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Additive Manufacturing Essentials

2.4 Liquid-Addition Processes

Additive Manufacturing Essentials2.4 Liquid-Addition Processes
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Learning Objectives

By the end of this section, students will be able to:

  • Understand material jetting.
  • Comprehend slurry-based AM systems.
  • Grasp the concept of direct ink write systems.

Material Jetting System Architecture

Material jetting is an AM process in which droplets of specialized materials sometimes referred to as ink are selectively applied to a build surface. The layer is typically cured using UV light, and the process repeats itself to construct the 3D object. The size limits of the machines can range from 500mm3 to 1200mm3. The basic machine architecture consists of the following:

  • Jetting Head
  • UV Lamp
  • Build Platform and Motion System
  • Build Plate
  • Roller
  • Computer / HMI
A printer block sits above a printing tray; it contains inkjet heads, a leveling roller, and a UV lamp. On the tray is the object being printed, and the tray can move up and down according to the z axis.
Figure 2.6 Material jetting system architecture

Material Feedstock

  • Polypropylene
  • ABS
  • Acrylic thermoset photopolymers
  • Nano ceramics
  • Electrically conductive nano metal particles

Slurry based system architecture

The sustainable and affordable housing industry has adopted slurry-based AM as a way to make quick housing on the worksite using cement deposited on a very large gantry system. Cement is fed as a slurry into a deposition head that is suspended from a gantry to additively construct housing.

By fabricating homes at the worksite, may pre-fabricated labor and shipping steps are eliminated, thereby making the homes more affordable.

Two large nearly spherical structures stand on the ground with a person walking by them. They are more than twice as tall as the person. Above the structures, a metal structure is suspended in the air with additional machinery connected to them.
Figure 2.7 AM structures can be created by a deposition head suspended from a gantry system. The system prints the cement or other material layer by layer from the ground up, with the gantry lifting the system as the layers are deposited. (credit: Modification of “The Tecla as of 2021,” by Alfredo Milano/Wikimedia Commons, CC-BY 2.5)

Direct ink-writing system architecture

Direct ink writing, also known as aerosol jetting or robocasting, is a process that allows for the additive manufacturing of functional electronics. In this process, a conducting ink made from silver or copper sprays 1 to 5 micron droplets onto a surface using an atomizer to create an aerosol mist that moves to the deposition head. In many cases, the machines capable of doing this work also operate on a 5 axis platform. This allows for direct writing of circuitry on conformal surfaces. This aerosol spray can apply the conductive ink to a variety of substrates. Features can be from 10 microns to a few millimeters in scale. Individual layer thicknesses can range from 10nm to greater than 10 microns. The basic machine architecture consists of the following:

  • Deposition Head
  • Atomizer
  • Sheath Gas
  • Build Plate
  • Ink Material Feed
  • Computer / HMI
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