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