Rack and Pinion

These two 3D printed parts are the rack and pinion, which will be mounted inside the thimble to convert the rotary motion of a servomotor into linear motion. The rack is a toothed bar that meshes with the pinion, a gear with a small number of teeth. When the pinion rotates, it drives the rack in a linear motion, resulting in precise and controlled movement of the thimble.

The rack and pinion mechanism is commonly used in mechanical systems to convert rotary motion to linear motion. In this particular case, it is used to translate the rotational motion of the servomotor to a linear motion that can be used to manipulate objects or instruments with the thimble. The 3D printed parts are designed to fit precisely inside the thimble and mesh smoothly with each other, ensuring reliable and accurate conversion of motion.


You can download the .stl file of the rack here and that of the pinion here.

In addition to converting rotary motion to linear motion, the rack and pinion mechanism also includes an ergonomic fingertip envelope at the end of the rack. This envelope is designed to apply equal pressure on all surfaces of the fingertip, ensuring precise and controlled manipulation of objects or instruments. The design of the 3D printed parts takes into account both functionality and comfort, allowing for efficient and ergonomic use.

Rack and Pinion image

The design of these 3D printed parts was also done with ease of printing in mind, using fused deposition modeling (FDM) technology. This method allows for quick and precise production of parts using a variety of materials. The design takes into account the limitations of FDM printing, ensuring that the parts can be printed easily and without errors. This ensures that the parts are readily available and easy to produce, making them a cost-effective and accessible solution for converting rotary motion to linear motion.