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3D printing software and design

In this section you will learn:

In the world of additive manufacturing or 3D printing, digital design is closely linked to computer numerical control (CNC), enabling digital three-dimensional models to materialize into physical objects. The applications of this technology span a wide range of industries, including aerospace, medical, automotive, construction, and science, thanks to the variety of available materials. Additionally, 3D printing is utilized in creative fields such as art, architecture, fashion, and sculpture, as well as in the fabrication of props for the film industry, and in marketing, where visual elements are crucial.

How is a 3D file transformed into a 3D printed part?

From 3D Model to 3D printing steps. Image source: IGORAZA, Medium.com

Anisoprint (Esch-sur-Alzette, Luxembourg) a manufacturer of continuous fiber 3D printing systems, has launched an update for its proprietary slicing software. Image source: CompositesWorld Magazine

To delve into 3D printing, it is crucial to understand 3D modeling software, whether CAD or organic, as well as slicing programs that convert digital designs into machine instructions. These skills are essential for getting started in this technology.

The first step involves having a 3D file compatible with the slicing software intended for use. While the standard choice is often STL, alternative formats like STEP or 3MF might yield superior outcomes due to their inclusion of more model information. This is particularly advantageous when seeking to eliminate polygonal intricacies in favor of smoother curves.

Following the import of the 3D file into the slicing software, it will generate instructions for the printing process. Typically, these instructions are a .gcode extension file, especially when employing CNC-based 3D printing technologies. However, the specific file extension may vary depending on the technology and the manufacturer’s brand.

 

In the market, there are thousands of 3D printing software options, both closed and open source, each equipped with its own optimized algorithms tailored to specific technologies.

 

A beautiful example on how the 3D slicer generates the 3D printing process from a 3D model is shown in the picture below. This slicing software not only facilitates the 3D printing of the parts in one material, but also contribute to making parts stronger. The user started with a 3D model, then added continuous fibers using the slicer to increase the object anisotropy (making it stronger in x and y axis). This serves as an excellent demonstration of the remarkable results that can be obtain with the correct use of the slicing software.

Which 3D files are compatible with 3D printing?

There exists a great number of 3D modeling software, each tailored to specific needs and boasting unique advantages. Some examples are:

Blender, a free and open-source tool, excels in its versatility, offering a comprehensive set of features suitable for both beginners and professionals. Fusion 360, developed by Autodesk, stands out for its seamless integration of CAD (Computer-Aided Design) and CAM (Computer-Aided Manufacturing) functionalities, making it an ideal choice for product design and engineering projects. SolidWorks, a Dassault Systems product, is renowned for its robust parametric modeling capabilities, enabling precise control over designs and facilitating collaboration among teams. And many more.

When it comes to exporting printable files, these software options typically support common formats such as STL, OBJ, 3MF, STP, and STEP. However, the accuracy of the exported files can vary depending on several factors. Precision settings play a crucial role in determining the fidelity of the exported model, ensuring that dimensions and geometric details are preserved accurately. Mesh quality also influences accuracy, with finer mesh resolutions yielding smoother surfaces and sharper edges. Additionally, the complexity of the model itself can impact accuracy, with more intricate designs requiring careful consideration to maintain precision during export. Therefore, while these software options offer a range of export capabilities, users must adjust settings and parameters accordingly to achieve the desired level of accuracy in their 3D printed creations.

From 3D Model to 3D printing steps. Image source: IGORAZA, Medium.com

What is an STL file and how can it be obtained from CAD design software?

Example of triangle tessellation. Image source: Protolabs

The .STL file format has become the standard for sharing 3D models in the Rapid Prototyping industry. It represents solid model surfaces with triangles. For example, a simple model like a cube might only need twelve triangles (two on each side). However, for more complex shapes, more triangles are required to approximate the surface.

“The process of covering a surface with one or more geometric shapes without any overlaps or gaps is called tessellation. STL uses triangle tessellation to approximate geometries.”

Here’s how triangle tessellation can approximate a rounded figure, using a sphere as an example:

Imagine a sphere. Now, let’s think about how to represent its surface with triangles. We can start with just a few large triangles that approximate the general shape of the sphere. However, to better capture the smoothness of the sphere’s surface, we need to add more triangles, making them smaller and more numerous. As we add more triangles, the surface representation becomes closer to the smoothness of the actual sphere. This process of adding more and more triangles to better approximate the curved surface is what we call triangle tessellation.

