What is a STEP file? Learn more about STEP files and STP

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What is a Step file?

A STEP file, which stands for “Standard for the Exchange of Product model data file”, is a standardized CAD file used to share designs between CAD softwares. The data in this file is in accordance with the ISO 10303 standard put together in 1994 by the ISO committee. The standard’s official name is “Industrial automation systems and integration – Product data representation and exchange.” The Step format (*.step, *.stp) contains all the information about a 3D design and saves it as a series of text documents. This article will make you learn step file utility, its advantages and disadvantages, and its differences from other neutral CAD formats.


What is a STEP file used for?

Today, with the different CAD systems available, interoperability between different CAD solutions has become more and more essential. The STEP file extension is therefore commonly used to share CAD designs between different CAD programs that are not able to read each other’s native files.

This feature makes the step/stp file an appropriate option for sharing 3D models between customers, other departments and even contractors. Moreover, because of its cross-platform nature, step files make editing and collaboration much easier. This is why many applications such as engineering, industrial, prosthetics and 3D printing rely on this format.


What is the main difference between source files and STEP files?

Source files are used when we design and create products in CAD software. These in-house designs are then shared with other CAD software using STEP files, not the original CAD file format. Home CAD files such as .CATProduct for Catia cannot be opened directly in Autodesk, for example. STEP files correct this problem.


What is the difference between a STP and a STEP file format?

The answer is that there is no difference between a *.step file and a *.stp file. Both are related, interchangeable and meet ISO standards. They are simply synonyms.


What is the difference between the step file AP203 and the step file AP214?

The AP203 file contains information about the geometry and configuration of a solid model. It does not contain information about colors and layers. In contrast, the AP214 file is an extension of the AP203 file, as it contains information about the geometry and configuration of a solid model, as well as colors, layers and tolerances.


Is a STP/STEP file a CAD file?

The step file is a standard CAD file. The file can be opened in any CAD software.


What are the most popular step file viewers?

The majority of CAD programs are capable of opening and exporting the Step file format extension. The most common programs for producing CAD drawings, and therefore Step/stp files, are SolidWorks, AutoCAD, Autodesk Inventor, Catia, PTC creo and Onshape. You may not be able to open a Step file if the CAD software is not up to date with the latest version. That is why it is important to check for updates regularly. Also, you will not be able to open a step file if it is corrupted or infected by a virus. It is possible to check if the step file is corrupted using Google’s virustotal page.


Can I open step files on Mac?

Yes, it is possible to open the step files on Mac. 3D software that works on Mac such as Autodesk Fusion 360 and IMSI TurboCAD can open the file easily.


How to export a step/stp file from a CAD software?

It is possible to export a 3D design as a step or stp file format directly into the export or save as tab of any popular CAD software. Here are the procedures to export a step file with SolidWorks, Inventor and Onshape.

How to export a step file with SolidWorks

  1. Click File > Save As
  2. Select the STEP file type for Save as type
  3. Click OK

How to export a step file with Autodesk Inventor

  1. Click File > Export
  2. Select STEP Files for Save as type
  3. Click OK

How to export a step file with Onshape

  1. Right click the tab you would like to export
  2. Click on Export
  3. Select STEP file for Format
  4. Click OK


How do step files encode data?

Step files (.step) encode 3D data in the EXPRESS language to store the 3D data of a model. For this reason, interpreting a step or stp file is easy as there is only one entity instance per line of code. Moreover, because the step file conforms to the ISO-10303-21 (Clear Text Encoding of the Exchange Structure), each step file is divided into the same sections: header, anchor, reference, data and signature. The header contains the implementation level, the file name and schema, the file population, the section context. The data section contains instance names of entities, attributes, data type mappings and more. In addition, the 3D geometric data is encoded as a boundary representation (B-rep), which means that the model is represented as a collection of closed surfaces. The complete documentation of the STEP standard can be found in the U.S. American National Standards Institute eStore.


Who is responsible for the development of the STEP standard?

