The H-Series standard printing configuration has 5 extruders. Why?

FDM is commonly seen as a crude form of 3D printing, suitable for hobbyist level work, but not to be taken seriously for commercial uses.  This attitude is mostly due to the reduced strength and coarse surface finish typical of extrusion printed parts.1  Resin printers create parts with more isotropic material properties and finer surface finishes, so they’ve become the processes of choice for commercial users. However, extrusion printing does have some legitimate advantages over its higher resolution counterparts. Probably the most underappreciated (and so far underutilized) advantage is the ability to deposit multiple materials during a single build.

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Dissolvable support is the most common and obvious use for multi-material printing.  By building a support body that connects the build platform to the underside of the part, many frustrations of extrusion printing can be avoided.  Unlike the tear-away low density support structures used in single-material prints, dissolvable materials allow a continuous and coincident interface with the part.  This results in much higher quality underside surfaces. But dissolvable support is only a starting point for multi-material printing.

 

Let’s step back a moment and look at product design in general. When we imagine the object we’re creating, we often think about each individual component and define its form and material based on the manufacturing processes available to us. Injection molding is the most commonly used process for the production of plastic parts, but the requirements for relatively thin walls and fully dense volumes of a single material limit the design space (much like resin printers). Injection molding has revolutionized product design, but less because of the engineering benefits and more because of the drastic reduction in cost when compared to other traditional manufacturing processes. If we keep the same design paradigm that we use for injection molded parts, then it’s no surprise that extrusion printing is not a suitable replacement. So the first thing we need to do is reject the one-part-one-material mentality.

 

Rather than thinking of products as assemblies of discrete parts of different materials, we need to think of them as distributions of material properties that serve a function. Consider the construction of a shoe sole.2  Even for the case of a simple sandal, three or more materials are often used: the tread features require high grip and high abrasion resistance, the footbed must be soft and compliant for comfort, and a third material is used to provide the overall stiffness and feel of the sole. In traditional manufacturing methods, these separate regions of the sole are formed as separate parts and bonded together during assembly steps. But when the sole is printed in a single build these materials can interlock and transition in ways that would be impossible with other techniques.

4-material partial sole

 

We encourage you to think broadly and creatively about the potential of true multi-material additive manufacturing. In any given part or application, what combination of material properties would be useful? If the ideas still aren’t flowing about how you would take advantage of multiple materials in a build, look up the material datasheets for commercial filaments. Just about every item on the list offers a suggestion of a useful composite structure – from elastic modulus, to strength, to electrical and thermal conductivity, to CTE, to density and others.

 

Notes:

1. Low strength and poor surface finish are problems that we’re tackling with other capabilities on the H-Series machine

2. We’ll do another entry specifically on footwear printing soon.