Files For 3D Printing
In order to 3d print, everything starts with a properly formatted 3d file.
Having a file is the starting point in the 3d printing process. Just like a normal office paper printer, a 3d printer needs to be sent a workable file in order to produce an object. The order of operations will look like this:
Q: Can I 3d print an object from an image?
A: No. Not unless you manually digitally sculpt the object represented in the image.
Q: What program do I have to use?
A: There is not specific program you need to use. You can export a 3d printable file from nearly any 3d modeling program.
What does a 3d model look like? This is an example of what a 3d model looks like:
3D Printing File Formats
It is important to note that each of the above 3d modeling programs will export to a 3d printable file. There isn’t a specific piece of software needed to produce a working .stl file. Nearly every 3d modeling program has a native file type, but will also export a .stl file and multiple other 3d file formats.
“Standard Triangle Language” or “Standard Tessellation Language” files are the most common file type for submitting a 3d model for 3d printing.
These file types are frequently used for both submitting files for 3d printing and for exporting a file type that is easily imported into other 3d modeling or 3d viewing software. OBJ files can have an associated MTL (material) file which can give the model a color texture. Some 3d printers are able to print these files in full color.
VRML files are 3d files with color and uv mapped textures baked into the file. Commonly used to color 3d printing, the file type is also used for animation and web based applications. These files are phonetically referred to as “vermals”, or as the initials, and also have the .wrl extension.
The X3D file format is the successor to the VRML file format and also is used for 3d models with color information.
3MF is an emerging filetype specifically for additive manufacturing applications. Because .STL files are prone to technical errors and weren’t specifically created for the purposed of additive manufacturing, there are some limitations. A group of 3D printing companies formed the 3MF Consortium in order to advocate for wider adoption of this file format.
Successful 3D Printing Files (Technical Specs)
The benefits of 3D printing can present some technical challenges. While 3d printing allows us to create highly custom, very complex, and very precise output, the input must be just as precise. Even though your 3d digital mesh might look fine when viewing it on a screen, there are a few criteria your file must meet to be a successful 3d printable file.
Zero Holes: model will be manifold, without any gaps between faces and edges
Zero Border Edges: a border edge is an edge on the side of a hole, or the edge side of a plane if another edge is it’s missing
Zero Invalid Orientations: In Netfabb, the direction of a face is shown in green if it points outward, red if it points inward. If you have red faces pointing out, that will be invalid orientation because it is inconsistent.
Positive Volume: All the green faces face out and the red face in, otherwise the printer will think that everything outside the model is material causing printer issues.
Closed Surfaces: A closed surface means that there are no holes or border edges.
Surface: All faces must be defined as in or out, with no stray edges or vertices.
While it is possible to manually fix errors in many cases, using file repair software like NetFabb has become a standard for ensuring repair of common model errors. Netfabb is available for $125/ month, but also has a free limited version as well.
It’s important to remember that depending on what 3d printer is being used, the hardware may not be able to physically capture a high digital resolution of a 3d model. Also, if a low resolution model is printed by a high resolution 3d printer,
Repairing 3D Files
Since manually correcting technical issues on files can be both difficult to fix and difficult to diagnose – there are several file repair options before sending your file to print. My recommendation is to use NetFabb, which has a free version you can use to make sure you files are 3d print-ready. If you use a service like Shapeways, the file uploader will automatically give you feedback on your file, including thin walls, and will allow you to fix some issues.
3D Model Resolution
The resolution of .stl files, or any mesh 3d file, can be measured by the number of polygons. Similar to a raster image, where resolution would be measured in DPI or pixel count, .stl files have their own resolution with polygon count. Instead pixels on a 2d image, 3d .stl files have surfaces covered by faceted triangles – typically the smaller and more populous these triangular facets are, the higher resolution and smoother surface quality the model will have. This is generally, but not universally true. It is possible that a high polygon model can be meshed in an inefficient way, just as a 2d image with higher pixel count may have lower spacial resolution.
For applications like gaming, having highly efficient models with the lowest polygon counts as possible is important. This may help games load faster with less lagging. Models with high polygon counts can be very large files that require significant processing power to open and edit.
Where to Download a 3D File
One way to obtain a 3d printable file, is to download one online. There are a number of online file repositories and libraries from which you can find objects ranging from figurines, accessories for gadgets, home goods, and spare parts.
My Mini Factory is 3D file library geared mainly towards offering files that have been tested on desktop 3d printers. Although the files are mainly figurines and toys from fictional fandom, it also has simple home goods and products.
Cults 3D is a well curated 3d model library offering downloads of 3d files both for sale and for free. One notable feature of Cults 3D is the “naughties” section, featuring – well – adult 3d models.
Sketchfab does a few things. Primarily, it is the “YouTube” of 3d printing, or as Sketchfab puts it, “a web service to publish, share and embed interactive 3D models on web pages, and display them in real-time without a plugin.“ This allows people link to embedded 3d models on facebook or on websites that can be viewed and spun around. Sketchfab also allows you to view 3d models in virtual reality and hosts a variety of real world 3d scanned objects.
Turbo Squid provides a stock of high quality 3d models available for purchase. The library of models is robust and geared towards professional use – from animation to architectural rendering. Not all files will be 3d printable, but it’s a great resource when a specific high quality file may be needed.
CG Trader is a high quality 3d file market place based in Lithuania. It is a 3d design market place primarily for computer graphics, virtual reality, and animation professionals – but many designs can be used for 3D printing.
Thingiverse is Makerbot’s file library for sharing and downloading 3d printable designs. It is very difficult to navigate and poorly designed, but has a good foundation of models uploaded by hobbyists.
Pinshape has an intuitive interface for searching for different categories of 3D models including figurines, toys, and home goods. However, many of the models cost money and many others are not printable. It is geared more for desktop printers. Pinshape was recently acquired by Form Labs.
Instructables, acquired by enterprise design software company Autodesk in 2011, is an online community of DIY enthusiasts sharing their projects. Although most of these projects are not 3d printing based, many are.
Remixing a File
Besides downloading a file, or creating your own, there is a third way of creating an object. You can download a file and then adapt it, or remix it. This might mean taking a product and improving it, customizing an object, or just being creative.
For example, once a 3d scan of Stephen Colbert was posted on thingiverse.com, many people made new 3d printable files like these: