Hybrid inkjet and direct-write multi-material additive manufacturing

Abstract

Recently there has been a trend towards combining multiple forms of additive manufacturing together for increased functionality, freedom and efficiency. In this work, two forms of multiple-material additive manufacturing technologies - inkjet and direct-ink writing - are combined in a hybrid system. Several advantages are realized due to the increased material library and geometric freedom as a result of new printing modalities. Initially, models of each process are reviewed and the processes are evaluated for compatibility. Then, the precision machine design of a passively-indexed, carousel-style, syringe tool holder is completed. An error budget employing Homogeneous Transformation Matrices was maintained to estimate the tooltip errors. In order to register these two non-contact printing processes, a unique approach to their registration to a common global origin was necessary. A single non-contact optical CCD micrometer is used to register the three spatial coordinates of the syringe tooltip. Measurements are performed to characterize the repeatability of the nozzle registration scheme and the constructed gantry and carousel system, which well exceeds the requirements and the predictions from the conservative error budget. This novel system can print with a wide array of inks, including those that solidify via polymerization or crosslinking, two part chemistries, solvent evaporation or sintering, as well as liquids, gels and pastes. These materials can have a wide range of mechanical properties and functionalities, for example electrical conductivity or force sensitive resistivity. Models for the extrudate flow rate are used alongside experimental determination of the extrudate cross-section to ensure accurate process congruence. Finally, printed results demonstrate the various printing techniques, highlight the expanded material library, and display novel assemblies not possible with conventional additive processes. One such example is a fully printed pressure sensor array.