Printer with 50 microns or close to 50 micron (z resolution)
I assume you mean a resolution of 50 microns (0.05 mm step size)
Most FDM printers can produce something useful upto 100 microns. If you want to print with more precision, try resin printers.
The reason for this is that an FDM printer uses an extruder with a specific nozzle diameter (typically around 0.4mm and minimum around 0.25 mm). plastic has too much viscosity to fit through a smaller diameter nozzle easy.