Arcol blog Just another RepRap weblog

3Apr/14Off hotend v4 for Rapman hotend v4 adaptation for Rapman machines

The assembled Rapman filament drive with the v4 hotend during extruding:

Get it here.


As you may be aware, back in 2010, the v3 version of the hotend (the PEEK based, so not the v4 all metal one),
was compatible mechanically and electrically with Rapman machines:

Starting from v4, the thermistor was intially switched to 104-GT2, which discontinued mechanical compatibility with the Rapman:

I then migrated to a Honeywell thermistor, which enabled me to leave out the fire cement, shown here:

These changes to the v4 hotend made it technically superior to the old one, and also way faster to assemble. However, it was neither mechanically nor electrically compatible with Rapman machines.

Recently, I have been approached by two people to get manufactured a fully compatible hotend for the Rapman. Two people are almost a crowd! :)

So with that in mind, I think I came up with a pretty good solution:

In detail

The length of the original v4 hotend was short by design,
however to maintain mechanical compatibility with the Rapman,
it needed a longer (73mm tall) hotend.
Pictured here is the assembled unit complete with nozzle, barrel and heatsink:

The new heatsink consists of two parts:
- The heatsink itself, which is 15.5mm longer than the standard one
- a disk, which goes on top of it, what you can mount on the Rapman machine using two M5 bolts.


The lower part of the hotend needs no modification, except it is
reverted back to the firecement version for using the 204-GT thermistor.

Summarizing the modification is basically a reworked heatsink and mounting plate.

I do hope it will serve well all the rapman users, who are still out there.

For reference, see this v3 hotend assembly page.

Some exotic combination

I will keep around the older heater block design which suits the
204-GT2 thermistor (and 104-GT2) because it is necessary for the Rapman.

The new and old heater blocks are compatible mechanically, so you can use the normal hotend with the older heater block if you need it for some reason.

Likewise you can get the Rapman version with the new heaterblock, if you have an exotic machine where this hotend suits better mechanically.


To date, I have only delivered two kits. Of these, one has
been installed and tested with very positive feedback.

Here is a quote from Rob:

I would like to add that the Hotend Unit you supplied is performing like a champion and has surpassed all of my expectations on its performance and reliability to date.
— Rob

How to get it

You have four variations to choose from:
- Assembled with 0.35mm nozzle
- Assembled with 0.5mm nozzle
- Unassembled with 0.35mm nozzle
- Unassembled with 0.5mm nozzle


Chrome beauty

Grab one here.

The chrome family:

Here is how the normal mini hyena v2.1 with 8mm bore looks like:

Here is how the mini hyena v2.1 looks chrome plated:

I think the normal hyena looks the most beautiful when chrome plated:

It is really shiny, it is almost like having a brand new bike:)

Here is a comparison photo between the mini hyenas:

30Oct/12Off hotend v4.1.1.


For previous announcement please read here:

The v4.1.1 version

Im really proud to announce hotend v4.1.1:

In a nutshell:
- v4.1. - aluminium mounting plate (that also means integrated setscrew in the heatsink)
- v4.1.1 - firesleeve

Aluminium mounting plate (v4.1.)

I replaced the wood mounting plate with an aluminium one.

Just to recall here is how the v4.0.5 looked like:

Here is the v4.1:

I also added an M3 setscrew, to fix the heatsink to the mounting plate
(prevent rotating the whole hotend at high speed).

Also here is how the hotend looks after 6 months of printing:

So the firecement is quite good solution, once it is applied.

Firesleeve added (v4.1.1)

To prevent skin burn, protect heater block against fan blow, and last but not least looks awesome:

Machine compatibility

This hotend is designed for reprap machines (or compatible).
However I had success reports from customers using in 24VDC system, like R2C2 electronics (you need different resistor, so definietly say it before purchase).

I would be really interested how others have mounted or adapted this hotend for their machine,
like or

If you happen to have a machine like the above, and you want assistance,
just drop me an email through preorder(at-arcoldothu.

