{"id":93,"date":"2019-05-09T13:16:12","date_gmt":"2019-05-09T13:16:12","guid":{"rendered":"https:\/\/ucrea.ca\/?page_id=93"},"modified":"2021-07-05T17:06:54","modified_gmt":"2021-07-05T17:06:54","slug":"resources","status":"publish","type":"page","link":"https:\/\/ucrea.ca\/fr\/resources\/","title":{"rendered":"Resources"},"content":{"rendered":"

Design guidelines for FDM 3D printing<\/h4>\n

Detailed mesh<\/h1>\n

Models must be uploaded as .STL (ST<\/strong>ereoL<\/strong>ithography) files. Most modern computer-assisted design tools allow to save 3D models under this format.<\/p>\n<\/div>

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An STL mesh is composed of triangular faces that are meshed together to form an approximation of the object you intend to print. That approximation can be way off if you don\u2019t save or export your file with the right settings. Let\u2019s look at different settings used to save a sphere as an *.STL file in SOLIDWORKS 2018.<\/p>\n<\/div><\/div><\/div>

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Comparison of coarse<\/em> and fine<\/em> export settings<\/h1>\n<\/div>
\"STL<\/span><\/div><\/div>
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\"STL<\/span><\/div><\/div>
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The 3D printer will print exactly what the *.STL mesh looks like so it\u2019s up to you to save it the way you want it to come out of the machine! Increase your triangle face count to ensure the best quality. We recommend a deviation setting of 0.02mm<\/strong> and an angle setting of 10 degrees<\/strong>. Saving the *.STL mesh with a higher resolution than this will result in a file that is very large without any gains in print quality.<\/p>\n<\/div>

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Recommended deviation setting: 0.02mm<\/strong><\/p>\n

Recommended angle setting: 10 degrees<\/strong><\/p>\n<\/div>

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Watertight mesh<\/h1>\n

Errors in the mesh can happen for a variety of reasons that can often be avoided by following proper design practices for the computer-assisted design suite you are using. Look online for resources. It\u2019s important to ensure your mesh is watertight. A watertight mesh is the result of closed geometry that creates a solid volume. If we fill in our geometry with water, will liquid escape? It is best to verify the normal of the triangles and ensure that they all face outwards.\u00a0 An inverted normal can be read as a hole by the 3D printer. Verify that no internal geometry was left behind from a Boolean operation like a Cut, Subtraction or a Boss\/Bass or Addition. This could cause problems.<\/p>\n

If you find it hard to find problematic regions, tools like MeshLab<\/a> and Net<\/em>Fabb<\/a> can be useful.<\/p>\n

Every border shared by more than 2 faces creates geometry that is non-manifold. Non-manifolds can be caused by self-intersecting surfaces, holes, inner faces or overlapping faces and separate objects<\/strong>. Find more information here<\/a>.<\/p>\n

When non-manifold geometry is present in a model, the 3D printer has difficulty reading the file properly.<\/p>\n<\/div>

Follow basic design guidelines<\/h1>\n<\/div>
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The nozzle used to create the models has a diameter, \u201dN<\/strong>\u201d, of 0.4mm<\/strong>. That said, plastic expands as it is extruded because the pressure in the nozzle is greater than that outside. Further, the plastic is squished down on the previous layer, at a layer height, \u201dH<\/strong>\u201d, typically of 0.2mm<\/strong>. For these reasons, the width of the extrusion is larger than the nozzle diameter. An extrusion multiplier, \u201dEM<\/strong>\u201d, of 1.05<\/strong> is used in the slicing process. The extrusion width, \u201dD<\/strong>\u201d, is then of 0.42mm<\/strong>. Every feature of your 3D print is created by the nozzle as it moves in space, as such, its dimensions dictate what is possible to print\u2026 or not!<\/p>\n<\/div>

45-degrees rule<\/h1>\n<\/div>
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The most important rule to follow when designing for 3D printing is the 45-degree rule. Because plastic must be deposited on a previous layer, the model cannot contain unsupported overhangs beyond 45 degrees with respect to the vertical axis. The above image illustrates the design limitations. Avoid fillets on the bottom face.<\/p>\n<\/div>

Bridging<\/h1>\n<\/div>
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