Prometheus V2 Hot End - Assembly Instructions

Table of Contents

    1. Assembly Instructions
      1. Kit Components
      2. Safety Precautions
      3. Assembly Steps
      4. Melt Zone Length Assembly
      5. Thermistor Assembly
      6. Transition-Zone Length Assembly
      7. Cooling Fan Assembly
      8. Collet and Tubing Assembly
      9. Direct Configuration Tubing Assembly
      10. Cable Management
      11. Electronics/Firmware Configuration

Assembly Instructions

Please read this entire document and follow ALL instructions carefully! No soldering skills required!
Assembly Time: < 20 minutes

**NOTE: Be very careful when opening the package! There is a tiny thermistor that is easily lost if you are not careful!

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Kit Components

Machined Parts:
  • 1x: 1-Piece Stainless Steel Nozzle (0.3mm, 0.4mm, 0.6mm, or 1mm orifice)
  • 1x: Aluminium Heater Block
  • 1x: Aluminium Heat Sink
    • 5x: Aluminium Hex Nut
    • 1x: Black (1.75mm) or Grey (3mm) Bowden Collet
    • 1x: Black 4mm ID (1.75mm) or 6.5mm ID (3mm) Rubber Spacer
    • 1x: 100mm length 2mm ID x 4mm OD (1.75mm) or 3mm ID x 6mm OD (3mm) PTFE Tubing (for Heat Sink)
    • 2x: Black 3mm ID Rubber Washer (for Cooling Fan)
    • 2x: M3x25mm Button Head Bolt
    • 1x: M3x4mm Button Head Bolt
    • 4x: M3x3mm Set Screw
    • 1x: M3 Washer
    • 1x: M2 Hex Wrench (for M3 Button Head Bolts)
    • 1x: M1.5 Hex Wrench (for M3 Set Screws)
    • 1x: 100mm Black Zip-Tie
      • 1x: 12V 40W 6mm x 20mm Heater Cartridge
      • 1x: 100KOhm Semitec 104GT2 NTC thermistor
      • 1x: 12V 25x25x10mm 3CFM Cooling Fan (for Heat Sink)
      • 1x: 80mm length 0.5mm ID 1mm OD High Temp Insulation Tubing (for Thermistor)
      • 1x: 60mm length 2.5mm ID Black 2:1 Heat Shink Tubing (for Thermistor)
      • 4x: 1mm^2 x 12mm Copper Wire Ferrules (Solder-Free Connection!)
      • 1x: 1m length Thermistor Wires with 2-pin Dupont Connector

        Required Tools and Skills

        • Heat Gun, Soldering Iron, or simply a Lighter (for Heat Shrink Tubing)
        • Small Pliers
        • Adjustable Spanner
        • Wire Strippers
        • Flush Cutters

          Safety Precautions (Important!)

          • Please follow ALL instructions in this document! If anything is unclear please contact me before trying something that may damage the product or harm the user.
          • Electricity can be dangerous! Ensure that your power is unplugged when you are hooking up the electronics.
          • Be careful with the 1-Piece SS Nozzles! While these Nozzles are quite strong, they do have a fairly thin wall of material. They will withstand all the normal stresses of operation, but please be careful when using heavy tools.
          • Be careful with the thermistors! The thermistor leads are very small and delicate and the bead is made of glass. To avoid shearing the thermistor leads or crushing the glass bead please handle this little thermistor like a newborn baby.
          • This “Hot End” gets very hot! Please do not touch the Heater Block or adjacent Hex Nuts while the hot end is in operation. It will hurt...

