DIY Hand Mixer Whips Coffee Into Shape

Along with the substantial rise in bread baking over the last few months, many people have been whipped into a frenzy over this tasty-looking frothy coffee beverage called Dalgona. It’s like a caffeinated meringue made from instant coffee, sugar, boiling water, and a whole lot of air that is then spooned onto milk or milk and ice.

Sure, you can use a whisk to mix it up if you don’t mind doing so continuously and vigorously for at least a full three minutes. [HimanshuS8] quickly got tired of making his wife’s coffee this way, and designed a small electric hand mixer especially for this task. [HimanshuS8] happens to be a hardware design engineer, which is why it looks so minimalist and beautiful.

The inside is just as beautiful, mixing junk bin parts like the 6 V motor from a cassette deck with printed gears and beaters. At the risk of reviving an old debate, we hope [HimanshuS8] used food-safe filament for those. If you replicate this, you could try to design it around standard metal beaters instead. Check out the demo after the break while you wait for the water to boil.

Coffee makes everything better, including 3D prints — the high cellulose content in coffee waste has been shown to drastically improve print strength.

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Improving 3D Printed Gears With… Hot Water

Being able to print out custom gears is one area where 3D printing can really shine, and [Karl Lew] has been busy doing exactly that with pinion gears printed in PLA and mounted to stepper motor shafts, but there are tradeoffs. Pinion gears need to grip a motor shaft tightly – normally done with a screw through the gear and onto the motor shaft. But a motor and its shaft can get quite warm when doing a lot of work, and a tight screw on a hot motor’s shaft will transmit that heat into the PLA, which can then deform.

[Karl Lew] managed to improve things in an unusual way: using a hot water bath to anneal the gear while it is attached to the stepper shaft. Annealing PLA has the effect of increasing the crystallinity of the material, which – according to an article going into some detail about the process of annealing PLA – increases stiffness, strength, and heat deflection. The annealing process also shrinks the part slightly, which happens to result in a very tight joint made between the gear and the slotted stepper shaft if the gear is annealed while connected to the motor.

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