Go grab one:

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If you have any thoughts to share about this article, please discuss it on's mailing list,
in this thread.


Arcol Hyena v1.1

Available at:

History (v1.0)

For previous v1.0 announcement, read here:
and here:

V1.1 update

This is a minor, but really handy upgrade to hyena.

At one end it has 6mm flats for wrenches. So no more pliers to holding while putting the big gear onto the shaft.

This is how it should be mounted (flat end is the opposite one from big gear):

Here is a closeup of the two flat sides:

Here is how you should put the big gear onto the hyena:

Also here it is mounted on the extruder pusher:

(Note the M8 nut with M3 grubscrew! It is *really* useful)

M8 nut with M3 grubscrew:

I closed down the commenting on this webpage due to the enormous number of penis enlargement suggestions.

If you have any thoughts to share about this article, please discuss it on's mailing list,
in this thread.

14May/12Off hotend v4.0.5 v4.0 hot-end for 3.0mm filament (works also for 1.75mm filament too).

It has been a long time since I announced v3.0.

The new features:

  • - Hot-zone is completely metal.
  • - high temp extrusion should be possible, like pp, hdpe, plexi, polycarbonate, nylon (hopefully, this will be confirmed within a month)
  • - shorter, more compact, a comparison photo between v3.0 and v4.0:
  • - easier to assemble
  • - reworked nozzle
  • - laping for wrenches on nozzle, on stainless steel, heatsink
  • - built for easy maintenance
  • - self cleaning (you can remove the hardened plastic using two wrenches:)
  • - built with dual extruder in mind
  • - mounting compatibility for the average/stock reprap hotends
  • - 100k thermistor (which seems to be a more common preference)

For assembly instructions please read here:

Regressions/future adaptations:
Dropped compatibility for Rapman, Makerbot. A new mounting needs to be designed for these machines.
For rapman a 200k thermistor also needs to be sourced to be electrically compatible.


Hobbed bar, hyena v1.0

This is my take of a new hobbed bolt replacement :)

I call it the hyena, because hyenas have the strongest jaw of all mammals.
All teeth are cut individually:

Here is a comparison photo with one of my hobbed bolts:

The brass one is the new version:)
You mount it with a M8 nylock nut, so the width of your extruder does not matter.

Key advantage over the old version

  • It's machined from straight, round brass stock. Regular bolts often have large tolerances and are not entirely straight. The hyena is guaranteed to be straight.
  • Each tooth is individually machines, so there is no "orphan tooth". An orphan tooth is an incompletely cut tooth that occurs during hobbed bolt production with a tap, because the teeth of the tap do not match the diameter of the bolt while cutting. This is a problems because it's the spot where filament begins to slip. It tends to bite a small piece of plastic off the filament as it does not reach deep enough to grip. The next (normal) tooth continues eating into the filament, resulting a complete filament strip, and no printing. The hyena prevents this by making sure every tooth grips by the same amount.

Installing on a Wade style extruder

Some pictures, from the top:

Also when opened (please note the washers around the bearings!):

(Also take note the really useful and special M8 nut. It will be the subject of an another announcement:)

Im a technical guy, any drawings?

Here it is:

Enough talk, I want one!


Guest article: Tiny’s first experience with Hotend v3.0

It was announced as "really big", but is the Hot-end v3.0 is that great?


Blender broke – Epilogue

My article titled "Blender broke" drew more media attention, than anything I've written lately. This is strange, as much cooler things have been happening around me:) Many sites picked it up.

I later read on a forum (I've forgotten which one), that the printed replacement part will break as it could not possibly be as strong as the original one. That did had some truth to it...

28Oct/10Off Hotend v3.0

This is a really big announcement.:-) The new hot-end has been born, and rocks!

15Sep/10Off hotend prototype one

I was quite excited about my new prototype. Interested in my findings?

Keep reading.