This is a double helical (aka. herringbone) gear set for the default Ultimaker filament feeder. I don't own an Ultimaker yet, but saw many YT videos, and I noticed that the gears on the feeder mechanism are working relatively loudly. This is because of they straight teeth. Helical gears are invented to ensure permanent contact between gears, as they roll on each other, just like they were wheels. If I have not made any serious mistake, this set will be operating much softer. Awaiting feedbacks on this too. :) There already are some similar modifications, but none of them are correct from a mechanical point of view: teeth should be bent properly, especially on the smaller gear, to maintain proper connection between the gears. Dimensions are from "official" lasercut PDF, so everything should be fine. There are two versions attached of the bigger gear: one with a knob socket, where you can insert a knob for easier manual feeding, and another standard version without any hole for the knob. Of course, the "knobbed" version can be used without the knob attached as well, thanks to the lego connector like design. I also rendered some additional images (orange ones), where you can examine the models. And here comes the important part: If someone, who can give proper feedbacks (with an engineer's eye) about the possible weaknesses or faults, would print and test it, I would be grateful for him/her. Theoretically, although the small gear has a slot for fastening purpose, it can't fall off from the feeder motor's axle, because of the double helical toothing. If tests confirm, that fastening is unnecessary, I will modify the model. Any further suggestions are welcomed. Write your remarks and experiences, so I can improve the set.Use highest resolution possible! A minimum of 80% filling should be set for the gears. The knob is designed to be printed with 100% filling, since it is hollow on purpose, where necessary. UPDATE 1: Knob updated (gear knob v2.STL) according to smorloc's feedbacks. Pin thickened from 4,5mm to 4,8mm, shouldn't be that loose anymore inserted into its 5mm hole. Pin's wall also thickened to ensure durability. Gears still need to be tested in operation.