Locked Heart

I have been trying to come up with something fun for Valentine’s Day and to be honest it has been a struggle (from a creative design perspective). The shape of a heart is really quite challenging to make into a functional thing. I have a few ideas and I am going to continue exploring those (probably for next year now). But while working on those ideas I made a breakthrough (for me at least) in evolving my spin to unlock designs. I made the latch system into a one piece compliant design. And, I love it. It is awesome.

If you are familiar with my older spin release locks (centrifugal unlock), you will see that I am still using four free weights that create the actual “lock,” but where there were previously four sprung latches, there is now one piece that includes the racks, springs and structure keeping them all in place. This has so many advantages over my earlier designs that I may have to go back and re-design those.

The new one-piece design makes printing, parts management, and assembly all much easier. In addition, this design eliminated the need for the posts that the previous designs used to hold the latches. This allows the entire design to be more compact and makes it possible to eliminate the cover that was included in the earlier designs as well.

If you don’t know, the box can only be opened by spinning it, which forces the slide weights outward and away from the centre sprocket. Any random movement will cause at least one of the slide weights forward to interfere with the sprocket and prevent the box from being unlocked.

On the outside of the box (heart) is a small heart-shaped handle that must be turned after the box is spun and before any other movement of the box, which may cause it to lock again. I made the sides of the handle fold up to make it easier to grip and hold.

Print Settings

Functional designs (such as this one) generally require more strength than non-functional designs and more strength than the typical default slicer settings provide, so please review your slicer settings carefully.

This product was designed for a 0.4mm nozzle, a 0.2mm layer height. For best results I suggest the following:

• Material = PLA / PETG
• Nozzle = 0.4mm
• Layer Height = 0.2mm
• Line Width = 0.4mm
• Wall Count = 4 (1.6mm)
• Top and Bottom Layer Count = 5
• Detect Thin Walls = ON
• Wall Generator = Arachne
• Infill = 40% (Cubic)
• Support = None required.
• Print orientation = As per the STL/3MF files

Assembly Notes

There is no print support required or included in this design, so as soon as it is removed from the build plate, you can put it together.

1. Flex the four slide weights into position on the underside of the lid. Ensure they float freely back and forth before proceeding.
2. Hold the folding heart handle on the outside of the lid, then place the crankshaft into the heart, and then through the sprocket on the inside of the lid. IMPORTANT: the notches in the sides of the sprocket must align with the free weights. So, let a few of the weights slide forward to ensure the sprocket is aligned with the weights.
3. Lay the one-piece latch system onto the inside of the lid and press the perimeter into place under the inside lip of the lid. To do this, you will need to flex each of the latches inward and then back out to their resting position, extended through the sides of the inner lid layer.
4. Now the entire assembly is together, ensure that each of the racks aligns on the sprocket with their corresponding latches in the fully extended position.