A system and method for forming 3D printed structures on a base component includes extruding material through a nozzle while moving the nozzle vertically. Extruded material flows from the nozzle and spreads outwardly upon contact with an underlying portion of material. The outward spread of material is controlled to form a desired geometry for the 3D printed structure. An optical sensing device may provide feedback for controlling the outward spread of material. Using a molding component, structures with anchored portions extending through openings in the base component can be formed.