<br> [MAS.865](../index.html) > [Additive](index.html) ## Additive Processes ### Introduction <div style="margin-left:2.5%"> <li><span style="text-decoration: underline;"><strong> AM Process Classification </strong></span> <ul> <li>Criteria: <ul> <li> application (visual prototyping, functional prototyping, rapid tooling and rapid manufacturing) <li> initial condition of the processed materials <li> underlying physical principle <li> here we follow the <a href = 'http://web.mit.edu/2.810/www/files/readings/AdditiveManufacturingTerminology.pdf'> <b>Standard Terminology for Additive Manufacturing</b> </a> defined by the <a href = 'https://www.astm.org/COMMITTEE/F42.htm'> <b> ASTM International Committee F42 on AM </b></a> </ul> ![additive-vs-subtractive](images/additive-vs-subtractive.jpg) <li><span style="text-decoration: underline;"><strong>Challenges in AM ==> Areas of opportunity</strong></span> <ul> <li>Build Speed <ul> <li>The term <i>rapid prototyping can be somewaht misleading</i> <li>AM is still slow in comparison to mass production technologies such as <b>injection molding</b> <li>key motivator for: a) advanced path planning procedures, b) processes that are continuous in nature (CLIP) to one-step holographic processes </ul> <li>Mechanical Properties <ul> <li> AM products inferior with respect to mechanical properties in many cases compared to subtractive processes. <li>limited choice of materials <li>layered production leads to anisotropic parts witht the interface between layers representing maximum residual stress <li><a href='https://www.emeraldinsight.com/doi/full/10.1108/RPJ-06-2012-0052'>commmercial AM materials comparison - anisotropy</a> </ul> <li>Resolution <li>Multimaterials Parts </ul> </div> ###Vat Photopolymerization Processes <b> Vat photopolymerization </b> is an additive manufacturing process in which liquid photopolymer in a vat is selectively cured by light-activated polymerization. Many of the lithography-based AM approaches (e.g., multiphoton polymerization (2PP), digital light processing (DLP), and stereolithography (SLA)) can be grouped into this category. <div> <div> <div style="margin-left: 2.5%;"><!--honghao start here, ask filipo's help on multiphoton--></div> <ul> <li>Techniques <ul> <li><u><span style="color: #333333;"><a href="sla/index.html"><strong>Stereolithography</strong></a></span></u></li> <li><u><strong>[Digital Light Processing/LCD](dlp/index.html)</strong></u></li> <li><u><strong>[Continuous Liquid Interface Production](clip.pdf)</strong></u></li> <li><u><strong>[Multiphoton Polymerization](multiphoton-polymerization/index.html)</strong></u></li> </ul> </li> </ul> </div> </div> ### Powder Bed Fusion Processes <b> Powder bed fusion </b> is an additive manufacturing process in which thermal energy (provided, e.g., by a laser or an electron beam) selectively fuses regions of a powder bed. These processes are used for metals as well as polymers. <div> <div style="margin-left: 2.5%;"> <ul> <li>Techniques <ul> <li><span style="text-decoration: underline;"><strong>[Selective Laser Sintering (3D Systems)/Laser Sintering (EOS)](selective-laser-sintering/index.html)</strong></span></li> </ul> </li> </ul> </div> </div> ### Material &amp; Binder Jetting Processes <b>Material jetting</b> is an additive manufacturing process in which droplets of build material (such as photopolymer or thermoplastic materials) are selectively deposited. Systems based on inkjet-printing fall into this category. <b>Binder jetting</b> is an additive manufacturing process in which a liquid bonding agent is selectively deposited to fuse powder materials. <div style="margin-left: 2.5%;"> <ul> <li><span style="text-decoration: underline;"><strong>[Inkjet Printing and Printing Inks](inkjet-printing/index.html)</strong></span> <ul> <li>Thermal Inkjet Printing</li> <li>Inkjet-based Lithography (The Polyjet Process)</li> </ul> </li> <li><span style="text-decoration: underline;"><strong>[Aerosol Jet Printing](aerosol-jet-printing/index.html)</strong></span> </li> </div> </div> ### 3D Material Extrusion <div> <div style="margin-left: 2.5%;"> <ul> <li><a href="fdm/index.html"><strong><u>Fused Deposition Modeling (FDM)</u></strong></a> <ul> <li>Tailoring Materials for FDM</li> </ul> </li> </ul> </div> </div> ###[Sheet Lamination and Laminated Object Manufacturing (LOM)](sheet-lamination-lom/index.html) <b>Sheet lamination</b> is an additive manufacturing process in which sheets of material are bonded together to form an object. ###[Molding](molding/index.html) <div> <div style="margin-left: 2.5%;"> <ul> <li>Prototyping</li> <li>Manufacturing</li> </ul> <br /> <div style="margin-left: 2.5%;">&nbsp;</div> </div> </div>