Introduction

With one exception, this hot-end is identical to the J-Head Mk V-B.  Due to the standard thermistor being discontinued, the thermistor hole is drilled to fit the Semitec 104GT-2 (thermistor 5 in most firmware tables).  In addition, this hot-end ships with the Semitec thermistor.

Note that the current image displays the J-Head Mk V-B.  The only difference is the hole size and location of the thermistor hole.

This hot-end 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.  The J-Head Mk IV-B has been proven to print reliably with both ABS and PLA.  (PLA will require a small fan to provide air-flow through the cooling vents milled in the sides of the nozzle holder.)

The following is a list of just some of the improvements made to the J-Head Mk V-BV:

• Over 13mm shorter than the Mk IV-B and earlier J-Head hot-ends.  This will increase the height of your print area.
• Longer melt zone to reduce the temperature required for extrusion.
• The top portion, of the melt zone, is insulated by the lower part of the PEEK nozzle holder.
• The lower taper, on the PTFE liner, is no longer required.  As a result, the liner can be tighted considerably without fear of jamming the hot-end.

This hot-end easily interfaces with the most popular RepRap extruders, including Wade's Extuder, Greg Frost's Hinged Accessible Extruder, etc.

Please note:  The maximum operating temperature is 247 degrees Celsius as PEEK will soften at 248 degrees Celsius.  Due to many variables, affecting the accuracy of the temperature readings and settings, caution is recommended when extruding at temperatures approaching this limit.

In the event that black PEEK is unavailable, tan PEEK may be substituted for the nozzle holder.

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 (and for 3mm hot-ends only), 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.

Included

• Assembled J Head MK V-BV Hot-End.
• Power Resistor, 5.6 ohm or 6.8 ohm (depending upon availability)
• Thermistor, 100k, 3%
• PTFE Insulation for the resistor and thermistor

Installation

• Insert power resistor into resistor hole, as pictured. Silicon heat compound is recommended for optimal heat transfer.
• Insert thermistor into thermistor hole. Secure resistor with Kapton Tape.
• Solder resistor and thermistor leads to appropriate wires/connectors as required by your electronics.
• See RepRap J Nozzle Wiki for attachment of assembled Mk V-B to extruder.

Suggested Items (Not Included)

• High-temperature wire for resistor, McMaster Part No. 8209K11 (or equivalent)
• Kapton tape for thermistor mounting

Links For More Information

• http://reprap.org/wiki/J_Head_Nozzle

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