Converting the E3D Tool Changer to Duet 3 with Hemera Tools (Part 1)

The E3D Tool Changer is a versatile platform for multi-material 3d printing, laser cutting/engraving, and associated techniques requiring a stable XYZ motion system. Although it is also available with fewer tools or no tools, the common configuration is four 3D printing heads using Titan extruders and 780mm Bowden tubes. It is generally recognised that direct-drive print heads can deliver better print quality than heads using long Bowden tubes, and the Titans are not as good as some competing extruders. So the arrival of the E3D Hemera direct drive extruder provides an interesting upgrade path for the Tool Changer.

Simplifying the wiring

The Tool Changer ships as standard with Duet WiFi or Duet Ethernet electronics plus DueX5 expansion board. This combination will drive Hemera tools just as easily as it will drive the original Bowden tools. However, the standard loom for a Bowden tool already has eight wires (for thermistor, heater and two fans). A direct drive extruder needs another four wires for the stepper motor. If a filament motion monitor is required (as opposed to a simple filament-out sensor), that requires another three wires, making fifteen in all. This is getting to be a large bundle of wires!

The wiring to the tool head can be simplified using the Duet 3 Tool Board. This is a complete extruder and hot end management system, providing connections for extruder motor, hot end heater, two fans, one or two thermistor or PT1000 sensors, and a filament motion monitor (also a connection for a Z probe and an endstop switch, which are not needed in a Tool Changer). The only connections back to the Duet 3 main board are 12V to 32V power (two wires), and CAN bus (normally two twisted pairs, but one will suffice when the distances are not great).

How many Hemera tools?

The Duet 3 MB6HC main board has six stepper motor outputs along with ten heater and fan outputs. The basic Tool Changer mechanics needs four stepper drivers for XYZ motion and the tool coupler. This leaves two stepper drivers free for driving tools, making a two-tool machine possible without using expansion boards or tool boards. To drive another two tools you would normally require a Duet 3 EXP3HC expansion board, which provides three more stepper motor outputs. However, if those two tools use Tool Boards, then no expansion board is needed. So it made sense to convert at least two tools to Hemera.

Of course, the remaining two tools could be converted to Hemera tools with tool boards too. But I only had one Hemera; so I converted tool 3, set up tool position 2 for another Hemera when I can get one, and left tools 0 and 1 as Titan Bowden tools.

Parts needed

To convert two Bowden tools to Hemera tools and the electronics to Duet 3, you will need the following (note, numbers and lengths of screws may no longer be quite right):

• 2 off Hemera extruders, with 24V heater cartridges and 12V cooling fans. Or you can replace the 24V fans normally supplied with 24V Hemeras by quiet Noctua NF-A4x10 FLX 12V as I did, which also gives you tacho readings.
• 2 off 12V blower fan, mechanically compatible with the original 24V ones from the Bowden tools. I purchased them here https://www.amazon.co.uk/WINSINN-Turbine-40x10mm-Brushless-Bearings/dp/B07RSV5LTH/ref=sr_1_4
• 1 off Duet MB6HC main board
• 2 off Duet 3 TOOL1LC tool board plus optional connector pack
• 1 off Duet 3 Tool Distribution Board
• 12 off M3x10mm cap head or button head screws (4 for each Hemera tool, 4 for securing the M3 standoffs to the acrylic)
• 4 off M3 threaded standoffs for mounting the tool distribution board, length not critical but e.g. 12mm (you could print your own and let the M3 screws self-tap them)
• 18 off M3x6mm screws (7 for each Hemera tool, 4 for securing the Tool Distribution Board to the standoffs)
• 4 off M3x16mm cap head screws (2 per tool)
• 4 off M3x25mm cap head screws (2 per tool)
• One 0.3m or 0.5m twisted pair RJ11 cable (e.g. “High Speed ADSL” cable)
• 5A red/black cable (about 1m per tool)
• 10A red.black cable (about 0.5m)
• 2mm I.D x 4mm O.D. PTFE tubing, about 1.6m per tool
• Zip ties, wires, sleeving etc.

UPDATE 2020-06-06: I recommend also one Omron D2FD-01L30-1T microswitch for each tool so that RepRapFirmware can tell which tools are docked. You will also need a small amount of epoxy resin to glue it in place. See Part 3 of this series for how to fit this.