              Assembly Steps

              • You will receive two bags containing the kit components. Make sure you have everything:

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              "Melt-Zone" Length Assembly:

              • The first step involves assembling the length of the "melt-zone". The "melt-zone" length is configured by threading Aluminium Hex Nuts against the Heat Sink. Adding additional hex nuts increases the length of the "melt-zone". A shorter "melt-zone" results in more precise extrusion and retraction, and less "ooze" (stringing) at the expense of a lower maximum feed rate. A longer "melt-zone" results in a higher maximum feed rate at the expense of less precise extrusion and retraction, and more "ooze" (stringing). You may customize the "melt-zone" length according to your specific needs.
              • Please read through the Prometheus V2 User Guide for recommendations on how to configure the hot end according to your specific needs. I highly recommend reading this before proceeding with assembly.
              • In the assembly steps below, I am assembling a 1.75mm hot end with a 16mm "melt-zone". Thread the Nozzle into the Heater Block and then thread two Hex Nuts against the Heater Block on the end of the Nozzle closest to the orifice:
              • While holding the Heater Block, tighten each Hex Nut against the Heater Block with a small spanner. Individually tighten down each hex nut hard enough so that you cannot unscrew the nuts with your finger. This step does not require excessive force! Be careful and make sure your hand doesn't slip!

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              Thermistor Assembly:
              • Cut (2) 25mm lengths of the Black Heat Shrink tubing:

              • Cut (2) 35mm lengths of the High Temperature Tubing:

                • Slide the High Temperature Tubing over the Thermistor leads. Make sure you push the tubing right up to the head of the Thermistor! **Orders shipped after July 25th 2016 also include two 15mm lengths of Fiberglass Sleeving. Slide this sleeving over the high temp tubing as shown in the image below:

                • Strip 10mm of the insulation off the end of the Thermistor Wires:

                  • Slide the lengths of Heat Shrink over the Thermistor Wires and the Copper Ferrules over the Thermistor leads. Bend the ends of the exposed wires into loops as shown in the below illustration:

                    • Hook the ends of each of the wires around each other:

                      • Slide the Copper Ferrules over the connection and clamp down on them using a set of pliers. Make sure the High Temperature Tubing extends right up to the Thermistor bead before you clamp the Ferrules!

                        • The connection should be strong and should look like this:

                          • Slide the Heat Shrink tubing over the Ferrules and apply heat using a Heat Gun, Soldering Iron, or Lighter:

                            • Bend the Thermistor leads at 90 degrees about 6mm from the tip as shown:

                              • Carefully insert the bead of the Thermistor into the Thermistor hole at the top of the Heater Block closest to the Heat Sink and secure it using the M3x4mm Button Head Bolt and an M3 Washer. Make sure there is an M3 Washer between the head of the bolt and the Thermistor leads to avoid shearing the leads! If your kit included Fiberglass Sleeving then make sure the washer is tightened against the sleeving which will provide an extra strain relief as shown. Tighten the bolt just enough so that the Thermistor leads cannot become loose. Do not overtighten! Use the supplied M2 Hex Wrench:

                                • Insert the Heater Cartridge into the hole in the Heater Block and tighten with an M3x3mm Set Screw. Tighten the Set Screw just enough so that the Heater Cartridge cannot become loose. Use the supplied 1.5mm Hex Wrench:

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                                  "Transition-Zone" Length Assembly:

                                  • Thread the Heat Sink onto the assembled Nozzle until the bottom of the Heat Sink is a distance of 2mm from the top of the Heater Block. Insert two M3 Set Screws into the threaded holes in the Heat Sink and tighten them using the supplied M1.5 Hex Wrench. Tighten the Set Screws just enough so that the nozzle assembly cannot turn in the Heat Sink. Do not over-tighten. 
                                  • This will create a short 2mm "transition-zone" which will prevent jamming especially when printing with PLA.

