{"id":157,"date":"2019-03-07T14:28:54","date_gmt":"2019-03-07T13:28:54","guid":{"rendered":"https:\/\/bonkers.de\/?page_id=157"},"modified":"2019-03-07T14:28:54","modified_gmt":"2019-03-07T13:28:54","slug":"merlin-hotend","status":"publish","type":"page","link":"https:\/\/bonkers.de\/?page_id=157","title":{"rendered":"Merlin Hotend"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

Construction<\/a><\/h2>\n\n\n\n

The Hotend is made up of the following parts:<\/p>\n\n\n\n

20 mm long 6mm diameter Brass Nozzle
\n30 mm long 10mm diameter PEEK Heatbarrier
\n20 mm long 6mm diameter PTFE Inlay
\n1 pcs. Airbrush Nozzle<\/p>\n\n\n\n

Heatblock for 6mm diameter nozzle, 10mm thick<\/p>\n\n\n\n

The Brass part is threaded with M6 on the upper half.
\nDrill diameter for 3mm filament is 3.2mm, for 1.75 filament it is 1.9mm.
\nDrill depth is ca. 18mm, you need at least 2mm material remaining at the lower end.
\nFor the airbrush Nozzle a hole with M 1.75 thread is needed at the lower end.
\nM1.75 is not the exact size of the thread of the airbrush nozzle, it \nmakes sure that the nozzle sits tight and does not leak. If you were to \nuse the correct thread the nozzle would leak and possibly unscrew itself\n during printing.<\/p>\n\n\n\n

The PTFE part needs an outer M6 thread.
\nDrill diameter for 3mm filament is 3.1mm, for 1.75 filament it is 1.8mm.<\/p>\n\n\n\n

The PEEK part needs an outer M10 thread and an inner M6 thread. When \ndrilling or machining PEEK take it slowly and use a lot of \ncoolant\/lubricant.<\/p>\n\n\n\n

The Hotend is simply assembled by screwing the PTFE fully into the PEEK until it sits flush. Then screw in the brass part from the other end and tighten it against the PTFE. I usually use a 1.8mm reamer to make sure the PTFE isn\u2019t blocking the filament path after this, for 3mm filament use a 3.1mm reamer.
The tight connection between the PTFE and the brass prevents leakage. Different to designs that use thinner PTFE liners the thick 6mm PTFE tube can take a lot more mechanical pressure and does not deform as easily.<\/p>\n\n\n\n

MerlinDocumentation<\/a>Herunterladen<\/a><\/div>\n\n\n\n

Assembling<\/h2>\n\n\n\n
  1. Doublecheck that the parts are clean, especially small PTFE parts can quickly jam the nozzle.<\/li>
  2. Make sure the inlay is screwed into the PEEK part deep enough, the upper end should sit flush in the PEEK.<\/li>
  3. Tighten the brass nozzle enough so it\n sits tight against the PTFE, check that a little bit of threading is \nstill visible so you know it sits tight against the PTFE, not the PEEK. \nIf you don\u2019t tighten this sufficently you get a small gap between PTFE \nand brass which will allow plastic to escape.
    \nYou can check the tightness by inserting some filament in the cold \nhotend, if you can easily push it right down to the end of the brass it \nisn\u2019t to tight. If it stops within the PEEK part it is to tight.<\/li>
  4. When inserting the Thermistor take care not to damage it, this happens faster then you think.<\/li>
  5. Glue the Thermistor in place using \nred seal, or similar heat resistent flexible glue. You can get away with\n thermal paste, but you have to make sure that the thermistor stays in \nthe heatblock using different means then and that the paste is rated for\n 250+ C\u00b0.<\/li>
  6. Make sure the Thermistor leads are sufficently insulated using heat resistant insulator. I prefer to use small PTFE tubes.<\/li><\/ol>\n\n\n\n

    Some requested more detailed info on the assemling of the heater block.<\/p>\n\n\n\n

    Attach you can see the heater block as it comes with the Merlin Nozzle from RRD and how the components belong together<\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    You should use a thermal glue or heat resistent silicone to mount the\n thermistor. Using thermal paste for thermal conductivity and Kapton to \nfixate it can work, but from my experience it is not a lasting solution.\n Also make sure that the wires of the thermistor are correctly isolated,\n especially if you use thermal compound since that is often conducting \nelectricity.<\/p>\n\n\n\n

    Personally i use very small PTFE tubings to isolate the thermistor \ncontacts, thermal glue to fix the thermistor and Kapton to hold it all \ntogether.<\/p>\n\n\n\n

    This is how a heater block might look after a couple of rolls of \ndifferent materials and some rough handling. Please note that it still \nworks just fine.<\/p>\n\n\n\n

    \"\"<\/a><\/figure>\n\n\n\n

    License<\/h2>\n\n\n\n

    The Merlin hotend is released under CERN OHL 1.2<\/a><\/p>\n\n\n\n

    <\/a>Replacing the Nozzle<\/h2>\n\n\n\n

    To replace the nozzle heat the hotend up to  beyond the glazing \ntemperature of the material last used. It needs to be very soft, but not\n fully liquid.<\/p>\n\n\n\n

    With a pair of flat pliers it is now easy to unscrew the nozzle without leaving much plastic residue.<\/p>\n\n\n\n

    In case the tip of the nozzle was damaged or broken off you can use a\n 1.5mm drill or similar to remove the thread from the brass part. If \ndone carefully the thread will not be damaged and a replacement nozzle \ncan be screwed in directly.<\/p>\n\n\n\n

    Where to get it<\/h2>\n\n\n\n

    The Merlin Hotend is meant as a DIY item, the minimum tools you need is a drillpress, though a lathe makes things easier.<\/p>\n\n\n\n

    If you want to buy one you can get it in several online stores, please note that i do not sell the hotend, i am merely the developer of it and use it myself.<\/p>\n\n\n\n