< > [additive](index.html)
<h1 id="binder-jetting">Binder Jetting</h1>
<p>Currently, the most pervasive use of Additive Manufacturing is everyday Inkjet Printers. These printers add small droplets of pigment to a page. </p>
<h2 id="inkjet-printing">Inkjet Printing</h2>
<p>For inkjet printers, they largely follow the same principle. Small droplets of ink are shot onto a page at an exact location. Multiple head means multiple colors can be printed. These Nozzles come in two varieties. </p>
<p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/Micro_Piezo_Comparison.gif/220px-Micro_Piezo_Comparison.gif" alt="Piezo vs Thermal Inkjet Printing Head"></p>
<pre><code><span class="hljs-bullet">- </span>Thermal Inkjet Printing
In this approach, the droplet are formed by placing the liquid on a resitive heating plate until an air droplet forms, pushing a droplet of ink out. Canon and HP printers use this approach. The only downside is that for specialty inks, the heating can affect the inks chemistry and resulting properties
<span class="hljs-bullet">- </span>Piezo Inkjet Printing
Another approach is to use a piezoelectric crystal the shake out droplets by an oscillating voltage. This approach is used to inkjet print with special conductive inks.
[<span class="hljs-string">This</span>](<span class="hljs-link">https://www.mpm.co.jp/electronic/eng/silver-nano/line-up.html</span>) off the shelf conductive material can be [<span class="hljs-string">printed on cheap printers</span>](<span class="hljs-link">https://www.instructables.com/Print-Conductive-Circuits-With-An-Inkjet-Printer/</span>) but requires a heat treatement to sinter the nanoparticles.
[<span class="hljs-string">This</span>](<span class="hljs-link">https://www.novacentrix.com/products/inkjet-starter-kits</span>) off the shelf conductive material can also be printed on cheap printer but requires pape with a special coating to chemically sinter nanoparticles.
The paper below details different ways of printing onto flexible surfaces with commodity inkjet printers
</code></pre><p><a href="https://www.dropbox.com/s/b34qe94w1kgw1ec/3332165.3347892.pdf?dl=0">https://www.dropbox.com/s/b34qe94w1kgw1ec/3332165.3347892.pdf?dl=0</a></p>
<pre><code>It also <span class="hljs-keyword">contains</span> this nice equation <span class="hljs-keyword">for</span> predicting whether <span class="hljs-keyword">or</span> <span class="hljs-keyword">not</span> <span class="hljs-keyword">a</span> novel ink can be inkjet printed <span class="hljs-keyword">without</span> clogging.
</code></pre><p><img src="https://paper-attachments.dropbox.com/s_598532E29A61E0758D4B53CA1E8A5F6907D2B7285FBB80C9D9D9151A8CDDF431_1619072915530_Screen+Shot+2021-04-22+at+2.28.31+AM.png" alt=""></p>
<h2 id="-inkjet-based-lithography-the-polyjet-process-"><strong>Inkjet-based Lithography (The Polyjet Process)</strong></h2>
<pre><code>Combining <span class="hljs-keyword">the</span> benefits <span class="hljs-keyword">of</span> lithographic methods (high feature resolution <span class="hljs-keyword">and</span> good surface quality) <span class="hljs-keyword">with</span> <span class="hljs-keyword">the</span> advantages <span class="hljs-keyword">of</span> material jetting (high build speed <span class="hljs-keyword">and</span> large build volume), <span class="hljs-keyword">the</span> <span class="hljs-literal">two</span> leading AM device producers (Stratasys <span class="hljs-keyword">and</span> <span class="hljs-number">3</span>D Systems) have both developed **inkjet lithographic <span class="hljs-number">3</span>D-printers** .
</code></pre><p><img src="https://fab.cba.mit.edu/classes/865.18/additive/inkjet-printing/polyjet.jpg" alt="polyjet"></p>
<pre><code>PolyJet process (<span class="hljs-keyword">from</span> Stratasys) consisting <span class="hljs-keyword">of</span> (a) vertically movable building <span class="hljs-keyword">platform</span>, (b) multinozzle inkjet head, (c) layers <span class="hljs-keyword">of</span> support material, (d) layers <span class="hljs-keyword">of</span> building material, <span class="hljs-keyword">and</span> (e) UV source attached <span class="hljs-keyword">to</span> inkjet head.
[The Polyjet Process](https:<span class="hljs-comment">//www.youtube.com/watch?v=Cz7pKRcuTgs)</span>
An inkjet head <span class="hljs-keyword">with</span> several hundred nozzles <span class="hljs-keyword">is</span> swept along the x-axis <span class="hljs-keyword">and</span> <span class="hljs-keyword">in</span> the process ejects small droplets <span class="hljs-keyword">of</span> photopolymer. After deposition <span class="hljs-keyword">of</span> one layer, a UV-lamp flash-cures the fresh layer <span class="hljs-keyword">and</span> the process <span class="hljs-keyword">is</span> repeated. <span class="hljs-keyword">In</span> a typical setup, the inkjet head deposits two types <span class="hljs-keyword">of</span> material: the building material <span class="hljs-keyword">and</span> the support material. The support material <span class="hljs-keyword">is</span> <span class="hljs-keyword">not</span> part <span class="hljs-keyword">of</span> the finished object but <span class="hljs-keyword">is</span> required <span class="hljs-keyword">to</span> support deposited build material <span class="hljs-keyword">in</span> regions <span class="hljs-keyword">with</span> voids <span class="hljs-keyword">or</span> overhangs. <span class="hljs-keyword">In</span> contrast <span class="hljs-keyword">to</span> conventional stereolithography, <span class="hljs-keyword">where</span> lightweight supports are only required <span class="hljs-keyword">in</span> areas <span class="hljs-keyword">with</span> severe overhangs, inkjet-based AM requires a completely dense support structure.
[**The Evolution <span class="hljs-keyword">of</span> Polyjet Materials**](https:<span class="hljs-comment">//www.youtube.com/watch?v=vsYy8z_rOTg)</span>
</code></pre><h2 id="-3d-powder-binding-process-3dpb-"><strong>3D Powder Binding Process (3DPB)</strong></h2>
<p>3DPPB comprised of (a) vertically movable build platform, (b) printed model embedded in supporting powder bed, (c) inkjet printing head for deposition of binder material, (d) support material feed stock, and (e) roller for powder distribution and leveling. </p>
<p><img src="https://fab.cba.mit.edu/classes/865.18/additive/inkjet-printing/binding-powder.jpg" alt="binding-powder"></p>
<p>The key features of a 3DPB machine are a powder distribution unit, a vertically movable building platform, and the inkjet printing head enabling CAD-guided ink dispensing. In the first step, prior to layer solidification, a powder layer is deposited by moving the powder dispenser horizontally across the building platform. In the second step, the inkjet printing head dispenses a liquid, which bonds or fuses the particles together, thus forming a solid layer. In the third step, the building platform moves downward by one layer thickness to enable printing of the next layer. Residual powder particles remain on the building platform, serving as support during the print job, and upon completion they may be recovered and reused. The finished green body can be cleaned of residual adherent powder with pressurized air and then post processed by treatments such as sintering or resin infiltration, respectively.</p>
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