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Jeff Rowe
Jeff Rowe
Jeffrey Rowe has more than 40 years of experience in all aspects of industrial design, mechanical engineering, and manufacturing. On the publishing side, he has written well over 1,000 articles for CAD, CAM, CAE, and other technical publications, as well as consulting in many capacities in the … More »

Is A Universal File Format Possible For 3D Printing? Part 3: 3MF

 
August 24th, 2017 by Jeff Rowe

Although the future of 3D printing continues to look bright, what is still needed is a new file format for 3D print data. Being very mindful of that fact, Autodesk, HP, Siemens, Stratasys, 3D Systems, and some others have come together to form the 3MF Consortium that espouses to get behind a truly ubiquitous file format for 3D printing. It’s really an industry partnership working toward the goal of finding a better, universally applicable 3D printing file format known as the 3D Manufacturing Format (3MF)—a file format originally developed by Microsoft, also a member of the Consortium.

The consortium admits that there is a problem that the 3D manufacturing must resolve –  the current file formats used for 3D printing are in serious need of an upgrade. I totally agree.

Typically, data is passed from computer to 3D printer in STL (stereolithography) or OBJ (object) files, common 3D printing file formats. The 3MF Consortium, which now includes the research wing of General Electric, say STL and OBJ are outdated and clunky file formats with interoperability issues when used by some of the newer 3D printers, as well as contribute to 3D printing failures.

3MF Consortium Introduction

Thus, one of the driving forces behind 3MF, an XML-based open format, this new file type could contain information on the texture of a 3D print, the color of the print, and other complex characteristics. If that sounds familiar, that’s because it is—the Additive Manufacturing File Format (AMF), which has been around since 2011, solves many of the issues STL files have, and 3MF and AMF are in many respects pretty similar file formats, but let’s take a closer look.

Even at this early stage, the Consortium wants to ensure that 3MF is compatible across printers, including ones coming to market – for example, the HP Multi Jet Fusion 3D printer. It could potentially support older STL files, so the transition from an old to a new file isn’t quite as rough. However, some older printers might still just have to use STL. Theoretically, 3MF could also support machines like CNC mills and laser cutters, tools of subtractive manufacturing that are complementary, not incompatible, with additive manufacturing.

It makes sense the format was originally developed by Microsoft—think about the millions of 2D printers that print documents and then apply that same thought process to 3D printing.

 That, ultimately, seems to be the biggest potential for a new industry-standard file format. Addressing the data gap now in 3D printing is a smart move. Mainstream adoption of 3D printing, especially in the industrial sector, and especially for something beyond mere prototyping, will be held up as problems with the speed and reliability of 3D printers continue to be worked out.

What the 3MF Consortium is trying to accomplish represents something bigger than a shift in file formats; it’s an introduction to making 3D printing as a critical component in future manufacturing beyond prototyping.

A Little 3MF History

Parallel with application development for Windows 8.1 and subsequent work with the upcoming Windows 10 OS, the 3MF file was developed by Microsoft with the goal of creating a seamless, high quality, 3D printing experience for consumers or manufacturers. After concluding that current formats would be incompatible with their print pipeline, the 3MF format was developed as a standardized framework for Microsoft hardware and software ecosystems, passing data from apps to their devices while retaining detailed model information.

3MF is also XML-based and features geometry representation similar to AMF, but in a more compact and size-friendly format. The file defines all standard, optional, and mandatory parts, with complete model information contained in a single archive. It centers on the concept of a “3D payload”, a collection of interdependent parts and relationships that reside in one standard package. The payload consists of a 3D model(s), core document properties, digital signatures, 3D print settings known as “PrintTicket”, thumbnail images of all models, and 3D texture information.

The goal is for 3D printing in Windows to be the same as any document – select a printer from list, choose options, and print. The application converts the model to .3MF and encapsulates it in an OpenXPS package. It’s then extracted by the print driver, converted into a readable format, and sent to the 3D printer. The .3MF file not only solves Microsoft’s own print pipeline, but also provides the following advantages for everyone across the board.

