a different spin on 3D printing that can make furniture out of yarn

Would you like to knit your own furniture? I’m talking about creating an entire couch, chair, and table by knitting, and not just the upholstery. How’s that even possible?

Well, researchers from Carnegie Melon University (CMU) have developed a technique, called solid knitting that creates sustainable, reconfigurable objects out of a special type of yarn.

“Solid knitting is a new technique to fabricate dense, firm objects via knitting. The objects are built up layer by layer in the style of 3D printing but are held together by intertwined strands of yarn rather than the use of adhesives,” the researchers said.

This unique technique is the brain-child of Yuichi Hirose, a PhD student working on solid knitting for a decade, and James McCann, a CMU professor who created the software that guides the 3D knitting device.

Along with colleagues, Hirose and McCann have developed a prototype solid knitting machine. It is the size of a washing machine and uses an elastic cord as yarn to knit different types of objects.

The science behind solid knitting

In order to knit an object using the solid knitting machine, a user first designs the object using its software program.

“In the tool (software), users design objects by connecting different types of blocks, what we call ‘augmented stitch volumes.’ They are associated with code fragments that represent machine operations, described in a language we also developed, ‘solid knitout.’ The tool combines the code fragments from each block into a program to run the machine,” Hirose wrote in a blog post

Once the design is uploaded, the prototype machine begins knitting layer after layer of the yarn material (both horizontally and vertically) with the help of a series of hooked needles and latches. This process continues till the object takes the desired shape. 

Apart from the knitting part, this technique sounds similar to traditional 3D printing but there are some key differences. 

For instance, “rather than being held together by glue or melted plastic (like in 3D printing), in knitted 3D objects, each new layer is stitched to the previous one. Also, “a solid knitted structure can easily be unraveled and re-knit, unlike other 3D printing methods which require finished objects to be laboriously melted down and re-extruded into filament in order to be recycled,” the study authors note.

Due to these differences, objects made through solid knitting are more sustainable and easier to recycle and reuse. 

“It can be hard to wrap your head around the concept, but it’s a very cool idea, and one that has a lot of promise,” James McCann added. 

Future of 3D knitting

The researchers have used this solid knitting machine to create rectangular and triangular objects. They even designed a pair of knitted slippers as a demonstration. In the future, they plan to make chairs, sofas, and other types of furniture using the same process. The best part is all of this furniture would be reconfigurable.

“For instance, a person who is moving to a new apartment could unwind the solid-knit furniture of the previous resident and reknit it into their own style,” the study authors said.

The researchers also plan to make knitting machines of different sizes. Larger machines will make large objects (ranging from bulky furniture to industrial goods) whereas smaller ones will knit designs that require in-depth detailing and precision. 

“We hope that other people out there are going to build their own solid knitting machines and come up with ideas we haven’t yet explored,” McCann said.

The study is published in the journal ACM Transactions on Graphics.