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                                  Cooling Fan Assembly: 

                                  • Thread the two M3x25mm Button Head Bolts into the two bottom mounting holes on the Cooling Fan so that the sticker on the Cooling Fan will face the Heat Sink. It is important that you assemble the Cooling Fan with the sticker facing the Heat Sink to ensure that the fan will blow air through the Heat Sink. You may need to use the supplied M2 Hex Wrench to thread the bolts through the Cooling Fan holes (or drill out the holes with a 3mm drill bit) as it may be a tight fit. Place the two Rubber Washers onto the bolts as illustrated below:

                                  • Fasten the Cooling Fan to the Heat Sink:

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                                  Collet and Tubing Assembly:

                                  • Push the Black (1.75mm) or Grey (3mm) Collet into the hole at the top of the Heat Sink:

                                  • The embedded Collet should resemble the below illustration:

                                  • Take the supplied 100mm length of PTFE Tubing (Direct Configuration) or your length of bowden tubing (Bowden Configuration) and push the Rubber Spacer onto the end. Cut a small piece off the end of the PTFE tubing using your Flush Cutters to get a good flat edge:

                                  • Insert the flat end of the PTFE tubing into the top of the Heat Sink. Use some force to ensure that the tubing is pushed all the way into the Heat Sink:

                                  • The tubing can be removed from the Heat Sink when required by simply pushing down on the Rubber Spacer while pulling on the tubing:

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                                  Direct Configuration Tubing Assembly: (Bowden Users can skip to the Cable Management step below)

                                  • It is recommended that you run this PTFE tubing right up into the extruder as close to the drive gear as possible. This will facilitate a smooth filament path from your extruder into the Nozzle which will provide optimal performance when printing flexible filaments such as NinjaFlex.
                                  • If you do not wish to extend the PTFE tubing into your extruder you can just cut it off flush with the top of the hot end. Push the tubing all the way into the Heat Sink as far as it will go and then mark the top with a thin marker. This PTFE tubing will facilitate a smooth filament path from your extruder directly into the Nozzle, so make sure you have pushed the tubing all the way into the Heat Sink before marking it.

                                  • Take the tubing out of the Heat Sink and cut along the mark:

                                  • Use a knife to bevel the inside edge of the top of the tubing. This is where the filament will enter the hot end so the bevel will allow for a smooth filament path from your extruder. Insert the tubing into the top of the Heat Sink with the beveled edge at the top of the Heat Sink:

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                                  Cable Management:

                                  • Bend the Heater Cartridge cables and use the Black Zip-Tie to tie the wires of the Heater Cartridge, Cooling Fan, and Thermistor together to provide appropriate strain-relief. Be careful not to bend the Heater Cartridge leads more than once or they will break from the strain! Ensure that the Cooling Fan wires and the Black Heat Shrink part of the Thermistor Wires are not in contact with the Heater Block:

                                  • Cut the excess length off the Zip-Tie. Your hot end is now fully assembled! 
                                  • You are now ready to hook your Prometheus V2 up to your electronics and configure your firmware. Proceed to the Electronics/Firmware Configuration steps below. Please DO NOT skip these steps!

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                                    Electronics/Firmware Configuration:

                                    • Wire the Cooling Fan directly to your power supply, red wire = (+), black wire = (-). This will ensure that the Cooling Fan runs continuously at full speed to provide optimal Heat Sink cooling. DO NOT connect the Cooling Fan to your controller board "Fan" output as this output is used to control fans for cooling the printed part, NOT hot end Heat Sink fans which must always be running. Please ensure that this Cooling Fan is always on!
                                    • Wire the Cartridge Heater and Thermistor to your controller board. This Heater MUST run on the rated voltage!
                                    • Reconfigure your firmware for the Semitec 104-GT2 Thermistor: 
                                      • In Marlin this means using thermistor definition number 5#define TEMP_SENSOR_0 5
                                      • In Repetier Firmware use thermistor definition number 8#define EXT0_TEMPSENSOR_TYPE 8
                                      • In Smoothieware use thermistor definition “Semitec”temperature_control.hotend.thermistor Semitec
                                      • For RepRapFirmware use the Beta value 4267K.
                                    • Upload the new firmware to your electronics board.
                                    • Connect to your printer and run M303 PID Autotune. If your firmware does not support this feature, calibrate your PID manually.
                                    • Set the hot end to 280C. Use your adjustable spanner to check that each hex nut is tight. Also, ensure that the Nozzle is not loose in the Heat Sink. If anything is loose carefully tighten it now.
                                    • Please note that you should not attempt to remove the thermistor after heating the hot end above 280C. The insulation tubing conforms and sticks to the heater block at this temperature and the thermistor leads can easily break if you try to remove the thermistor. If you need to reassemble the hot end just unscrew the heat sink to avoid removing the thermistor or heater cartridge.
                                    • Mount Prometheus V2 to your printer and start printing!
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                                    User Guide

                                    Here are some general tips for printing with Prometheus and customizing the thermal zones according to your specific needs. Enjoy!

