What are STL and OBJ files, and how to optimise them for 3D printing

What are STL files?

STL, which stands for Standard Triangulation Language, indicates a file extension (or file format) that simplifies the surfaces of a solid model using triangles.

For example, suppose you want to approximate the dimensions of a box. In that case, the result may be twelve triangles, but – if this figure has more complex parameters – the number of geometric figures in the document will increase.

STL files have become the most widely used document for transmitting standard data in 3D printing and rapid prototyping.

This format has numerous advantages for users; first and foremost, it is straightforward, as this extension is straightforward to generate and process.

A downside, however, is the approximate geometry and structure of the data; in particular, the latter—even if it is simple—can have excessive repetition of the same vertex.

STL files are produced through all CAD systems, which means software that supports 3D design.

The user who wishes to save such a design must select the file and save the document with the STL extension.

It is possible to use the best CAD systems on the market, in which the STL document is exported as a binary file: this procedure saves time and project size.

If the user chooses to change the settings for chord tolerance and angular control, the resolution of the STL document will also be altered. Furthermore – as mentioned above – the larger the size of the STL file, the greater the number of triangles on the model’s surface.

The STL file’s encoding can either be in ASCII format, which is easier for the user to interpret but heavier, or in binary format, which is far lighter but more complicated.

For example, if the file is exported in ASCII, it may occupy 11 MB, while if it is exported in binary, its size will be 3 MB.

Anyone wanting geometry with few curves and, therefore, simplicity will have to create a file that does not exceed a couple of hundred Kbytes; on the other hand, for more complex files, the user will be faced with files of 1-5 MB, which will allow for high-quality parts.

Files with 5 MB are not indispensable for certain types of geometry and are unnecessarily time-consuming and costly.

What is the minimum thickness for most materials and processes? It is usually 0.020; if you go below this parameter, the model features may not be reproduced optimally.

Finally, high-quality SLA follows features down to 0.010, while SLS flex material needs a thickness of 0.040 to produce the desired features.

Consequently, the advice is to make the necessary changes to the document before proceeding with three-dimensional printing.

How to optimise STL files for 3D printing?

To optimise STL files, you can use several software packages available online.

Below are the main programs with which you can create and edit the most suitable STL format file for 3D printing.

1) AutoCAD

AutoCAD is one of the most widely used technical drawing software for optimising STL files. The design must consist of a three-dimensional solid figure for the output to be a document suitable for this format.

The user must check that the model is in positive space and that Facetres is set to 10.

After typing the STLOUT in the command prompt, you can select the objects; at this point, you can choose the name of the STL file.

2) I-DEAS

Using the I-DEAS software, the file can be optimised by being exported as a rapid prototype file.

At this point, the user must select the part they wish to prototype, select the prototype device with the entry SLA500.dat and click OK, setting the absolute deviation to 0.000395 and the binary.

3) SolidDesigner

Users who prefer the SolidDesigner software must select the external file option and save it in STL format. Again, he must select the binary mode and choose the part of interest for saving.

The user must select 0.001 mm for the maximum deviation distance to optimise the file.

4) Solid Edge

Solid Edge allows the user to optimise the document with two options:

• the conversion tolerance on 0.001 inch or 0.0254 mm;
• the surface plane angle is 45.00.

These are the ideal values for saving an STL file correctly.

5) Unigraphics

In the case of Unigraphics, the file will be exported in STL format with the rapid prototyping option.

Further settings for optimal 3D printing include:

• output on binary;
• adjacency tolerance on 0.12;
• triangle tolerance to 0.0025;
• standard display on off;
• triangle display on on;
• auto regular gen on on.

6) CadKey/KeyCreator

With CadKey/KeyCreator, it is possible to optimise the STL document by selecting stereolithography in the file export options. At this point, the user can save the file in STL format for 3D printing.

7) IronCAD

After selecting the part of interest using the right button, the file must be optimised by modifying the rendering aspect and smoothing the surface facet to 150.

Exporting the file in STL format and printing the optimised STL file will be possible.

8) ProE

ProE is a programme supported by the Microsoft Windows system and is highly appreciated for its function as a three-dimensional CAD modeller.

To save a copy of the file in STL format optimally in this software, change the chord height settings to 0 and the angle control to 1.

9) SolidWorks

On the SolidWorks software, the user saves the file in .STL format by setting in the options:

• output – binary;
• units – inches.

