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Sana Kazilbash

Innovation

A Look Into 3MF and Its Volumetric Design Extension

3MF Consortium continues its mission to create a universal specification for 3D printing

Published: Thursday, February 10, 2022 - 13:02

The 3MF Consortium recently announced its latest volumetric design extension for encoding geometrical shapes and spatially diverse properties through a volume-based description. The organization, which seeks to advance a universal specification for 3D printing, is currently calling for public feedback before the new extension reaches 1.0. I spoke with Luis Baldez, executive director of 3MF, to learn more.

Baldez has a background in electronics and software, with the bulk of his career spent at Hewlett-Packard. After being introduced to the world of 3D printing in 2008 and observing the growth of HP’s 3D printing business unit, Baldez saw the need to implement better design tools and file formats for capturing what engineers were trying to design and send to 3D printers.

Luis Baldez 3MF consortium executive director
Luis Baldez, 3MF Consortium’s executive director (Image courtesy of Vicens Gimenez/HP).

“I reached out to some people I knew in the industry from Microsoft, Autodesk, and Siemens,” says Baldez. “We had similar insights and agreed to create a consortium, which was announced in 2015.”

Today, the 3MF Consortium is composed of 20 leading additive manufacturing (AM) hardware and software companies—all of which are collaborating on a geometry data exchange format that would serve the needs of the AM industry. The consortium manages the 3MF specifications that allow design applications to send 3D models to a mix of other applications and printers.

The need for 3MF

Baldez believes that 3MF, an XML-based data format designed specifically for additive manufacturing, is essential for the future of 3D printing. “Printers can do so many new things today, but the software and data format are lagging behind,” he says. “They’re actually limiting what you can do. The whole digital workflow needs to improve to match the capabilities of the hardware.”

3D printing has evolved from very basic 3D print formats to 3MF for communicating intricate information about color, materials, lattices, and more. One of the original file formats is STL, which is still relatively popular despite having been created during the 1980s. Along with not supporting various properties, STL has no extensibility mechanism and doesn’t save mesh topology—leading to ambiguity in specifications.

“STL was developed in a time when computing resources were very limited,” says Baldez. “It’s a fairly simple file format because of the limitations of those times. What vendors have been doing to support different use cases is either creating proprietary file formats—but then, you can’t choose a different software or printer—or borrowing files for other applications, which also have limitations. Where 3MF wants to make a difference is on the completeness of specs to cover everything you can do with 3D printing.”

Companies often face challenges when customizing tools for different industries and applications. For example, a scan-to-print workflow in automotive demonstrates differences from when it’s implemented in healthcare. These differences could be related to things like tolerances, units, geometry descriptions, confidentiality requirements, and so on. Conversely, 3MF can be configured to any application in any industry.

Baldez has a vision where 3MF achieves the same level of ubiquity as the PDF.

“You can open a PDF on your phone, your browser—Windows, Mac, Linux—and it always renders the same. When you send it to a printer, it always prints exactly what you see on screen. That’s what we want to achieve.”

One of the areas where 3MF has proved nifty is its ability to encapsulate details like units and orientation inside a file. According to Baldez, approximately 80 percent of service bureaus today receive files without units. This leads to increased back-and-forth with customers, a higher chance of error, and a general lack of streamlined operations.

When it comes to 3MF’s various applications, Baldez is particularly proud of a partnership between HP, Siemens, and a company called Unlimited Tomorrow that creates personalized prosthetic arms. Although such prosthetics often cost upwards of $80,000, Unlimited Tomorrow leverages 3D printing to bring their price point down to $5,000–$10,000.

“Unlimited Tomorrow got feedback from their customers about prosthetics always being the same color, while people around the world are of different colors,” recounts Baldez. “They needed a robust way to capture the color of the patient’s skin and describe it all the way up to the printing side—so when they 3D-print that prosthetic arm, it looks similar to the rest of the body. From a psychological point of view, it’s super-powerful.”

Color palettes for skin tones
Color palettes for skin tones (image courtesy of Unlimited Tomorrow)

This necessitated accurately capturing the skin tone at the beginning of the workflow and reproducing it all the way until the final product.

“When they didn’t have 3MF, they would see differences between what they intended to print and what actually came out in the printer,” explains Baldez. “Then they used 3MF as a vehicle to transport that information end to end and ensure that color accuracy was respected. It’s a very cool story where 3MF is delivering real value to customers. I get goosebumps.”

So, how does the 3MF specification work? It starts out with a mandatory core specification for defining the outer surface of the object. The user then selects a combination of optional extensions: slice, material, color, beam lattice, volumetric design, and security. For example, to describe the aforementioned arm prosthetic, the core specification would be used in conjunction with the color extension.

The slice extension has more to do with the language that the printers speak. When an object is represented using slices, it can become easier for a 3D printer to replicate certain designs. As for the beam lattice extension, it is a smarter way to describe geometries composed of repeated nodes and beams connecting those nodes. The resulting geometric representation is lightweight and flexible. Beam lattices allow designers to control the mechanical properties of a part by modifying the beam dimensions without changing the topology. This enables a fine level of control of the part behavior with minimum edits on the file. As an example, if beam lattices are applied to an elastomeric material, the stiffness can easily be altered, among other properties.

