Improving the wear resistance of 3D printed spur gears through a free-form tooth flank optimization process oleh Kalligeros Christos, Papalexis Christos, Georgiou Dimitrios, Krifos Dimitrios, Vakouftsis Christos, Terpos Klearchos, Goudas Konstantinos, Balis Panagiotis, Kontaris Theodoros, Kaisarlis Georgios, Tsolakis Antonios, Zalimidis Pavlos, Sapidis Nickolas, Provatidis Christopher G., Spitas Vasilios