Triangle tessellation of a sphere, an example of what is an STL model. Image source: FOXDOC

How to export your 3D file into STL file for 3D printing

Most modeling software today can create an STL file easily. Usually, users just need to click File, Save As, and STL. Here are steps for making high-quality STL files with some popular CAD systems. 

General Steps:

– Most CAD programs offer options that affect STL quality.

– Adjusting a “Deviation” value changes overall output.

– Adjusting an “Angle Tolerance” value changes smaller details.

– Tighter parameters mean more triangles on the model’s surface.

– Simple designs are usually a few hundred kilobytes.

– Complex models are 1-5MB and still work well.

– Files larger than 5MB might not be necessary and can slow down quotes and model returns.

– Always export STL files as Binary for faster processing and smaller size.

ProeE

*              File > Export > Model

*      STL

*      Set chord height to 0. The field will be replaced by minimum acceptable value.

*      Set Angle Control to 1

*      OK

 

Alibre

*      File

*      Export

*      Save As > STL

*      Enter File Name

*      Save

 

AutoCAD (Versions: R14-2000i)

*      At the command prompt type “FACETRES”

*      Set FACETRES between 1 and 10. (1 Being low resolution and 10 high resolution for STL Triangles)

*      At the command prompt type “STLOUT”

*      Select Objects

*      Choose “Y” for Binary

*      Choose Filename

 

I-DEAS

*      File > Export > Rapid Prototype File > OK

*      Select the part to be prototyped

*      Select prototype device > SLA500.dat > OK

*      Set absolute facet deviation to 0.000395

*      Select Binary > OK

 

IronCAD

*      Right Click on the part

*      Part properties > Rendering

*      Set Facet Surface Smoothing to 150

*      File > Export

*      Choose .STL

 

Mechanical Desktop

*      Use the AMSTLOUT command to export your STL file.

*      The following command line options affect the quality of the STL and should be adjusted to produce an acceptable file.

*      Angular Tolerance – This command limits the angle between the normals of adjacent triangle. The default setting is 15 degrees. Reducing the angle will increase the resolution of the STL file.

*      Aspect Ratio – This setting controls the Height/Width ratio of the facets. A setting of 1 would mean the height of a facet is no greater than its width. The default setting is 0, ignored.

*      Surface Tolerance – This setting controls the greatest distance between the edge of a facet and the actual geometry. A setting of 0.0000 causes this option to be ignored.

*      Vertex Spacing – This option controls the length of the edge of a facet. The default setting is 0.0000, ignored.

 

ProE Wildfire

*      File > Save a Copy > Model

*      Change type to STL (*.stl)

*      Set Chord Height to 0. The field will be replaced by minimum acceptable value.

*      Set Angle Control to 1

*      OK

 

Rhino

*      File > Save As

*      Select File Type > STL

*      Enter a name for the STL file

*      Save

*      Select Binary STL Files

 

SolidDesigner (Version 8.x)

*      File > Save

*      Select File Type > STL

*      Select Data

*      OK

 

SolidEdge

*      File > Save As

*      Set Save As Type to STL

*      Options

*      Set Conversion Tolerance to Inches of Millimeters

*      Save

 

SolidWorks

*      File > Save As

*      Set Save As Type to STL

*      Options > Fine > OK

*      Save

 

Think3

*      File > Save As

*      Set Save As Type to STL

*      Save

 

Unigraphics

*      File > Export > Rapid Prototyping

*      Set Output type to Binary

*      Set Triangle Tolerance to 0.0025

*      Set Adjacency Tolerance to 0.12

*      Set Auto Normal Gen to On

*      Set Normal Display to Off

*      Set Triangle Display to On

 

CADKey

*      Choose Stereolithography from Export options

*      Enter the filename

*      Click OK

 

Inventor

*      Save Copy As

*      Select STL

*      Choose Options > Set to High

*      Enter File Name

*      Save

 

3D Studio Max

*      First check for errors

*      An STL object must define a complete and closed surface. Use STL-Check modifier to test your geometry before export your object to STL.

*      Select an object.