Building the Hemera tools

Before you take your Tool Changer apart, print the parts you need to convert two of your Bowden tools to Hemera. You can use Greg Holloway’s printable designs at https://www.thingiverse.com/thing:4008778 with the following modifications:

• Replace Greg’s Hemera Dock Bracket and Hemera PCF Duct V6 by the modified parts I published at https://www.thingiverse.com/thing:4194982. I recommend you replace the Dock Brace by my double dock brace part too.
• The V6 Receiver Top and the V6 Cable Support are the same as on the Bowden tool, so you don’t need to print those if you are converting Bowden tools.
• Greg’s Dock Adapter isn’t compatible with the Tool Board because it shifts the dock back, so that there is no longer any clearance between the back of the tool and the acrylic panel. This clearance is needed to accommodate the Tool Board. So print my TCHemeraDock instead, which shifts the dock to the left by 8mm but not back.
• You must orient the remainder of Greg’s original parts so that the flattest face is on the bed.
• If you are keeping some Bowden tools, you need to shift the docks for them forwards, which you can do with the Bowden Dock Extender parts.

Correctly oriented, all parts will print without support material. I printed them in PETG.

Once you have printed all the parts, dismantle the two Bowden tools. Before you build the Hemera tool, you need to extract the dock receiver (the plastic part containing the magnet, that mates with the docking pins); also the receiver top and cable support if you didn’t print them.

Assembly of the tools is as shown in Greg’s instructions, except that the Tool Board sits on top of the feet of the modified Hemera Dock Bracket and Hemera PCF Duct V6, using the longer screws with the nylon washers under the heads.

Attach 1m of 5A red/black cable to the VIN connector. The wires to the power connector only just clear the dock. [UPDATE: we’ve moved the connector down a few mm on later production tool boards to provide greater clearance.] Use a zip tie to hold them clear.

The cable from the Hemera extruder motor must be terminated in a 4-pin JST PH connector to plug into the tool board. Make sure you get the connections in the same order as on the original 4-way Dupont plug. If you forget, pins 1-2-3-4 on the Tool Board must connect to pins 1-4-3-6 on the motor.

UPDATE 2020-06-06: see Part 3 of this series for how to fit and wire the dock sense microswitch, and Part 4 for photos of the other side of the tool showing the double dock brace fitted.

Changing the electronics

With mains power disconnected, disconnect all the wires from the Duet and DueX5; except that if your remaining tools use PT100 sensors, leave them connected to the daughter board and remove the daughter board from the Duet. Then remove the Duet and DueX5, along with the supporting pillars.

Remove the T2 and T3 tool looms and the T2 and T3 motor cables from the loom bundle.

You need to drill new mounting holes for the Duet 3. I chose to use the bottom right (looking from the rear) original Duet mounting hole for the bottom right hole in the Duet 3 main board. This leaves room above for the optional Raspberry Pi, avoids lengthening the VIN wires, and maintains good clearance from the mains voltage bed heater wires. So I drilled three new 4mm holes for the other 3 mounting holes, then I attached the Duet 3 main board using 4 of the original standoffs.

You also need to drill four 3mm mounting holes for the Tool Distribution Board. I chose to mount it centrally (ready for 2 more Hemeras), approximately at the same height as the Titan extruders.

This is how my Tool Changer looked at this point (one of the unused Titans is still fitted).

Duet 3 Main Board wiring

The main task is to connect all the connectors from the original loom (less the wires already removed) to the Duet 3. The connectors in the original loom are all labelled, which helps a great deal. Here’s how to connect everything:

