Combination of 3D printing and injection molding: Overmolding and overprinting

Nowadays, two of the most important polymer processing technologies are injection molding and 3D printing. Injection molding is ideal for mass production, while 3D printing is ideal for producing products with a complicated geometry. When these two technologies are combined, such complex products can be manufactured economically that would be too costly if produced traditionally. We present the possibilities of combining injection molding and 3D printing. We introduced a novel concept to study and compare the bonding strength of polylactic acid (PLA) parts prepared by overprinting and overmolding. We developed a special injection mold for overmolding, with which we injection molded ribs on a preform. The geometry of the overprinted part was similar for comparability. The thermal properties of the samples were determined by differential scanning calorimetry and thermogravimetric analysis. To analyze the strength of mechanical bonding, we developed a rib pull-off test. We tested all four manufacturing combinations with this test: overmolding onto a molded or printed plate and also overprinting onto a molded or printed plate.