Sonos Roam holder

When my friend asked me to create a holder for his new speaker, I said sure — but then asked why he'd even need a speaker mount for a bike. Isn't cycling about enjoying nature, escaping the city, pushing your limits, and discovering new places? He just smiled, and I realized that's my view of why cycling is one of the best sports you can try. He enjoys music festivals, and music is simply part of his cycling experience. If nothing else, playing music through a speaker is probably safer than riding with earphones in anyway.
He lent me his new speaker so I could take measurements and try the first prototypes. At the time I had no 3D scanner, so I had to work with calipers — but that was totally fine. The speaker's design is very clean, built around a triangle as its base shape.
The requirements for the holder were straightforward: it had to keep the speaker firmly in place while riding both on-road and off-road, and it had to survive crashes.

Material Choices
Since the holder's primary use is outdoors, I needed something that would hold up after prolonged sun exposure. That's when I discovered ASA — compared to ABS, it's UV-stable and much less prone to shrinking. I ordered a spool and was looking forward to seeing how the surface would turn out after acetone vapor smoothing.
What I was about to learn the hard way was warping.

Warping
If you've ever tried printing ASA — or any other technical material — on a printer without an enclosure, you're familiar with warping. As plastic is extruded, it's hot and expands. When it cools, it contracts. Different layers cool at different rates, creating internal thermal stresses. When those stresses overcome bed adhesion, the part lifts and deforms.

Anisotropy
The broader term here is anisotropy — a material is anisotropic when its mechanical properties differ depending on the direction in which you measure or load them.
Why did I run into this during this particular project? The arms designed to hold the speaker were meant to flex slightly on insertion, gripping the speaker firmly once it snapped into place.

As printed, the layers ran in the same direction as the force applied when inserting or removing the speaker — far from ideal, and especially bad in a crash scenario. Layers stack on top of one another, and the force needed to separate that bond is much lower than the force needed to break across the perpendicular direction.
Fortunately, my friend's speaker survived this lesson. Plenty of holders did not.

Solving the Anisotropy Problem
The fix was obvious in hindsight: change the layer orientation in the holder arms. The only practical way to do that was to print the arms as separate parts from the body. Printed independently, the arms came out strong with the right infill settings. The new question was how to attach them back to the body.

Gluing ASA
You'd think you could just grab any plastic glue off the shelf and call it done. What I didn't realize was that many of these "glues" actually contain acetone or similar solvents — meaning they're not adhesives at all. They work by dissolving the surface layer of both parts, allowing the polymer chains to intermingle and entangle. When the solvent evaporates, the material re-solidifies as essentially one continuous piece.
That sounds great in theory. In practice, applying a solvent directly to a joint that's already been weakened by splitting the body didn't go well at all. What made it worse was the delay. On the first batch — which I had already started selling on Etsy — everything looked fine. The holders felt sturdy; I couldn't break them by hand. Then the customer feedback started coming in. Every unit where I'd used that glue had become brittle. It took weeks to fully manifest, but when it did, it was catastrophic.
After trying several plastic glues, I eventually landed on a combination of a mechanical lock and standard super glue.

Looking back, this was a lot of lessons packed into a single project. It took months to find the right combination of solutions. Along the way I added a Velcro loop mount point, and discovered that some customers actually want to use the holder indoors — in their homes or caravans.
As of this writing, I've sold nearly 150 holders, which gave me the budget to upgrade from a Prusa Mini to an enclosed Prusa MK4S. It helped enormously with warping — but as always, it brought a whole new set of challenges. More on that later.