Arcol blog Just another RepRap weblog

4Oct/10Off prototype v2.0

This design is almost final. It simply rocks, truely awesome!

Keep reading.

I learned from my previous prototype, and kicked out all its flaws.


1. I switched over more conservative approach of the nozzle inner section, does not have a big inner chamber anymore:

2. Also I eliminated the firecement for heating. Now it is a round resistor:

3. I think it is a huge improvement, I keept the mechanical design the same short length, so two birds with one stone;-)

4. Replacable nozzle

It has two goals, you can easily switch to different nozzle sizes (0,5mm, 0.35mm, etc). So even if you buy your hot-end initially with 0.5mm nozzle size (seems like this will be the default, and other nozzles will come later), then you only need to replace a small nozzle:

Maybe in the future you can experiment with different inner structure for the least force required to push the plastic.
I think my filament is a pretty good testbed, as it has the worst coss section ever.

So me for example, I will constantly experiment with different nozzles, even after this hot-end design is sold.

5. Maintenability

Everything is screwed together, so no glue used, only a little firecement for the thermistor.
Also the nozzle is so small, that you can easily see inside, so you can clean it throughfully.
Trust me, I know how pita can it be, as I dealt with a pretty contaminated filament in the past.

6. Wire relief

My stock rapman hot-end sometimes has thermistor reading error during print, and the symptom is simply it prints without motor turning and the temperature is below few degrees of the target temp.

It is because the thermistor connector failed, because if I gently move, sometimes I can cause the failure or fix it when it fails. It's pain in the ass. This design prevents it:

7. Connector

To be able to disassemble the hot-end from the machine. No further explanation needed I think, maybe a photo:

8. Compatibility

This hot end compatible (or will be) with any existing reprap and reprap-like machine. It is compact enough to achieve this.

For rapman you only need 3 additional disks (and also longer bolts) to achieve the same length as rapman stock hot-end, as this design by default is shorter with 12 mm.

Here is a comparison photo:

Prusajr mendel variation

I worked with him on this, and his x-carriage can already accept my hot-end, see this git commit.

No additional stuffs needed.

Standard mendel

There are already two variation up on thingiverse. From arhimed (Bogdan) and from Domonoky aka


I agreed with Kliment, that he will adapt this hot-end for Makerbot, and write an extensive article on it. Also I will provide adapter for it, if required.


Not decided yet sadly. Maybe prusajr will work on it, but no real commitment on it. So if you have one and want to work on it, contact me on order (at) arcol [dot] hu.

Also Wade's driver already modified for this hot-end.

Also I'm already selling hobbed bolts for the drive mechanism.

So basically only RP parts (and a motor) required to have a working extruder.

Ok, its all great, but why is it a prototype?

Sadly the nozzle is too close to the printed plastic, and sometimes it touches it, and peels it off of the table.
Here is a photo how close is it:

As you can see the nozzle is 1mm close to the printed surface.
A bottom view also:

Im already working on the next nozzle, and I manufacture 3 variation of it. Fortunately only a small part needs to be modified:

So the final version should be done and tested before the end of this week.

For having an idea how compact is design, here is a comparison photo between the standard variation, the longer one (with rapman adapter) and with stock rapman hot-end:

And two other one:

From the other end:

Demonstration video

Here is a 12 min long demonstration video: hot-end v1 from Khiraly on Vimeo.

If you are impatient fast-forward to 10:30.


This design turned out really great except a small flaw, but the next version will fix it.
Im intend to sell this hot-end for every possible machine.
If you are interested please drop me an email to order (at) arcol (dot] hu.
The price will be between 40-50EUR depending how many people express his interests.
Payment as usual via paypal or wire transfer.

I hope you enjoyed this article, and stay tuned for the next (hopefully final) version!
This will simply turn the reprap world upside-down.