Sunday, February 19, 2017

J-Head Mk 8's available!

I have a small quantity of J-Head Mk 8's that I put up for sale at The J-Head Mk 8 is an improvement over the previous J-Heads as it has two internal seals to make leakage practically impossible. By using a heater cartridge and an axial thermistor, this makes it the best J-Head hot-end ever!

Genuine J-Heads are great for printing with PLA as they are designed to keep the heat from building around the filament until the filament gets to the melt zone.

Thursday, January 14, 2016

Genuine J-Heads Are Still Available

There seems to be some confusion. I am still selling J-Head hot-ends at and will remain open for some time. I might take some of the obvious improvements of the Mk 8 and make an improved J-Head Mk V hot-end with them. I am just simply no longer creating any new versions due to the "cloners".

Monday, December 21, 2015

J-Head Mk 8 and Mk 9 hot-ends

Lately, I have been asked if I will be making more J-Head Mk 8 hot-ends. In addition, I have developed a proper J-Head bowden hot-end that is based off of the J-Head Mk 8 and have named it the J-Head Mk 9.

However, I will not be producing nor selling more of the J-Head Mk 8's and Mk 9's because of what has happened to the J-Head hot-end.

The chinese made a poor, rough, copy of a J-Head and spammed it all over the online markets. People bought the cheap knock-offs and those hot-ends failed. The result was that all J-Head hot-ends got blamed for this failure even though the cheap chinese knock-offs were (and are) very different from the real J-Head hot-end. Most of these people now buy other hot-end designs.

The closest open-source analogy that I can think of is this example: Imagine if somebody took FreeBSD, introduced a couple hundred bugs, then released it as a new Linux distribution. Because of this, people begin to dislike Linux. In my opinion, this is what happened to the J-Head hot-ends. (Please note that this is not meant to say anything negative about FreeBSD, it is just an example.)

The concept of open-source design is to take a product and improve it then release the source code or blueprints. It is not to take a product, break it, then not release any information.

Because of this, I have stopped all research and development work towards better J-Head hot-ends. I absolutely refuse to create new designs given what has already happened. I have also noticed that a lot of Reprap-related R&D has stopped in other areas as well. This makes me wonder if the other developers have left due to similar reasons.

I would also like to add that you get what you pay for. Quality products and new research and development cost money and a company that sells both will have to charge a higher price. A cheap, poorly made, knock-off will be cheap in both price and in quality.

I am still selling the J-Head Mk V-BV hot-ends at

Sunday, August 23, 2015

Sales of J-Head Mk 8 Hot-ends

I have been quietly selling J-Head Mk 8 hot-ends.  However, due to the poor quality Chinese counterfeits I am absolutely refusing to sell them openly as I will not be the Chinese R&D guy for their counterfeiting effort.

Sunday, February 8, 2015

J-Head Mk 8 Status Update

The J-Head Mk 8 has been performing quite well.  About 1/2 of the Mk 8's were even sent out without any sealer on the threads and the primary seal worked perfectly as no leaks were reported.

The only minor issue is that I have had a couple of reports of problems with the initial feeding of filament into the hot-end.  Because of this, I may need to make a custom set-screw to resolve the problem.

Wednesday, December 24, 2014

J-Head Mk 8 Prototype

A J-Head Mk 8 hot-end prototype has been machined using concepts borrowed from the Mk IV, Mk VI, and Mk VII J-Head hot-ends as well as the mini J-Head Mk II.

In order to accommodate 3mm filament, and use the axial thermistor, I would have to re-visit the larger heater blocks as used with the Mk IV-B and earlier hot-ends.  Since the market is moving towards 1.75mm filament, I decided to design the new Mk 8 for 1.75mm filament only.  I'll continue to make Mk V through Mk VII variants for users of 3mm filament.

The goals of the Mk 8 hot-end were to fix two main problems.  The first problem is that sealing the threads with ptfe tape still results in a minimal number of failures due to leakage.  So, I re-added the tapered internal sealing surface between the brass and PEEK as was used in Mk IV and earlier hot-ends.  In theory, no ptfe tape should be required.  However, I will still use it so as to provide for a second seal.

The second issue to resolve was related to the thermistor.  While dual thermistors will allow for a safe shut-down in the event that one thermistor falls out, it would be better to make for an easier thermistor installation.  Therefore, I decided that the Mk 8 would use an axial thermistor like the 1.75mm MK VI hot-ends.  Unfortunately, there is not enough space to properly install an axial thermistor in 3mm hot-ends. 

Since this hot-end is for 1.75mm only, and 2mm/4mm tubing had been tested with the mini J-Head, I decided to switch over to using the smaller tubing as a liner.

The cooling vent design has been borrowed from the Mk VII design, which was derived from a modified Mk II.  Originally, the fluted design was used to simply lighten an old Mk II hot-end.  However, it also helped considerably to cool the core of the hot-end.  So, the fluted design was adapted for use on the Mk VII design as well.  For the Mk 8, the flutes were modified so as to be closer to the core of the PEEK nozzle holder.

A set-screw stack of a solid set-screw and hollow set-screw has also been borrowed from the Mk VI and Mk VII designs so as to secure the heater cartridge.  By using a hollow set-screw, as the top set-screw, it is possible to loosen or tighten both set-screws without having to remove them.  The top, hollow, set-screw is used to jam against the bottom set-screw and lock it in place.

In the near future, I am going to run off a limited production run of these hot-ends for both field testing and to explore additional minor design improvements.