3MF beam lattice extension
An illustration of 3MF’s beam lattice extension (image courtesy of 3MF Consortium)

The security extension provides an underlying structure for users to choose the basic elements of encryption and decryption within a file format. “For example, you may want to share files in a hostile environment such as a public web page, where multiple people have access to the file, but you only want one individual to access what is inside,” explains Baldez. “You can encrypt the content so that only the individual who has the correct key can decrypt the file and access the content.”

The volumetric design extension

Traditional modeling uses boundaries—such as nonuniform rational basis spline (NURBS) and triangular meshes—for the description of surfaces or bodies.

“Today, CAD software supports multiple representations—from NURBS for curved surfaces, to solid bodies,” says Baldez. “You can choose the one you want, depending on what you’re trying to design. If you’re trying to design an airplane, you would use a certain type of geometry representation. If you’re designing a car, you might use a different one. If you’re using scan data from a patient as an input, you would use another one.

“However, CAD software has never really had a good way to describe the inside of the part,” Baldez continues. “It has just described what’s outside—with the inside assumed to be uniform or void. I think part of the limitation has been that even if you could model a part and describe its interior, you couldn’t make it with traditional subtractive manufacturing processes. Fast forward to this last decade, and there’s this explosion of different 3D-printing technologies that are pushing the envelope of what design tools need to support. It goes back to the mathematical representation they used, which has to evolve to be able to cover everything you can make today.”

NURBS model of a sports car
NURBS model of a sports car (image courtesy of Holocreators)

Volumetric modeling, on the other hand, relies on a mathematical, field-based description of an object’s entire volume—internal guts and all. Its benefit is that it supports how properties vary in space. Baldez provided an example of a human body model, whose multicolored internal components could be demonstrated within a transparent exterior shell.

“Inside, you could have bone structure that’s rigid and white,” he says. “You could 3D-print muscles of different colors, textures, and stiffness. How you’d model that in a computer software is actually not very easy. You’d model every single piece individually, and then try to attach them together. It becomes cumbersome and leads to error. What the volumetric specification is trying to do is, within an outer shell, you can describe the interior of an object using several techniques. You could have multiple sub-objects inside an object. Each one could have a different range of properties, from transparency gradients to weight, strength, material distribution, and composition.”

There are applications beyond the ability to view the inside of a part. For example, the volumetric design extension can be used for developing wear indicators (for items like running shoes or toothbrushes). This can be achieved by printing a layer on the inside of the object that becomes displayed once the object is sufficiently worn out. Similarly, the extension can be used in games as a way to encode hidden messages inside 3D-printed parts.

Another application involves optimizing the build of items. “Imagine you have a support structure, like a table,” he says. “When you apply pressure, not all parts of the table are under the same amount of pressure. If you know the pressure profile that is optimal for your part, you can use the volumetric extension to describe those regions and tell the 3D printer to put less material where you don’t need it and more material where you need it.”

Advancing the 3MF specification

When it comes to putting together a universal specification for 3D printing, the 3MF Consortium has several workstreams. Although the core of the work is addressed by lead engineers from the consortium’s members, emphasis is also placed on marketing and outreach to customers.

“I spend a lot of my time talking to users, understanding what gaps they see in the current design tools and file formats—so that I can go back to the technical team and guide what they need to work on,” explains Baldez. “We really welcome input and try to stay connected to the industry.”

Ideas are already in development for future extensions. One feature that customers have requested is a toolpath extension, similar to the G-code in machining. Another one involves quality inspection, for tolerance specifications to be included within a file for after an object is printed. Although 3MF currently doesn’t support NURBS, there’s discussion about incorporating the higher-order representation to cover certain types of objects.

When asked about the long-term goals for 3MF, Baldez chuckles. “The absolutely final vision for the consortium is that it stops existing. We want it to be so mainstream that you don’t even think about it. It just works. I think our mission will be accomplished when everybody in the world uses 3MF as a means of communicating design intent to any application, software, service, or printer. When it just becomes part of the underlying infrastructure to get good parts. We’re not quite there yet. There’s still a lot of work to do around adoption, bringing in new members, defining new specifications.”

Down the road, the 3MF Consortium is also looking into making an official ISO standard, which may be required for industries such as automotive, aerospace, and healthcare.

The 3MF Consortium’s member companies include 3D Systems, Autodesk, General Electric, Hewlett-Packard, Materialise, Microsoft, nTopology, Stratasys, Siemens, Hexagon, and Prusa. So far, the specification has been implemented in more than 50 products across 38 companies.

brake pedal designed by nTopology
A brake pedal designed by nTopology and saved as a 3MF file (image courtesy of nTopology)

“Five years ago, we would ask people to adopt 3MF, but there was no software or hardware supporting it. Nowadays, that’s not really true. All the major 3D software and 3D printers in the market support 3MF,” Baldez points out. “I welcome all members to keep pushing on the message, and all end users to start using the specification. If they don’t like what they see, come back to us. We’re all ears when it comes to making changes that will solve real customer problems. We’re a very open organization; we’re not doing this in the wild. Anybody can reach out to me on LinkedIn and ask a question. We’re here to help the industry move forward.”

Discuss

About The Author

Sana Kazilbash’s picture

Sana Kazilbash

Sana Kazilbash is an editor at engineering.com and has a chemical engineering background with experience in petroleum, pharmaceutical, and software development companies. Passionate about food and travel, Sana enjoys water-based activities such as stand-up paddleboarding.