It’s a 3D Printer, but not as we know it

Schematic representation of printer and ultrasonic manipulation rig. (a) Switchable laser module is attached to the print head carriage, and traces out the shape of the printed part. The laser can be deliberately defocused to cure large regions slowly by increasing the height of the laser module. (b) Focused laser beam cures resin within the cavity of the ultrasonic manipulation device. P = PMMA, W = Water, PZT = lead zirconate titanate transducers, R = spot-a low Viscosity photocurable resin. Cross sections of the bundles of fibres lying within traps are shown, and are separated by half a wavelength.

An engineering team has developed a new type of 3D printing that can print composite materials, which are used in many high performance products eg tennis rackets, golf clubs and airplanes. This technology will soon enable a much greater range of things to be 3D printed at home and at low cost. Ultrasonic waves are used to carefully position millions of tiny reinforcement fibres as part of the 3D printing process. The fibres are formed into a microscopic reinforcement framework that gives the material strength. This microstructure is then set in place using a focused laser beam, which locally cures the epoxy resin and then prints the object.

Optical microscopy images (1)–(4) of various sections of a printed part (centre top) reinforced with ultrasonically aligned glass microfibres, with desired orientation direction shown (centre bottom). In each of the sections, ‘stripes’ of aligned fibres can be seen with uniform dispersion and an average trap spacing of 300 μm. Sections 2 and 3 show discernible features of the printed part, with fibres extending to the edge of the part and maintaining their alignment.

To achieve this the research team mounted a switchable, focused laser module on the carriage of a standard 3-axis 3D printing stage, above the new ultrasonic alignment apparatus. Tom Llewellyn-Jones, a PhD student in advanced composites who developed the system, said: “We have demonstrated that our ultrasonic system can be added cheaply to an off-the-shelf 3D printer, which then turns it into a composite printer.”

In the study, a print speed of 20mm/s was achieved, which is similar to conventional additive layer techniques. The researchers have now shown the ability to assemble a plane of fibres into a reinforcement framework. The precise orientation of the fibres can be controlled by switching the ultrasonic standing wave pattern mid-print. This allows complex fibrous architectures. The versatile nature of the ultrasonic manipulation technique also enables a wide-range of particle materials, shapes and sizes to be assembled, leading to the creation of a new generation of fibrous reinforced composites that can be 3D printed.

Demonstration of varying fibre angle within a printed component, with desired microstructure shown in inset. All parts had dimensions 20 mm (l) × 2 mm (w) × 1 mm (t). (a) Fibres aligned along part axis. (b) Fibres aligned at 45◦ to part axis. (c) Fibres aligned at 90◦ to part axis. (d) Demonstration of orthogonally aligned reinforcement within the same printed layer.

Prof. Bruce Drinkwater: “Our work has shown the first example of 3D printing with real-time control over the distribution of an internal microstructure and it demonstrates the potential to produce rapid prototypes with complex microstructural arrangements. This orientation control gives us the ability to produce printed parts with tailored material properties, all without compromising the printing.”

Dr Richard Trask added: “As well as offering reinforcement and improved strength, our method will be useful for a range of smart materials applications, such as printing resin-filled capsules for self-healing materials or piezoelectric particles for energy harvesting.” http://www.bristol.ac.uk/news/2016/january/3d-printer.html http://iopscience.iop.org/article/10.1088/0964-1726/25/2/02LT01/pdf