Dual Color Extruder With A Single Stepper


Once you have a 3D printer able to build a few objects in a single color, the next logical upgrade is a dual extruder. A dual extruder allows for multiple color prints, and by adding a dissolvable filament, the ability to print object that would otherwise be impossible. Fitting a dual extruder on an existing 3D printer presents a problem: simply by using a second stepper motor, you reduce the print area of your printer significantly. That’s the problem Dglass 3D aims to solve with their extruder. It’s a dual filament extruder that uses only one stepper motor and takes up less space than some other single filament extruders.

This isn’t the first time the guys at Dglass 3D have tried Kickstarting a dual filament extruder; last year we saw a very similar mechanism that used a single stepper motor to feed two filaments. This older model lacked retraction, though, meaning two colored prints would range somewhere between messy, inaccurate, to impossible.

The new extruder uses a servo to ‘latch’ the filament and drive it into the hot end. This means retraction of the filament is possible and from the sample prints with this extruder, the results look pretty good.

Below You’ll see a few video demos of the dual color/retraction extruder printing an object in black and white filaments at the same time. It’s very cool, and with the addition of a dissolvable filament means very complex objects can be printed very easily.

18 thoughts on “Dual Color Extruder With A Single Stepper

    1. The current design is for 1.75mm only. 3mm will physically work, however, we haven’t fully tested the 3mm, the majority of our focus has been on the 1.75. There is a chance that the 3mm is so stiff that it will resist the gear change from extruder 1 to extruder 2 so thorough testing is necessary before we can claim 3mm functionality.

    1. Evan,

      The Stratasys is actually much more complicated than our design, they actually use a solenoid or some other actuator to make their change. Our unit is quite different from the Stratasys because ours automatically switches from filament 1 to 2 when you reverse the motor. The servo is necessary to prevent the gear change. Stratasys uses their solenoid to activate the change from Filament 1 to 2.

  1. Both of the videos were quite disappointing. A bunch of moving nozzle video that could have been skipped with no loss of information, and then they just fade to some blocks that don’t look anything like what they had so far, and and the second one didn’t even show the final product.

    1. Rich,

      We found it difficult to fully capture a video of the print as well as the finished part in a time frame that didn’t lose the viewers interest. We received countless requests to show the printer in action so those videos were our attempt to provide some video proof. One of the red Hilbert cubes shown in the end was actually printed in that particular video. All 3 Hilbert cubes shown were printed with our HPX2-MAX head. In fact, the HPX2-MAX is the only head we have been running on our printer for months.

      If you would like, please send us a file you would like us to print (a file that can be printed by any standard dual extruder) and we will video tape the print, post the video and send you the part.

      1. Thanks for the offer, but I have no idea how to produce a printable drawing. The thing is, you could have skipped over about two minutes of just the printhead moving back and forth, and showed it finishing and the operator taking the part off the printer.

        Sorry I don’t have more to contribute than complaints, but how hard could it be?

  2. So, they put ball bearings everywhere? Good job on raising the cost, bad job on engineering sense. The same goes for the stainless steel gears: where the brass ones breaking? And a hobbed bolt they designed themselves: colour me unimpressed.

    1. On top of that, they did not solve the problem that is holding back dual extrusion: you will still get oozing (material lost + material deposited at the wrong spot) and the idle nozzle bumping into the work of the other.
      Space is not holding back dual extrusion, no one needs large shitty dual prints. learn how to make small good ones first, then solve the loss of building space problem.

    2. Jelle,

      Actually bearings are quite important to ensure long term performance and durability. Many of the issues found in consumer level 3D printers are a result of poor engineering design. The bearings are an incredibly small component of the overall cost.

      The stainless gears are necessary because we have repeated gear changes every time the extruder switches from filament 1 to 2. Further, brass is not readily available in hub-less design gears and doesn’t offer the toughness of Stainless.

      The custom Hobbed wheel was necessary for us to keep the gear train compact and also allowed us to manufacture a diameter hub which also helps to increase the print resolution. We have performed substantial testing on Hobbed wheel teeth and optimized the hobbing on our hub accordingly. Going custom allowed us to create the most effective solution.

      If retraction was not possible then you would get oozing, since our design includes retraction, the oozing (stringing) is virtually eliminated. This HPX2-MAX performs as well, and in many cases better, as any standard consumer level extruder (dual or single). Many of the smaller printers on the market have very small build volumes and aren’t designed to accept the weight of a traditional dual extruder on the gantry. The HPX2-MAX was designed to allow consumers to increase the capability of their printer, which would likely not be possible otherwise.

      Thanks for your comments,


    1. hboy007,

      Helical gears in the diameters we are working with are definitely source-able but the cost is substantially greater. With the 2:1 gear reduction and the diameter of the final drive (i.e. high resolution), backlash isn’t a factor that appreciably affects the system. Further, any amount of backlash (fractions of a mm) that may exist are dialed-out by dialing-in the amount of retraction.


  3. We have a stratasys at school at it lifts (via solenoid) and wipes (via silicone wiper and brass brush) the unused nozzle every switch. Perfectly reliable.

    All these misguided attempts at dual color extrusion are guaranteed to fail if both nozzles are kept on the same Z plane.

    1. Ryan,

      The Stratasys system is definitely impressive! As is their cost.

      Our HPX2-MAX is designed to function in standard consumer level printers where space, electronics, and budgets do not support the level of complexity found in the Stratasys Uprint and other high end printers.

      Our print head is designed to provide the additional functionality of dual extruders to small hobby and DIY printers that are not otherwise able to be expanded to dual extruders.

      In order for a dual extruder to create high quality prints, it is critical for the nozzles to be set on the same plane and critical for the retraction to be dialed in.

      There are currently tens of thousands of hobby style printers in use with dual extruders that are able to create high quality prints (Makerbot among them). Admittedly, they may not create prints with the same quality of a Stratasys machine but the hobby machines come mighty close for less than 1/10 the price.

      Thanks for the comments.


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