This is a demonstrator of a rack-and-pinion gear mechanism. The 20 pinion gear teeth have an involute profile, while the 15 rack teeth have a flat trapezoidal profile. Both have a module of 2mm.
This builds on an earlier gear demonstrator of mine which investigated the involute tooth profile.
The holes in the base a meant to accomodate a #8 screw for mounting.
Print with a low bed heat (or none) to avoid any elephant's foot, which will cause mechanical interference between the gear teeth and make additional post processing necessary.
This model is designed to be assembled using three M3x5mm Threaded Inserts, inserted into the slightly undersized holes using a soldering iron. (Matterhackers has a good guide to this method). The pinion is held by a small (~8mm x m3) machine screw. The rack is guided by two screws of the same type.