FilaLoom Makes a Bambu Lab A1 Pick Up a Yarn Needle and Weave Twill Into Its Own Prints

A Bambu Lab A1 prints a ring of stubby pillars, each with a little crease in it. Then the print head drives over to the edge of the bed, locks onto a tool holding a spool of cotton yarn and a blunt dispensing needle, and snakes that yarn from pillar to pillar. It parks the tool, prints the next stretch of pillars on top, and goes back for more yarn.

That’s FilaLoom, from Joram de Haas, Mehmet Ozdemir, Holly McQuillan and Zjenja Doubrovski at Delft University of Technology. Their preprint, dated October 10 and headed for the ACM Symposium on Computational Fabrication in Tokyo this December, says the whole thing “operates through the printer’s existing motion system, requiring no additional electronics.”

The hardware list is short. The parts are printed in PETG, plus three store-bought bits: a blunt-tip dispensing needle, a 1.5x10x15 mm compression spring and “several 8x2mm neodymium magnets.” The spring presses a washer against the spool, and turning a bolt sets the yarn’s tension, which the paper says users get right by feel over repeated runs, a bit like setting the drag on a fishing reel.

The pickup is the clever part. A cover on the print head has a plus-shaped key that slides into a keyhole on the yarn tool, and three cones line the two up. The sideways move that docks the tool also slides a lock shut. Parking it on the station, which screws onto the bed, pulls that lock back open, with magnets holding the tool in place. The team says the coupling is “similar to those in the tool changers” of the Prusa XL and Snapmaker U1, printers that use their locks to swap whole print heads rather than a yarn needle.

The weave pattern is a binary sequence, so the same script turns out plain weave, 2x1 twill, 3x1 twill and satin. The paper shows all four on matching hexagons, a bowl that alternates blue and lilac yarn row by row, and a lampshade with a curved surface, an example of the “3D geometries that are not possible with traditional weaving.”

Why it matters

No motor this time. Earlier yarn printers needed extra hardware. The preprint describes Rhapso as a rotating ring whose yarn carrier is positioned by a stepper motor under custom software. FilaLoom gets the same job done by moving the print head the printer already has, and the team says the setup attaches and detaches “in a few minutes.”

Real yarn in the print. Printers have faked fabric for years with thin TPU meshes and printed weaves. The paper says those methods “cannot replicate the unique tactile qualities found in traditional textiles,” because everything in them is printed plastic. Here the soft part is the 1.5 mm cotton or 0.6 mm polyester yarn the team fed through the needle.

The tool change is reliable. “The tool changing itself has a reliability of 99.6%, with 3 unsuccessful tool changes observed across the 700 performed,” the paper says. For a tool changer printed in PETG on the printer it rides on, that’s a number most DIY rigs never get around to measuring.

The same trick does more than baskets. Lay yarn over a flat layer and print another layer on top, and the yarn is clamped in between for flexible “semi-woven” sheets cut to any outline. Print lines across a web of yarn held up off the bed, and the plastic droops between the strands into loops, a pile texture. The team mapped a grayscale image onto those loop heights and printed a smiley at roughly 25 DPI. Route one yarn through a channel, anchor both ends, and pulling a tab makes a printed textile bend or coil.

Some materials are off the table. “Because the mechanism relies on yarns being easily pulled along in any direction, stiff yarns such as metal wire or straw are not suitable,” the paper says. The A1 also can’t cut yarn, so everything it embeds is one continuous strand until someone takes scissors to it.

The weaving costs space and time, too. The station and the clearance behind it eat bed space, and the needle sits 40 mm behind the nozzle and dips 25 mm below it, so only 54% of the A1’s 256 mm cube can be both printed and woven. Each pickup takes about three seconds and each parking about twelve, including a nozzle wipe.

The GCode is still the hard part. Three of the five print strategies come out of Grasshopper scripts as finished files. For the other two, the user marks layers in a normal slicer and pastes the weaving moves into the GCode by hand in a text editor, which the team calls “time-consuming and sensitive to mistakes.” The paper’s own answer is future software for laying out yarn paths, and nobody has written it yet.

Steal this

Turn on brims before you weave anything into a print. Dragging yarn pulls sideways on the part, and the paper says a weak first layer lets the print rip off the plate. This is like staking a tent before you tighten the guy lines.
When you plan a path for the needle, leave 1.5 mm of clearance on each side of it. With the 15G needle the team used, that means a gap at least 3.34 mm wide, and each anchor’s crease should be about half the yarn’s diameter. Kind of like when you measure the doorway before you buy the couch.
Keep the weaving moves at 25 mm/s or below. The paper says placement gets less accurate past that, even though the pickup and parking run reliably up to 133 mm/s. Kind of like when you slow down to thread a needle by hand, then speed back up once it’s through.
Before you sell anything made with it, read the license. The GitHub repo is Attribution-NonCommercial 4.0, so the parts and scripts are free to use and remix but not to sell.

Tool changers have mostly been a premium feature, motors and toolheads and a price tag to match. FilaLoom’s station suggests the cheap version may be a passive tool the printer picks up with moves it can already make. The paper’s own wish list points the same way: more stations on the bed for more yarns, and maybe a nozzle hot enough to burn through the yarn so it can cut its own thread. The team writes that it hopes more designers and researchers start embedding yarn in prints, and the STLs and Grasshopper scripts are already up for anyone with an A1 and a spool of cotton.

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