This original toothpaste tube container has two rollers which press the tube when the outer shell is rotated (while maintaining the container's top with the other hand). The tube doesn't move, its opening is always aligned with the container's top. Or, rather, this is how it was supposed to work… See the Testing section for details.

Currently it's not really usable but, are toothpaste squeezer really essential… at least this one has gears :-).

Mechanical design

The two rollers have a gear on each end which meshes with a vertical rake. This keeps the rollers horizontal, and ensure that they roll on the tube according to the vertical motion.

The vertical motion is caused by two threads on the outer shell's inside, which push the rollers' shafts upward (only on one end of each roller).

Particular gear design

A particularity of this gear / rack application is that the pitch radius of the gears is slightly smaller than it should be according to the number of teeth and the rack tooth size. This is because the number of teeth must match the actual perimeter of the rollers (for rolling-only motion on the tube) while the pitch radius has to be smaller than the roller radius to make room for the rack. So, the tooth size for the gears is slightly smaller than for the racks.

As a consequence, the gears slightly “slip” on the rack, and the teeth are cut with a custom shape to account for this motion.

Another thing to note is that the gears are helical. The reason is simply to make the racks print better by avoiding sharp steep overhangs. I use a similar trick for the internal threads, which are slightly trapezoidal (almost square),  just to avoid sharp overhangs.

Printing and assembly

The inner and outer shells both print without support (I used PLA and 0.15 layer height for everything). For the top part, I used supports only for the screwing holes. I used some plastic screw with an approximate diameter of 3.5mm.

The roller parts must be printed twice (the two rollers are identical). For each roller, the gear and shaft at one end is printed separately for better print quality. The shaft part has an hexagonal end for assembly. There is no alignment issue as the number of teeth (18) is a multiple of 6.

To put everything together, the two shells must first be nested, aligning the thread “entrances” on the top with the notches for the roll shafts. Then, insert the two rollers, making sure that they are horizontal, and finally screw the top part.

Testing

My first test didn't work as good as I expected : the friction between the rollers and the toothpaste tube is not sufficient to prevent slipping, so when rotating the container, it pushes the tube upwards instead of just the toothpaste… unless somehow maintaining it with two fingers.

I have tried a version where the rollers covered with a knurled tube printed in TPU, without any improvement. Maybe another material would work better… hot glue ? silicone ? double-sided adhesive tape ? or using meshing gears instead of flat rollers ?