Material Jetting of Polymers

Abstract

Material jetting (MJ) is a classification of additive manufacturing processes that involves the selective jetting and subsequent solidification of liquid droplets onto a substrate in a layerwise manner. This article focuses solely on MJ of polymers, providing a process overview and describing the functional characteristics that distinguish it from other AM technologies. It provides information on the properties and design considerations of both build and support materials. Process-related effects on final part properties and overall quality, as well as corresponding design considerations are also covered. The article also discusses the applications and future scope of polymer MJ systems.

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“…Material jetting is defined in ASTM F2792 [13] as "an additive manufacturing process in which droplets of build material are selectively deposited." Here, an array of inkjet printheads on a shared carrier simultaneously deposit and solidify material in a linear fashion, similar to the standard 2D ink jetting process [19]. Post processing includes removal of support material and in some cases a second curing cycle.…”

“…As thermoset photopolymer resins are jetted and cured in place, multimaterial and graded material parts (termed "digital materials") are feasible when multiple inkjets with different materials are used. Dots per inch (dpi) gradients can be leveraged to transition material Durometers, Shore hardness, or colors for unique part functionality and aesthetic [19]. These processes boast high dimensional accuracy, excellent surface finish, and a low risk of warping, with layer heights as low as 13μm [19,21,22].…”

“…Dots per inch (dpi) gradients can be leveraged to transition material Durometers, Shore hardness, or colors for unique part functionality and aesthetic [19]. These processes boast high dimensional accuracy, excellent surface finish, and a low risk of warping, with layer heights as low as 13μm [19,21,22]. Resolution in XY may be as fine as 600 dpi, with 1600 dpi in Z [19,23].…”

“…These processes boast high dimensional accuracy, excellent surface finish, and a low risk of warping, with layer heights as low as 13μm [19,21,22]. Resolution in XY may be as fine as 600 dpi, with 1600 dpi in Z [19,23]. The major limiting factor to process scalability is the unit price of feedstock materials, which is quite high ($100's/kg) for both wax materials and thermosets [24,25].…”

“…The major limiting factor to process scalability is the unit price of feedstock materials, which is quite high ($100's/kg) for both wax materials and thermosets [24,25]. Technical challenges for this process include materials selection, machine reliability, and part consistency [19]. Vertical build rates are typically in the 10's mm/hr, with volumetric rates of 10's cc/hr [23,26].…”