*      Click <Modify>

*      Click <More…>

*      Select “STL-Check” under Object-Space Modifiers

*      Select <Check>

*      If there are no errors, continue to export the STL file by:

*      <File> <Export>

*      Select “StereoLitho [*.STL]” in <Save as type>

*      Select location in <Save in>

*      Enter a name in <File name>

*      <Save>

*      <OK>

*      Export To STL dialog:

*      Object Name: Enter a name for the object you want to save in STL format.

*      Binary/ASCII: Choose whether the STL output file will be binary or ASCII (character) data. ASCII STL files are much larger than binary STL files.

*      Selected Only: Exports only objects that you selected in the 3D Studio scene.

 

ADT

*      Select AEC object . Go to 3D SOLID menu & select convert to 3D SOLID (ENTER)

*      After that you will have an option: Erase selected object [Yes/No] <Yes>: Enter Y

*      All the objects are converted into 3D Solid using the same procedure for each AEC objects

*      Select a single solid for STL output… (Must be ONE solid to export to STL)

*      Command entry: stlout

*      Select objects: Use an object selection method and press ENTER when you finish

*      Create a binary STL file? [Yes/No] <Yes>: Enter Y

 

Revit
Revit doesn’t allow direct export to STL files. We have to first save in dwg file and open in AutoCAD to create STL files.

*      Go to 3D view

*      Go to File menu , select Export CAD format

*      A dialog box opens

*      Select option

*      Scroll down the drop down menu (3D view only) & select 3D polymesh

*      Select “ AutoCAD 2004 DWG “ in <Save as type>

*      Next open the saved file AUTO CAD

*      Enter < Explode > on the command menu

*      Select the object and press <enter>

*      All the objects are converted into 3D solid

*      Select a single solid for STL output… (Must be ONE solid to export to STL)

*      Enter < stlout> or <export > on the command menu

*      Select objects: Use an object selection method and press < ENTER > when you finish

*      Create a binary STL file? [Yes/No] <Yes>: Enter y

Is Every STL File 3D Printable?

Unfortunately, not all 3D designs are printable. Only those specifically tailored for 3D printing, with adequate wall thickness and geometry, can be printed. The STL file merely contains the data and doesn’t guarantee printability. Ensure your file meets these criteria to avoid wasted time, frustration, and filament.

How can a 3D file be optimized for 3D printing

The STL file format approximates CAD models with triangles, as shown in the picture. Smaller triangles result in smoother models, but also increase file size. Finding the right balance between print quality and file size is crucial. Most CAD software offers settings to adjust triangle size for optimal results.

The 3D printer replicates the object’s coarseness from the STL file. Smaller triangles improve quality but increase file size, making sharing difficult. Balancing triangle size optimizes quality and file size. CAD software settings control this balance.

The perfect spherical surface on the left is approximated by tessellations. The figure on the right uses big triangles, resulting in a coarse model. The figure on the center uses smaller triangles and achieves a smoother approximation. Image source: Materialize

Chord Height and tolerances

CAD software typically offers a parameter called chord height or tolerance. This value determines the maximum distance between the original design surface and the STL mesh. Optimal tolerance ensures smooth, non-pixelated prints. Smaller chord heights result in more accurate surface representation by the facets.

 

Tolerance settings between 0.01 to 0.001 millimeters generally produce high-quality prints. Further reduction is unnecessary, as 3D printers cannot achieve finer detail.

The chord height is the height between the STL mesh and the actual surface. Image source:www.3dhubs.com

Angular deviation or angular tolerance

Angular tolerance limits the angle between the normals of adjacent triangles. The default angle is usually set at 15 degrees. Decreasing the tolerance (which can range to 0 to 1) improves print resolution.

The recommended setting for this parameter is 0.

Angular tolerance is the angle between the normals of adjacent triangles. Image source: www.3dhubs.com

Binary or ASCII?

When exporting an STL file, binary format is preferred for 3D printing due to smaller file sizes. However, for manual inspection or debugging, ASCII format is easier to read. It’s crucial to recognize that effective design for manufacturing goes beyond software. Understanding the unique advantages and limitations of manufacturing processes and materials is essential. Tailoring designs to accommodate these nuances, including post-processing, tolerances, and resolution, ensures optimal results.

Curious about 3D Models and design, dive into this innovative world with us! There’s always more to discover. Reach out to us for an insightful conversation about 3D printing materials and their applications in education and industry.

 

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