the tricky bit is getting the part right in CAD, allowances need to be made for how the printer used converts the file for printing, mine for instance prints to the outside dimensions, but internal holes need to be made 0.4mm oversize to allow for the nozzle thickness if you need the hole to be precise.
then there is material, some filaments for 3d printers are water soluble, better would be a resin 3d printer that cures layers of resin with a laser, this gives a better finish than laying down layers of filament.