One of the ladies in my local craft guild commissioned this WooLee Winder bobbin from me in mid-2025. She asked me to recreate the original design provided with her WooLee Winder flyer system, but with a few small improvements to better suit her needs.
The main benefit of the WooLee Winder system over the standard flyer and bobbins is the gear-based feed system. As the flyer turns, the white drive gear turns a worm screw that moves one of the rings back and forth. This evenly distributes newly spun yarn across the whole bobbin, rather than letting it clump up in one spot.
The original bobbins made by WooLee Winder have wooden ends with a sturdy plastic shaft, perfectly designed to fit the flyer. The gear on top of the bobbin is made from the same durable plastic as the shaft, and meshes with the white drive gear on the flyer. To work as a drop-in replacement, my bobbin design had to exactly match the original bobbin’s dimensions.
Looking for existing designs
My first step when starting a new design project is to browse existing design solutions. An existing design by Djahnstar3D on Thingiverse looked very promising at first, but I quickly discovered it was for the Jumbo flyer instead of the Regular. My client, naturally, had a Regular flyer. Even so, Djahnstar3D’s design was still valuable and I printed one of them for reference.
I borrowed a WooLee Winder bobbin from my client so that I could effectively measure it and create my CAD files. Djahnstar3D’s design is five pieces and requires support scaffolding when printing, which isn’t ideal from both a manufacturing and an assembly perspective. I simplified the design by integrating the bottom bushing and top gear directly into the bobbin ends. I also improved printability by modifying the insides of the bobbin ends and the ends of the shaft so that it doesn’t need supports anymore.
Design challenges
It took several iterations to get to the final design. I ran into challenges I wasn’t expecting:
- Measuring the WooLee Winder flyer’s axle as well as the hole in the original bobbin didn’t give me a useable dimension for my bobbin design.
- The inside of my bobbin’s shaft had a Z-seam on the inside, like a zipper where each layer starts and stops. This meant that the bobbin didn’t fit correctly even though my CAD file’s dimensions were correct.
- Adding a keyhole slot to catch the end of a length of leader yarn was more difficult than I expected.
- I struggled assembling the bobbins to be perfectly square.
Fixing the fitment issues
Given that measuring the original flyer and bobbin weren’t working, I chose to print a set of test rings of different sizes to see which fit best on the flyer’s axle. Nothing beats a real-world small scale test, after all. That gave me the dimension I needed to get the correct output on my 3D printer.
Next, I fixed the Z-seam issue by adding a small channel inside the bobbin’s shaft and telling my 3D printer to place the seams in that channel. This hid them from the axle, and prevented them from messing up the dimensions.
The yarn keyhole
When starting to spin, you need a length of leader yarn on the bobbin to act like a guide to pull your newly spun fiber onto the bobbin. There’s a few different methods to tie the leader yarn on and prevent it from slipping, but I prefer bobbins that actually grab onto a knot instead. I chose to add keyholes to both ends of the bobbin shaft to do just that, as a way to “upgrade” the original bobbin design and put my own spin on it.
I went through several versions of the keyholes. The first few didn’t work at all, and the next few worked but not as well as expected. I had to make the hole for the yarn knot larger and the keyhole slot narrower. The knot also caught against the axle at first and prevented the bobbin from spinning, so I carved out some space internally for the knot. The final design is secure, easy to use, and adaptable to both directions of spinning.
Making assembly easier
My first few prototypes were difficult to glue together and keep the shaft fully perpendicular to the bobbin ends. I could either design a jig to hold everything in place while the glue cured, or adjust my CAD model to tighten up the tolerances. I chose to adjust my design first, to see if I could make assembly as straightforward as possible.
The shaft and bobbin ends have very tight tolerances relative to each other, so they fit without much slop in the final design. I also added some alignment fins and sockets to help hold it all in place. My goal was to make these easy for others to 3D print and assemble themselves, without having to also print an assembly jig.
I tried E6000, GS Hypo Cement, and regular superglue to see which worked best. The E6000 proved to be too pliable and allowed the bobbin to wobble while spinning, and the GS Hypo Cement didn’t actually bond to the PLA plastic successfully. I stuck with tried-and-true superglue, and it’s worked perfectly for every bobbin I’ve made so far.
The final design
My client loved the final design I came up with – especially since she got several more bobbins than she expected as I tested out new prototypes. They swap in directly without any modification to the WooLee Winder flyer, and just need a bit of adjustment on the tension band to balance it all out.
Improvements
While the glued bobbins work perfectly fine, I chose to redesign the bobbins to have threads on each part for a few reasons:
- The ability to ship disassembled and flat, and reduce risk of shipping damage
- Easier assembly and alignment, especially for people 3D printing their own
- More compact storage
The new threaded parts fit together snugly, ensuring a perfectly-aligned bobbin every single time. And since the threads are the same diameter, pitch, and direction, it doesn’t matter which way the user assembles the bobbin.
If desired, end users can add a drop of glue to the threads before assembly to make sure it’s extra secure while spinning.