• VIN: cut off the ferrules and DuetX5 extension wires from the red Board VIN and black Board GND wires. Crimp a red fork terminal on to Board GND and connect it to the bottom terminal of the barrier strip. Also cut off the ferrule from the red Heatbed wire. Twist that wire and Board VIN together, crimp a blue fork terminal on it, and connect it to the second terminal up (this avoids running a wire from VIN to Bed Heater+ on the Duet, which would be wise if running a bed heater directly from the Duet, but not needed when the output is driving a SSR). Alternatively, you can crimp a red fork terminal to each red wire, and connect both of them to the second terminal up (you will need to bend the top one a little).
• Bed heater: the red Heatbed wire is already taken care of. Cut the ferrule off the black Heatbed wire, crimp a red fork terminal to it, and connect it to the top terminal. [There are other outputs on the Duet 3 that these wires could be connected to; but this scheme follows the Duet 2 scheme.]
• Bed thermistor (unlabelled blue wires coming from the bed heater cable chain terminated by 2-pin KK connector): plug it into TEMP0.
• Tool thermistors: plug T0-E0 Temp into TEMP1, and plug T1-E1 Temp intoTEMP2. If your tools use PT100 sensors instead of thermistors, just plug the daughter board that they are connected to and its mounting posts into the Duet 3.
• Fans: the Duet 3 has three 4-pin fan connectors (with support for 4-wire PWM fans) labelled OUT4..OUT6, and three 2-pin fan connectors labelled OUT7..OUT9. I chose to leave OUT9 free because it has an alternative 5V signal level connector labelled LASER/VFD that might be useful for a laser in future. So I connected T1-Fan3-Hotend Fan to OUT7, and T1-Fan4-Part Cooling Fan to OUT8. For the T0 fans, remove the pins from 2-pin plastic shells by inserting a suitable tool (e.g. very small screwdriver or the points of tweezers) into the slot to release the barb, then pull gently on the wire. Insert the wires into the correct two positions of the 4-way shells provided with the Duet 3 (see image). Check that the barbs lock the pins into the shell; if they don’t (which sometimes happens when the pins and the shells are from different manufacturers) then you will have to crimp new pins on the wires. I plugged T0-Fan1-Hotend Fan into OUT4, and T0-Fan2-Part Cooling into OUT5.
• Z probe (labelled TCH-Z-Endstop-Z Switch): use the same method to replace the 3-way shell by a 5-way shell and connect it between the IN and GND pins of to one of the IO_n connectors. If you have a PanelDue, leave IO_0 free for that. I used IO_3 as shown here.
• Tool detect (labelled TCH-E0-Endstop-Tool-Detect): this is not connected at the tool pickup head. To avoid leaving it dangling and allow for future use, you can connect it to another IO_n connector as for the Z probe. I used IO_4.
• Tool heaters (T0-E0-Heater and T1-E1-Heater): cut off the ferrules, strip the ends and crimp a JST VH pin on to each wire. I recommend the Engineer PA21 crimp tool for this. Fit 2-way shells and plug them into OUT1 and OUT2.
• Motors: the six 4-pin KK connectors must be replaced by JST VH connectors, preserving the wiring order (red-blue-green-black on most of them). The wires are rather thin for the VH connectors. So after cutting off the old connectors, I suggest you strip double the amount of insulation off the ends and then double the bare ends back on themselves. Also slip a short length of 2mm heatshrink sleeving over the insulation and shrink it on, to thicken the insulation. [One user has also reported success without using heatshrink, by cutting shorter the wings of the crimp pin that bite into the insulation.] The coupler wire motor connector had wiring order blue-red-black-white, but I changed this to red-blue-white-black so that the order is the same as for the other motors, with white substituted for green. As this involved reversing the polarity of 2 phases, it doesn’t change the motor direction.

I plugged the motors into the most convenient motor connectors, given the lengths of the cables coming out of the loom. These were: X Motor to Driver 2, Y Motor to Driver 1, E0 Motor to Driver 3, E1 motor to Driver 4, Z Motor to Driver 0, TCH-E4 Motor to Driver 5.

It was apparent that the weight of the wiring loom was putting stress on the B motor connector, so I drilled a couple of 3mm holes in the acrylic below the holes of the T3 extruder and secured the loom to the panel using a zip tie.

Tool Distribution Board wiring

The thick red and black wires go to the Tool Distribution Board

The Tool Distribution Board needs 24V power from the PSU. Use the 10A red/black cable for this, and crimp fork terminals on both ends.

Connect the RJ11 cable between CAN_IN on the distribution board and the CAN connector on the Duet 3 main board. Place a jumper across the termination pins next to the CAN_OUT connector on the distribution board.

Part 2 of this series will cover configuring and commissioning of the system as it now stands (without the Hemera tools), installing and wiring the Hemera tools, and final configuring and commissioning of the new tools.

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