Arcol.hu Hot-End Version 3.0
This hot-end is compatible (or adaptable) almost all known 3D printer.
- It is electrically and mechanically compatible with RapMan from Bits From Bytes.
- Mendel has already a modified x-carriage for single and double head to accept this hot-end, and also modified Wade's extruder can drive it.
- Prusajr Mendel variation accept this hot-end by default.
- MakerBot mount exist in 2 versions (simple and complex)
- ShaperCube, UP! printer needs volunteers. (not supported attm)
|FILE ID#||TYPE||DESCRIPTION||AVAILABLE FORMATS||CREATED/RESERVED BY|
|arcol.hu hot-end v3.0.dxf||CAD File - 2D drawing||This is the DXF for the SCAD||.dxf.bz2||--Bogdan Kecman 09:21, 2011-02-23 (UTC)|
|arcol.hu hot-end v3.0.scad||SCAD file - 3D assembly||This is the openSCAD model of the hot end||.scad.bz2|| --Bogdan Kecman 09:21, 2011-02-23 (UTC)|
|arcol_HotEnd_v3.0_parts.zip||ZIP archive||Archive of scad files containing all parts hot end consists of||.zip||--Bogdan Kecman 15:25, 2011-02-23 (CET)|
- Mechanical and electrical compatibility with Rapman. It has the same mountings, and use the same range of heater element (power resistor), and the exact same of thermistor.
- Completely separated hot and cold zones. The filament only melts 10mm in total in the hot-end (including nozzle too). So it is very unlikely it blocks because of heat traveling.
- Maintenability. You can unscrew everything, nothing glued or mounted permanently together. You can easily clean if some contamination blocks inside the nozzle. You can see inside, because the nozzle is about 10mm. Look at this article, if you wonder why it was important to me.
- Compact. The overall height is about 70mm. The rapman needs some additional spacer disks to not modify the machine at all. (and also I dont see a point to have ability to print taller objects on rapman. Or having bigger Z travel)
- Wire relief. It is secured, so its hard to broke one of the connections (especially the thermistors' one). I have some connection issue with my stock rapman hot-end, but I would need to destroy the nozzle and thermistor to examine it. It sucks.
- Easy assembly. That basically means eliminated fire cement. Only the thermistor needs a tiny bit. I can mount a nozzle within 20 minutes with connectors, and everything.
- Purpose machined. Everything is made with a CNC machine or lathe. That means virtually no leakage possible anywhere. I always prefered the better solution then cheaper one. That means additional heatsink (even if it is not really required), lathe on everything, etc.
- Exchangable nozzle. Only the nozzle needs to be changed for different orifice size, or inner structure. So it is easily upgradable in the future for a fraction of price…;-)
This extruder is designed with idea to minimize the heat propagation from the heater up the extruder in order to reduce transition zone so that higher level of control can be achieved. This way we achieve also better precision as filament movement is more precise, ooze caused by pressure change is reduced to minimum and filament require less force to be extruded because transition zone is very short. The only path for the heat to move upwards is trough the filament alone and even this is reduced by introduction of extra cooling "pipe". You can read more about problems with heat propagation on Bogdan's post about modifications to the RapMan extruder
Hot end of this extruder consist of 4 parts.
- Heater block
- Heating element
- Temperature probe
Nozzle is made out of aluminium on the lathe. It comes with 0.35 and 0.5mm orifice (minimum useful orifice size is 0.25mm and Arcol might decide to produce those too but for now it is not available - this does not prevent anyone to make the nozzle himself using any orifice size :D ). The outside of the nozzle is threaded so it can be easily screwed into the heater block.
There are 2 important features of this nozzle
- threads to attach rest of the extruder
Orifice on this extruder is "long". Much longer then on standard extruders. The reason for the short orifice channel usually is that it is very hard to drill long hole with a very small drill. Drilling 0.35mm hole 2mm in length is a seriously nasty task that requires special tools. What this feature provides is zero turbulence. If we go back to basics of fluid dynamics we'll find that to remove turbulence caused by pushing liquid trough reduced diameter pipe length of the pipe must be 5 times longer then radius of the pipe. This means that if we need to completely remove turbulence for 0.35mm nozzle we have to have 0.35mm channel be at least 1.75mm long, and for 0.5mm nozzle we need this to be 2.5mm. As same piece is used for both the 2mm channel length is selected. There is a downside to this long channel too. The longer channel increases the force needed for the filament to be extruded, but considering that other design choices reduced the force needed my opinion is that this is worth it.
The acceptor on the nozzle is threaded with self-closing thread - M10x1
Heater block is just a piece of aluminium 10mm thick with a threaded hole for nozzle and 2 smooth holes, one for heating element and another for temperature probe
Heating element used is 4R7 5W axial resistor.
Depending on the electronics you use this extruder with, you need to use appropriate temperature probe. If you use it with RapMan you need GT204 100K NTC, if you use standard genX you need 200K NTC, some custom electronics use J or K type thermocouples ...
Hot end of the extruder is linked to the rest (cold end) using "peek hat". This is a PEEK pipe threaded on one side (M10x1) so it can screw into nozzle, and with smooth hole inside (6mm) so it can take the PTFE tube that allows for smooth feed of the filament. This peek pipe has a flange on one side so it can hold the cold end.
PTFE tube goes trough all of the extruder.
MDF+Steel heat barrier
MDF + Steel barrier act like a barrier to prevent heat rising from the heater + it secures top part of the extruder to the PEEK. The PEEK's flange is squeezed between steel triangle and aluminium heat sink (tube).
There are two heat sinks. First - outer heat sink is made out of copper and it cools the PEEK top and MDF+steel barriers. Other is the aluminium heat sink (tube) that removes heat from PTFE tube.
Top disks are made from MDF and provide
- input for the filament
- mount point for the extruder (to connect to extruder drive - like wade's drive)
- secure point for wires (from heater and from thermal probe)
Top disks are connected to the steel triangle + mdf heat barrier via 3 steel distancers.