|
|
|
|
Department of Mechanical, Nuclear and Production Engineering |
MICROASSEMBLY
Scientific Coordinator: Prof. Marco Santochi
MICROASSEMBLY Scientific Coordinator: Prof. Marco Santochi
|
Overview
|
Electrostatic Alignment The research work focuses on the development of a contact less electrostatic feeder able to orient and move mini and micro-components. The aim of the feeder is the handling of a wide range of components different in dimensions, shapes and materials. The physical principle is that both conductive and dielectric objects are attracted towards regions with an higher electric field, e.g. a dielectric or metallic plate is attracted inside the plates of a charged capacitor. The vibrating platform is used to reduce friction and adhesion forces between the components and the working surface, so the microcomponents exhibit random free motion on the working area. The electrode, connected to the HVS, consists of an electric wire and is kept parallel to the working surface, a conducting plate connected to the ground and covered by a thin glass disk (diameter=25mm, thickness= 0.15 mm). See figure 1 for more details.
Figure 1 - Experimental set-up Therefore the capacitor is composed by the wire (positive electrode) and the vibrating platform (negative plate electrode). In figure 2 the FEM analysis, the electric field and the direction of the electrostatic force are shown.
Figure 2 - FEM analysis The electric field, in the region next to the working surface, has a maximum under the electrode. It is easy to predict that micro components are attracted towards this region (Figure 3a) and tend to align their axes under the charged wire (Figure 3c).
Figure 3 - Alignment principle Under the influence of the controlled vibration, even a little difference in the electric field makes the micropart move: therefore a very small tilt of the electrode can modify the electric field and the direction of component movement (Figure 3b). Preliminary tests have shown that with the electrode tilted on the working area, the cylinders first go under the electrode, then start moving under the electrode towards regions where the electric field is higher (and where distance h is lower).
Figure 4 - Photo of the experimental apparatus As theory and FEM simulation predict, experiments have shown the possibility of aligning, 2D positioning and transporting axisymmetric microcomponents, different in materials, dimensions and shapes by using an electrostatic field. The promising results show that the 2 DOF (x, y) positioning apparatus presents the following advantages: short response time, no energy need, absence of current and so magnetic fields, low cost and simplicity. The future improvement of the device, after the improvement of the vibrating platform, will be the study and validation of a feeder composed by a series of several parallel electrodes, supplied with a travelling high electric voltage, that feed an assembly station.
For
more information:
|
Last Update 2004/06/01 |
