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Tesi etd-07192007-145550

Thesis type
Tesi di dottorato di ricerca
Porta, Marcello
email address,
Microhandling devices for the assembly of Hybrid Microproducts
Settore scientifico disciplinare
Corso di studi
Relatore Prof. Santochi, Marco
Parole chiave
  • Microproducts
  • Microfactory
  • Microassembly
Data inizio appello
Riassunto analitico
Hybrid microproducts are very important in every application where small dimension and light weigh are fundamental.
They are used in different fields, such as the automotive, the aeronautic/aerospace, the automation, the medical and
biomedical field, the watch industry, but also in the sport and entertainment sectors. These microproducts differ from
MOEMS because they consist of several components with some features of few hundreds microns made of different
materials. The final product is obtained by the assembly of the various components and this gives hybrid microproducts a
high 3D aspect and better mechanical performance than MOEMS.
The main problem that limits the market diffusion of these products is the enormous assembly cost that represents up to
the 80% of their final cost. This is due to their manual assembly that is a time consuming activity. Actually, traditional
assembly systems are not suitable because when dimensions of objects are less than 1 mm, many problems arise:
surface forces become bigger than gravity, there are difficulties due to the vision and force control, objects can be fragile,
tolerances become very narrow, there is not a systematic design for microassembly, methods and models are not
developed enough in microdomain.
Different approaches can be found in literature as an alternative to manual assembly to reduce costs. One of the most
promising strategies is the assembly microfactory. It is a miniaturization of an assembly system with the aims of
improving precision and reducing the ratio, in terms of energy, material and space consumption, between the assembly
facilities and the microproducts obtained. Therefore, many assembly and control devices have to work in a very little area
with low energy consumption and high precision.
Nowadays, one of the main problems that makes difficult the development of these microfactories is the lack of handling
devices able to manipulate components that have dimension of few hundreds microns. The required handling devices
are microfeeders to transport, orient and position microparts, microsorters to arrange components, microgrippers to
grasp and release them, micromanipulators and microrobots to support microgrippers.
In the PhD research activity various innovative handling devices for manipulating parts of different materials and shapes
have been designed, developed and tested. These systems are able to solve some critical issues in the automatic
handling of objects with dimensions of few hundreds microns such as feeding and transporting, grasping and releasing,
positioning. The developed systems are an electrostatic centering device and an electrostatic sorter, some mechanical
and adhesive grippers and a 2 DOF microrobot. The two electrostatic devices make use of electrostatic force to transport
and position microparts (the centering device) and to sort and arrange a group of objects randomly positioned (the sorter
system). Two kinds of gripper have been designed: the mechanical (piezo actuated) and the adhesive gripper. The first
kind uses a piezoelectric actuator to close and open the fingers, the second exploits capillary forces to grasp and center
microobjects. Finally, the 2 DOF manipulator is an electromagnetic device able to support light grippers as electrostatic
and adhesive ones.
These devices have been integrated in the assembly microfactory in progress at the Department of Mechanical, Nuclear
and Production Engineering of the University of Pisa within the Italian research PRIN project “Development of innovative
technologies for the assembly of hybrid microproducts”. In this microfactory, the assembly strategy makes use of a
carrier that contains the components of the products to be assembled and moves from an assembly station to the next
one. This assembly system is confined in a controlled environment and consists, at the moment, of an assembly station
equipped with various grippers (on the basis of the assembly tasks to be carried out) and controlled by vision systems.