While still in its infancy, 3MF is gradually becoming accepted by the 3D printing industry. However, there is concern about how 3MF handles hardware resource issues when working with larger meshes. Doubts have also arisen on 3MF. Would it become proprietary with the larger Consortium companies monopolizing and snuffing out competition or would it be released as open source? Would this open the door to DRM issues, resulting in 3MF derivatives that would be subject to lawsuits? Was it simply a matter of benevolently advancing the concept of “plug & play” for 3D printing?

Despite the skepticism, Microsoft chose to donate the code to Github and help form a consortium of companies that would help manage the process. You can also get the 3D Printing SDK and 3MF format specifications by contacting ask3dprint@microsoft.com.

3MF: The Lingua Franca of 3D Printing?

So, what are the primary features and benefits of 3MF? Some of them include:

  • While both formats are gradually creating their own path, plenty of development still lies ahead. Some would argue that since the development of the AMF file, there’s no need for .3MF. Technical differences aside, both accomplish what they were set out to do. The real difference is the backing and publicity behind .3MF as well as buzz about Microsoft’s modus operandi. Customer demand and acceptance for is also a factor that remains to be seen. But from a design and engineering standpoint, a unified file format is a welcome relief in a sea of crisscrossing compatibilities.
  • As a zipped XML package, 3MF is generally smaller (often significantly) than other comparable 3D formats. Transforms and object references are supported, with multiple objects contained within the single archive. Single objects can be referenced or moved without changing the mesh, and multiple identical objects can be placed referencing the same mesh.
  • The 3MF consortium decided the benefits of human readability for ease of development outweighed the performance gain from going to a binary format. By using ASCII numbers in XML, the format is easy to extend, and by leveraging the benefits of variable precision decimals and compression, the efficiency gains of binary are relatively small.
  • 3MF provides a clear definition of manifoldness and open source code is available for rapid validation. The strictly positive fill rule specifies the exact interpretation of any model with self-intersections or overlaps. Likewise, color and property interactions are clearly specified so that the end result is the same for any conforming implementation of 3MF.
  • The 3MF consortium maintains a cross-platform open source library for reading, writing and validating 3MF files, which also contains sample objects and test cases. Microsoft has also made APIs available in Windows 10 for reading, writing, validating, repairing and simplifying 3MF files, and 3MF is also used as the format to submit 3D print jobs to the print pipeline.
  • 3MF is focused on additive manufacturing; (theoretically) it can be used with CNC or laser cutters, but the consortium is not putting effort into supporting the nuances of those processes as they seem to be reasonably well-served by existing formats (CNC by IGES and STEP, laser by DXF and PDF).
  • Unlike 3MF, STL does not contain color or other material/property information, and has no extensibility mechanism to add it. STL does not save mesh topology, leading to larger file size, loss of manifoldness due to rounding errors, resulting in ambiguity. 3MF solves all of these problems.
  • AMF inspired the foundations of 3MF, but AMF is widely held to have gone into a standards body too early, having some features not clearly defined and other features missing. The 3MF consortium was formed to bring the industry leaders together to agree on a format that would serve the industry’s needs.
  • 3MF is not intended to compete in the CAD space, as it does not and will not support higher-order representations such as NURBS. However, it will be a useful export format for these systems by creating unambiguous geometry for manufacturing that can be read more universally, as 3MF is designed to be much simpler to implement than the full CAD formats.
  • MF is geometry focused and has no intention of building in the kind of complexity necessary to represent manufacturing process and instructions,such as 3D PDF or JT. The simplicity of 3MF is ensured by a focus on defining what is manufactured, not how.

While STL reigns, the Additive Manufacturing Format (AMF) and the 3D Manufacturing Format (3MF) file formats are vying for the ultimate dominant position. At this point, trying to declare or even predict the ultimate winner is futile. Ultimately, market forces, acceptance, and adoption will determine the winner. There’s no doubt that STL will be superseded, but by which file format? AMF, 3MF, or something else? That all remains to be seen, and may the best format win!

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