3MF Expands Capability of Universal 3D Printing File Format
Michael Molitch-Hou posted on August 02, 2016 | 4178 views

When the 3MF file format was first released last year, the numerous 3D printing companies behind it had promised that that first iteration was only the beginning for 3MF. Together, through the Microsoft-founded 3MF Consortium, companies like GE, Autodesk, 3D Systems and more began work on expanding the 3MF format so that it might streamline the 3D printing process and provide a more efficient and manageable workflow. 

Today, the 3MF Consortium has announced the most recent fruits of its labor, two new extensions meant to improve productivity for high-volume additive manufacturing (AM): the 3MF Production Extension and Slice Extension. To learn more about these developments, ENGINEERING.com spoke with Adrian Lannin, executive director of the 3MF Consortium.

How Does 3MF Work?

Before understanding how the Production and Slice Extensions work, it’s necessary to understand how the 3MF file format itself is organized. Lannin was able to shed some light on what a 3MF file actually looks like and how it operates.

The XML structure of a 3D model for 3MF. (Image courtesy of the 3MF Consortium.)

The XML structure of a 3D model for 3MF. (Image courtesy of the 3MF Consortium.)

“3MF uses open packaging conventions, and Zip compression,” Lannin explained. This means that the 3MF file condenses multiple items into a single file in such a way that different file types can be called on to produce the ultimate 3D-printed object. 

Unlike an STL file, which only describes the geometry of an object through a series of surface triangles (known as “facets”), a 3MF file is able to store a variety of interdependent files that represent other qualities, such as color or texture. If you were to change the “.3mf” extension on your 3D model to “.zip,” you’d actually be able to see the contents just as you would with a standard Zip file.

“The file is an open package convention for where the 3D model information is going to reside: what are the top-level elements going to be called, where do we put meshes, and things like that. Essentially, it’s just a big bundle of stuff and the specification describes exactly how that stuff is structured. So, when you write a file, you know what order to write the stuff in. And when you read it back again, you know what order to expect that information in,” Lannin elaborated.

Through the use of what Microsoft calls “Open Packaging Conventions,” the file organizes and reads the multitude of files within it. At the very least, a 3MF file must contain the geometry of a 3D printable model and, at the most, it can contain information necessary for a growing variety of 3D printing processes. This includes production or slicing information, which is now possible with the new extensions.

The 3MF Production Extension

As 3MF is meant to become a universal file format for 3D printing, the 3MF Consortium is working to make it useful to all stakeholders, including those leveraging AM for serial production. The 3MF Production Extension is designed to allow high-volume users to manage print jobs with multiple parts in a more efficient manner.

If all of the models for a single multipart print job were to be stored in a single XML file, Lannin said, a printer might have to parse the file multiple times. The Production Extension, however, allows a consumer (such as a printer) to access a given model within the set, without having to parse the whole file. This also makes it possible to assemble multiple separate jobs into a single production job very quickly, because the incoming files can be assembled without rewriting them. Ultimately, this means that the printer can process large multipart print jobs much more efficiently.  

“Imagine if you’re printing something that’s composed of a bunch of different pieces, like a disassembled Rubik’s Cube or a case with some pieces inside of it,” Lannin explained. “From a management point of view, it’s easier to manage as a single unit because you know you’re going to assemble it into one thing at the end of the day, but there may be multiple parts. Some of the parts might be very large, so if you’re trying to manage a single file that’s got lots of parts in it and some of the parts are really large, you end up managing a very large file.”

The user is still able to find all of the separate models within the 3MF package, but the overhead of parsing very large files is eliminated. 

The 3MF Slice Extension

The process of slicing a 3D model is familiar to all 3D printer users, both at the hobbyist and industrial level. As an additive process, 3D printing requires a model to be broken up into individual layers. As all of those users know, there is no standard method for slicing. One platform may translate slices into PNG, while another might use SVG, which is just the beginning of the variation that has occurred among 3D printer manufacturers and software developers. With the Slice Extension, the 3MF Consortium has chosen to define contours that are directly translatable from 3MF meshes, thus preserving the integrity of the data.  

The 3MF Consortium has whipped up the 3MF Slice Extension as a means of defining slices with a single standardized format. Lannin elaborated, “The Slice Extensions is exactly the kind of thing that the consortium was set up to solve. There are a number of different ways to solve this problem, but there’s no industry consensus on how to solve this problem.”

He added, “Any time you need to set up a 3D printing system, you have to decide to what approach you’re going to take for handling how the slice is sent to the printer. If you pick a particular component that works in a particular way, then that might limit your choice of using something that works with it. The consortium felt that there was good value in just getting general agreement in picking a way for doing slice formats that everyone agreed upon and drive that as general acceptance across the industry. Then, we can all move on and work on our apps or services that are more interesting.” 

It should be noted that the Slice Extension does not negatively affect the way a file is used by a 3D printer, in that, if a printer cannot use some of the data contained within the 3MF package, it will just ignore that data. 

Meeting the Needs of the Consortium

While a standard for slicing may be necessary for just about every 3D printer user, the Production Extension seems to particularly enable those that perform batch manufacturing. Within the consortium, this includes a number of the members, such as Shapeways, Materialise, GE, FIT, Stratasys and 3D Systems. 

Founding members of the 3MF Consortium. (Image courtesy of the 3MF Consortium.)
Founding members of the 3MF Consortium. (Image courtesy of the 3MF Consortium.)

As the consortium continues to work on the various discrepancies within the larger 3D printing industry, however, it’s becoming increasingly clear that these members aim to fit just about every consortium member’s needs within the 3MF package. According to Lannin, this means the best solutions possible.

“One of the great things about the consortium is that we’ve got a number of experts from all across the industry, so the solutions that we produce are the best practices from a whole bunch of experiences that people have had in trying to solve this problem before. I feel really good about the solutions,” Lannin said. 

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