                                    The image below illustrates the thermal zones of Prometheus V2:

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                                    Melt-Zone (MZ) Length Configuration

                                    This is the first thermal zone configured in the assembly. The Melt-Zone (MZ) length parameter has the most significant impact on the maximum feed rate (extrusion rate) of the hot end. In general, the max feed rate is proportional to the MZ length so a longer MZ means that the hot end can melt and extrude plastic faster. However, there are other tradeoffs involved in lengthening the MZ.

                                    These affects of MZ length on performance are outlined in the table below:

                                     Change in MZ Length Maximum Feed Rate "Ooze" (stringing) Extrusion/Retraction Responsiveness
                                    Longer Increased Increased Decreased
                                    Shorter Decreased Decreased Increased

                                    The primary advantage of a longer MZ is a higher maximum feed rate. If you want to print thicker layers at higher speeds then you should assemble your Prometheus with a longer MZ.

                                    The table below lists the recommended standard MZ length configurations for each nozzle size:

                                     Nozzle Orifice Size Recommended MZ Length # of Hex Nuts below the Heater Block
                                    0.3 mm 12 mm 1
                                    0.4 mm  16 mm 2
                                    0.6 mm 20 mm 3
                                    1.0 mm 24 mm 4
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                                    Transition-Zone (TZ) Length Configuration

                                    This is the next thermal zone that is assembled. The Transition-Zone (TZ) length parameter has the most significant impact on the reliability of the hot end. In general, the friction in the hot end is proportional to the length of the TZ so a short TZ will result in the lowest internal friction and therefore the most reliable "jam-free" printing. However, just like the MZ, there are tradeoffs involved here too.

                                    These affects of TZ length on performance are outlined in the table below:

                                     Change in TZ Length Friction Heat Loss to Cold-Zone Temperature Stability Maximum Retract Length Maximum Feed Rate
                                    Longer Increased Decreased Slightly Increased Increased Slightly Increased
                                    Shorter Decreased Increased Slightly Decreased Decreased Slightly Decreased

                                    The primary advantage of a shorter TZ is that it decreases the friction in the hot end, therefore reducing the extrusion force and increasing the reliability. A short TZ is especially important when printing PLA. However, a short TZ also means that more heat is lost to the Cold-Zone (CZ).

                                    Higher temperature plastics like ABS have a higher glass transition temperature (Tg), so you can get away with a longer TZ. This can be beneficial when printing at temperatures above 250C as it reduces the heat lost to the CZ and increases the stability of the temperature reading during extreme fluctuations in the feed rate.

                                    The table below lists the recommended TZ length configuration for printing various thermoplastics:

                                    Thermoplastic Recommended TZ Length
                                    PLA, Nylon 2 mm
                                    ABS, PC, PET, etc... 3 mm to 4 mm
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                                    Bowden Users: Keep in mind that the maximum retract length is proportional to the length of the TZ.

                                    The max retract length can be approximated as follows:

                                    Max Retract Length = TZ Length     (e.g. a 2mm TZ means that the maximum retract length is also 2mm)

                                    This is an important relation for bowden users to consider. If you retract longer than the TZ, molten plastic will be pulled into the Cold-Zone and will cool, fusing to the inside of the barrel and jamming the hot end. I recommend a 2 mm max retract and a short 2 mm TZ. However, a very long bowden tube may require longer retraction. If you have a geared extruder then you may be able to get away with a longer TZ of 4mm with 4 mm retractions, even with PLA.