The ISO technical committee is responsible for the development and management of the step file, which it reviews annually.


How to open step files?

It is possible to open a CAD file in all major computer-aided design softwares. The easiest way to open a step file is to first locate the document on your computer. Then simply right click on the file and select open. From there you should be able to see the CAD software program already installed on your own computer. By clicking on the program, you should see the step file automatically open in it. Alternatively, it is possible to open step files directly online for free.


Can you print a STEP file?

Due to the nature of the Step file extension, it is not possible to use it for 3D printing.  A Step file describes shapes in complex mathematical formulas, making it a very complex and heavy file that 3D printing softwares cannot handle properly. It is therefore recommended to convert and use an STL file instead for 3D printing because shapes are organized as a list of 3D triangles and meshes ( and are therefore readable by 3D printing softwares). It is also possible to convert a step file into an OBJ (Mesh) for the 3D printer to print the model.


What are the advantages and disadvantages of using step files?

The main advantage of using a step file format is that it is the most common and accepted neutral CAD file, and so no matter the industry. Therefore, as mentioned above, it makes sharing CAD files on the cloud much more convenient.

However, there are some disadvantages with using step files. For instance, because of its compression, there is some degradation of data quality. It is also important to mention that step files do not include information about materials and textures, only the shape and form of the 3D data. Also, step files do not include lightning and camera data. To include such information, a FBX or a USDZ file has to be used instead. Finally, as mentioned above, it is not possible to directly print a step file. Moreover, a STEP file contains a lot of information, which demands a lot of time and effort to create. It is also not possible to directly render a step file. The file has to be processed first to create a series of triangles.


What are alternatives to step files?

There exist other neutral computer-aided design file formats that have similar functions as the step file. Below is a list of the most common ones.


What is the difference between the STL and STP file?

The .stl file, which stands for “stereolithography file”, contains 3D data about the geometry and shapes of the surface. Like the step file, it can be shared and exported by different CAD software. However, the .stl file does not store the 3D data in the same manner as the step file. First, the model’s geometric information is stored as triangles woven into a mesh, making the data readable for 3D printing softwares. Second, this file does not contain information about the colors, textures and attributes of a model. Therefore, this less detailed file is also used for storage efficiency reasons. 


What is the difference between the OBJ and STEP file?

The OBJ file is similar to the step file because it can also be interpreted on different CAD platforms. One key difference, however, is that OBJ files can contain texture and color data (unlike step files). For this reason, OBJ files are commonly used with multi-color 3D printers. However, the OBJ file is much less common than the step file, which means that fewer 3D design softwares support it.


What is the difference between the 3MF and STEP file?

The 3MF file is a new open-source file that is able to contain information about the colors and textures of a 3D model, unlike step files. This XML-based file works in a similar way to a ZIP archive because it actually compresses the 3D model data. With a 3MF file, the body of the 3D model is captured as a triangular mesh, reducing the amount of detail. Nevertheless, similar to the obj file, the 3mf file is not commonly used, and many computer aided design programs do not support it.


What is the difference between the IGES and STEP file?

IGES (.igs, .iges, .ige) is a neutral CAD format, just like the step file. However, it is mainly used for surface models, while the step file is used for solid models. This means that the IGES file may contain gaps between surfaces. This is why the STEP file is in fact the successor of the IGES file. It has solved many problems encountered with the IGES file.  The IGES file was last updated in 1996, whereas the STEP file is continuously updated to this day. The general consensus is to use the STEP file, rather than the IGES file, because it is more up-to-date with current technology, less likely to contain errors, and widely recognized.


How to convert step files?

It is possible to convert step files into most native CAD software formats (.dwgj, .3ds, .dxf, etc.). Converting a step file can be done directly in a CAD program ( that accepts step files).  It is also possible to convert a step file into another neutral 3D file format (such as .stl .obj and .3mf). This conversion can be done directly in a CAD program ( that accepts step files) or with an online step converter for free. 


Need help with your step file?

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