzle holder to help keep the nozzle holder cold at the cold-end. (Grooves, with supports have been milled in a test nozzle holder.)
  12. Shorten the brass nozzle and reduce the number of threads. This will result in there being less brass to heat up and the heat-sink could be moved closer to the hot-end. (The threaded end, of the MK V, has been reduced to 0.500" from 0.560".)

Testing Phase

Under Consideration

  1. Use an axial thermistor installed in a through-hole. (Due to the limited amount of brass, in the J-Head Mk V-B, an axial thermistor cannot be installed properly and efficiently without a re-design of the nozzle.)
  2. Add a thermal fuse to prevent the PEEK from melting in the event of a thermistor (or other) failure. (See testing notes, above.)

Rejected

Note: Rejected ideas may be re-visited in the future.

  1. Add the capability to mount a thermocouple.
  2. Improve the thermistor mounting by adding a clamp or retaining system.
  3. Add shallow grooves, in the PEEK over the end with the 3/8-24 threads. This will add more surface area to the PEEK and may help with the cooling of the nozzle holder.


Miscellaneous

  1. A Mini J-Head nozzle design has been started. This design is a heavily modified version of the J-Head Nozzle.
  2. This design could be scaled down to create a mini version using a 4mm OD and 2mm ID PTFE sleeve. (See the Mini J-Head nozzle .)