Research | Laboratorio di Prototipazione Rapida

Presentation

The Rapid Prototyping Laboratory or RPL is inspired by the principles of the circular economy to design and manufacture prototypes of materials and structures with innovative shapes and "unconventional" physical-mechanical characteristics.

For example, we design and manufacture 3D printable seismic isolators, innovative tensegrity-type structures for civil engineering and reinforcing fibers for newly developed structural materials.

Our eco-sustainable materials are largely obtained through the recycling of post-consumer plastic bottles, nylon nets recovered from the sea and waste of various materials, using a shredder and an extruder of filaments for 3D printing.

The RPL prototypes are configured as mechanical "metamaterials", ie structures with internal "engineered" architecture with properties not found in traditional materials.

the Rapid Prototyping Laboratory is located in study 3 of the L2 Structures Laboratory (Archibus code FL-ING03S01028).

presentation video

Equipment

The RPL is equipped with:

1. a) 3 new generation deskop 3D printers and related accessories;
2. b) Material shredder;
3. c) Filament extruder for 3D printing;
4. d) "shake-table" testing machine made within the "Strength" Laboratory;
5. e) Projection micro-stereolithography "(PμSL) built in-house, using parts assembled in-situ, usable for printing reticular structures at the microscale with resolution of the order of a micron. This set-up is of fundamental utility for the completion of the equipment at the service of the Rapid Prototyping Laboratory, allowing it to establish itself as an avant-garde structure in the 3d printing sector, in line with the objectives of excellence of research and teaching pursued. from the DiCiv. The parts assembled on site and purchased from various exclusive suppliers of international standards and reputations concerned the following components:

- the high resolution (405 nm) DLi CEL5500 “Compact Embeddable Light Engine” light generator;

- the Thorlabs B7575A anti-vibration table instrumented with optical accessories;

- photopolymers and photo-initiators.

Research activities

The seismic "metaisolators" made in the Laboratory are "bio-inspired" being formed by periodic arrays of unit cells that replicate the mechanics of the human body.

This research is inspired by the recent realization of a seismic isolator of the friction and extension type ("Stretching-Sliding Isolator" or SSI).

The unit cell of the SSI device is composed of rigid links that mimic the function performed by bones in the human body and of stretchable membranes that replicate the mechanical behavior of muscle tendons. The vertical load transferred from the superstructure to the SSI device is applied to the B-pillar, which moves by sliding against the base of the system.

Animals are known to adjust their vibration frequencies to achieve a state of resonance with the forces produced by the contraction of muscles during locomotion. This frequency tuning process produces energy-efficient motion. The bones of the legs and arms behave like pendular systems that are bent by the muscles to tune their resonant frequency, while the tendons act as non-linear springs and shock absorbers.

The metaisolators built in the Rapid Prototyping laboratory work in the opposite way: they tune the non-linear stiffness of the “tendon” elements in order to avoid resonance with the main frequencies of earthquakes.

The effective properties of such devices (e.g. the effective vibration period and the effective damping coefficient) can be adjusted by playing with the geometry of the device, the friction coefficient of the sliding elements, the preconditioning and the energy dissipation capacity of the tendons, the ratio between the design value of the re-centering force of these elements and the maximum vertical load.

Their manufacture does not require heavy industrial processes or expensive materials, being partially or completely achievable with ordinary 3D printers. We can design and build these systems "on demand", obtaining specific performances requested by the customer.

In the Rapid Prototyping laboratory we also design and manufacture reinforcing elements of structural materials with geometry inspired by natural shapes. These are bars, fibers and reinforced meshes with optimized adhesion, designed using fractal algorithms.

To test the isolators made by RPL, a "shake-table" test machine was designed and set up capable of verifying the behavior of prototypes of reduced dimensions, consisting of isolation devices suitable for the seismic protection of works of art and machinery light.

The test machine allows the simultaneous application of two forces: a vertical force up to 30 kN, which simulates the weight of the structure to be insulated, and a horizontal force up to 3 kN, which simulates the seismic action.

The sample under test can be mounted between a 0.7 x 0.7 m top plate. which slides on 4 vertical guides with circular section, operated by 4 jacks and a 0.7 x 0.7 m base plate that slides on two horizontal linear guides, operated by a linear actuator.

The system is controlled by 2 electronic drives and a programmable logic controller using software installed on a PC.

The "shake-table" device was built in-house by working in collaboration with the Structural Engineering Laboratory of the University of California in San Diego.