Benchtop Machining of Self-Standing Alumina Doughs for Low-Number Fabrication and Prototyping

Cold isostatic pressing, gel casting, and protein coagulation are the most common techniques to produce green bodies prior to computer numerical control (CNC)-based machining for the near-net-scale shaping of ceramics. These methods typically involve various additives and entail several steps to create a green body that is capable of withstanding machining forces. Here, utilizing a single additive, we first introduced a facile benchtop method to generate self-standing, malleable doughs of alumina in under 2 min. We then optimized the parameters of CNC machining to obtain surfaces with minimum surface roughness and produced custom-sized crucibles as a showcase for low-number production. To consolidate a dough from highly loaded suspensions of alumina, we employed a poly(ethylene glycol)-grafted random copolymer of acrylic acid and N-[3-(dimethylamino)propyl]methacrylamide at 0.75 wt % with respect to the weight of alumina powder. We surveyed machining parameters with spindle speeds ranging from 5000 to 30000 rpm and cutting speeds from 1000 to 1800 mm/min using 1 and 2 mm tool sizes. The highest surface quality, characterized by the minimal surface roughness as evaluated by profilometry, was achieved at a spindle speed of 20000 rpm and a cutting speed of 1200 mm/min with a 1 mm tool and at a spindle speed of 15000 rpm and a cutting speed of 1800 mm/min with a 2 mm tool. Upon sintering, the hardness of the machined samples was measured to be 15.16 ± 1.15 GPa. Additionally, we demonstrated the recycling of alumina (up to 30 wt % of alumina content) sourced from intentionally broken parts in the green state. The recycling scheme contributes to the lowering of the use of resources and emphasizes the possibility of a greener future for ceramic production on a broader scale. Overall, this cost-effective and easy-to-implement methodology starts at the materials formulation level and parametrization of the machining paves the way for immediate industrial adaptation.