TL smoothers are popular little printed circuit boards (PCBs) that are often used in FDM 3D printers to not surprisingly, smooth out the look of prints. In other words, they reduce surface artifacts caused by irregular stepper motor motion, often dubbed “zebra stripes,” “salmon skin,” etc. These smoothers are often sold as 4- and 8-diode variants, with the 8-diode ones (pictured above) offering a stronger smoothing effect.

They plug into any 3D printer between the stepper drivers and the stepper motors, working their electrical “magic” without any other setup needed. Their low cost, plug-and-play functionality, and seemingly magical effect have made them quite beloved, albeit slightly controversial.