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                                    Cold-Zone (CZ) Length Configuration

                                    The length of the CZ is not user configured as it does not affect performance. However, when you are assembling your hot end and configuring your MZ and TZ, please ensure that at least 10mm of the end of the nozzle is threaded into the bottom of the Alu Heat Sink. Therefore, when you are determining your MZ length, consider the following:

                                    Nozzle Length = Nozzle Tip (2 mm) + MZ Length + TZ Length + CZ Length,      MZ >= 8 mm,      TZ >= 2 mm,      CZ >= 10 mm

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                                    Printing Temperatures

                                    The printing temperature can have a significant impact on layer adhesion, bridging, overhangs, and "ooze" (stringing). Higher printing temperatures generally result in stronger layer adhesion, but at the expense of a loss of performance in other aspects of your print. 

                                    The effects of printing temperature are listed in the table below:

                                    Change in Printing Temperature Layer Adhesion Bridging/Overhangs "Ooze" (stringing) Maximum Feed Rate
                                    Increased Stronger Worse Increased Slightly Increased
                                    Decreased Weaker Better Decreased Slightly Decreased

                                    Since each user has different Slic3r settings, part cooling, etc, it is very difficult to recommend a specific printing temperature. Below are a range of recommended temperatures for printing various thermoplastics with Prometheus:

                                    Thermoplastic Recommended Printing Temperature
                                    PLA, PHA 180 C - 240 C
                                    ABS, PET (T-Glase) 220 C - 260 C
                                    Nylon (Taulman) 250 C - 280 C
                                    PC (Ultimachine) 270 C - 290 C
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                                    Part Cooling

                                    Enabling a part cooling fan can have a positive impact on the quality of bridges, overhangs, and corners of your print, especially when printing PLA. However, there are also some detrimental side effects of a part cooling fan, especially with regards to layer adhesion. 

                                    The below table lists the effects of part cooling on a print:

                                    Change in Part Cooling Layer Adhesion Bridges, Overhangs, and Corners
                                    Increased Weaker Better
                                    Decreased Stronger Worse

                                    In general, PLA prints benefit from increased part cooling with minor negative effects on layer adhesion. On the other hand, optimal ABS print results are achieved with minimal part cooling. Excessive part cooling on ABS prints can cause severe layer delamination. 

                                    *Important*: If using a part cooling fan you must ensure that the air flow is NOT blowing over the nozzle tip. Excessive cooling of the Stainless Steel Nozzle tip can result in inconsistent extrusion and increased extrusion pressure.

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                                    Cleaning the 1-Piece Nozzle

                                    The 1-Piece Nozzle can become clogged from foreign debris in your filament or from dust that has accumulated on the filament. The symptoms of a blocked nozzle are inconsistent extrusion and periodic clogging which can lead to "filament grinding" and "air printing".

                                    Please DO NOT:

                                    • Soak the nozzle in a solvent
                                    • Burn the nozzle with a torch
                                    • Hit the nozzle with a hammer (I am not sure why anyone would do this?? but just don't...)

                                    The solution is the "Cold-Pull" method! (AKA the PLA Pipe Cleaner method). This involves heating the hot end slightly above the Tg of the plastic and pulling the entire length of filament out of the Melt-Zone. This conveniently removes any debris in a non-destructive manner.

                                    The PLA Pipe Cleaner method is detailed here on NopHead's Blog.

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                                    V2 Nozzle Identification

                                    V2 nozzles are available in various sizes (0.3mm, 0.4mm, 0.6mm, and 1.0mm) and the nozzle length scales with orifice size so that the larger nozzles can be assembled with a longer melt-zone to allow for higher feed rates. This also makes nozzle identification much easier as you just have to measure the length of the nozzle.
                                    The table below shows the respective length of each nozzle size:
                                    Nozzle Orifice Size Nozzle Length
                                    0.3 mm 33 mm
                                    0.4 mm 34 mm
                                    0.6 mm 36 mm
                                    1.0 mm 40 mm

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                                    CAD Drawings for the Prometheus V2 Hot End: