How to install a dual extruder on your 3D printer


The extruder is one of the most essential components of a 3D printer and is directly responsible for the quality and complexity of 3D printing. The idea behind a dual extrusion system is to have a 3D printer capable of printing an object with two color schemes. Let’s take a look at how 3D printing extruders work before we delve deeper into the details of the dual extruder upgrade.

How do 3D printing extruders work?

The extruder is made up of two parts:

Bowden extruders: graphic image of their operation

Cold end: The cold end consists of a stepper motor, a gear, a spring tensioner to hold the filament, and a PTFE tube to guide the filament into the hot end.

hot end: The Hot End is the part where the filament is melted and extruded out of the nozzle. In a Bowden 3D printer extrusion system, a filament feed tube inserts the filament directly into the thermal break through the heat sink. The molten filament is then injected out of a nozzle.

The following paragraphs will guide us on how to upgrade a single extruder system to a Bowden dual extruder system by adding an extruder motor and a hot end for mixing filaments. The modification will give us the possibility of using two filaments and printing unique objects with two-color schemes.

Related: Turn Your Cheap 3D Printer Into A Manufacturer’s Dream

What do you need to start the upgrade?

You need the following components for the modification.

  • Spool holder: For the second filament, you would need an additional spool holder.
  • Step-by-step engine : This additional stepping motor will be used as part of the extruder assembly for feeding the second filament. To connect the stepper motor to the control board, a stepper motor driver is also required.
  • Extruder: An extruder assembly similar to the original extruder is required to accompany the stepper motor, as the firmware requires that both extruders have the same e-steps.
  • hot end: The hot-end for the modification used here is the BIGTREETECH Mixed Color 2 In 1 Out Hotend double extruder kit. The hot-end kit comes with a thermistor, cooling fan and PTFE tube.

Bigtreetech 2 in 1 Hot End Complete Kit

Image Credit: BIQU
  • Control board: The control board of most 3D printers comes with four stepper motor slots. To install the additional stepper motor, an additional location on the control board is required. BIGTREETECH SKR Pro v1.2 is our choice of control board for this upgrade, but any control board with five stepper motor driver slots is suitable for modification.

How to set up a dual extruder

The upgrade requires the following changes to be made to hardware, electronics, firmware, and slicing program.

Hardware modification

Spool holder

The additional spool holder can be printed to the specifications of the 3D printer frame using models available on Thingiverse or a universal spool holder can be purchased online. The assembly of the spool holder is quite simple and requires a bracket screwed to the frame on which the spool is mounted or bolted. One trick to making the two coils work efficiently is to position them parallel so that they mirror each other.

Extruder and stepper motor

The extruder assembly is attached to the stepper motor and is mounted on top of the frame using an extruder mounting bracket. Thingiverse provides great media designs for different 3D printers which can also be customized as needed. The extruder motor assembly should be similar to the default extruder and positioned the same on the frame.

Extruder Mounting Kit with Bracket

Image Credit: KerseyFabrications /Thingiverse.com

Hot end

The default hot end of the 3D printer should be replaced with the hot end BIGTREETECH Mixed Color 2 Into 1. Assembly requires the hot mount bracket, which can be downloaded from here. The fan is screwed onto the hot end and the thermistor wire is connected from the hot end to the controller board. The PTFE tube is then coupled from the extruder to the hot end.

Electronics modification

Control board

As we need a controller with five stepper motor drivers, we will replace our existing board with BIGTREETECH SKR Pro v1.2 if the default board only has four stepper motor driver slots. Wiring from the extruder-stepper motor assembly will be connected to the control board in the fifth location. If you don’t know how to set up a controller card, we’ll cover that in detail in the future.

BTSKR 1.2 pro control card

Image Credit: BIQU

Firmware modification

Marlin is the most compatible firmware for 3D printers and supports a wide variety of controller boards. Firmware configuration is fairly straightforward and only requires the following changes to be made to the Marlin firmware configuration.h file. The files can simply be opened using Visual Studio code and the following changes need to be made:

In configuration.h:

#define MIXING_EXTRUDER (Uncomment)
#define MIXING_STEPPERS 2 (Set to 2)
#define GRADIENT MIX (Uncomment)
#E1_DRIVER_TYPE (Uncomment and set to match the stepper motor driver being used)

Check that the direction of both extruders is the same:

#define INVERT_E0_DIR true
#define INVERT_E1_DIR true

Check current and micro-steps for extruders:

#define E0_CURRENT
#define E0_MICROSTEPS
#define E1_CURRENT
#define E1_MICROSTEPS

Once the firmware is updated, we can perform PID autotuning on the new hot-end. This can be done by the console or if the 3D printer has an LCD interface, there is an option for PID autotuning where you can set the desired temperature value and the number of cycles for the PID tuning.

Modification of the slicer

The cutter software we will be using for our modified printer is Cura, but the upgrade is compatible with all cutter software with minor configuration changes. In Cura, we just go to settings and add a 3D printer. Once the printer has been added, go to the machine settings and enter all the values ​​for the printer dimensions. Change the number of extruders to two, then configure each extruder individually. Finally, import a two-color model from Thingiverse and start printing with the upgraded 3D printer.

Cura-Settings

Try a dual extruder today

The dual extruder upgrade is a detailed modification and requires an intermediate level of understanding of working with 3D printers. It’s a great learning experience for users interested in upgrading their 3D printers and willing to spend time tweaking their printer settings.


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