In the resolution, however, the user must set the parameters to:

• deviation tolerance – minimum;
• angular tolerance – 5 degrees.

At this point, it will be possible to save the file in optimised STL format.

10) Mechanical Desktop

The user must use the AMSTLOUT command for the mechanical desktop to export the STL file.

To produce an optimised file, the following settings must be set in the command line:

• Angular tolerance is a parameter that limits the angle between the normals of adjacent triangles: the standard setting is 15 degrees, but – if the angle is reduced – the resolution of the STL file ;
• surface tolerance, a number that designates the most significant distance between the edge of a facet and the actual geometry: a setting of 0.0000 allows this option to be ignored
• proportions, an aspect that determines the ratio between the height and width of the facets: a value of 1 shows that the height of a facet does not exceed its width, while the standard parameter is 0;
• Vertex spacing is an option that defines the length of the edge of a facet; if you wish to ignore this parameter, you must set it to 0.0000.

What are OBJ files?

The OBJ format is often called Wavefront 3D Object File, as the Wavefront Technologies company of the same name developed it.

OBJ is a file extension suitable for printing a 3D object with three-dimensional coordinates, such as polygonal lines and points.

Various image editing programs can export the three-dimensional image format contained in this file format.

OBJ files have many features: first, users can represent irregularly shaped and complex objects using triangles. What is the purpose of this? It certainly simplifies the manipulation and visualisation of the structure because it is possible to adjust each component in isolation from the other parts of the object.

In addition, OBJ files can determine the geometry of three-dimensional objects and surface properties, including shading and texture mapping.

For these reasons, OBJ files are versatile and excellent for creating realistic renderings, such as in highly complex XNUMXD scenes.

OBJ format files also present free-form surface patch information, aspects that designers can correct to generate smooth surfaces in which distortions or seams are absent; this allows realistic materials such as leather or fabric to be created.

How do you optimise OBJ files for 3D printing?

Numerous applications on the net allow you to compress and optimise OBJ files.

Online compression programs allow you – as with software for STL files – to create a lighter format for files to be printed in three dimensions.

In addition, some applications allow the file to be compressed in ASCII or binary format and also support extra compression, an essential tool for making the document even lighter for three-dimensional printing.

Online sites – available for Windows, Linux and iOS – allow the user to drag the file directly onto the application page and let the program itself set the editing parameters for the OBJ file.

This way, optimisation will be carried out automatically, even by those less experienced in the field.

What are the differences between STL and OBJ files?

Usually, STL and OBJ file formats are associated with 3D design, as designers of three-dimensional models most often produce documents saved in these extensions.

But what are the differences between STL and OBJ files? First, OBJ is an open format chosen by other applications for three-dimensional graphics to exchange data with different design programmes.

This extension uses a data format only interested in three-dimensional geometry: the UV coordinate for textures, the faces and normals that characterise the model, and the position of each vertex.

Another feature of OBJ files is that the coordinates in this file do not have units of measurement; they only contain information about the scale of the model. The latter is contained in a line of code with a comment.

On the other hand, the Standard Triangulation Language format is a file extension created for CAD stereolithography software and is, for this reason, favoured for rapid prototyping using CAD software.

A file saved in this format identifies a solid whose surface has been simplified into triangles and contains the X, Y, and Z coordinate data. These are repeated for each of the three vertices of the model triangles with a vector that describes the orientation of the surface normal.

Files in STL format can be viewed or corrected with open-source tools, such as those described above, first and foremost AutoCAD; furthermore, the STL extension is still one of the main preferred formats for 3D printing.

Finally, unlike the STL, the OBJ format can support high-resolution data. Furthermore, while the former can store many textures and colours in the same model, the latter only supports one colour per object.

Where can STL and OBJ files be printed?

Printing STL and OBJ files is difficult for non-experts, so they are always recommended to contact 3D printing professionals.

Although you may think buying a 3D printer to develop your prototypes is always the best choice, this can be a costly and non-functional expense in the long run.

If, for example, you need to develop numerous models in STL and OBJ format, a 3D print made by a team of professionals is the only option that guarantees precise and punctual compliance with all the required features.

Do you need professional 3D printing for your STL and OBJ files? Then Fama 3D is the right partner for you!

Indeed, the professionalism in realising our prints will quickly guarantee you an optimal result.

If you want more information, you can contact our experts at the number on our website or by email. We will provide a quote for your requirements and answer all your questions.