If you are new to 3D printing, it’s important to know the common 3D print file formats you will be working with. This article provides and overview of the most common file formats for 3D print models.
Almost everyone knows the types of files used to save images. We have PNG, JPG, BMP, TIFF and others. But what about the types of files for saving volumetric models?
With volumetric models, it would seem that we are adding a third dimension to the image. However, the file size is often smaller than even the image of the same model. How so?
In this article, you will learn about 3D print files, how to convert them, the features of each type of file, as well as the file format for 3D printing.
Let’s get started.
How 3D Models Are Stored
Unlike images, the voxel (voxel – volumetric pixel) storage method has not taken root in the world of 3D models. Only a few craftsmen use it when creating games or in scientific research. This is due to the history of the appearance of volumetric graphics.
Unlike the appearance of photographs, volumetric graphics were originally created on a computer, and were used for animation. Voxels are much more difficult to animate. Therefore, animators started using polygonal storage method instead of voxels.
With polygonal storage method, the entire model consists of many polygons – straight-sided shapes (3 or more sides), defined by three-dimensional points (vertices) and straight lines that connect them (edges).
Think of it like making sculptures out of paper. By connecting many flat pieces, you can get something voluminous and even smooth.
Although this method of saving as polygons cannot be called raster, the two methods have much in common. These include the inability to increase the quality, the direct relationship between the quality and weight of the file, and ease of editing. This is the most practical format for saving and using models in 3D printing. However, it is not the only one.
Next, we’ll take a look at the most popular formats for storing 3D models.
Universal Formats for 3D Print File Models
There are as many different methods for storing 3D models as there are for storing photos and videos. However, there are also universal formats that, although with some restrictions, can be opened in almost any program.
These formats include
STL
Contrary to misconceptions, STL was not originally intended for artistic modeling. The file format was developed by the Albert Consulting Group and was intended for an early method of 3D printing – stereolithography. The file name STL comes from the 3D printing technology “STereoLithography”. After some time, the company openly published the format and since then, it has gained immense popularity.
The STL format is widely used due to its simplicity of structure: polygons (facets) and their normals. The former are needed to define the surface, and the latter to indicate where the outer side of the polygon is. Therefore, this format can be considered the most versatile.
Since the model is specified using many triangles, it is impossible to accurately define curved surfaces, because this will require an infinite number of polygons, and therefore an infinite data storage. But when used in 3D printing, this negative is not an issue since the accuracy specified using the polygons higher than the printing accuracy.
OBJ
This format is very similar to STL but differs in the ability to apply textures, specify the material and store other information. Therefore, OBJ can be called an extended version of the STL. The format is mainly intended for artistic modeling programs such as Blender, Autodesk Maya, 3Ds Max, Meshlab and others.
STEP
Now we turn to the engineering side of 3D-modeling. STEP is the only 3D print file format that can be opened in any program for engineering simulation and freely be edited in the built-in tools. STEP was originally developed as a world standard format for storing products on a computer. It was intended for a full cycle of part development. That is why all professional engineering modeling and physics simulation programs can work with this format.
The hallmark of STEP is its high precision. The model is created with tools that allow you to define curves using formulas. Therefore, the accuracy in this format is infinite. No matter how much you increase it, the curved line will remain a curve, and not become many straight lines.
CAD (Computer Aided Design) is used to create models in STEP format. Thanks to the ISO standard, all CAD programs can work in this format.
However, not all data is freely transferred from one program to another via STEP. For us involved in 3D printing, the most important thing is the transfer of model geometry, and simulations. Material and other data that the STEP format does not store are of secondary importance.
Proprietary 3D Print File Formats
This category includes file formats that can be opened in only one program, i.e., the program on which the files were created. The files are intended only for storing projects, and are often impossible to use in 3D printing.
The exception to this is the Ultimaker Cura slicer. The functionality of the slicer can be extended through plugins to enable you to open files of programs such as Inventor, Siemens NX, Solidworks and others directly from the slicer.
Engineering Software
As mentioned earlier, these programs are called CAD systems. Since this software is often intended for production, they also have a common file format (STEP). Some programs, often produced by one company, allow you to work in a common ecosystem. For example, format compatibility can be found in many Autodesk engineering programs: Fusion 360 can open a file created in Inventor.
However, with this method of opening, some of the information about the product will still be lost,e.g., information about the physical simulations performed. Therefore, if a part is not fully developed, it should not be moved between different programs.
Art Software
This category includes programs created for visualization, i.e, animation, special effects, creating figures and models for video games. Unlike is the case with engineering programs, art modeling software are rarely compatible. Each program has its own format, and the general STL format limits the functionality of each program to the simplest tools.
Despite the shortcoming, the generated STL is still enough to create models that will later be printed on a 3D printer, since only the geometry of the model is important.
Gcode Format for 3D Printing
Gcode is more than just a file format. It is a separate programming language. However, instead of executing commands by a computer, commands in this language are executed by a 3D printer. Initially, this language was developed for complex CNC machines, and a 3D printer is one of the simplest representatives of this type of device.
Unlike the other 3D model file formats we’ve covered above, gcode can be easily edited manually. This means you can write commands for the printer directly, bypassing the computer. This being the case, you can create macros that make it easier to work with a 3D printer.
Converting 3D Model File Formats
If you need to move a model between programs for 3D modeling, then it is worth determining which group the program falls in and where you want to move the model. If you are transferring it from one CAD program to another, then it is best to use the STEP format so as not to limit the number of tools for further modeling. In all other cases, the only option would be the STL format, which some CAD systems can recognize and into which art programs can save the model.
Keep in mind that when transferring a model from an art program to a CAD system, each polygon is transferred as a separate surface. Therefore, working with STL files in engineering programs can cause difficulties both in processing and in simple viewing of the model. The difficulties arise due to the principles of CAD:
Tip: If the quality of the model is not so important when transferring a model from an artistic modeling program to a CAD system, then it is better to reduce the number of polygons as much as possible. This reduces the load on the computer and increases the performance when processing the model in CAD.
