makerbotlogoWhen it comes to 3D printing, one of the issues that many people face, is that they are bound by one build material or color per print. That is unless you want to manually switch out material while the printer is in the middle of printing. By no means is it impossible to do. For example, with the MakerBot Replicator and other 3D printers, you can pause the print, load in the new material, and then resume printing. However, this isn’t all that desirable, and it means that you must constantly be watching for the right time to switch materials.

Some may ask, “Why would you wish to switch materials mid print?”

There could be several reason. One may be that you wish to have a multiple color print, one which perhaps has designs on it in separate colors. Another reason may be that you wish to transfer from PLA, to ABS, Nylon, Wood based filament, or another desired material.  There are new materials coming out on a monthly basis, all of which have different textures, looks, and other desired physical properties.

MakerBot has invented a new type of process which, if it works properly, will allow 3D printers to change build material mid print.  They have filed a patent to protect this solution over a year and a half ago, but just recently was it published for the public to see, and has uncovered it.

The way this printer would work, is that it would have a specialized extruder, that includes multiple build materials, multiple build material feeds, and a filament changer as seen in the diagram below (we’ve edited it to make it easier to understand).


While the example above only shows 2 build materials, the patent application allows for an indefinite amount of materials and material feeds.  The multiple materials would be fed into their individual feeds, which are connected to a filament changer (or build material changer).  The filament changer would be able to slide the extrusion head from material to material, in a fluent motion.  It would also consist of a blade or other cutting edge, that would cut the 1st material before proceeding to the second.  The patent also allows for each feed to have its own motor, to enable the feed changing process to occur uninterrupted.

The patent application would ensure that MakerBot holds the rights to this invention, if the above features differ slightly.  It covers them for other types of print processes other than FDM, and also allows for two separate extruders to be alternately positioned along the tool path for a similar effect to what is outlined above.

MakerBot explains some of the reasons for wanting to automatically switch between build materials, other than for the sole purpose of changing filament colors.

“For example, different build materials may have different optical properties (opacity, color, finish, etc.), different mechanical properties (elasticity, strength, melting point, etc.), different chemical properties (curing conditions, solubility, etc.), thermal properties (insulation, etc.), electrical properties (conductance, etc.) and so forth, any of which might usefully be combined in an object fabricated from a model. The techniques described herein may be usefully employed to enable switching of build materials in any such multi-material models.”

One problem that surely could arise, is that residue from the first build material could, and probably would remain in the extrusion nozzle after switching to the next build material.  To take care of this issue, MakerBot also has a solution. They plan on allowing for transition segments of a print, that will allow the nozzle to basically rid itself of the previous material prior to printing in a new color or build material (see image below).


MakerBot explains this in a bit more detail:

“A first segment 402 of a tool path 400 may traverse a portion of an exterior surface of an object with a first color, such as red. The tool path 400 may then turn in toward an interior of the object and infill with a transition segment 404 between the first color and a second color, such as blue. After the transition is complete and the second color can be extruded without mixing from the first color, the tool path 400 may return to the exterior of the object and the tool path 400 may provide a third segment 406 traversing a different portion of the exterior with the second color.”

The transition of build materials may occur away from the object on the build plate, or inside of the object, in a location where it would not be visible and would not effect the printed object in any way.


MakerBot also covers the ‘tool instructions’, which will help the printer know when to switch materials, and how much material to use. The 3D printer could also have an onboard scanner that is able to detect when a change needs to be made. Also touched on, is a method of splicing build materials together in order to print in multiple materials. This could be a separate method from the method described previously, where a filament changer is utilized. Instead, the filament would be spliced together using one of several methods, but this would require the need for predetermined lengths of filament (build material).  The splicing strategy seems to be more complicated for the end user, as there would have to be a method that determines the exact amount of each build material that would need to be spliced together.

While this patent was filed for by MakerBot, it does not indicate with certainty that they are working on, or plan to work on a 3D printing process which involves these methods.  The patent has been applied for but has not yet been granted.  It is an invention that they have come up with, but the question remains if they will actually produce a product that utilizes this technology or not. What do you think? Would this be something that you would be interested in having on your 3D printer? Could it work? Discuss in the “MakerBot’s Unknown Invention” thread on

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