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Building from Proof of Concept Design
Published in Bahram Nassersharif, Engineering Capstone Design, 2022
Standard 3D printer slicing software requires the model file to be in stereolithography (STL) format. The STL format is old and inefficient, but it is broadly accepted as the norm. The CAD software can export the design model in several different formats, including STL. The STL file is an approximate representation of the detailed geometry in the CAD model. The approximation is achieved by converting the model surfaces to a triangle mesh and outputting the triangle vertices coordinates and the normal vector to the triangle plane to the STL file in 3D Cartesian coordinates. Therefore, the STL files are large and compute-intensive to process. The user can set a system of units and precision intervals to adjust the resolution and size of the STL file. For 3D printers, it is best to use the highest resolution model allowed by the CAD software (Figure 9.14).
3D Printed Gears
Published in Stephen P. Radzevich, Dudley's Handbook of Practical Gear Design and Manufacture, 2021
Most common method for printing plastic gears and parts is the filament method where a plastic filament on a spool is fed into an extruder head that is heated and the molten plastic is laid down in layers on top of one another to build the part from bottom to top. Typical layer thickness is 0.1 mm but it is adjustable in what is called the slicing software that creates the NC code for the 3D printer. These types of printers are commonly available, and many AM enthusiasts have them in their homes. Common Materials are ABS and PLA but there are hundreds to choose from, from different suppliers. The layers are clearly visible and the surface roughness perpendicular to the layers is higher than along the layers. For a gear this means that the surface roughness will be better in the rolling/sliding direction on the flanks of a cylindrical gear than perpendicular, unless the gear was printed standing up which does not make sense. The tolerances are not very good, but it will be functional and there are plenty of examples in the maker community of functioning 3D printed gear trains made this way. The weaknesses of these prints are the tolerances (around 0.05–0.1 mm) and the intra layer adhesion, meaning the prints don’t exhibit the same mechanical properties in all directions. They tend to break between layers rather than perpendicular to them.
Gear Manufacturing Essentials
Published in Alexander L. Kapelevich, Direct Gear Design, 2021
There are several 3D gear printing methods:Fused Filament Deposition (FFD). The most common way to print plastic gears is the filament method. A plastic filament on a spool is fed into a heated extruder head that extrudes the molten plastic in a thin line, making layers on top of one another to build the part from bottom to top. A principle of the FFD method is shown in Figure 9.26. The layer thickness is usually 0.1 mm, but this is adjustable in the slicing software. These types of printers are commonly available, and many AM enthusiasts have them in their homes. Typical materials are acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) polymers. The layers are clearly visible, and the surface roughness perpendicular to the layers is higher than along the layers. For a gear, this means that the surface roughness is better in the sliding direction on the flanks of a cylindrical gear compared to the perpendicular one. The gear accuracy is not high but sufficient for functioning plastic gear trains. The weaknesses of these prints are the tolerances (around 0.1 mm), and the intra layer adhesion, meaning the parts don´t exhibit the same mechanical properties in all directions. They tend to break between layers rather than perpendicular to them.
Uniaxial tensile testing standardization for the qualification of fiber reinforced plastics for fused filament fabrication
Published in Mechanics of Advanced Materials and Structures, 2021
William H. Ferrell, Jason Clement, Stephanie TerMaath
For traditionally manufactured continuous fiber reinforced plastics, orientation of mechanical properties is typically aligned relative to the reinforcement. Chopped fiber reinforced composites, traditionally manufactured, have high levels of anisotropy that do not exist within the extrudate in FFF, making FFF advantageous with regards to fiber alignment [57–59]. However, with FFF, the control of raster patterns and build direction provides tremendous potential for the manufacture of customized parts but results in many new considerations in defining mechanical property orientation. When a model is uploaded into a printer control software, such as RepetierHost, a slicing software is used to take the stereolithography file (.stl) and create a G-Code, the numerical programing code for automated machine tools that controls build pattern and path. Part placement in the software and the user selected slicer code affects the raster pattern and build orientation, such that these user choices can result in significant print variations, limiting FFF as a true “plug and play” technology. The build direction on the platform and the raster angle affect the mechanical properties of FFF specimens and must be consistently designated along with the corresponding tensile property values.
Direct rapid prototyping from point cloud data without surface reconstruction
Published in Computer-Aided Design and Applications, 2018
Tianyun Yuan, Xiaobo Peng, Dongdong Zhang
As shown in Tab. 2, the processing times range from 129 second to 402 second. With the traditional process, a CAD model needs to be created from point cloud data using software, such as ImageWare, or X design. Then, the CAD file will be refined and converted into STL model using modeling software, such as NX Siemens, or SolidWorks. Slicing software, like Cura, Slic3r, is required to slice the STL model and export G code for 3D printing. Such processes require professional knowledge and skills. Compared to the traditional process, the processing time using the direct 3D printing system is dramatically reduced.