The Effect of Printing Parameters and Wood Surface Preparation on the Adhesion of Directly 3D-Printed PLA on Wood

As additive manufacturing technologies advance, new opportunities are opening up for their application in the furniture industry. Wood remains one of the leading raw materials in the furniture industry; therefore, possible options for combining it with 3D printing have been researched. The bonding of 3D-printed polymer parts with wood or 3D printing with wood-plastic composites is already known, but in our research we attempted to directly 3D print polylactic acid (PLA) on wood surfaces. The effect of printing parameters, as well as the surface preparation of wood on the shear strength of the bond between wood and on-printed material was tested. Microscopic images of cross-sections of samples were analyzed. The results show that with a lower initial layer thickness (0.1 mm), a higher printing temperature (220 degrees C), and with the use of polyvinyl acetate (PVAc) primer on the wood surface before 3D printing, a higher bond strength (5.4 MPa) was achieved, but the values for the bond strength remain low compared to the conventional bonding of wood to wood with PVAc adhesive (around 10 MPa). Microscopy studies revealed barely visible penetration of PLA into the lumens of the wood cells. However, the PVAc adhesive used as primer penetrated more into the cell lumens and served as interface layer between deposited melted PLA and the wood, thus creating stronger joints.